Ecology

Topic: Ecosystem and Energy Flow; Subtopic: Ecological Pyramids

Keyword Definitions:

• Pyramid of Energy: A graphical representation showing the energy flow at different trophic levels in an ecosystem; always upright due to energy loss at each level.

• Pyramid of Biomass: Depicts the total mass of organisms at each trophic level; can be inverted in aquatic ecosystems due to small phytoplankton biomass supporting larger consumers.

• Upright Pyramid: A pyramid with decreasing size from producers to top-level consumers, indicating energy or biomass decrease at higher trophic levels.

• Inverted Pyramid: A pyramid where higher trophic levels have greater biomass or energy than the lower level, often seen in aquatic systems.

• Energy Efficiency: The proportion of energy transferred from one trophic level to the next, usually around 10% per level.

Lead Question – 2022 (Abroad)
Given below are two statements:
Statement - I: Pyramid of energy is always upright and is the most efficient
Statement-II: Pyramid of biomass in sea is generally inverted
In the light of the above statements, choose the most appropriate answer from the options given below:
1. Statements-I is correct but statement-II is incorrect
2. Statements-I is incorrect but statement-II is correct
3. Both statement-I and statements-II are correct
4. Both statement-I and statements-II are incorrect

Explanation:
The correct answer is Both statement-I and statement-II are correct. Energy pyramids are always upright because energy decreases at each trophic level due to metabolic losses, making them the most efficient representation of energy flow. In aquatic ecosystems, phytoplankton have low biomass but reproduce rapidly, supporting larger consumers, causing the pyramid of biomass to appear inverted. The inversion does not affect energy flow, which remains upright. These distinctions reflect fundamental ecological principles, where energy diminishes consistently through trophic levels, but biomass distribution can vary depending on reproductive rates and turnover of primary producers, particularly in marine ecosystems.

1. Which type of ecological pyramid always remains upright?
1. Pyramid of numbers
2. Pyramid of energy
3. Pyramid of biomass
4. Pyramid of nutrients
Explanation: The correct answer is Pyramid of energy. Energy decreases at each successive trophic level due to metabolic processes and heat loss, ensuring the pyramid of energy is always upright. Unlike biomass or numbers, which may be inverted in aquatic systems or due to specific population structures, energy flow consistently diminishes, representing the efficiency of trophic transfers and ecosystem energy dynamics.

2. Inverted pyramid of biomass is commonly observed in:
1. Terrestrial forests
2. Desert ecosystems
3. Aquatic ecosystems
4. Grasslands
Explanation: The correct answer is Aquatic ecosystems. In oceans and lakes, phytoplankton have low standing biomass but high productivity. They support large consumers like zooplankton and fish, resulting in an inverted biomass pyramid. Energy pyramids remain upright because energy transfer efficiency is low, but rapid turnover of producers allows a smaller biomass to sustain higher trophic levels.

3. Energy transfer efficiency between trophic levels is approximately:
1. 50%
2. 10%
3. 30%
4. 70%
Explanation: The correct answer is 10%. Typically, only about 10% of energy at one trophic level is transferred to the next level. The remaining 90% is lost as heat, used in metabolism, or excreted. This low efficiency is why energy pyramids are always upright and why higher trophic levels have less energy available, influencing population sizes and ecosystem structure.

4. The primary cause for inversion of pyramid of biomass in aquatic ecosystems is:
1. High energy loss
2. High productivity of phytoplankton with low biomass
3. Presence of carnivorous fish
4. Decomposition by bacteria
Explanation: Correct answer is High productivity of phytoplankton with low biomass. Phytoplankton reproduce rapidly and sustain large zooplankton and fish populations despite having lower total biomass. This results in an inverted biomass pyramid. Energy pyramids remain upright because energy transfer decreases at each level, but rapid turnover allows support of higher trophic levels with minimal biomass.

5. Pyramid of numbers can be inverted in:
1. Grassland ecosystem
2. Forest ecosystem
3. Parasitic food chains
4. Aquatic ecosystem
Explanation: Correct answer is Parasitic food chains. In parasitic relationships, a single host supports numerous parasites, causing an inverted pyramid of numbers. Unlike energy pyramids, the pyramid of numbers does not always reflect trophic efficiency. This demonstrates that pyramids of numbers can be upright or inverted depending on population distributions and ecological relationships, while energy pyramids are consistently upright.

6. Which pyramid type best reflects the actual energy flow in an ecosystem?
1. Pyramid of numbers
2. Pyramid of biomass
3. Pyramid of energy
4. Pyramid of productivity
Explanation: Correct answer is Pyramid of energy. Energy pyramids accurately depict the decrease of energy across trophic levels and cannot be inverted. Other pyramid types, like biomass or numbers, can be inverted under certain conditions. Therefore, the pyramid of energy is the most reliable indicator of ecosystem function and energy dynamics.

7. Assertion-Reason Type:
Assertion (A): Pyramid of energy is always upright.
Reason (R): Energy is lost at each trophic level through heat and metabolism.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Correct answer is option 1. The upright nature of energy pyramids is due to energy loss at each level through metabolic activities and heat. This limits energy transfer to higher trophic levels, ensuring the pyramid consistently narrows towards the top, accurately reflecting ecosystem energy dynamics and efficiency.

8. Matching Type:
Match the ecosystem with its typical pyramid of biomass:
A. Forest – (i) Upright
B. Grassland – (ii) Upright
C. Ocean – (iii) Inverted
D. Pond – (iv) Variable
1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–i, C–iv, D–iii
3. A–iii, B–ii, C–i, D–iv
4. A–iv, B–iii, C–ii, D–i
Explanation: Correct answer is option 1. Forests and grasslands have upright biomass pyramids due to large producer biomass. Oceans show inverted biomass pyramids because small phytoplankton sustain larger consumers. Ponds can be variable depending on species composition and productivity. This demonstrates the diversity of biomass pyramids across ecosystems, unlike the consistently upright energy pyramids.

9. Fill in the Blanks:
The pyramid that can be inverted in aquatic ecosystems but always upright for energy flow is called ___________.
1. Pyramid of numbers
2. Pyramid of biomass
3. Pyramid of energy
4. Pyramid of nutrients
Explanation: Correct answer is Pyramid of biomass. In aquatic systems, low phytoplankton biomass supports larger consumers, inverting the pyramid.

Topic: Environmental Pollution; Subtopic: Biomagnification and Toxicants

Keyword Definitions:

• Biomagnification: The process by which the concentration of toxic substances increases at each trophic level of a food chain.

• Toxicants: Harmful chemical substances released into the environment from industrial or agricultural sources.

• Eutrophication: Enrichment of water bodies with nutrients, leading to excessive algal growth and oxygen depletion.

• Algal Bloom: Rapid proliferation of algae in water, often due to nutrient enrichment.

• Biochemical Oxygen Demand (BOD): A measure of oxygen required by microorganisms to decompose organic matter in water.

Lead Question – 2022 (Abroad)
Which biological process leads to a decrease in the fish-eating bird population near a water body containing toxicants from industrial drainage?
1. Algal bloom
2. Biochemical oxygen demand
3. Accelerated Eutrophication
4. Biomagnification

Explanation:
The correct answer is Biomagnification. Toxicants released into water accumulate in small aquatic organisms and progressively concentrate in higher trophic levels. Fish-eating birds consume contaminated fish, leading to high toxin accumulation in their bodies. This results in reduced reproduction, health issues, and a decline in population. Unlike eutrophication or algal bloom, which affect oxygen levels, biomagnification specifically concentrates chemical pollutants through the food chain, directly impacting top predators like fish-eating birds and mammals.

1. Which trophic level experiences the highest concentration of toxins in a polluted food chain?
1. Primary producers
2. Primary consumers
3. Secondary consumers
4. Top predators
Explanation: Top predators accumulate the highest toxin levels due to biomagnification. As smaller organisms containing toxins are consumed, these harmful chemicals concentrate in successive trophic levels, causing severe health impacts, reproductive failure, and population decline among apex predators in aquatic and terrestrial ecosystems.

2. Biomagnification primarily involves:
1. Increase in oxygen levels
2. Accumulation of toxic substances
3. Decrease in nutrient concentration
4. Algal decomposition
Explanation: Biomagnification refers to the progressive accumulation of toxic substances like heavy metals or pesticides along a food chain. Each successive consumer accumulates more toxins from its prey, leading to adverse effects on top predators and biodiversity, unlike processes affecting oxygen or nutrient levels such as eutrophication or BOD changes.

3. Which of the following is a common toxicant that biomagnifies in aquatic food chains?
1. DDT
2. Nitrate
3. Phosphate
4. Oxygen
Explanation: DDT, a persistent pesticide, accumulates in organisms at each trophic level and magnifies up the food chain. Aquatic animals like fish absorb it from water and prey. Birds consuming contaminated fish experience reproductive and health issues, demonstrating the harmful effects of biomagnification, unlike nutrients or oxygen which do not magnify biologically.

4. Algal bloom affects aquatic life primarily by:
1. Increasing toxin concentration
2. Depleting dissolved oxygen
3. Directly killing birds
4. Increasing fish-eating bird population
Explanation: Algal bloom depletes dissolved oxygen as algae die and decompose, creating hypoxic conditions harmful to aquatic life. It does not directly increase toxicant concentration or impact top predators through accumulation, unlike biomagnification, which concentrates pollutants in fish-eating birds and other apex species.

5. Which process is measured to assess organic pollution in water?
1. Biomagnification
2. Biochemical Oxygen Demand (BOD)
3. Algal bloom
4. Eutrophication
Explanation: BOD quantifies the oxygen required by microorganisms to decompose organic matter in water. High BOD indicates organic pollution. While BOD can indirectly stress aquatic animals, it does not directly concentrate chemical toxicants like biomagnification does, which affects top predators such as fish-eating birds.

6. Accelerated eutrophication leads to:
1. Oxygen depletion
2. Toxin accumulation in top predators
3. Direct chemical poisoning
4. Biomass reduction in birds only
Explanation: Accelerated eutrophication results from nutrient enrichment, causing excessive algae growth and subsequent oxygen depletion. It indirectly affects aquatic life due to hypoxia but does not directly concentrate toxic chemicals in higher trophic levels. Biomagnification, in contrast, increases pollutant concentration in fish-eating birds causing population decline.

7. Assertion-Reason Type:
Assertion (A): Fish-eating birds near polluted water show declining populations.
Reason (R): Toxicants accumulate through food chains and magnify in top predators.
1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.
Explanation: Correct answer is option 1. Biomagnification concentrates toxicants in apex predators like fish-eating birds, causing reproductive failure, health issues, and population decline, directly explaining the observed decrease in their numbers near polluted water bodies.

8. Matching Type:
Match the term with its effect:
A. Biomagnification – (i) Oxygen depletion
B. Algal bloom – (ii) Accumulation of toxins
C. BOD – (iii) High microbial activity
D. Eutrophication – (iv) Nutrient enrichment
1. A–ii, B–i, C–iii, D–iv
2. A–i, B–ii, C–iv, D–iii
3. A–iii, B–ii, C–i, D–iv
4. A–ii, B–iv, C–i, D–iii
Explanation: Correct answer is option 1. Biomagnification leads to accumulation of toxins, algal bloom causes oxygen depletion, BOD indicates microbial decomposition, and eutrophication arises from nutrient enrichment, collectively describing impacts of pollution in aquatic ecosystems.

9. Fill in the Blanks:
The process by which toxic substances increase in concentration at each trophic level is called ___________.
1. Eutrophication
2. Biomagnification
3. BOD
4. Algal bloom
Explanation: The blank is correctly filled with Biomagnification. Industrial toxicants enter aquatic organisms and concentrate progressively in higher trophic levels, causing significant health and population effects in top predators like fish-eating birds, while processes like eutrophication or algal bloom primarily affect oxygen and nutrient dynamics.

10. Choose the Correct Statements:
Statement I: Biomagnification increases toxicant concentration in top predators.
Statement II: Algal bloom directly causes toxin accumulation in birds.
1. Statement I is correct, Statement II is incorrect
2. Both statements are correct
3. Statement I is incorrect, Statement II is correct
4. Both statements are incorrect
Explanation: Correct answer is option 1. Biomagnification concentrates toxins in top predators like fish-eating birds, whereas algal bloom primarily affects oxygen levels in water and does not directly cause chemical accumulation in birds. Biomagnification is the main driver of population decline in contaminated ecosystems.

Topic: Population Ecology; Subtopic: Population Growth Curve

Keyword Definitions:

• Population: A group of individuals of the same species living in a particular area.

• Resources: Essential materials like food, water, and shelter required for survival.

• Logistic Growth: Growth pattern in which population size stabilizes due to resource limitation.

• Lag Phase: Initial slow growth period when population adapts to the environment.

• Acceleration Phase: Period of rapid population growth under favorable conditions.

• Deceleration Phase: Growth slows as resources become limiting and competition increases.

• Stationary Phase: Population growth stabilizes at the carrying capacity of the environment.

• Asymptote: Maximum population size that the environment can sustain.

• Carrying Capacity: Maximum number of individuals that can be supported sustainably.

• Population Dynamics: Study of changes in population size and composition over time.

• Finite Resources: Limited availability of essential materials in the ecosystem.

Lead Question - 2022 (Abroad)

A population with finite resources shows a logistic growth curve where the correct sequence of events will be:

1. Stationary phase → Acceleration phase → Lag phase → Asymptote

2. Acceleration phase → Deceleration → Asymptote

3. Acceleration phase → Lag phase → Stationary phase

4. Lag phase → Acceleration phase → Deceleration → Asymptote

Explanation: The correct sequence is Lag phase → Acceleration phase → Deceleration → Asymptote. Initially, the population grows slowly as it adjusts to the environment (Lag phase). Growth then accelerates due to abundant resources (Acceleration). Growth slows as resources become limiting (Deceleration), and eventually, population stabilizes at carrying capacity (Asymptote). This is characteristic of logistic growth. Answer: 4

1. SINGLE CORRECT ANSWER MCQ

Which factor primarily limits population growth in logistic growth?

1. Abiotic factors only

2. Availability of resources

3. Predation exclusively

4. Mating behavior

Explanation: Population growth in logistic models is mainly limited by the availability of resources. As population increases, resources like food and space become scarce, slowing growth and eventually stabilizing it at carrying capacity. Other factors like predation and abiotic conditions may influence growth but resources are primary. Answer: 2

2. SINGLE CORRECT ANSWER MCQ

During which phase of logistic growth is population growth rate maximum?

1. Lag phase

2. Acceleration phase

3. Deceleration phase

4. Stationary phase

Explanation: The maximum growth rate occurs during the Acceleration phase of the logistic curve. After the initial Lag phase, the population multiplies rapidly due to sufficient resources. This growth slows in the Deceleration phase as limiting factors appear, and stabilizes in the Stationary phase. Understanding this helps predict population dynamics. Answer: 2

3. SINGLE CORRECT ANSWER MCQ

Which term describes the environment’s maximum sustainable population size?

1. Carrying Capacity

2. Lag Phase

3. Asymptote

4. Deceleration

Explanation: Carrying Capacity refers to the maximum population size that an environment can sustain indefinitely given finite resources. Logistic growth approaches this limit gradually after deceleration, reaching the Asymptote where population stabilizes. Lag and Acceleration phases are initial growth phases, not the maximum sustainable size. Answer: 1

4. SINGLE CORRECT ANSWER MCQ

What happens to the population in the Stationary phase?

1. Population declines rapidly

2. Population remains stable

3. Population grows exponentially

4. Population goes extinct

Explanation: In the Stationary phase, population size remains stable as birth rate equals death rate and resources are fully utilized. This occurs after the Deceleration phase in logistic growth. Exponential growth happens earlier, and decline or extinction only occurs if resources fail drastically. This stability reflects carrying capacity. Answer: 2

5. SINGLE CORRECT ANSWER MCQ

Which of the following is NOT a feature of logistic growth?

1. Exponential initial growth

2. Carrying capacity

3. Unlimited growth

4. Deceleration phase

Explanation: Logistic growth is characterized by initial exponential growth, Deceleration phase, and stabilization at carrying capacity. Unlimited growth is absent because resources are finite, preventing indefinite population increase. Understanding these phases helps predict population trends under resource limitation. Answer: 3

6. SINGLE CORRECT ANSWER MCQ

Which phase immediately follows Lag phase in logistic growth?

1. Stationary phase

2. Deceleration phase

3. Acceleration phase

4. Extinction phase

Explanation: Acceleration phase follows Lag phase in logistic growth. After initial slow adaptation in Lag phase, population multiplies rapidly as resources are abundant. Deceleration occurs later as growth slows and Stationary phase stabilizes the population. Extinction is not a normal part of logistic growth. Answer: 3

7. ASSERTION-REASON MCQ

Assertion (A): Logistic growth eventually stabilizes at carrying capacity.

Reason (R): Population growth is limited by finite resources.

1. Both A and R are true and R is the correct explanation of A

2. Both A and R are true but R is not the correct explanation of A

3. A is true but R is false

4. A is false but R is true

Explanation: Logistic growth stabilizes at carrying capacity because finite resources limit further population increase. The Assertion is true, and the Reason correctly explains why the population cannot grow indefinitely. Understanding this relationship is key in population ecology. Answer: 1

8. MATCHING TYPE MCQ

Match the following phases with their descriptions:

Column A:

1. Lag phase

2. Acceleration phase

3. Deceleration phase

4. Stationary phase

Column B:

1. Rapid growth due to abundant resources

2. Population growth stabilizes

3. Slow initial growth

4. Growth slows due to limiting resources

Explanation: Correct matching: Lag phase → Slow initial growth, Acceleration → Rapid growth, Deceleration → Growth slows, Stationary → Population stabilizes. Each phase reflects a distinct stage in logistic growth determined by resource availability. Recognizing these phases aids in predicting population dynamics in finite environments. Answer: Lag-3, Acceleration-1, Deceleration-4, Stationary-2

9. FILL IN THE BLANKS / COMPLETION MCQ

The point where population growth rate becomes zero is called _______.

1. Lag phase

2. Carrying capacity

3. Acceleration phase

4. Deceleration phase

Explanation: The growth rate becomes zero at carrying capacity, which is the maximum population an environment can sustain. This occurs in the Stationary phase of logistic growth, when births equal deaths. Lag and Acceleration phases involve active growth, while Deceleration is still positive growth. Answer: 2

10. CHOOSE THE CORRECT STATEMENTS MCQ

Statement I: Logistic growth occurs due to limited resources.
Statement II: Exponential growth continues indefinitely.

1. Only Statement I is correct

2. Only Statement II is correct

3. Both Statements I and II are correct

4. Both Statements I and II are incorrect

Explanation: Logistic growth is a result of limited resources, causing population stabilization at carrying capacity. Exponential growth is unsustainable indefinitely because resources are finite. Hence, only Statement I is correct, while Statement II is incorrect. Recognizing these patterns is critical in understanding population dynamics and environmental carrying limits. Answer: 1

Topic: Ozone Layer Depletion; Subtopic: Measurement of Ozone Concentration

Keyword Definitions:

• Ozone Layer: A protective layer in the stratosphere that absorbs most of the Sun’s harmful ultraviolet radiation.

• Dobson Unit (DU): A unit that measures the total amount of ozone in a column of air from the Earth's surface to the top of the atmosphere.

• Stratosphere: The atmospheric layer located above the troposphere, extending from about 10 to 50 km altitude.

• Ozone Depletion: The gradual thinning of the ozone layer caused mainly by chlorofluorocarbons (CFCs).

• Ultraviolet Radiation: Invisible rays from the Sun that can cause skin cancer and DNA damage if not filtered by the ozone layer.

Lead Question - 2022 (Abroad)
The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of:
1. Balton units
2. Swedberg units
3. Monomeric units
4. Dobson units

Explanation: Ozone concentration is measured in Dobson Units (DU). One Dobson Unit equals a 0.01 mm thick layer of pure ozone at standard temperature and pressure. A normal ozone layer has 300 DU thickness, while depletion indicates values below 220 DU, especially over the Antarctic region during spring.

1. The unit used to express ozone concentration in the atmosphere is called:
1. Decibel
2. Dobson Unit
3. Dalton
4. Tesla
Explanation: The Dobson Unit quantifies total ozone in a column of air. It provides a standardized way to compare ozone levels globally. A value of 300 DU means if all ozone were compressed at STP, it would form a 3 mm thick layer, representing normal stratospheric ozone levels.

2. Ozone layer is mainly found in which part of the atmosphere?
1. Troposphere
2. Mesosphere
3. Stratosphere
4. Thermosphere
Explanation: The ozone layer is located in the lower part of the stratosphere, around 15–35 km above Earth. It plays a crucial role in filtering ultraviolet radiation, preventing skin cancer, cataracts, and genetic damage in living organisms.

3. Which of the following compounds is mainly responsible for ozone depletion?
1. Methane
2. Carbon dioxide
3. Chlorofluorocarbons
4. Nitrous oxide
Explanation: Chlorofluorocarbons (CFCs) are the main agents causing ozone depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms that react with ozone molecules, leading to their destruction and forming oxygen gas.

4. The Montreal Protocol (1987) was signed to control:
1. Global warming
2. Ozone depletion
3. Acid rain
4. Deforestation
Explanation: The Montreal Protocol, adopted in 1987, is an international treaty designed to phase out the production and consumption of substances that deplete the ozone layer, such as CFCs and halons. It is considered one of the most successful environmental agreements globally.

5. The ozone hole is predominantly seen over which region?
1. Arctic
2. Antarctic
3. Equator
4. Himalayas
Explanation: The ozone hole is mainly observed over Antarctica during the Southern Hemisphere spring. The cold stratospheric temperatures and the presence of polar stratospheric clouds accelerate ozone destruction by chlorine and bromine compounds derived from CFCs.

6. The most abundant gas released from CFC decomposition in the stratosphere is:
1. Chlorine
2. Nitrogen
3. Oxygen
4. Argon
Explanation: CFCs, when exposed to UV light, release chlorine atoms in the stratosphere. These chlorine radicals are highly reactive and destroy ozone molecules by converting them into molecular oxygen. A single chlorine atom can destroy thousands of ozone molecules.

7. Assertion (A): Chlorine released from CFCs causes ozone depletion.
Reason (R): Chlorine reacts with oxygen to form ozone.
1. (A) is correct but (R) is not correct
2. (A) is not correct but (R) is correct
3. Both (A) and (R) are correct, and (R) explains (A)
4. Both (A) and (R) are correct, but (R) does not explain (A)
Explanation: The correct answer is option 1. Chlorine atoms from CFCs catalytically destroy ozone molecules, not form them. They convert ozone (O₃) into oxygen (O₂), depleting the ozone layer while remaining chemically active to repeat the process many times.

8. Match the following:
A. CFCs → 1. Ozone depletion
B. CO₂ → 2. Greenhouse effect
C. SO₂ → 3. Acid rain
D. NO₂ → 4. Photochemical smog
1. A-1, B-2, C-3, D-4
2. A-2, B-3, C-4, D-1
3. A-4, B-1, C-2, D-3
4. A-3, B-2, C-1, D-4
Explanation: The correct match is A-1, B-2, C-3, D-4. Each pollutant is linked with a specific environmental issue: CFCs with ozone depletion, CO₂ with greenhouse effect, SO₂ with acid rain, and NO₂ with photochemical smog formation in urban areas.

9. Fill in the blank: The ozone layer is mainly depleted by __________ compounds.
1. Nitrogen-based
2. Chlorine-based
3. Carbon-based
4. Hydrogen-based
Explanation: The correct answer is chlorine-based compounds such as CFCs and halons. These compounds release chlorine radicals in the stratosphere that react with ozone, leading to its breakdown and decreasing the ozone concentration significantly.

10. Choose the correct statements:
a. Ozone absorbs harmful ultraviolet radiation.
b. Ozone is destroyed by chlorine and bromine atoms.
c. Ozone is found in the mesosphere.
d. Ozone layer depletion causes skin diseases.
1. a, b, and d
2. a and c
3. b and c
4. a, c, and d
Explanation: The correct answer is a, b, and d. Ozone protects living organisms by absorbing UV radiation. Its destruction by chlorine and bromine causes harmful effects such as skin cancer, cataracts, and ecological imbalance due to increased UV exposure.

Subtopic: Decomposition of Wastes

• Decomposition: Biological breakdown of organic matter into simpler substances by microorganisms.

• Detritus: Dead organic matter available as food for decomposers.

• Fungi: Eukaryotic organisms that decompose complex organic materials.

• Bacteria: Microorganisms that play a key role in nutrient recycling through decomposition.

• Aerobic: Processes that require oxygen.

• Anaerobic: Processes that occur without oxygen.

• Temperature effect: Decomposition rate depends on temperature; low temperature slows microbial activity.

• Moisture effect: Warm and moist environments favor microbial growth and decomposition.

• Enzymes: Proteins secreted by microbes that break down complex organic molecules.

• Inorganic substances: Simple molecules like CO2, H2O, nitrates formed after decomposition.

• Organic matter: Carbon-containing substances derived from plants and animals.

Lead Question - 2022 (Abroad)

Which of the following are not correct regarding decomposition of wastes?

1. (b) and (c) only

2. (c), (a) and (d) only

3. (c) and (d) only

4. (c), (d) and (e) only

Explanation: Decomposition is primarily an aerobic process, so statement (c) is incorrect. It is faster if detritus is rich in proteins and carbohydrates, making statement (d) wrong. Low temperature slows decomposition (statement a is correct), and warm moist conditions favor decomposition (statement b is correct). Microbes convert detritus to inorganic substances (statement e is correct). Answer: (c) and (d) only. Answer: 3

Q1: Which microorganism is most active in aerobic decomposition?

1. Fungi

2. Bacteria

3. Actinomycetes

4. All of the above

Explanation: Fungi, bacteria, and actinomycetes are all active in aerobic decomposition. They secrete enzymes that break down complex organic compounds into simpler inorganic molecules. Warm and moist conditions favor their activity, ensuring efficient nutrient recycling. Answer: All of the above. Answer: 4

Q2: Anaerobic decomposition mainly produces:

1. Carbon dioxide and water

2. Methane and organic acids

3. Nitrates

4. Ammonia only

Explanation: Anaerobic decomposition occurs in the absence of oxygen, leading to production of methane, organic acids, and sometimes hydrogen sulfide. This process is slower compared to aerobic decomposition. Aerobic decomposition produces carbon dioxide and water instead. Answer: Methane and organic acids. Answer: 2

Q3: Which factor accelerates decomposition of organic wastes?

1. Low temperature

2. Dry conditions

3. Warm and moist environment

4. High salinity

Explanation: Warm and moist environments favor microbial activity and enzymatic breakdown of organic matter. Low temperatures and dry conditions slow down decomposition, while high salinity can inhibit microbial growth. Optimal moisture and temperature enhance nutrient cycling. Answer: Warm and moist environment. Answer: 3

Q4: Detritus rich in which of the following decomposes faster?

1. Lignin

2. Cellulose

3. Proteins and carbohydrates

4. Wax

Explanation: Proteins and carbohydrates are easily metabolized by microbes, accelerating decomposition. Lignin and waxy substances are resistant, slowing decomposition. Cellulose is moderately degradable. Efficient nutrient recycling depends on easily degradable organic matter. Answer: Proteins and carbohydrates. Answer: 3

Q5: Which enzyme is secreted by microbes to degrade cellulose?

1. Cellulase

2. Amylase

3. Protease

4. Lipase

Explanation: Cellulase is secreted by fungi and bacteria to break down cellulose into glucose. Amylase breaks down starch, protease digests proteins, and lipase digests fats. Efficient decomposition of plant detritus relies on cellulase activity. Answer: Cellulase. Answer: 1

Q6: Composting is an example of:

1. Aerobic decomposition

2. Anaerobic decomposition

3. Both aerobic and anaerobic

4. Neither

Explanation: Composting involves aerobic decomposition, where microbes degrade organic matter in the presence of oxygen, producing nutrient-rich compost. Anaerobic decomposition occurs in oxygen-free conditions producing methane. Aerobic composting is faster and more efficient. Answer: Aerobic decomposition. Answer: 1

Q7: Assertion (A): Low temperature slows decomposition.
Reason (R): Microbial activity is reduced at low temperatures.

1. A is correct but R is not correct

2. A is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Low temperature inhibits microbial growth and enzyme activity, slowing decomposition. The reason correctly explains the assertion. Both statements are true and logically connected. Answer: Both A and R are correct and R explains A. Answer: 3

Q8: Match the process with its product:

1. Aerobic decomposition    A. Methane
2. Anaerobic decomposition    B. Carbon dioxide and water
3. Composting    C. Nutrient-rich humus

1. 1-B, 2-A, 3-C

2. 1-A, 2-B, 3-C

3. 1-C, 2-B, 3-A

4. 1-B, 2-C, 3-A

Explanation: Aerobic decomposition produces CO2 and water, anaerobic decomposition generates methane, and composting yields nutrient-rich humus. This matching clarifies the relationship between decomposition type and products. Answer: 1-B, 2-A, 3-C. Answer: 1

Q9: ______ is the main microbial group responsible for degradation of proteins in detritus.

1. Fungi

2. Bacteria

3. Actinomycetes

4. Protozoa

Explanation: Proteins in detritus are degraded primarily by proteolytic bacteria, although fungi and actinomycetes also contribute. Protease enzymes break proteins into amino acids, which are further mineralized. Efficient protein decomposition ensures nitrogen cycling in ecosystems. Answer: Bacteria. Answer: 2

Q10: Select correct statements regarding decomposition:

1. Decomposition is faster in warm and moist conditions

2. Low temperature slows microbial activity

3. Detritus rich in proteins and carbohydrates decomposes faster

4. Fungal and bacterial enzymes degrade organic matter to inorganic substances

Explanation: Decomposition is influenced by temperature, moisture, and substrate composition. Warm, moist conditions favor microbial activity. Easily degradable detritus such as proteins and carbohydrates is decomposed faster. Fungal and bacterial enzymes convert organic matter into CO2, water, nitrates, and other inorganic substances. Answer: All of the above. Answer: 1,2,3,4

Topic: Population Ecology

Subtopic: Population Growth

• Exponential Growth: Population growth under ideal conditions where the rate is proportional to current population.

• Population (N): Number of individuals in a population at a given time.

• Growth Rate (r): The per capita rate of increase of a population.

• Nt: Population size at time t.

• N0: Initial population size at time t=0.

• e: Base of natural logarithms, approximately 2.718, used in continuous growth calculations.

• Time (t): Duration over which population growth is measured.

• Exponential Equation: Mathematical model to describe population increasing continuously over time.

• Continuous Growth: Growth occurring without discrete time intervals.

• Nt = N0 e^rt: Standard equation representing exponential population growth.

• Population Dynamics: Study of changes in population size and composition over time.

Lead Question - 2022 (Abroad)

Which of the following is the correct equation of exponential growth?

1. N2

2. Nt = N0 e^(rnt)

3. Nt = N0 e^(rpt)

4. Nt = N0 e^(rt)

Explanation: Exponential growth occurs when population increases continuously at a constant per capita rate. The correct mathematical representation is Nt = N0 e^(rt), where N0 is initial population, r is intrinsic growth rate, t is time, and e is base of natural logarithms. Answer: Nt = N0 e^(rt). Answer: 4

Q1: If a population doubles in size every 5 years, which growth model is appropriate?

1. Linear growth

2. Exponential growth

3. Logistic growth

4. Zero growth

Explanation: Continuous doubling of population indicates exponential growth, where the rate of increase is proportional to current population size. Linear growth would increase by fixed numbers, not proportionally. Answer: Exponential growth. Answer: 2

Q2: In Nt = N0 e^(rt), what does r represent?

1. Initial population

2. Population at time t

3. Intrinsic growth rate

4. Time

Explanation: The symbol r in the exponential growth equation represents the intrinsic growth rate or per capita rate of increase. It determines how fast the population grows per individual over time. Answer: Intrinsic growth rate. Answer: 3

Q3: Which of the following represents continuous population growth mathematically?

1. Nt = N0 + rt

2. Nt = N0 e^(rt)

3. Nt = N0 (1 + r)^t

4. Nt = N0 rt

Explanation: Continuous population growth is modeled using Nt = N0 e^(rt), where population grows continuously at rate r. Discrete growth uses geometric progression like Nt = N0 (1 + r)^t. Answer: Nt = N0 e^(rt). Answer: 2

Q4: Doubling time of a population can be calculated using:

1. Td = ln2 / r

2. Td = r / ln2

3. Td = 2r

4. Td = N0 / Nt

Explanation: In exponential growth, doubling time Td is the time required for a population to double, given by Td = ln2 / r. It depends solely on the intrinsic growth rate, not initial population. Answer: Td = ln2 / r. Answer: 1

Q5: Exponential growth occurs under which conditions?

1. Unlimited resources and ideal environment

2. Limited resources

3. High predation only

4. Seasonal changes

Explanation: Exponential growth is observed when populations face no limiting factors, with unlimited resources and favorable environmental conditions, allowing continuous proportional increase. Answer: Unlimited resources and ideal environment. Answer: 1

Q6: In the exponential growth equation, what does Nt signify?

1. Initial population size

2. Population size at time t

3. Growth rate

4. Doubling time

Explanation: Nt represents the population size at a specific time t during exponential growth. It depends on initial size N0, growth rate r, and elapsed time t. Answer: Population size at time t. Answer: 2

Q7: Assertion (A): Exponential growth is unlimited.
Reason (R): Resources in nature are infinite.

1. A is correct but R is not correct

2. A is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Exponential growth model theoretically assumes unlimited growth. In nature, resources are limited; hence R is incorrect. Thus, A is correct but R is not correct. Answer: A is correct but R is not correct. Answer: 1

Q8: Match the growth equation with its type:

1. Nt = N0 + rt    A. Linear growth
2. Nt = N0 e^(rt)    B. Exponential growth
3. Nt = K / (1 + (K-N0)/N0 e^(-rt))    C. Logistic growth
4. Nt = N0 (1+r)^t    D. Discrete geometric growth

1. 1-A, 2-B, 3-C, 4-D

2. 1-B, 2-C, 3-A, 4-D

3. 1-D, 2-A, 3-B, 4-C

4. 1-C, 2-D, 3-B, 4-A

Explanation: Linear growth: Nt = N0 + rt, Exponential growth: Nt = N0 e^(rt), Logistic growth: Nt = K / (1 + ((K-N0)/N0)e^(-rt)), Geometric growth: Nt = N0 (1+r)^t. Correct match: 1-A, 2-B, 3-C, 4-D. Answer: 1

Q9: In exponential growth, the population increases ________ over time.

1. Linearly

2. Proportionally to current size

3. By fixed numbers

4. Not at all

Explanation: Exponential growth occurs when the rate of increase is proportional to the current population, resulting in rapid population expansion over time. This contrasts linear growth which increases by fixed numbers. Answer: Proportionally to current size. Answer: 2

Q10: Select correct statements about exponential growth:

1. Population grows continuously at a constant per capita rate

2. Nt = N0 e^(rt) is the equation representing it

3. Occurs only when resources are unlimited

4. Doubling time depends on r

Explanation: Statements 1, 2, 3, and 4 are correct. Exponential growth is continuous, represented by Nt = N0 e^(rt), occurs under ideal conditions, and doubling time is Td = ln2/r. Answer: 1, 2, 3, 4

Subtopic: Species-Area Relationship

• Species-Area Relationship (SAR): Ecological principle describing how species richness increases with area sampled.

• Species Richness (S): Number of species present in a given area.

• Area (A): Habitat size under consideration in ecological studies.

• Logarithmic Transformation: Mathematical method to linearize power relationships for analysis.

• Z-value: Slope of species-area curve in log-log plot.

• Y-intercept: Constant in log-transformed linear equation representing base species number.

• Ecological Sampling: Technique to estimate biodiversity in a habitat.

• Power Law: Relationship of form S = C*A^Z describing SAR.

• Biodiversity: Variety of species in a particular ecosystem.

• Conservation Biology: Study of biodiversity protection and habitat management.

• Species Density: Number of individuals per species per unit area.

Lead Question - 2022 (Abroad)

Species-Area relationship is described by the following equation:

log S = log C + Z log A

Where Z is:

1. Area

2. Species richness

3. Slope of the line

4. Y-intercept

Explanation: In the species-area relationship, log S = log C + Z log A, S represents species richness, A is area, and Z is the slope of the line in a log-log plot. It reflects the rate at which species richness increases with area. Answer: Slope of the line. Answer: 3

Q1: In the SAR equation S = C*A^Z, increasing A results in:

1. Decrease in species richness

2. Increase in species richness

3. No change in species richness

4. Decrease in Z-value

Explanation: Species richness (S) increases with area (A) as per the species-area relationship. Larger habitat supports more species due to higher resource availability and niche diversity. Z-value remains constant as slope of log-log plot. Answer: Increase in species richness. Answer: 2

Q2: In SAR, C represents:

1. Slope of log-log plot

2. Y-intercept

3. Area sampled

4. Species richness

Explanation: In log S = log C + Z log A, C is the intercept of the log-log line, representing species richness at unit area. It sets the baseline for species number. Slope is represented by Z, not C. Answer: Y-intercept. Answer: 2

Q3: Higher Z-value indicates:

1. Slower increase in species richness with area

2. Faster increase in species richness with area

3. No effect on species richness

4. Species decline with area

Explanation: Z-value is slope of log S vs log A. Higher Z indicates rapid increase of species richness with increasing area, typical of islands or heterogeneous habitats. Low Z represents slower species accumulation. Answer: Faster increase in species richness with area. Answer: 2

Q4: SAR is most useful for:

1. Estimating extinction rates

2. Predicting species richness in habitats

3. Designing conservation areas

4. All of the above

Explanation: Species-area relationship helps predict species richness, design protected areas, and estimate potential species loss due to habitat reduction. It is widely applied in conservation biology. Answer: All of the above. Answer: 4

Q5: Which log transformation is applied in SAR?

1. Natural log of S and A

2. Base-10 logarithm of S and A

3. Logarithm of Z and C

4. No transformation

Explanation: SAR uses log-log transformation, typically base-10 or natural log, to linearize the power law S = C*A^Z, allowing linear regression analysis of slope Z. This helps interpret species richness patterns. Answer: Base-10 logarithm of S and A. Answer: 2

Q6: In SAR, a low Z-value (~0.1) indicates:

1. Steep increase in species with area

2. Shallow increase in species with area

3. No relation with area

4. Species extinction

Explanation: Low Z (~0.1) shows a shallow slope; species richness increases slowly with increasing area, typical of continuous mainland habitats. High Z (~0.3-0.4) indicates steeper accumulation, common in islands. Answer: Shallow increase in species with area. Answer: 2

Q7: Assertion (A): Species richness doubles when area doubles if Z=1.
Reason (R): Z-value represents slope in log-log SAR.

1. A is correct but R is not correct

2. A is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Z is the slope of log S vs log A. If Z=1, S doubles when A doubles, as log S = log C + Z log A. Both assertion and reason are correct, and reason explains assertion. Answer: Both A and R are correct and R explains A. Answer: 3

Q8: Match habitats with typical Z-values:

1. Islands    A. 0.1
2. Continental mainland    B. 0.3
3. Archipelago    C. 0.2
4. Fragmented forests    D. 0.25

1. 1-B, 2-A, 3-C, 4-D

2. 1-A, 2-B, 3-C, 4-D

3. 1-B, 2-C, 3-D, 4-A

4. 1-D, 2-B, 3-A, 4-C

Explanation: Islands generally have high Z (~0.3) due to isolation. Continental mainland shows low Z (~0.1). Archipelagos ~0.2, fragmented forests ~0.25. This reflects rate of species accumulation with area. Correct match: 1-B, 2-A, 3-C, 4-D. Answer: 1

Q9: The equation S = C*A^Z represents _______ relationship.

1. Species-Area

2. Predator-Prey

3. Competition

4. Succession

Explanation: S = C*A^Z is the species-area relationship equation, describing how species richness increases with habitat area following a power law. It is unrelated to predator-prey, competition, or succession equations. Answer: Species-Area. Answer: 1

Q10: Choose correct statements about SAR:

1. Log transformation linearizes power law

2. Z varies with habitat type

3. Higher Z means steeper species accumulation

4. C represents slope of log-log plot

Explanation: Log-log transformation linearizes S = C*A^Z. Z varies among habitats and higher Z indicates faster species accumulation. C is intercept (baseline species number), not slope. Correct statements: 1, 2, 3. Answer: 1, 2, 3

Topic: Nitrogen Cycle

Subtopic: Denitrification

• Nitrogen cycle: Biogeochemical cycle describing the transformations of nitrogen in the environment.

• Denitrification: Microbial process where nitrate is reduced to gaseous nitrogen forms (N2, N2O), releasing it into the atmosphere.

• Ammonification: Conversion of organic nitrogen from dead organisms into ammonium by decomposers.

• Biological nitrogen fixation: Conversion of atmospheric nitrogen into ammonia by nitrogen-fixing bacteria.

• Industrial nitrogen fixation: Chemical process (Haber-Bosch) converting N2 to ammonia for fertilizers.

• Nitrification: Oxidation of ammonia to nitrate via nitrite by microbes.

• Nitrogen gas (N2): Inert atmospheric gas forming 78% of air, released by denitrification.

• Microbial activity: Actions of bacteria and fungi influencing nutrient cycles.

• Nitrate reduction: Step in denitrification reducing nitrate to nitrite, then to N2 or N2O.

• Atmospheric nitrogen release: Returning nitrogen from soil and organic matter to the air through microbial processes.

• Nitrogen loss: Reduction in bioavailable nitrogen due to denitrification or leaching.

Lead Question - 2022 (Abroad)

Which one of the following processes is responsible for the release of nitrogen into the atmosphere?

1. Industrial Nitrogen fixation

2. Ammonification

3. Denitrification

4. Biological nitrogen fixation

Explanation: Denitrification is a microbial process where nitrate (NO3-) is converted into nitrogen gas (N2) or nitrous oxide (N2O), which is released into the atmosphere. This step closes the nitrogen cycle by returning nitrogen to the air. Industrial fixation, ammonification, and biological fixation do not release nitrogen to the atmosphere. Answer: Denitrification. Answer: 3

Q1: Which bacteria are primarily responsible for denitrification?

1. Rhizobium

2. Clostridium and Pseudomonas

3. Azotobacter

4. Nitrosomonas

Explanation: Denitrifying bacteria like Pseudomonas and Clostridium reduce nitrate to nitrogen gas under anaerobic conditions, releasing nitrogen to the atmosphere. Rhizobium and Azotobacter fix atmospheric nitrogen, while Nitrosomonas oxidizes ammonia. Hence, Clostridium and Pseudomonas are the primary denitrifiers. Answer: Clostridium and Pseudomonas. Answer: 2

Q2: Ammonification converts organic nitrogen into:

1. Nitrate

2. Ammonium

3. Nitrogen gas

4. Nitrite

Explanation: Ammonification is the microbial decomposition of organic nitrogen from dead organisms or waste into ammonium (NH4+). It does not produce nitrate, nitrite, or nitrogen gas directly. Ammonium then enters nitrification or assimilation pathways. Answer: Ammonium. Answer: 2

Q3: Industrial nitrogen fixation produces:

1. Nitrogen gas

2. Ammonia

3. Nitrate

4. Nitrite

Explanation: Industrial nitrogen fixation (Haber-Bosch process) converts atmospheric nitrogen into ammonia for fertilizers. This ammonia is later converted to nitrate in soils. It does not release nitrogen gas. Answer: Ammonia. Answer: 2

Q4: Biological nitrogen fixation occurs in association with:

1. Fungi

2. Leguminous plants

3. Algae only

4. Decaying matter

Explanation: Biological nitrogen fixation is performed by nitrogen-fixing bacteria like Rhizobium in root nodules of legumes, converting atmospheric nitrogen to ammonia. Free-living bacteria like Azotobacter also fix nitrogen. It is not limited to fungi, algae, or decaying matter. Answer: Leguminous plants. Answer: 2

Q5: Which step completes the nitrogen cycle by returning nitrogen to the atmosphere?

1. Ammonification

2. Nitrification

3. Denitrification

4. Biological nitrogen fixation

Explanation: Denitrification converts nitrate or nitrite to gaseous nitrogen, releasing it back to the atmosphere. Ammonification and nitrification transform nitrogen in soil but do not release it to air. Biological fixation captures atmospheric nitrogen into organic forms. Answer: Denitrification. Answer: 3

Q6: Which gas is primarily released during denitrification?

1. Ammonia

2. Nitrogen gas (N2)

3. Carbon dioxide

4. Oxygen

Explanation: Denitrification reduces nitrate to nitrogen gas (N2) or nitrous oxide (N2O), which is released into the atmosphere. Ammonia, CO2, and oxygen are not the main products of denitrification. Answer: Nitrogen gas (N2). Answer: 2

Q7: Assertion (A): Denitrification occurs under anaerobic conditions.
Reason (R): Denitrifying bacteria require oxygen to reduce nitrate to nitrogen gas.

1. A is correct but R is not correct

2. A is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Denitrification is carried out by bacteria like Pseudomonas in anaerobic or low-oxygen conditions. The reason given is incorrect, as oxygen inhibits denitrification. Therefore, assertion is correct but reason is not. Answer: A is correct but R is not correct. Answer: 1

Q8: Match the process with its product:

A. Ammonification    1. Nitrogen gas
B. Nitrification    2. Nitrate
C. Denitrification    3. Ammonium
D. Nitrogen fixation    4. Ammonia

1. A-3, B-2, C-1, D-4

2. A-4, B-3, C-2, D-1

3. A-2, B-4, C-1, D-3

4. A-1, B-2, C-3, D-4

Explanation: Ammonification produces ammonium (A-3), nitrification converts ammonium to nitrate (B-2), denitrification releases nitrogen gas (C-1), and nitrogen fixation produces ammonia (D-4). This correctly matches processes with their products. Answer: A-3, B-2, C-1, D-4. Answer: 1

Q9: Microbial conversion of nitrate to nitrogen gas is called ______.

1. Nitrification

2. Denitrification

3. Ammonification

4. Nitrogen fixation

Explanation: Denitrification is the microbial process in which nitrate is reduced to nitrogen gas (N2), releasing it into the atmosphere and completing the nitrogen cycle. Other processes like nitrification and ammonification do not produce nitrogen gas. Answer: Denitrification. Answer: 2

Q10: Which of the following statements are correct about denitrification?

1. Carried out by Pseudomonas and Clostridium

2. Occurs in anaerobic conditions

3. Converts nitrate to nitrogen gas

4. Occurs primarily in the atmosphere

Explanation: Denitrification is performed by bacteria like Pseudomonas and Clostridium in anaerobic soil or water conditions, converting nitrate to nitrogen gas. It does not occur primarily in the atmosphere. Correct statements are 1, 2, 3. Answer: 1, 2, 3

Topic: Population Ecology

Subtopic: Migration and Population Dynamics

• Immigration: Movement of individuals into a population or habitat from elsewhere.

• Emigration: Movement of individuals out of a population or habitat to another location.

• Association: Coexistence of different species in the same habitat.

• Competition: Interaction between individuals or species for limited resources.

• Population dynamics: Study of changes in population size and composition over time.

• Habitat: Natural environment where organisms live and interact.

• Species: Group of organisms capable of interbreeding to produce fertile offspring.

• Carrying capacity: Maximum population size an environment can support.

• Migration: Seasonal or periodic movement of animals from one region to another.

• Dispersal: Movement of individuals away from their origin or parent population.

• Population growth: Increase in number of individuals in a population over time.

Lead Question - 2022 (Abroad)

The process of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration is referred as:

1. Association

2. Emigration

3. Competition

4. Immigration

Explanation: Immigration refers to the movement of individuals into a population or habitat from outside. It increases population size and genetic diversity. Emigration is the opposite process. Association and competition describe interactions, not movements. This definition is fundamental to understanding population dynamics. Answer: Immigration. Answer: 4

Q1: Which term describes individuals leaving a population to join another?

1. Immigration

2. Emigration

3. Association

4. Competition

Explanation: Emigration is the movement of individuals out of a population to another area. Immigration is entry, association refers to cohabitation, and competition is for resources. Understanding emigration is crucial in population studies. Answer: Emigration. Answer: 2

Q2: The interaction between species for the same resource is called:

1. Immigration

2. Emigration

3. Association

4. Competition

Explanation: Competition occurs when two or more organisms vie for limited resources such as food, water, or space. It can influence population size and survival. Association is coexistence without direct conflict, and immigration/emigration describe movement. Answer: Competition. Answer: 4

Q3: The coexistence of different species in the same habitat is called:

1. Immigration

2. Emigration

3. Association

4. Competition

Explanation: Association refers to different species living together in the same habitat without necessarily competing. Immigration and emigration refer to movement, competition is for shared resources. Recognizing association helps understand community structure. Answer: Association. Answer: 3

Q4: Population growth is affected by:

1. Birth rate

2. Death rate

3. Immigration and emigration

4. All of the above

Explanation: Population growth depends on birth rate, death rate, immigration, and emigration. Births and immigration increase size, deaths and emigration decrease it. Monitoring these parameters is essential in ecology. Answer: All of the above. Answer: 4

Q5: Seasonal movement of animals from one region to another is called:

1. Immigration

2. Emigration

3. Migration

4. Dispersal

Explanation: Migration is periodic or seasonal movement, often for breeding or food. Immigration/emigration are general movements into or out of populations, dispersal is movement away from origin. Migration impacts population distribution and ecology. Answer: Migration. Answer: 3

Q6: Dispersal primarily helps in:

1. Increasing resource competition

2. Reducing population density

3. Causing emigration only

4. Maintaining association

Explanation: Dispersal allows individuals to move away from origin, reducing local density and minimizing competition. It can lead to colonization of new areas. Emigration is one outcome, but dispersal emphasizes distribution. Answer: Reducing population density. Answer: 2

Q7: Assertion (A): Immigration increases genetic diversity of a population.
Reason (R): New individuals bring different alleles into the population.

1. (A) is correct but R is not correct

2. (A) is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Immigration introduces new alleles into a population, enhancing genetic diversity and potentially improving adaptability. Both assertion and reason are correct, and reason directly explains the assertion. Answer: Both A and R are correct and R explains A. Answer: 3

Q8: Match the terms with their definitions:

A. Immigration    1. Individuals leaving population
B. Emigration    2. Movement into population
C. Migration    3. Seasonal movement
D. Dispersal    4. Movement away from origin

1. A-2, B-1, C-3, D-4

2. A-1, B-2, C-4, D-3

3. A-2, B-1, C-4, D-3

4. A-3, B-4, C-1, D-2

Explanation: Immigration is entry, emigration is exit, migration is seasonal movement, dispersal is spreading from origin. Correct matching clarifies population movement types. Answer: A-2, B-1, C-3, D-4. Answer: 1

Q9: Movement of individuals out of a habitat to another population is called ______.

1. Immigration

2. Emigration

3. Association

4. Dispersal

Explanation: Emigration is the movement of individuals out of a population to another habitat, decreasing local population size. Immigration is movement in, association is coexistence, dispersal refers to spreading. Answer: Emigration. Answer: 2

Q10: Which statements about population movement are correct?

1. Immigration adds individuals to a population

2. Emigration removes individuals from a population

3. Competition is movement of individuals

4. Dispersal can reduce local density

Explanation: Immigration increases, emigration decreases population size. Dispersal spreads individuals reducing local density. Competition is resource interaction, not movement. Correct statements are 1, 2, and 4. Answer: 1, 2, 4

Topic: Nutrient Cycling

Subtopic: Humus Formation and Properties

Keyword Definitions:

• Humus: Dark, organic material formed in soil from decomposed plant and animal matter.

• Detritus Food Chain: A food chain that begins with dead organic matter decomposed by microbes.

• Nutrient Cycling: Continuous movement of nutrients through the biotic and abiotic components of an ecosystem.

• Microbial Action: Breakdown of complex organic matter by microorganisms in soil.

Lead Question - 2022 (Abroad)

Identify the correct set of statements with regard to properties of humus:
(a) Highly resistant to microbial action
(b) Dark-colored amorphous substance
(c) End product of detritus food chain
(d) Reservoir of nutrients
(e) Undergoes decomposition very fast
Choose the correct answer from the options given below:
1. (a), (b) and (d) only
2. (a), (b) and (e) only
3. (a) and (b) only
4. (b), (c) and (a)

Explanation: Humus is dark-colored, amorphous, and highly resistant to microbial decomposition. It acts as a nutrient reservoir and improves soil structure. It decomposes slowly, maintaining long-term fertility. Therefore, the correct answer is (a), (b), and (d) only.

1. Humus plays a major role in soil fertility because it:

1. increases soil aeration
2. acts as a nutrient reservoir
3. promotes leaching of salts
4. decreases water-holding capacity

Explanation: Humus increases soil fertility by holding nutrients and enhancing water retention. It prevents leaching and supports plant growth. Therefore, the correct answer is acts as a nutrient reservoir.

2. Which of the following organisms initiates humus formation?

1. Fungi
2. Earthworms
3. Protozoa
4. Blue-green algae

Explanation: Fungi are primary decomposers that break down complex organic matter into simpler compounds, initiating humus formation. They play a vital role in nutrient cycling. Hence, the correct answer is fungi.

3. Humus formation is a part of which ecological process?

1. Photosynthesis
2. Decomposition
3. Succession
4. Mineralization

Explanation: Humus is produced during decomposition, where dead organic matter is broken down into simpler compounds. It represents the stable organic fraction in this process. Thus, the correct answer is decomposition.

4. Which of the following statements about humus is incorrect?

1. It decomposes very rapidly
2. It improves soil structure
3. It stores nutrients
4. It resists microbial breakdown

Explanation: Humus decomposes very slowly due to its resistance to microbes. The statement “It decomposes very rapidly” is incorrect. Hence, the correct answer is it decomposes very rapidly.

5. The main source of humus in soil is:

1. Animal wastes
2. Dead plant matter
3. Minerals
4. Atmospheric gases

Explanation: Humus mainly originates from the decomposition of dead plant matter, including leaves, roots, and stems. Microbial activity converts these residues into stable humus. Therefore, the correct answer is dead plant matter.

6. Which property makes humus a good soil conditioner?

1. High decomposition rate
2. High nutrient content
3. Crystalline structure
4. Low moisture content

Explanation: Humus improves soil texture and moisture retention due to its high nutrient and water-holding capacity. This makes it a natural soil conditioner. Thus, the correct answer is high nutrient content.

7. (Assertion–Reason Type)
Assertion: Humus improves soil fertility.
Reason: It undergoes rapid decomposition releasing nutrients quickly.

1. Both Assertion and Reason are true, and Reason is the correct explanation.
2. Both Assertion and Reason are true, but Reason is not the correct explanation.
3. Assertion is true, but Reason is false.
4. Both are false.

Explanation: Humus improves fertility, but it decomposes slowly, providing nutrients gradually. Hence, the Assertion is true, but the Reason is false. The correct answer is Assertion is true, but Reason is false.

8. (Matching Type)
Match the components with their roles:

A. Humus — (i) Nutrient reservoir
B. Clay — (ii) Ion exchange
C. Sand — (iii) Drainage
D. Microbes — (iv) Decomposition
1. A-i, B-ii, C-iii, D-iv
2. A-ii, B-i, C-iii, D-iv
3. A-i, B-iii, C-iv, D-ii
4. A-iv, B-ii, C-i, D-iii

Explanation: Humus acts as a nutrient reservoir, clay helps in ion exchange, sand aids in drainage, and microbes decompose organic matter. Hence, the correct matching is A-i, B-ii, C-iii, D-iv.

9. (Fill in the Blanks)
Humus contributes to soil ___________ by increasing its ability to retain water and nutrients.

1. fertility
2. acidity
3. dryness
4. salinity

Explanation: Humus enhances soil fertility by improving nutrient and water retention. It prevents erosion and promotes plant growth. Thus, the correct answer is fertility.

10. (Choose the Correct Statements)
Choose the correct statements about humus:
(a) Formed during decomposition
(b) Chemically stable
(c) Poor in nutrients
(d) Improves soil texture

1. (a), (b), and (d) only
2. (a), (c), and (d) only
3. (b) and (c) only
4. (a) and (c) only

Explanation: Humus forms during decomposition, is chemically stable, and improves soil texture. It is rich, not poor, in nutrients. Therefore, the correct answer is (a), (b), and (d) only.

Topic: Air Pollution Control
Subtopic: Scrubbers and Electrostatic Precipitators

Keyword Definitions:

• Scrubber: A device used to remove particulate matter or gases from industrial exhaust streams using liquid spray or chemical reactions.

• Exhaust: Waste gases released from thermal plants or combustion processes.

• Electrostatic Precipitator: An air pollution control device that uses electrical charges to remove fine particulate matter from exhaust gas.

• Particulate Matter (PM2.5): Airborne particles smaller than 2.5 micrometers that can penetrate deep into lungs and are difficult to remove.

• Thermal Plant: An industrial facility generating electricity through combustion of fossil fuels.

Lead Question (2022):
Given below are two statements:
Statement I: In a scrubber the exhaust from the thermal plant is passed through the electric wires to charge the dust particles.
Statement II: Particulate matter (PM2.5) cannot be removed by scrubber but can be removed by an electrostatic precipitator.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Both statement I and statement II are incorrect
(2) Statement I is correct but statement II is incorrect
(3) Statement I is incorrect but statement II is correct
(4) Both statement I and statement II are correct

Explanation: Scrubbers remove pollutants using liquid sprays or chemical reactions, not electric charges; this makes Statement I incorrect. Electrostatic precipitators effectively remove PM2.5, which scrubbers cannot efficiently capture. Therefore, Statement II is correct. Hence, the correct answer is option (3).

1. Which device is primarily used to remove fine particulate matter from industrial exhaust?
(1) Scrubber
(2) Electrostatic Precipitator
(3) Cyclone Separator
(4) Bag Filter

Explanation: Electrostatic precipitators use high voltage to charge and collect fine particulate matter like PM2.5, which is difficult for scrubbers to capture. Therefore, the correct answer is option (2).

2. Scrubbers remove pollutants mainly by:
(1) Electrical charge
(2) Filtration with mesh
(3) Chemical reactions or liquid spray
(4) Centrifugal force

Explanation: Scrubbers use chemical reactions or liquid sprays to remove pollutants from exhaust gases. They are effective against soluble gases and larger particulates but not PM2.5. Hence, the correct answer is option (3).

3. Which particulate size is difficult to remove using scrubbers?
(1) PM10
(2) PM2.5
(3) PM50
(4) PM100

Explanation: PM2.5 particles are very fine and can bypass scrubbers, requiring devices like electrostatic precipitators or high-efficiency filters. Scrubbers are less efficient for particles this small. Hence, the correct answer is option (2).

4. Cyclone separators remove particulates based on:
(1) Electric charge
(2) Chemical absorption
(3) Centrifugal force
(4) Filtration mesh

Explanation: Cyclone separators remove larger particulate matter by creating a vortex that applies centrifugal force, forcing particles to the walls and separating them from the exhaust. Hence, the correct answer is option (3).

5. What is the main limitation of scrubbers in controlling air pollution?
(1) Cannot remove gaseous pollutants
(2) Cannot remove fine PM2.5 particles efficiently
(3) High operational cost
(4) Not suitable for industrial use

Explanation: Scrubbers are efficient for soluble gases and larger particles, but they struggle to remove fine PM2.5 particles. Electrostatic precipitators are better suited for such fine particulates. Hence, the correct answer is option (2).

6. Which device is most suitable for removing sulfur dioxide from thermal plant exhaust?
(1) Scrubber
(2) Electrostatic Precipitator
(3) Cyclone Separator
(4) Bag Filter

Explanation: Scrubbers can remove soluble gases like sulfur dioxide from exhaust by using chemical reactions in a liquid medium. Electrostatic precipitators do not remove gases effectively. Hence, the correct answer is option (1).

7. Assertion (A): Electrostatic precipitators are effective for PM2.5.
Reason (R): They charge particles and collect them on plates using electric fields.
(1) Both A and R are true and R is correct explanation
(2) Both A and R are true but R is not correct explanation
(3) A is true, R is false
(4) A is false, R is true

Explanation: Electrostatic precipitators remove fine particulate matter by charging particles and collecting them on plates through an electric field. This method is particularly effective for PM2.5. Hence, the correct answer is option (1).

8. Matching Type: Match devices with their primary function:
A. Scrubber – 1. Removes PM2.5
B. Electrostatic Precipitator – 2. Removes soluble gases and larger particles
C. Cyclone Separator – 3. Removes large particulates using centrifugal force
(1) A–2, B–1, C–3
(2) A–1, B–2, C–3
(3) A–3, B–1, C–2
(4) A–2, B–3, C–1

Explanation: Scrubbers remove soluble gases and larger particles (A–2), electrostatic precipitators remove fine PM2.5 (B–1), and cyclone separators remove larger particles using centrifugal force (C–3). Hence, the correct answer is option (1).

9. Fill in the blanks:
The device that removes fine particulate matter using an electric field is called __________.

(1) Scrubber
(2) Cyclone Separator
(3) Electrostatic Precipitator
(4) Bag Filter

Explanation: Fine particulate matter, especially PM2.5, is efficiently removed by an electrostatic precipitator that charges particles and collects them on plates. Scrubbers and cyclone separators cannot remove these fine particles effectively. Hence, the correct answer is option (3).

10. Choose the correct statements:
(a) Scrubbers use liquid sprays or chemical reactions.
(b) Electrostatic precipitators are effective for fine particulate matter.
(c) PM2.5 can be efficiently removed by scrubbers.
(d) Cyclone separators use centrifugal force to remove larger particles.
(1) a, b, d only
(2) a and c only
(3) b and c only
(4) a, b, c, d

Explanation: Scrubbers remove pollutants using liquid sprays or chemical reactions, electrostatic precipitators remove fine particles, and cyclone separators remove larger particles via centrifugal force. PM2.5 is not efficiently removed by scrubbers. Hence, the correct answer is option (1).

Topic: Population Ecology
Subtopic: Population Death Rate

Keyword Definitions:

• Drosophila: A genus of small flies, commonly known as fruit flies, often used in genetic and ecological studies.

• Population: A group of individuals of the same species living in a specific area.

• Death Rate: The number of deaths per unit population per unit time, usually expressed per week, month, or year.

• Laboratory Population: A population of organisms maintained under controlled conditions for experimental purposes.

Lead Question (2022):
If ‘8’ Drosophila in a laboratory population of ‘80’ died during a week, the death rate in the population is __________ individuals per Drosophila per week:
(1) 10
(2) 1.0
(3) zero
(4) 0.1

Explanation: Death rate = Number of deaths / Total population = 8 / 80 = 0.1 individuals per Drosophila per week. This measures the fraction of the population dying per unit time. Hence, the correct answer is option (4).

1. Which of the following factors can affect death rate in a population?
(1) Predation
(2) Disease
(3) Resource scarcity
(4) All of the above

Explanation: Death rate in a population is influenced by multiple factors, including predation, diseases, and scarcity of resources. Environmental conditions and competition also contribute. Hence, the correct answer is option (4).

2. If no individuals die in a population, the death rate is:
(1) 1
(2) 0
(3) Infinity
(4) Cannot be determined

Explanation: Death rate is calculated as the number of deaths divided by the total population. If no individual dies, the numerator is zero, so the death rate = 0. Hence, the correct answer is option (2).

3. In a population of 200 insects, 10 die in a week. The weekly death rate is:
(1) 0.05
(2) 0.5
(3) 2
(4) 20

Explanation: Death rate = deaths / total population = 10 / 200 = 0.05 individuals per insect per week. Hence, the correct answer is option (1).

4. Death rate is expressed in terms of:
(1) Absolute number of deaths only
(2) Deaths per unit population per unit time
(3) Births minus deaths
(4) Total population size

Explanation: Death rate measures the number of deaths relative to the population size and time period. It provides a standardized way to compare mortality across populations. Hence, the correct answer is option (2).

5. Which of the following is NOT a direct measure of population mortality?
(1) Death rate
(2) Life table
(3) Population growth rate
(4) Survival rate

Explanation: Population growth rate measures net change considering births and deaths. Death rate, life tables, and survival rate directly indicate mortality. Hence, the correct answer is option (3).

6. If the death rate of a population doubles while the birth rate remains constant, the population will:
(1) Increase
(2) Decrease
(3) Remain constant
(4) Oscillate randomly

Explanation: If death rate increases without a change in birth rate, more individuals die than are born, leading to population decline. Hence, the correct answer is option (2).

7. Assertion (A): Death rate depends only on population size.
Reason (R): Environmental and biological factors affect mortality.
(1) Both A and R are true and R is correct explanation
(2) Both A and R are true but R is not correct explanation
(3) A is true, R is false
(4) A is false, R is true

Explanation: Death rate is influenced by many factors including predation, disease, and environmental conditions. It does not depend solely on population size. Hence, the correct answer is option (4).

8. Matching Type: Match population terms with definitions:
A. Birth rate – 1. Number of deaths per population per time
B. Death rate – 2. Number of individuals born per population per time
C. Growth rate – 3. Net change in population size
(1) A–2, B–1, C–3
(2) A–1, B–2, C–3
(3) A–3, B–1, C–2
(4) A–2, B–3, C–1

Explanation: Birth rate measures new individuals per population per time, death rate measures deaths per population per time, and growth rate is net change in population size. Hence, the correct answer is option (1).

9. Fill in the blanks:
Death rate in a population is calculated by dividing the number of deaths by the __________.

(1) Number of births
(2) Total population
(3) Growth rate
(4) Time elapsed only

Explanation: Death rate is the number of deaths divided by total population over a defined time period. It standardizes mortality for comparison across populations. Hence, the correct answer is option (2).

10. Choose the correct statements:
(a) Death rate is influenced by predation.
(b) Death rate can be zero if no individual dies.
(c) Death rate measures population growth.
(d) Death rate is expressed per unit time.
(1) a, b, d only
(2) a and c only
(3) b and c only
(4) a, b, c, d

Explanation: Death rate is influenced by predation, can be zero if no deaths occur, and is expressed per unit time. It does not directly measure population growth. Hence, the correct answer is option (1).

Topic: Decomposition
Subtopic: Steps and Processes in Decomposition

Keyword Definitions:

• Detritus: Dead and decaying plant and animal matter that serves as a source of energy for decomposers and detritivores.

• Detritivores: Organisms like earthworms and termites that feed on detritus and break it into smaller particles.

• Fragmentation: The process of breaking down detritus into smaller pieces by detritivores.

• Humification: Formation of humus during decomposition from partially decomposed organic matter.

• Mineralisation: Conversion of organic matter into inorganic nutrients like nitrates, phosphates, and sulphates.

Lead Question – 2022
Detritivores breakdown detritus into smaller particles. This process is called:
(1) Fragmentation
(2) Humification
(3) Decomposition
(4) Catabolism

Explanation: Detritivores such as earthworms feed on dead organic matter and break it into smaller particles in a process called fragmentation. This increases surface area for microbial action and enhances decomposition efficiency. Hence, the correct answer is (1).

1. The decomposition of detritus is faster when:
(1) Temperature is low
(2) Moisture content is high and temperature is warm
(3) Oxygen is absent
(4) Humus content is low
Explanation: Warm temperature and adequate moisture promote rapid microbial activity, increasing the rate of decomposition. Anaerobic conditions slow it down. Hence, the correct answer is (2).

2. The conversion of complex organic compounds into simple inorganic substances is known as:
(1) Humification
(2) Fragmentation
(3) Mineralisation
(4) Catabolism
Explanation: Mineralisation is the final stage of decomposition where organic matter is converted into inorganic nutrients like ammonium, nitrate, and phosphate. Hence, the correct answer is (3).

3. Which of the following is not a step of decomposition?
(1) Fragmentation
(2) Humification
(3) Nitrification
(4) Leaching
Explanation: Nitrification is a microbial process in the nitrogen cycle, not a direct step in decomposition. Fragmentation, humification, and leaching are true steps of decomposition. Hence, the correct answer is (3).

4. Which organisms are mainly responsible for mineralisation?
(1) Fungi and bacteria
(2) Earthworms only
(3) Algae
(4) Protozoa
Explanation: Bacteria and fungi play a major role in the mineralisation of organic matter by breaking complex compounds into simpler inorganic forms. Hence, the correct answer is (1).

5. Humus is:
(1) Highly resistant to microbial action and slowly degraded
(2) Readily decomposable and short-lived
(3) Composed of inorganic matter
(4) Formed by mineralisation
Explanation: Humus is a dark, amorphous, and highly stable organic substance formed during humification. It resists further microbial decomposition and slowly releases nutrients. Hence, the correct answer is (1).

6. Which of the following factors does not directly affect the rate of decomposition?
(1) Soil moisture
(2) Temperature
(3) Chemical composition of detritus
(4) Atmospheric pressure
Explanation: Decomposition depends on temperature, moisture, and detritus composition, not on atmospheric pressure. Hence, the correct answer is (4).

7. Assertion (A): Detritivores help in the process of fragmentation.
Reason (R): They convert inorganic matter into organic compounds.
(1) Both A and R are true, and R explains A
(2) Both A and R are true, but R does not explain A
(3) A is true, R is false
(4) A is false, R is true
Explanation: Detritivores indeed perform fragmentation, but they do not convert inorganic matter into organic compounds. Hence, Assertion is true but Reason is false. Correct answer is (3).

8. Match the following:
A. Fragmentation — (i) Earthworm
B. Humification — (ii) Formation of humus
C. Mineralisation — (iii) Bacteria
D. Leaching — (iv) Downward movement of soluble nutrients
Options:
(1) A-(i), B-(ii), C-(iii), D-(iv)
(2) A-(iii), B-(i), C-(iv), D-(ii)
(3) A-(ii), B-(iv), C-(i), D-(iii)
(4) A-(iv), B-(i), C-(iii), D-(ii)
Explanation: Fragmentation is done by earthworms, humification leads to humus formation, mineralisation by bacteria, and leaching involves downward movement of nutrients. Hence, the correct answer is (1).

9. Fill in the blank:
The partially decomposed dark coloured organic matter in soil is called _______.
(1) Humus
(2) Detritus
(3) Compost
(4) Peat
Explanation: The dark-coloured, partially decomposed organic matter formed during humification is known as humus. It improves soil fertility and water retention. Hence, the correct answer is (1).

10. Choose the correct statements:
(1) Humification produces inorganic nutrients rapidly.
(2) Mineralisation converts inorganic matter to organic matter.
(3) Leaching results in the loss of soluble nutrients from topsoil.
(4) Decomposition occurs faster in dry and cold climates.
Explanation: Leaching indeed results in downward movement and loss of soluble nutrients. Humification and mineralisation differ in process and speed, and decomposition is slow in dry climates. Hence, only statement (3) is correct.

Topic: Population Interactions
Subtopic: Interspecific Interactions

Keyword Definitions:
• Interspecific Interaction: Interaction between individuals of different species in an ecosystem.
• Amensalism: Interaction where one species is harmed and the other unaffected (–, 0).
• Commensalism: Interaction where one species benefits and the other is unaffected (+, 0).
• Competition: Interaction where both species are harmed (–, –) due to resource overlap.
• Predation: Interaction where one species benefits (+) and the other is harmed (–).
• Mutualism: Interaction where both species benefit (+, +).
• Neutralism: Interaction where both species are unaffected (0, 0).
• Population: Group of individuals of same species living in a habitat.
• Beneficial Interaction: Positive effect on fitness or growth of species.
• Detrimental Interaction: Negative effect on fitness or growth of species.

Lead Question (2022):
While explaining interspecific interaction of population, (+) sign is assigned for beneficial interaction, (–) sign is assigned for detrimental interaction, and (0) for neutral interaction. Which of the following interactions can be assigned (+) for another species involved in the interaction?
Options:
1. Amensalism
2. Commensalism
3. Competition
4. Predation

Explanation: The correct answer is 2. Commensalism. In commensalism, one species benefits (+) while the other remains unaffected (0). Other interactions like amensalism (–, 0), competition (–, –), and predation (+, –) do not assign a positive effect to the second species. Commensalism examples include epiphytic orchids on trees.

Guessed MCQs:

1. In which interaction do both species benefit?
Options:
(a) Mutualism
(b) Commensalism
(c) Amensalism
(d) Competition
Explanation: The correct answer is (a) Mutualism. Both species gain positive effects (+, +) in mutualism, enhancing survival or reproduction. Examples include bees and flowering plants, where pollination benefits both partners, unlike commensalism or competition where benefits are asymmetric or negative.

2. Which interaction harms both species involved?
Options:
(a) Amensalism
(b) Competition
(c) Predation
(d) Commensalism
Explanation: The correct answer is (b) Competition. Both species are negatively affected (–, –) due to limited resources, reducing growth or reproduction. Amensalism affects one species only, predation benefits one, and commensalism benefits only one species.

3. Assertion-Reason MCQ:
Assertion (A): Predation is beneficial for one species and harmful for the other.
Reason (R): The predator gains energy while the prey loses fitness.
Options:
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: The correct answer is (a). Predation benefits the predator (+) by providing food, while harming the prey (–). The energy gain by predator directly explains the positive effect on one species and negative effect on the other.

4. Matching Type MCQ:
Match the interaction with its effect on species:
List - I List - II
(a) Amensalism (i) +, 0
(b) Commensalism (ii) –, 0
(c) Mutualism (iii) +, +
Options:
1. a-i, b-ii, c-iii
2. a-ii, b-i, c-iii
3. a-iii, b-ii, c-i
4. a-ii, b-iii, c-i
Explanation: The correct answer is 2. Amensalism harms one species (–) while the other is unaffected (0), commensalism benefits one (+) while the other is unaffected (0), and mutualism benefits both (+, +). Correct matching helps understand the effect of interactions on fitness and survival.

5. Which interaction has no effect on either species?
Options:
(a) Neutralism
(b) Commensalism
(c) Predation
(d) Amensalism
Explanation: The correct answer is (a) Neutralism. Both species remain unaffected (0, 0), as they do not compete or benefit from each other. Commensalism benefits one, predation harms one, and amensalism harms one species while the other is unaffected.

6. Single Correct Answer:
Which interaction benefits one species without affecting the other?
Options:
(a) Commensalism
(b) Competition
(c) Mutualism
(d) Amensalism
Explanation: The correct answer is (a) Commensalism. One species gains benefits (+) while the other remains unaffected (0). Examples include barnacles on whales. Other interactions either harm one or both species or benefit both, distinguishing commensalism as an asymmetric positive interaction.

7. Fill in the Blanks:
In __________, both species are harmed due to resource limitation.
Options:
(a) Competition
(b) Commensalism
(c) Mutualism
(d) Neutralism
Explanation: The correct answer is (a) Competition. Both species experience negative effects (–, –) due to overlapping requirements for food, space, or other resources. This reduces growth, reproduction, and survival, unlike commensalism or mutualism which provide benefits to at least one species.

8. Which interaction benefits the predator only?
Options:
(a) Amensalism
(b) Competition
(c) Predation
(d) Commensalism
Explanation: The correct answer is (c) Predation. The predator gains energy (+), whereas the prey is harmed (–). This positive-negative interaction affects population dynamics and evolutionary pressures, unlike commensalism (benefits one, neutral for other) or competition (negative for both).

9. Single Correct Answer:
Which interaction is represented by barnacles on whales?
Options:
(a) Commensalism
(b) Predation
(c) Competition
(d) Amensalism
Explanation: The correct answer is (a) Commensalism. Barnacles benefit (+) by gaining a substrate for attachment, while whales are unaffected (0). This exemplifies asymmetric positive interaction, characteristic of commensalism in ecosystems.

10. Choose the correct statements:
(i) Mutualism is beneficial for both species
(ii) Commensalism benefits one species
(iii) Predation harms both species
(iv) Amensalism harms one species
Options:
(a) i, ii, iv
(b) i, iii, iv
(c) ii, iii
(d) i, ii, iii
Explanation: The correct answer is (a) i, ii, iv. Mutualism provides benefits to both (+, +), commensalism benefits one (+, 0), and amensalism harms one (–, 0). Predation is positive-negative, not negative-negative, distinguishing interactions based on their effects on species fitness and survival.

Topic: Air Pollution and Control Measures
Subtopic: Use of CNG and Vehicular Emission Control

Keyword Definitions:

• CNG (Compressed Natural Gas): A clean fuel consisting mainly of methane, used in vehicles to reduce pollution.

• Diesel: A petroleum-based fuel known to emit high levels of particulate matter and nitrogen oxides.

• Vehicular Emission: Air pollutants released from vehicles, contributing significantly to urban air pollution.

• Adulteration: Mixing cheaper substances like kerosene with fuel to increase profit, leading to pollution.

• Air Quality: The measure of pollutants present in the atmosphere affecting health and environment.

Lead Question (2022):
The entire fleet of buses in Delhi were converted to CNG from diesel. In reference to this, which one of the following statements is false?
(1) The same diesel engine is used in CNG buses making the cost of conversion low
(2) It is cheaper than diesel
(3) It cannot be adulterated like diesel
(4) CNG burns more efficiently than diesel

Explanation: CNG vehicles require specially designed or modified engines; the same diesel engine cannot be used directly. Hence, statement (1) is false. CNG is cheaper, burns more efficiently, and does not cause fuel adulteration, reducing air pollution levels. The correct answer is (1) The same diesel engine is used in CNG buses.

1. Guessed Question:
Which of the following gases is the main component of CNG?
(1) Ethane
(2) Methane
(3) Propane
(4) Butane

Explanation: CNG (Compressed Natural Gas) is mainly composed of methane (CH₄), a clean-burning hydrocarbon that produces less carbon monoxide and nitrogen oxides. Hence, the correct answer is (2) Methane.

2. Guessed Question:
Which of the following is not an advantage of using CNG over diesel?
(1) Lower emission of pollutants
(2) Cheaper fuel cost
(3) Higher engine maintenance cost
(4) Better fuel efficiency

Explanation: CNG engines have lower maintenance costs and emit fewer pollutants than diesel engines. Hence, the incorrect statement is (3) Higher engine maintenance cost, as CNG reduces engine wear and pollution significantly.

3. Guessed Question:
What was the main reason for converting Delhi’s buses to CNG?
(1) To reduce air pollution
(2) To reduce noise pollution
(3) To increase vehicle speed
(4) To promote foreign fuel imports

Explanation: Delhi converted its public transport fleet to CNG mainly to reduce air pollution from vehicular emissions, as ordered by the Supreme Court. Hence, the correct answer is (1) To reduce air pollution.

4. Guessed Question:
Which pollutant is most effectively reduced by switching from diesel to CNG?
(1) Carbon monoxide
(2) Sulphur dioxide
(3) Ozone
(4) Ammonia

Explanation: CNG drastically reduces carbon monoxide, hydrocarbons, and nitrogen oxides compared to diesel combustion. Hence, the correct answer is (1) Carbon monoxide, since it decreases significantly in CNG vehicles.

5. Guessed Question:
Which of the following is a disadvantage of using CNG as fuel?
(1) It emits greenhouse gases
(2) It requires high-pressure storage cylinders
(3) It is highly toxic
(4) It is a non-renewable resource

Explanation: CNG must be stored at high pressure, making vehicle design more complex. It emits fewer greenhouse gases and is non-toxic. Hence, the correct answer is (2) It requires high-pressure storage cylinders.

6. Guessed Question:
Which city in India first adopted CNG on a large scale for public transport?
(1) Mumbai
(2) Delhi
(3) Chennai
(4) Hyderabad

Explanation: Delhi was the first Indian city to switch its entire fleet of buses, autos, and taxis to CNG under Supreme Court orders to control air pollution. Hence, the correct answer is (2) Delhi.

7. Assertion-Reason Question:
Assertion (A): CNG vehicles emit fewer pollutants than diesel vehicles.
Reason (R): CNG is a mixture of carbon monoxide and nitrogen oxides.
(1) Both A and R are true, and R explains A.
(2) Both A and R are true, but R does not explain A.
(3) A is true, R is false.
(4) A is false, R is true.

Explanation: CNG vehicles emit fewer pollutants because methane burns completely, not because CNG contains pollutants. Hence, A is true, R is false. The correct answer is (3) A is true, R is false.

8. Matching Type Question:
Match the following fuels with their key characteristics:
A. Diesel — (i) High particulate emissions
B. CNG — (ii) Compressed methane gas
C. Petrol — (iii) Higher CO emission
Options:
(1) A–i, B–ii, C–iii
(2) A–iii, B–i, C–ii
(3) A–ii, B–iii, C–i
(4) A–i, B–iii, C–ii

Explanation: Diesel produces high particulate emissions, CNG is compressed methane, and petrol produces more carbon monoxide. Hence, the correct answer is (1) A–i, B–ii, C–iii.

9. Fill in the Blanks:
CNG is mainly composed of ______ which is a ______ gas.
(1) Ethane, heavy
(2) Methane, light
(3) Butane, heavy
(4) Propane, dense

Explanation: CNG primarily consists of methane, a light and clean-burning hydrocarbon that reduces harmful emissions. Hence, the correct answer is (2) Methane, light.

10. Choose the Correct Statements:
(a) CNG is stored under high pressure.
(b) It produces no particulate matter on burning.
(c) It causes more air pollution than diesel.
(d) It reduces greenhouse gas emissions.
(1) (a), (b), and (d) only
(2) (b) and (c) only
(3) (a) and (c) only
(4) (a), (b), and (c) only

Explanation: CNG is stored at high pressure, produces no particulate matter, and lowers greenhouse gas emissions. Hence, the correct answer is (1) (a), (b), and (d) only.

Topic: Decomposition and Nutrient Cycling
Subtopic: Factors Affecting Decomposition

Keyword Definitions:

• Decomposition: Biological process in which organic matter is broken down into simpler substances by microbes.

• Detritus: Dead organic matter including plant and animal remains.

• Lignin: Complex polymer in plant cell walls providing rigidity and resistance to decomposition.

• Chitin: Structural polysaccharide found in fungal cell walls and exoskeletons of arthropods.

• Microbes: Microorganisms like bacteria and fungi that degrade detritus.

• Nutrient Cycling: Recycling of essential elements through ecosystems via decomposition and other processes.

• Rate of Decomposition: Speed at which organic matter is broken down; influenced by composition, temperature, moisture, and microbial activity.

• Organic Matter: Carbon-containing substances derived from living organisms.

• Humus: Stable, dark-colored organic matter formed after decomposition.

• Decomposers: Organisms that break down dead material, releasing nutrients back into the ecosystem.

Lead Question (2022)
Given below are two statements :
Statement I : Decomposition is a process in which the detritus is degraded into simpler substances by microbes
Statement II : Decomposition is faster if the detritus is rich in lignin and chitin
In the light of the above statements, choose the correct answer from the options given below:
(1) Both Statement I and Statement II are incorrect
(2) Statement I is correct but Statement II is incorrect
(3) Statement I is incorrect but Statement II is correct
(4) Both Statement I and Statement II are correct

Explanation:
Statement I is correct as decomposition involves microbial breakdown of detritus into simpler substances. Statement II is incorrect because detritus rich in lignin and chitin decomposes slowly due to their complex structure. Microbial activity is hindered by these resistant compounds. Correct answer is (2).

1. Single Correct Answer MCQ:
Which of the following detritus components slows down decomposition?
(1) Proteins
(2) Lignin
(3) Sugars
(4) Starch

Explanation:
Lignin is a complex polymer resistant to microbial degradation, slowing decomposition. Proteins, sugars, and starch are more easily broken down by microbes. Correct answer is (2).

2. Single Correct Answer MCQ:
Decomposition releases nutrients primarily in the form of:
(1) Inorganic compounds
(2) Proteins
(3) Lipids
(4) Vitamins

Explanation:
Microbial decomposition breaks down organic matter, releasing nutrients like nitrogen, phosphorus, and minerals in inorganic form, making them available for plants. Correct answer is (1).

3. Single Correct Answer MCQ:
Which of the following are decomposers?
(1) Fungi and bacteria
(2) Herbivores
(3) Carnivores
(4) Producers

Explanation:
Fungi and bacteria are primary decomposers, breaking down dead organic matter into simpler substances and releasing nutrients. Herbivores, carnivores, and producers do not perform decomposition. Correct answer is (1).

4. Single Correct Answer MCQ:
Which factor accelerates decomposition?
(1) Low temperature
(2) Dry environment
(3) High microbial activity
(4) High lignin content

Explanation:
High microbial activity enhances decomposition by rapidly breaking down detritus. Low temperature, dryness, or high lignin content slows the process. Correct answer is (3).

5. Single Correct Answer MCQ:
Humus formation is a result of:
(1) Photosynthesis
(2) Decomposition
(3) Respiration
(4) Transpiration

Explanation:
Decomposition of detritus by microbes results in humus, a stable organic matter that enriches soil. Photosynthesis, respiration, and transpiration are unrelated processes. Correct answer is (2).

6. Single Correct Answer MCQ:
Which detritus component is easily decomposed?
(1) Chitin
(2) Cellulose
(3) Lignin
(4) Keratin

Explanation:
Cellulose is relatively easily decomposed by microbes compared to chitin, lignin, and keratin, which are resistant structural polymers. Correct answer is (2).

7. Assertion-Reason MCQ:
Assertion (A): Decomposition is slower in detritus rich in chitin.
Reason (R): Chitin is a complex nitrogen-containing polysaccharide resistant to microbial breakdown.
Options:
(1) Both A and R are correct, R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both A and R incorrect

Explanation:
Chitin is complex and resistant to microbial degradation, making decomposition slower. Both the assertion and reason are correct, and R explains A. Correct answer is (1).

8. Matching Type MCQ:
Match the detritus type with decomposition rate:
A. Lignin — 1. Fast
B. Sugars — 2. Slow
C. Proteins — 3. Moderate
D. Cellulose — 4. Moderate
Options:
(1) A–2, B–1, C–3, D–4
(2) A–1, B–2, C–3, D–4
(3) A–2, B–3, C–1, D–4
(4) A–2, B–1, C–4, D–3

Explanation:
Lignin decomposes slowly, sugars rapidly, proteins moderately, and cellulose moderately. Correct matching is A–2, B–1, C–3, D–4. Correct answer is (1).

9. Fill in the Blanks MCQ:
_________ are microorganisms that degrade detritus into simpler substances.
(1) Producers
(2) Decomposers
(3) Herbivores
(4) Carnivores

Explanation:
Decomposers like fungi and bacteria degrade detritus into simpler substances, facilitating nutrient cycling. Producers, herbivores, and carnivores do not perform this function. Correct answer is (2).

10. Choose the correct statements MCQ:
(a) Lignin slows decomposition
(b) Microbial activity enhances decomposition
(c) Decomposition does not release nutrients
(d) Chitin-rich detritus decomposes slowly
Options:
(1) a, b, d only
(2) a, c, d only
(3) b, c, d only
(4) a, b, c only

Explanation:
Lignin and chitin-rich detritus decompose slowly (a, d). Microbial activity enhances decomposition (b). Statement c is incorrect because decomposition releases nutrients. Correct answer is (1).

Topic: Population Interactions
Subtopic: Predation

Keyword Definitions:

• Predation: Interaction in which one organism (predator) feeds on another (prey), impacting prey population and ecosystem balance.

• Extinction: Complete disappearance of a species from an ecosystem or Earth.

• Species Diversity: Variety and abundance of species in a community.

• Ecological Balance: Stable state of ecosystems where species coexist sustainably.

• Community: Group of interacting populations of different species in a habitat.

• Population: Group of individuals of the same species in a given area.

• Interaction: Relationship between organisms affecting survival, growth, or reproduction.

• Predator: Organism that hunts and consumes other organisms for food.

• Prey: Organism consumed by a predator.

• Ecosystem: Community of organisms interacting with their physical environment.

Lead Question (2022)
Which one of the following statements cannot be connected to Predation?
(1) It might lead to extinction of a species
(2) Both the interacting species are negatively impacted
(3) It is necessitated by nature to maintain the ecological balance
(4) It helps in maintaining species diversity in a community

Explanation:
Predation benefits the predator and controls prey populations, maintaining species diversity and ecological balance. Only the prey suffers, while the predator benefits, so both species are not negatively impacted. Therefore, statement (2) is incorrect. Correct answer is (2).

1. Single Correct Answer MCQ:
Which interaction involves one species benefiting while the other is harmed?
(1) Predation
(2) Competition
(3) Mutualism
(4) Commensalism

Explanation:
In predation, the predator benefits by feeding on prey, while the prey is harmed. Competition negatively affects both species, mutualism benefits both, and commensalism benefits one without affecting the other. Correct answer is (1).

2. Single Correct Answer MCQ:
Predation contributes to:
(1) Overpopulation
(2) Maintaining species diversity
(3) Elimination of predators only
(4) Decreasing resource availability

Explanation:
Predation regulates prey populations, preventing overpopulation and maintaining species diversity in ecosystems. It does not eliminate only predators nor necessarily decrease resources. Correct answer is (2).

3. Single Correct Answer MCQ:
Predators directly affect:
(1) Only producers
(2) Prey populations
(3) Abiotic factors
(4) Soil fertility

Explanation:
Predators feed on prey species, directly controlling their population size. Abiotic factors, producers, or soil fertility are indirectly affected, but the primary effect is on prey populations. Correct answer is (2).

4. Single Correct Answer MCQ:
Which term describes species completely disappearing due to predation?
(1) Extinction
(2) Invasion
(3) Coexistence
(4) Adaptation

Explanation:
Extinction occurs when a species disappears entirely from an ecosystem, which can result from excessive predation. Invasion is introduction of alien species, coexistence refers to species living together, and adaptation is evolutionary change. Correct answer is (1).

5. Single Correct Answer MCQ:
A predator-prey interaction that stabilizes population numbers is an example of:
(1) Mutualism
(2) Ecological balance
(3) Parasitism
(4) Commensalism

Explanation:
Predation helps regulate populations and prevents prey overgrowth, maintaining ecological balance. Mutualism benefits both, parasitism harms one, and commensalism benefits one without affecting the other. Correct answer is (2).

6. Single Correct Answer MCQ:
Which is a direct effect of predation?
(1) Increased biodiversity
(2) Reduced prey numbers
(3) Enhanced mutualism
(4) Soil enrichment

Explanation:
Predation directly reduces prey populations by consumption. Biodiversity may increase indirectly, mutualism is unrelated, and soil enrichment is an indirect ecosystem effect. Correct answer is (2).

7. Assertion-Reason MCQ:
Assertion (A): Predation maintains ecological balance
Reason (R): Predators reduce prey numbers and prevent overpopulation
Options:
(1) Both A and R correct, R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both A and R incorrect

Explanation:
Predators control prey populations, preventing overpopulation, which stabilizes ecosystems and maintains ecological balance. Both the assertion and reason are correct, and the reason explains the assertion. Correct answer is (1).

8. Matching Type MCQ:
Match species interaction with its effect:
A. Predation — 1. Both harmed
B. Competition — 2. One benefits, other harmed
C. Mutualism — 3. Both benefit
D. Commensalism — 4. One benefits, other unaffected
Options:
(1) A–2, B–1, C–3, D–4
(2) A–1, B–2, C–3, D–4
(3) A–2, B–3, C–1, D–4
(4) A–2, B–1, C–4, D–3

Explanation:
Predation: predator benefits, prey harmed (A–2); competition: both harmed (B–1); mutualism: both benefit (C–3); commensalism: one benefits, other unaffected (D–4). Correct answer is (1).

9. Fill in the Blanks MCQ:
Interaction where one species benefits and the other is harmed is called ________.
(1) Mutualism
(2) Commensalism
(3) Predation
(4) Competition

Explanation:
Predation involves one organism (predator) benefiting by consuming another (prey), which is harmed. Mutualism benefits both, commensalism benefits one without affecting the other, and competition negatively affects both. Correct answer is (3).

10. Choose the correct statements MCQ:
(a) Predation controls prey population
(b) Predation benefits the predator
(c) Predation negatively affects both predator and prey equally
(d) Predation helps maintain species diversity
Options:
(1) a, b, d only
(2) a, c only
(3) b, c only
(4) a, b, c, d

Explanation:
Predation reduces prey population (a), benefits the predator (b), and helps maintain species diversity (d). It does not negatively affect both species equally; only prey is harmed. Correct answer is (1).

Topic: Pollution Control
Subtopic: Air Pollution and Control Devices

Keyword Definitions:

• Particulate Matter: Tiny solid or liquid particles suspended in the air, often from combustion, causing air pollution.

• Thermal Power Plant: Facility generating electricity by converting heat energy from fuel combustion.

• Incinerator: Device that burns waste materials at high temperatures to reduce volume and destroy pollutants.

• Electrostatic Precipitator: Air pollution control device that removes particulate matter from exhaust gases using electric charges.

• Catalytic Converter: Device in vehicles that reduces harmful gases like CO, NOx, and hydrocarbons by chemical reactions.

• STP (Sewage Treatment Plant): Facility to treat wastewater to reduce biological and chemical pollutants before discharge.

• Exhaust Gases: Emissions released from combustion processes in power plants or vehicles.

• Air Pollution: Contamination of air by harmful substances including gases, particulates, and biological molecules.

• Flue Gas: The gas that exits to the atmosphere via a stack from combustion processes.

• Control Device: Equipment used to remove or reduce pollutants from industrial emissions.

Lead Question (2022)
The device which can remove particulate matter present in the exhaust from a thermal power plant is:
(1) Incinerator
(2) Electrostatic Precipitator
(3) Catalytic Convertor
(4) STP

Explanation:
Particulate matter in exhaust gases from thermal power plants is effectively removed by electrostatic precipitators, which charge particles and collect them on electrodes. Incinerators burn waste, catalytic converters reduce vehicle emissions, and STPs treat sewage. Therefore, the correct answer is (2).

1. Single Correct Answer MCQ:
Which device reduces carbon monoxide, nitrogen oxides, and hydrocarbons from vehicle exhaust?
(1) Electrostatic Precipitator
(2) Catalytic Converter
(3) Incinerator
(4) STP

Explanation:
Catalytic converters in vehicles reduce harmful gases like CO, NOx, and hydrocarbons through oxidation and reduction reactions. Electrostatic precipitators remove particulates, incinerators burn waste, and STPs treat wastewater. Correct answer is (2).

2. Single Correct Answer MCQ:
Which air pollutant control device uses electric charges to remove dust?
(1) Chimney
(2) Electrostatic Precipitator
(3) Cyclone Separator
(4) Bag Filter

Explanation:
Electrostatic precipitators remove dust by imparting an electric charge to particles and collecting them on charged plates. Chimneys release flue gas, cyclones use centrifugal force, and bag filters mechanically filter dust. Correct answer is (2).

3. Single Correct Answer MCQ:
Particulate matter from coal combustion is mainly removed by:
(1) Electrostatic Precipitator
(2) Wet Scrubber
(3) Catalytic Converter
(4) Incinerator

Explanation:
Coal combustion produces particulate matter like fly ash, which is removed by electrostatic precipitators using charged electrodes. Wet scrubbers remove soluble gases, catalytic converters treat vehicle exhaust, and incinerators burn solid waste. Correct answer is (1).

4. Single Correct Answer MCQ:
Which device is primarily used for sewage treatment?
(1) STP
(2) Electrostatic Precipitator
(3) Catalytic Converter
(4) Incinerator

Explanation:
Sewage Treatment Plants (STPs) treat wastewater to remove biological and chemical pollutants. Electrostatic precipitators and catalytic converters are for air pollution, while incinerators burn solid waste. Correct answer is (1).

5. Single Correct Answer MCQ:
Which device reduces fly ash emissions from power plants?
(1) Electrostatic Precipitator
(2) Catalytic Converter
(3) Chimney
(4) Wetland

Explanation:
Electrostatic precipitators remove fine fly ash particles from power plant exhaust, preventing air pollution. Catalytic converters are for vehicles, chimneys only release gases, and wetlands do not treat industrial emissions. Correct answer is (1).

6. Single Correct Answer MCQ:
Which method uses high temperature to destroy hazardous waste?
(1) Electrostatic Precipitator
(2) Incinerator
(3) Catalytic Converter
(4) Wet Scrubber

Explanation:
Incinerators burn hazardous waste at high temperatures, reducing volume and destroying pollutants. Electrostatic precipitators remove dust, catalytic converters treat gases, and wet scrubbers remove soluble pollutants. Correct answer is (2).

7. Assertion-Reason MCQ:
Assertion (A): Electrostatic precipitator is used in thermal power plants
Reason (R): It removes particulate matter from exhaust gases
Options:
(1) Both A and R correct and R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both incorrect

Explanation:
Electrostatic precipitators are used in thermal power plants to remove particulate matter like fly ash from exhaust gases. Both assertion and reason are correct, and the reason explains the assertion. Correct answer is (1).

8. Matching Type MCQ:
Match the device with its function:
A. Electrostatic Precipitator — 1. Treats wastewater
B. Catalytic Converter — 2. Reduces vehicle emissions
C. STP — 3. Removes dust from exhaust
D. Incinerator — 4. Burns solid waste
Options:
(1) A–3, B–2, C–1, D–4
(2) A–2, B–1, C–4, D–3
(3) A–4, B–3, C–2, D–1
(4) A–1, B–3, C–2, D–4

Explanation:
Electrostatic precipitator removes dust (A–3), catalytic converter reduces vehicle emissions (B–2), STP treats wastewater (C–1), and incinerator burns solid waste (D–4). Correct answer is (1).

9. Fill in the Blanks:
The device used to remove fine particulate matter from industrial exhaust gases is ________.
(1) Incinerator
(2) Electrostatic Precipitator
(3) Catalytic Converter
(4) STP

Explanation:
Electrostatic precipitators remove fine particulate matter from industrial exhaust gases by charging particles and collecting them on plates. Incinerators burn waste, catalytic converters treat vehicle gases, and STPs treat wastewater. Correct answer is (2).

10. Choose the correct statements MCQ:
(a) Catalytic converters reduce harmful gases from vehicles
(b) Electrostatic precipitators remove particulate matter from exhaust
(c) STPs remove air pollutants
(d) Incinerators burn solid waste
Options:
(1) a, b, d only
(2) a, c only

Subtopic: Ecological and Physiological Adaptations

Keyword Definitions:

• Allen's Rule: Principle stating animals in cold regions have shorter appendages, while those in warm regions have longer ones to regulate heat.

• Physiological adaptation: Internal functional adjustment of organisms to survive environmental stress.

• Behavioural adaptation: Actions or habits adopted by animals to survive, such as migration or burrowing.

• Biochemical adaptation: Molecular and chemical changes in organisms allowing survival under extreme conditions.

• Kangaroo rat: Desert rodent adapted to arid environments.

• Desert lizard: Reptile with behaviours to cope with high temperature and low water availability.

• Marine fish at depth: Organisms adapted to high pressure, low light, and low temperature underwater.

• Polar seal: Mammals adapted to cold regions with insulating fat and short extremities.

• Adaptation: Any anatomical, physiological, or behavioural trait that increases survival in a specific environment.

• Environmental stress: External factors like temperature, water, or salinity affecting organism survival.

• Survival strategy: Traits or behaviours enhancing reproductive success under environmental pressures.

Lead Question - 2021

Match List - I with List - II
List - I List - II
(a) Allen's Rule (i) Kangaroo rat
(b) Physiological adaptation (ii) Desert lizard
(c) Behavioural adaptation (iii) Marine fish at depth
(d) Biochemical adaptation (iv) Polar seal
Choose the correct answer from the options given below.
(1) (a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
(2) (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
(3) (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
(4) (a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)

Explanation: Allen's rule corresponds to polar seal (a-iv), physiological adaptation is observed in desert lizard (b-ii), behavioural adaptation is seen in kangaroo rat (c-i), and biochemical adaptation occurs in marine fish at depth (d-iii). Therefore, the correct match is option (4).

1. Single Correct Answer:
Which animal shows behavioural adaptation in desert regions?
(1) Polar seal
(2) Kangaroo rat
(3) Marine fish
(4) Desert lizard
Explanation: Kangaroo rats exhibit behavioural adaptation such as nocturnal activity and burrowing to survive high desert temperatures. Polar seal, marine fish, and desert lizard show other forms of adaptation. Correct answer is option (2).

2. Single Correct Answer:
Allen's rule applies to:
(1) Kangaroo rat
(2) Desert lizard
(3) Polar seal
(4) Marine fish
Explanation: Allen's rule describes shorter appendages in cold environments for heat conservation. Polar seals have short extremities to reduce heat loss, making them examples of Allen's rule. Correct answer is option (3).

3. Single Correct Answer:
Physiological adaptation example is:
(1) Desert lizard
(2) Kangaroo rat
(3) Polar seal
(4) Marine fish
Explanation: Desert lizards adjust internal body functions, like conserving water and regulating body temperature, to survive arid conditions. This is a physiological adaptation. Correct answer is option (1).

4. Single Correct Answer:
Which organism shows biochemical adaptation?
(1) Marine fish at depth
(2) Kangaroo rat
(3) Polar seal
(4) Desert lizard
Explanation: Marine fish at depth adapt biochemically to high pressure and low oxygen by producing specialized enzymes and proteins. Kangaroo rat, polar seal, and desert lizard show other adaptations. Correct answer is option (1).

5. Single Correct Answer:
Behavioural adaptation includes:
(1) Enzyme production
(2) Burrowing and nocturnal activity
(3) Short extremities
(4) Antifreeze proteins
Explanation: Behavioural adaptation involves actions such as burrowing and nocturnal activity in desert animals to avoid heat stress. Other options are physiological or biochemical adaptations. Correct answer is option (2).

6. Single Correct Answer:
Which adaptation helps polar seals conserve heat?
(1) Burrowing
(2) Short appendages
(3) Nocturnal activity
(4) Enzyme modification
Explanation: Polar seals follow Allen's rule with short extremities to reduce heat loss in polar climates. Other options are unrelated. Correct answer is option (2).

7. Assertion-Reason:
Assertion (A): Marine fish at depth have specialized proteins.
Reason (R): To survive high pressure and low oxygen.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: Marine fish produce biochemical adaptations like pressure-resistant proteins to survive deep-sea conditions. This demonstrates both the assertion and reason, with reason explaining assertion. Correct answer is option (1).

8. Matching Type:
Match adaptation type with description:
(a) Allen's rule - 1. Short appendages in cold regions
(b) Behavioural adaptation - 2. Nocturnal activity in desert
(c) Physiological adaptation - 3. Water conservation in lizard
(d) Biochemical adaptation - 4. Specialized enzymes in deep fish
(1) a-1, b-2, c-3, d-4
(2) a-1, b-3, c-2, d-4
(3) a-2, b-1, c-3, d-4
(4) a-1, b-2, c-4, d-3
Explanation: Allen's rule applies to short appendages (a-1), behavioural adaptations include nocturnal activity (b-2), physiological adjustments occur in lizard (c-3), and biochemical changes are in deep-sea fish (d-4). Correct answer is option (1).

9. Fill in the Blank:
_____ is an example of physiological adaptation in desert animals.
(1) Desert lizard
(2) Polar seal
(3) Kangaroo rat
(4) Marine fish
Explanation: Desert lizards conserve water and regulate internal temperature, which is a physiological adaptation. Polar seals, kangaroo rats, and marine fish show other forms of adaptation. Correct answer is option (1).

10. Choose the correct statements:
(a) Kangaroo rat shows behavioural adaptation
(b) Polar seal demonstrates Allen's rule
(c) Desert lizard is physiologically adapted
(d) Marine fish shows behavioural adaptation
(1) a, b, c
(2) a, b, d
(3) b, c, d
(4) a, c, d
Explanation: Kangaroo rat is behavioural (a), polar seal follows Allen's rule (b), desert lizard is physiological (c). Marine fish shows biochemical, not behavioural adaptation (d). Correct answer is option (1).

Topic: Ozone Depletion

Subtopic: Measurement of Ozone

Keyword Definitions:

• Ozone A molecule of three oxygen atoms (O3) forming a protective layer in the stratosphere against harmful UV radiation.

• Dobson Unit (DU) A unit of measurement describing the total amount of ozone in a column of air overhead.

• Stratosphere The atmospheric layer above the troposphere where the ozone layer is concentrated.

• Troposphere The lowest layer of the atmosphere where weather changes occur.

• CFCs Chlorofluorocarbons are synthetic compounds responsible for ozone depletion.

Lead Question - 2021

Dobson units are used to measure thickness of:
(1) Stratosphere
(2) Ozone
(3) Troposphere
(4) CFCs

Explanation: The Dobson Unit (DU) is the standard unit for measuring ozone thickness in the stratosphere. One DU corresponds to a 0.01 mm layer of pure ozone at standard temperature and pressure. Average global ozone measures about 300 DU. Hence, the correct answer is ozone.

1. Which gas is mainly responsible for ozone depletion?
(1) CO2
(2) CH4
(3) CFCs
(4) N2

Explanation: CFCs release chlorine atoms in the stratosphere, which catalytically destroy ozone molecules. One chlorine atom can destroy thousands of ozone molecules. Other gases like CO2 and CH4 contribute to greenhouse effect but not directly to ozone depletion. Thus, the correct answer is CFCs.

2. The ozone hole is most prominently observed over:
(1) Arctic
(2) Antarctic
(3) Equator
(4) Himalayas

Explanation: The Antarctic region shows the largest ozone hole, particularly during spring due to unique climatic conditions that allow accumulation of chlorine and bromine radicals. Arctic depletion occurs but is less severe. Therefore, the correct answer is Antarctic.

3. Which radiation increases due to ozone depletion?
(1) Infrared
(2) UV-B
(3) Gamma rays
(4) Visible light

Explanation: Ozone absorbs most harmful UV-B radiation. Depletion allows UV-B to reach Earth, causing skin cancer, cataracts, and reduced crop yield. Infrared and visible light are not absorbed by ozone. Thus, the correct answer is UV-B.

4. Assertion (A): Montreal Protocol was signed to protect ozone layer.
Reason (R): It targeted reduction in greenhouse gases.
(1) Both A and R are true, and R explains A
(2) Both A and R are true, but R does not explain A
(3) A is true, R is false
(4) A is false, R is true

Explanation: The Montreal Protocol (1987) was signed to phase out CFCs and ozone-depleting substances. It was not focused on greenhouse gases but on protecting the ozone layer. Thus, Assertion is true, Reason is false. Correct option is (3).

5. Match the following:
A. CFCs - i. Ozone depletion
B. CO2 - ii. Global warming
C. SO2 - iii. Acid rain
Options:
(1) A-i, B-ii, C-iii
(2) A-iii, B-i, C-ii
(3) A-ii, B-iii, C-i
(4) A-i, B-iii, C-ii

Explanation: CFCs are linked to ozone depletion, CO2 causes global warming, and SO2 contributes to acid rain. Therefore, the correct matching is A-i, B-ii, C-iii, making option (1) correct.

6. The average thickness of ozone layer over equator is approximately:
(1) 100 DU
(2) 300 DU
(3) 500 DU
(4) 50 DU

Explanation: The ozone column thickness averages around 300 Dobson Units worldwide. At equatorial regions, it is typically near this global average. Hence, the correct answer is 300 DU.

7. Fill in the blank:
The protective ozone layer is found in the ______.
(1) Troposphere
(2) Stratosphere
(3) Mesosphere
(4) Exosphere

Explanation: The ozone layer is concentrated in the stratosphere, about 15–35 km above Earth. It plays a vital role in absorbing UV-B and UV-C radiation. Therefore, the correct answer is stratosphere.

8. Choose the correct statements about ozone:
(1) It protects from harmful UV rays
(2) It is present in stratosphere
(3) Its depletion leads to skin cancer
(4) All of these

Explanation: Ozone acts as a protective shield in stratosphere by absorbing harmful ultraviolet rays. Its depletion results in diseases like skin cancer and ecological imbalance. Therefore, the correct option is all of these.

9. Which of the following substances is a substitute for CFCs?
(1) HCFCs
(2) Halons
(3) Hydrocarbons
(4) DDT

Explanation: Hydrochlorofluorocarbons (HCFCs) and hydrocarbons are safer alternatives to CFCs with less ozone-depleting potential. Halons are harmful fire extinguishing agents. DDT is an insecticide unrelated to ozone. Thus, HCFCs serve as substitutes, making option (1) correct.

10. Which environmental treaty is directly related to ozone layer protection?
(1) Kyoto Protocol
(2) Montreal Protocol
(3) Paris Agreement
(4) Stockholm Convention

Explanation: The Montreal Protocol (1987) is specifically designed to phase out ozone-depleting substances like CFCs. Kyoto and Paris agreements deal with climate change. Stockholm focuses on persistent pollutants. Thus, the correct answer is Montreal Protocol.

Topic: Population Ecology

Subtopic: Population Growth

• Exponential Growth: Rapid population increase under ideal conditions without limiting factors.

• Nt: Population size at time t.

• N0: Initial population size at t = 0.

• r: Intrinsic rate of natural increase of the population.

• e: Mathematical constant used in natural logarithms (~2.718).

• Natural Logarithms: Logarithms with base e.

• Geometric Growth: Population increase at discrete intervals.

• Carrying Capacity: Maximum population size the environment can support.

• Density-Dependent Factors: Factors limiting population growth based on density.

• Density-Independent Factors: Factors limiting population growth irrespective of density.

• Population Dynamics: Study of changes in population size and composition over time.

Lead Question - 2021

In the exponential growth equation Nt = N0 e^rt, e represents:

Options:
A. The base of exponential logarithms
B. The base of natural logarithms
C. The base of geometric logarithms
D. The base of number logarithms

Explanation: In the exponential growth equation, e is the mathematical constant approximately equal to 2.718. It serves as the base of natural logarithms and allows continuous modeling of population growth under ideal conditions. Answer: The base of natural logarithms.

1. Which parameter represents intrinsic rate of increase in Nt = N0 e^rt?
Options:
A. Nt
B. N0
C. r
D. e

Explanation: r represents the intrinsic rate of natural increase, determining how fast the population grows per individual under ideal conditions. Nt is population at time t, N0 is initial population, and e is base of natural logarithms. Answer: r.

2. Nt in the equation Nt = N0 e^rt indicates:
Options:
A. Initial population
B. Population at time t
C. Growth rate
D. Base of logarithm

Explanation: Nt is the population size at any given time t during exponential growth. It increases continuously from N0 based on the intrinsic rate r. Answer: Population at time t.

3. Exponential growth assumes:
Options:
A. Unlimited resources
B. Constant carrying capacity
C. Density-dependent regulation
D. Seasonal fluctuations

Explanation: Exponential growth models assume unlimited resources with no environmental resistance. Population grows continuously without limitations. Answer: Unlimited resources.

4. In geometric growth, population changes occur:
Options:
A. Continuously
B. At discrete intervals
C. Independently of resources
D. Randomly

Explanation: Geometric growth refers to population increase at discrete time intervals, unlike exponential growth which is continuous. It is often modeled with factors affecting discrete generations. Answer: At discrete intervals.

5. Which factor limits exponential growth in nature?
Options:
A. Density-independent factors
B. Unlimited resources
C. No predators
D. No carrying capacity

Explanation: In reality, density-independent factors like weather, fire, or pollution can limit population growth, preventing indefinite exponential increase. Ideal models ignore such factors. Answer: Density-independent factors.

6. Which of the following is true for continuous growth?
Options:
A. Modeled by Nt = N0 e^rt
B. Population grows in steps
C. Ignores intrinsic rate
D. Cannot use e

Explanation: Continuous growth is modeled using the exponential growth equation Nt = N0 e^rt. It accounts for continuous change in population over time using e as the base of natural logarithms. Answer: Modeled by Nt = N0 e^rt.

7. Assertion-Reason:
Assertion (A): e in population growth equation allows continuous modeling.
Reason (R): e is base of natural logarithms useful for growth calculations.
Options:
A. Both A and R are true, R is correct explanation
B. Both A and R are true, R is not correct explanation
C. A is true, R is false
D. A is false, R is true

Explanation: Using e allows modeling continuous population changes. As the base of natural logarithms, it ensures accurate exponential growth calculations. Both assertion and reason are correct, and reason explains assertion. Answer: Both A and R are true, R is correct explanation.

8. Match the following:
Column I: 1. N0 2. Nt 3. r 4. e
Column II: A. Population at time t B. Initial population C. Base of natural log D. Intrinsic growth rate
Options:
A. 1-B, 2-A, 3-D, 4-C
B. 1-A, 2-B, 3-C, 4-D
C. 1-D, 2-C, 3-A, 4-B
D. 1-C, 2-D, 3-B, 4-A

Explanation: Correct matching: N0 – initial population (B), Nt – population at time t (A), r – intrinsic growth rate (D), e – base of natural logarithms (C). Answer: 1-B, 2-A, 3-D, 4-C.

9. Fill in the blank: The mathematical constant e is approximately equal to _______.
Options:
A. 2.718
B. 3.141
C. 1.618
D. 2.302

Explanation: The constant e is approximately 2.718 and is fundamental in continuous growth calculations, including population ecology and finance models. Answer: 2.718.

10. Choose the correct statements:
1. e is the base of natural logarithms.
2. Nt = N0 e^rt models continuous growth.
3. r is the intrinsic rate of increase.
Options:
A. 1 and 2 only
B

Topic: Ecosystem Energetics
Subtopic: Primary Productivity

Keyword Definitions:

• QPP (Gross Primary Productivity): Total amount of energy captured by producers through photosynthesis per unit area per unit time.

• NPP (Net Primary Productivity): Energy remaining after accounting for respiration losses, available for growth and consumption by herbivores.

• R (Respiration losses): Energy used by plants for metabolic activities including maintenance, growth, and reproduction.

• Primary productivity: Rate of energy fixation by producers in an ecosystem.

• Ecosystem energy flow: Transfer of energy from producers to consumers and decomposers in a food chain.

• Gross vs Net productivity: Gross productivity is total energy fixed; net productivity is energy remaining after respiration.

• Herbivores: Organisms consuming plant biomass and energy.

• Energy budget: Calculation of energy captured, lost, and transferred within an ecosystem.

Lead Question - 2021

In the equation QPP – R = NPP, R represents:
(1) Retardation factor
(2) Environment factor
(3) Respiration losses
(4) Radiant energy

Explanation: Correct answer is (3) Respiration losses. In ecosystems, plants utilize part of the energy fixed during photosynthesis for respiration (R). The net primary productivity (NPP) is the remaining energy available for growth and consumption by herbivores, reflecting the actual energy contribution to the ecosystem.

Guessed Questions:

1) Single Correct Answer: Net primary productivity (NPP) is calculated as:
(1) QPP + R
(2) QPP – R
(3) R – QPP
(4) QPP × R

Explanation: Correct answer is (2) QPP – R. Net primary productivity (NPP) is the energy remaining after plants consume a portion for respiration (R), representing the energy available for growth and herbivore consumption.

2) Single Correct Answer: Gross primary productivity minus respiration gives:
(1) Secondary productivity
(2) Net primary productivity
(3) Trophic efficiency
(4) Energy loss

Explanation: Correct answer is (2) Net primary productivity. NPP measures the energy fixed by producers minus the energy they expend for respiration, reflecting energy available for higher trophic levels.

3) Single Correct Answer: The portion of energy used by plants for metabolism is called:
(1) NPP
(2) QPP
(3) Respiration losses
(4) Solar energy

Explanation: Correct answer is (3) Respiration losses. Plants use a part of fixed energy for metabolic functions including growth, repair, and maintenance, reducing the energy available for other organisms in the ecosystem.

4) Single Correct Answer: NPP represents energy:
(1) Used by plants only
(2) Lost as heat
(3) Available for consumers
(4) Absorbed from atmosphere

Explanation: Correct answer is (3) Available for consumers. NPP is the portion of energy fixed by plants that remains after respiration, forming the basis for herbivore consumption and energy transfer along the food chain.

5) Single Correct Answer: Gross primary productivity minus which factor gives net productivity?
(1) Solar radiation
(2) Respiration losses
(3) Water availability
(4) Nutrient limitation

Explanation: Correct answer is (2) Respiration losses. NPP is determined by subtracting plant respiration (R) from total energy fixed during photosynthesis (QPP), reflecting actual energy for growth and ecological functions.

6) Assertion-Reason:
A: NPP is always less than QPP.
R: Plants use part of QPP for respiration.
Options:
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Since plants expend energy for respiration, NPP (QPP – R) is always less than QPP, demonstrating that the difference represents energy available for growth and consumers.

7) Matching Type: Match the terms with definitions:
List–I List–II
(a) QPP    (i) Energy remaining after respiration
(b) NPP    (ii) Total energy fixed by producers
(c) R    (iii) Energy used for metabolic activities
(d) Secondary productivity    (iv) Energy stored by herbivores

Explanation: Correct answer: (a) ii, (b) i, (c) iii, (d) iv. QPP is total energy fixed, R is respiration, NPP is energy after R, and secondary productivity is energy accumulated in consumers.

8) Single Correct Answer: The main factor reducing gross primary productivity is:
(1) Solar radiation
(2) Respiration losses
(3) Decomposition
(4) Evapotranspiration

Explanation: Correct answer is (2) Respiration losses. Respiration consumes a portion of energy fixed during photosynthesis, leaving NPP as the net energy available for growth and consumption.

9) Fill in the blank: Net primary productivity is equal to ______ minus respiration losses.
(1) NPP
(2) QPP
(3) R
(4) Secondary productivity

Explanation: Correct answer is (2) QPP. Net primary productivity (NPP) = Gross primary productivity (QPP) minus respiration losses (R), representing the energy available for plant growth and herbivores.

10) Choose the correct statements:
(a) NPP = QPP – R
(b) Respiration reduces available energy
(c) Secondary productivity is part of NPP
(d) QPP is always less than NPP
Options:
(1) a, b, c
(2) a, c, d
(3) b, d
(4) All of the above

Explanation: Correct answer is (1). Statements a, b, and c are correct. QPP is total energy, R reduces energy leading to NPP, and secondary productivity comes from NPP. Statement d is false because QPP is always greater than NPP.

Topic: Species Interactions
Subtopic: Types of Symbiotic Relationships

Keyword Definitions:

• Amensalism: An interaction where one species is harmed while the other is unaffected.

• Symbiosis: A close and long-term biological interaction between two species.

• Mutualism: Both species benefit (+/+).

• Commensalism: One species benefits while the other is unaffected (+/0).

• Competition: Interaction where both species are negatively affected (–/–).

• Parasitism: One species benefits while the other is harmed (+/–).

• Species A/B: Labels representing two interacting species.

• Ecological Interaction: The relationship between organisms within an ecosystem affecting survival or reproduction.

Lead Question - 2021

Amensalism can be represented as:
(1) Species A (+); Species B (+)
(2) Species A (–); Species B (–)
(3) Species A (+); Species B (0)
(4) Species A (–); Species B (0)

Explanation: Correct answer is (4) Species A (–); Species B (0). In amensalism, one species (A) is negatively affected while the other (B) is unaffected. An example is Penicillium secreting antibiotic substances that inhibit bacterial growth; the bacteria are harmed while the fungus remains unaffected.

Guessed Questions:

1) Single Correct Answer: Commensalism is represented as:
(1) (+/–)
(2) (–/0)
(3) (+/0)
(4) (–/–)

Explanation: Correct answer is (3) (+/0). One species benefits while the other is unaffected, such as epiphytic plants growing on trees without harming them.

2) Single Correct Answer: Parasitism interaction can be represented as:
(1) (+/–)
(2) (–/–)
(3) (+/0)
(4) (–/0)

Explanation: Correct answer is (1) (+/–). The parasite benefits while the host is harmed, such as tapeworms in the intestines of animals.

3) Single Correct Answer: Competition between species is represented as:
(1) (+/0)
(2) (–/–)
(3) (+/–)
(4) (0/0)

Explanation: Correct answer is (2) (–/–). Both species are negatively affected due to shared resource limitation, e.g., two plant species competing for sunlight in a dense forest.

4) Single Correct Answer: Mutualism is represented as:
(1) (+/–)
(2) (0/–)
(3) (+/0)
(4) (+/+)

Explanation: Correct answer is (4) (+/+). Both species benefit from the interaction, such as bees pollinating flowers while obtaining nectar.

5) Single Correct Answer: Which interaction involves no effect on either species?
(1) Neutralism
(2) Amensalism
(3) Parasitism
(4) Competition

Explanation: Correct answer is (1) Neutralism. Both species are unaffected by each other, e.g., different plant species living in distant areas of a habitat without interaction.

6) Assertion-Reason:
A: Amensalism occurs when one species is harmed and the other is unaffected.
R: Penicillium secretes penicillin that inhibits bacterial growth.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). The harm to bacteria demonstrates amensalism; Penicillium is unaffected, perfectly illustrating the definition of amensalism.

7) Matching Type: Match the interaction with its symbol:
List-I List-II
(a) Mutualism    (i) (+/–)
(b) Commensalism    (ii) (+/0)
(c) Amensalism    (iii) (–/0)
(d) Parasitism    (iv) (+/+)

Explanation: Correct answer: (a) iv, (b) ii, (c) iii, (d) i. Each interaction has a standard symbolic representation used in ecology for quick identification.

8) Single Correct Answer: Example of amensalism is:
(1) Lichen on tree
(2) Cattle egrets following cattle
(3) Penicillium inhibiting bacteria
(4) Bees pollinating flowers

Explanation: Correct answer is (3). Penicillium secretes antibiotics that harm bacteria, showing amensalism: one harmed, the other unaffected.

9) Fill in the blank: Amensalism is represented as Species A (–) and Species B (___).
(1) (+)
(2) (0)
(3) (–)
(4) (+/+)

Explanation: Correct answer is (2) (0). Species B remains unaffected while Species A is negatively affected in amensalism, such as trees shading smaller plants.

10) Choose the correct statements:
(a) Amensalism harms one species and leaves the other unaffected.
(b) Penicillium secreting penicillin is an example of amensalism.
(c) Both species benefit in amensalism.
(d) Amensalism is represented as (–/0).
Options:
(1) a, b, d
(2) a, c, d
(3) b, c
(4) a, c

Explanation: Correct answer is (1). Statements a, b, and d accurately describe amensalism; statement c is incorrect as both species do not benefit.

Topic: Ecosystems
Subtopic: Ecological Pyramids

Keyword Definitions:

• Pyramid of Biomass: Represents the total mass of living organisms at each trophic level.

• Pyramid of Energy: Represents the flow of energy through each trophic level; always upright.

• Pyramid of Numbers: Shows the number of organisms at each trophic level; can be upright or inverted.

• Grassland Ecosystem: Ecosystem dominated by grasses and herbivores, typically showing upright pyramids of numbers and biomass.

• Marine Ecosystem: Ecosystem in aquatic environments; pyramid of biomass is often inverted due to small phytoplankton biomass and large consumer biomass.

• Trophic Level: Position of an organism in a food chain or food web.

• Producer: Organism that synthesizes organic compounds from inorganic substances using sunlight or chemical energy.

• Consumer: Organism that depends on producers or other consumers for energy.

Lead Question - 2021

Which of the following statements is not correct?
(1) Pyramid of biomass in sea is generally upright.
(2) Pyramid of energy is always upright.
(3) Pyramid of numbers in a grassland ecosystem is upright.
(4) Pyramid of biomass in sea is generally inverted

Explanation: Correct answer is (1). In marine ecosystems, the pyramid of biomass is generally inverted because small phytoplankton have low biomass yet support larger consumer populations. Pyramids of energy are always upright, and pyramids of numbers and biomass in grasslands are typically upright.

Guessed Questions:

1) Single Correct Answer: In which ecosystem is the pyramid of biomass generally inverted?
(1) Grassland
(2) Desert
(3) Sea
(4) Forest

Explanation: Correct answer is (3) Sea. In aquatic ecosystems, phytoplankton have low biomass yet support large herbivorous populations, causing the pyramid of biomass to be inverted.

2) Single Correct Answer: Pyramid of energy is:
(1) Sometimes upright
(2) Always upright
(3) Inverted in grassland
(4) Inverted in sea

Explanation: Correct answer is (2) Always upright. Energy decreases at each trophic level due to heat loss and metabolism, so the pyramid of energy is consistently upright across ecosystems.

3) Single Correct Answer: Pyramid of numbers in grassland is:
(1) Upright
(2) Inverted
(3) Always flat
(4) Cannot be determined

Explanation: Correct answer is (1) Upright. Grasslands have many producers and fewer herbivores and carnivores, so the pyramid of numbers typically decreases from base to apex, making it upright.

4) Single Correct Answer: Which pyramid always represents energy flow correctly?
(1) Pyramid of numbers
(2) Pyramid of biomass
(3) Pyramid of energy
(4) Pyramid of nutrients

Explanation: Correct answer is (3) Pyramid of energy. It depicts the actual energy flow through trophic levels, always upright, and accounts for energy lost as heat or metabolism.

5) Assertion (A): Pyramid of biomass in sea is generally inverted.
Reason (R): Phytoplankton have low biomass but reproduce rapidly to support consumers.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Marine pyramids of biomass are inverted because small phytoplankton have low biomass yet reproduce quickly, supporting large consumer populations. The reason explains the observation.

6) Single Correct Answer: In which ecosystem is the pyramid of numbers inverted?
(1) Grassland
(2) Tree-based forest
(3) Parasitic organisms on trees
(4) Desert

Explanation: Correct answer is (3) Parasitic organisms on trees. A single tree can support many parasites, resulting in an inverted pyramid of numbers with more consumers than producers.

7) Matching Type: Match pyramid type with typical shape in sea:
List-I  List-II
(a) Pyramid of biomass    (i) Upright
(b) Pyramid of numbers    (ii) Inverted
(c) Pyramid of energy    (iii) Always upright

Explanation: Correct answer: (a) ii, (b) i, (c) iii. Biomass is inverted due to low phytoplankton mass, numbers can be upright depending on organism size, and energy pyramid is always upright.

8) Single Correct Answer: Pyramid that decreases at each trophic level is:
(1) Pyramid of numbers
(2) Pyramid of biomass
(3) Pyramid of energy
(4) Pyramid of nutrients

Explanation: Correct answer is (3) Pyramid of energy. Due to energy loss at each level, energy consistently decreases from producers to apex consumers, keeping the pyramid upright.

9) Fill in the blank: In marine ecosystems, the pyramid of ______ is generally inverted.
(1) Numbers
(2) Energy
(3) Biomass
(4) Nutrients

Explanation: Correct answer is (3) Biomass. Marine pyramids of biomass are inverted because tiny phytoplankton have less mass than the consumers they support.

10) Choose the correct statements:
(a) Pyramid of energy is always upright.
(b) Pyramid of biomass in sea is inverted.
(c) Pyramid of numbers in grassland is inverted.
(d) Pyramid of numbers can be upright or inverted depending on the ecosystem.
Options:
(1) a, b, d
(2) a, c, d
(3) b, c, d
(4) a, b, c

Explanation: Correct answer is (1). Statements a, b, and d are correct. Energy pyramids are always upright, sea biomass pyramids are inverted, and number pyramids vary depending on organism size and ecosystem type. Statement c is incorrect; grassland number pyramids are usually upright.

Topic: Interspecific Competition
Subtopic: Mechanisms of Survival

Keyword Definitions:

• Interspecific competition: Interaction between different species competing for the same limited resources.

• Competitive release: Process where a species expands its niche when competitors are absent.

• Mutualism: Interaction where both species benefit from each other.

• Predation: One species feeds on another species.

• Resource partitioning: Dividing resources to reduce competition and allow coexistence.

• Evolutionary adaptation: Changes in species traits enhancing survival under competitive pressures.

• Ecological niche: Role and position of a species in an ecosystem.

• Survival mechanism: Strategy developed by species to persist despite competition.

Lead Question - 2021

In spite of interspecific competition in nature, which mechanism the competing species might have evolved for their survival?
(1) Competitive release
(2) Mutualism
(3) Predation
(4) Resource partitioning

Explanation: The correct answer is (4) Resource partitioning. Competing species often evolve to utilize different portions of shared resources or occupy slightly different ecological niches. This reduces direct competition, allowing coexistence. Resource partitioning is a widely observed survival strategy in ecosystems, enabling species to persist and maintain biodiversity under interspecific competition.

Guessed Questions:

1) Single Correct Answer: Which phenomenon allows a species to expand its niche when competitors are absent?
(1) Competitive release
(2) Mutualism
(3) Predation
(4) Resource partitioning

Explanation: Correct answer is (1) Competitive release. When competing species are removed, a species may exploit resources previously unavailable due to competition. This mechanism helps species adjust their ecological niche and increases their survival and reproductive success.

2) Single Correct Answer: Mutualism is an interaction where:
(1) One species benefits and the other is harmed
(2) Both species benefit
(3) Both species compete
(4) One species preys on another

Explanation: Correct answer is (2) Both species benefit. Mutualism enhances survival or fitness of both interacting species. Examples include pollination and seed dispersal by animals. Unlike competition, it promotes coexistence and ecosystem stability.

3) Single Correct Answer: Which strategy reduces direct competition among coexisting species?
(1) Resource partitioning
(2) Predation
(3) Mutualism
(4) Competitive exclusion

Explanation: Correct answer is (1) Resource partitioning. Species divide available resources spatially or temporally, minimizing overlap in resource use. This strategy allows multiple species to coexist in the same habitat by reducing direct interspecific competition.

4) Assertion (A): Resource partitioning helps species coexist.
Reason (R): It reduces overlap in resource use among species.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Resource partitioning minimizes direct competition by dividing resources among species. This reduces conflicts and enables coexistence, explaining why it is an important evolutionary adaptation for survival under interspecific competition.

5) Single Correct Answer: Competitive exclusion principle states that:
(1) Two species cannot coexist if they occupy identical niches
(2) Species always cooperate
(3) Species cannot evolve
(4) Predation prevents competition

Explanation: Correct answer is (1). The competitive exclusion principle predicts that if two species occupy exactly the same niche, one will outcompete the other, leading to local extinction. This drives evolutionary adaptations like resource partitioning to allow coexistence.

6) Single Correct Answer: Which of the following is not a survival mechanism under interspecific competition?
(1) Mutualism
(2) Resource partitioning
(3) Competitive release
(4) Allelopathy in unrelated species

Explanation: Correct answer is (4). Allelopathy affects unrelated species but is not specifically a mechanism evolved to cope with direct competition between coexisting species. Resource partitioning, competitive release, and mutualism directly influence survival under interspecific competition.

7) Matching Type: Match ecological strategies with definitions:
List-I  List-II
(a) Resource partitioning    (i) Division of resources to reduce competition
(b) Competitive release    (ii) Expansion of niche when competitors absent
(c) Mutualism    (iii) Both species benefit
(d) Predation    (iv) One species consumes another

Explanation: Correct answer: (a) i, (b) ii, (c) iii, (d) iv. Resource partitioning divides resources, competitive release expands niches, mutualism benefits both species, and predation involves one species feeding on another.

8) Single Correct Answer: Which mechanism allows coexistence by temporal or spatial separation of resource use?
(1) Mutualism
(2) Resource partitioning
(3) Predation
(4) Competitive exclusion

Explanation: Correct answer is (2) Resource partitioning. By using resources at different times or locations, species reduce overlap, decrease competition, and achieve stable coexistence in shared habitats.

9) Fill in the blank: When a species expands its niche after competitor removal, it is called ______.
(1) Competitive release
(2) Mutualism
(3) Predation
(4) Resource partitioning

Explanation: Correct answer is (1) Competitive release. Absence of competitors allows species to occupy previously restricted areas or resources, increasing its survival and reproduction opportunities.

10) Choose the correct statements:
(a) Resource partitioning reduces direct competition.
(b) Mutualism always harms one species.
(c) Competitive release allows niche expansion.
(d) Predation involves consumption of another organism.
Options:
(1) a, c, d
(2) a, b, c
(3) b, c, d
(4) a, b, d

Explanation: Correct answer is (1). Statements a, c, and d are correct. Resource partitioning reduces competition, competitive release allows niche expansion, and predation involves consumption. Statement b is false; mutualism benefits both species.

Topic: Ecosystem Components
Subtopic: Nutrient Availability

Keyword Definitions:

• Standing State: The quantity of nutrients like carbon, nitrogen, phosphorus, and calcium present in the soil at a given time.

• Standing Crop: The total biomass or weight of living organisms in a unit area at a particular time.

• Climax Community: A stable and final stage of ecological succession where the ecosystem is in equilibrium.

• Nutrient Cycling: Movement and exchange of nutrients between organisms and environment.

• Biomass: Mass of living biological organisms in a given area or ecosystem.

• Ecosystem: Functional unit of nature comprising living organisms and their physical environment.

Lead Question - 2021

The amount of nutrients, such as carbon, nitrogen, phosphorus and calcium present in the soil at any given time, is referred as:
(1) Climax community
(2) Standing state
(3) Standing crop
(4) Climax

Explanation: The correct answer is (2) Standing state. Standing state refers to the quantity of inorganic nutrients present in the soil at a specific moment. These nutrients are available for uptake by producers. It is different from standing crop, which refers to living biomass present at a given time.

Guessed Questions:

1) Which term represents the total biomass of producers in an area at a given time?
(1) Standing state
(2) Standing crop
(3) Net primary productivity
(4) Climax community

Explanation: The correct answer is (2) Standing crop. Standing crop refers to the mass of living matter, primarily producers, present in a unit area at a given time. It is measured as biomass or number. It differs from standing state, which involves non-living nutrients in the ecosystem soil or environment.

2) In nutrient cycling, which organisms act as decomposers?
(1) Fungi and bacteria
(2) Green plants
(3) Herbivores
(4) Carnivores

Explanation: The correct answer is (1) Fungi and bacteria. Decomposers break down dead organic matter into simpler inorganic substances, returning nutrients to the standing state in soil. Plants, herbivores, and carnivores contribute to energy flow but decomposers recycle nutrients, ensuring sustainability and continuity of biogeochemical cycles within ecosystems.

3) Which process directly increases the nitrogen standing state in soil?
(1) Photosynthesis
(2) Nitrogen fixation
(3) Respiration
(4) Transpiration

Explanation: The correct answer is (2) Nitrogen fixation. Nitrogen-fixing bacteria such as Rhizobium convert atmospheric nitrogen into ammonium compounds, increasing soil nutrient availability. This adds to the nitrogen standing state, enhancing fertility. Photosynthesis, respiration, and transpiration are physiological processes but do not directly enrich soil nitrogen levels.

4) Assertion (A): Standing crop refers to biomass.
Reason (R): Standing state refers to nutrient content of soil.
(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: The correct answer is (2). Both statements are true, but R does not explain A. Standing crop and standing state are two distinct ecological parameters. Standing crop is the biomass of living organisms, while standing state is the nutrient reserve in soil, both crucial for ecosystem functioning.

5) Match the following:
a. Standing state - i. Nutrients in soil
b. Standing crop - ii. Biomass of producers
c. Climax community - iii. Stable ecosystem stage
(1) a-i, b-ii, c-iii
(2) a-ii, b-iii, c-i
(3) a-iii, b-i, c-ii
(4) a-i, b-iii, c-ii

Explanation: The correct answer is (1) a-i, b-ii, c-iii. Standing state represents nutrients in soil, standing crop refers to living biomass, and climax community represents a stable endpoint of ecological succession. These terms describe different components of ecosystem structure and function, critical for understanding energy flow and sustainability.

6) Fill in the blank: The endpoint of ecological succession where the ecosystem attains stability is called ________.
(1) Standing state
(2) Standing crop
(3) Climax community
(4) Primary productivity

Explanation: The correct answer is (3) Climax community. A climax community is the final stable stage of succession where the ecosystem remains in equilibrium with its environment. Energy flow and nutrient cycles reach balance, and species composition remains relatively unchanged until disturbed by external factors like fire or human activity.

7) Choose the correct statements:
a. Standing state refers to inorganic nutrient reserves.
b. Standing crop measures living biomass.
c. Decomposers help replenish standing state.
d. Climax community represents unstable stage.
(1) a, b, c
(2) a, c, d
(3) b, d only
(4) a, b, c, d

Explanation: The correct answer is (1) a, b, c. Standing state involves nutrients in soil, standing crop refers to biomass, and decomposers restore nutrients, maintaining standing state. Climax community, however, represents a stable not unstable stage. Thus, the correct combination includes the first three statements but not the last.

8) Which nutrient cycle involves weathering of rocks as the main source?
(1) Nitrogen cycle
(2) Carbon cycle
(3) Phosphorus cycle
(4) Oxygen cycle

Explanation: The correct answer is (3) Phosphorus cycle. Phosphorus is released into soil and water bodies through weathering of phosphate rocks. Unlike carbon and nitrogen, it does not enter the atmosphere significantly. This geochemical cycle maintains phosphorus standing state in soil, crucial for plant energy transfer and genetic material synthesis.

9) Standing state of carbon in the biosphere is mainly maintained by:
(1) Photosynthesis and respiration
(2) Nitrogen fixation
(3) Rock weathering
(4) Evaporation

Explanation: The correct answer is (1) Photosynthesis and respiration. Carbon enters producers through photosynthesis and returns to atmosphere by respiration. This cycling maintains the standing state of carbon in ecosystems. Nitrogen fixation and rock weathering influence other cycles, while evaporation is part of the water cycle, not carbon balance.

10) In which ecosystem is the standing crop of phytoplankton highest?
(1) Desert
(2) Ocean
(3) Grassland
(4) Tundra

Explanation: The correct answer is (2) Ocean. Phytoplankton form the primary producers in aquatic ecosystems and have the highest standing crop in oceans. Their rapid turnover and reproduction sustain marine food chains. Deserts and tundra have low productivity, while grasslands support producers but not as extensively as oceans.

Chapter: Environmental Pollution and Management

Topic: Air Pollution and Particulate Matter

Subtopic: Health Impact of Fine Particulates (PM2.5)

Keyword Definitions:

• Particulate Matter (PM): Tiny solid or liquid particles suspended in air that can affect human health.

• PM2.5: Particulates with diameter ≤2.5 micrometers, capable of penetrating deep into lungs and bloodstream.

• PM10: Particulates with diameter ≤10 micrometers, less harmful than PM2.5 but still a respiratory risk.

• CPCB: Central Pollution Control Board, India, monitors air quality and sets pollutant standards.

• Air Quality: Measure of cleanliness and pollutant levels in the atmosphere.

• Respiratory diseases: Illnesses affecting lungs and breathing caused by air pollutants.

• Cardiovascular risk: Increased likelihood of heart-related problems due to inhaled fine particulates.

• Diameter: Measurement of particle size which determines its deposition in respiratory tract.

• Health hazard: Potential of a pollutant to cause disease or injury.

• Pollutant standard: Legal limit of pollutant concentration to protect human health.

• Airborne particles: Any solid or liquid material suspended in air including dust, smoke, or droplets.

Lead Question - 2020 (COVID Reexam)

According to the Central Pollution Control Board [CPCB] what size (in diameter) of particulate is responsible for causing greater harm to human health?

1. 3.5 micrometers

2. 2.5 micrometers

3. 4.0 micrometers

4. 3.0 micrometers

Explanation: PM2.5, particulate matter with diameter ≤2.5 micrometers, can penetrate deep into the alveoli and bloodstream, causing respiratory and cardiovascular diseases. CPCB identifies PM2.5 as more harmful than larger particulates. Correct answer is option 2.

1. Single Correct Answer: Which of the following is the main source of PM2.5 in cities?

a) Vehicle emissions

b) Pollen

c) Rainwater

d) Soil erosion

Explanation: PM2.5 originates mainly from combustion in vehicles, industries, and biomass burning, penetrating deep into lungs. Pollen and rain do not generate harmful PM2.5. Option a is correct.

2. Single Correct Answer: Which organs are primarily affected by PM2.5 exposure?

a) Lungs and heart

b) Skin only

c) Eyes only

d) Hair and nails

Explanation: PM2.5 particles reach alveoli, enter bloodstream, causing respiratory and cardiovascular problems. Skin, eyes, and hair are minimally affected. Option a is correct.

3. Single Correct Answer: PM10 differs from PM2.5 because:

a) Larger in size, less penetrative

b) Smaller, more harmful

c) Contains no carbon

d) Only found indoors

Explanation: PM10 are coarser particles ≤10 micrometers and deposit in upper airways. PM2.5 is finer and more harmful. Option a is correct.

4. Single Correct Answer: Air quality monitoring in India is primarily done by:

a) CPCB

b) ISRO

c) NASA

d) CSIR

Explanation: CPCB monitors air pollutants, sets standards, and issues advisories. ISRO and NASA have satellite data but not direct regulatory role. Option a is correct.

5. Single Correct Answer: Which law regulates ambient air quality in India?

a) Air (Prevention and Control of Pollution) Act, 1981

b) Water Act, 1974

c) Forest Conservation Act, 1980

d) Wildlife Protection Act, 1972

Explanation: Air (Prevention and Control of Pollution) Act, 1981, amended in 1987, sets pollutant limits including PM2.5. Water, forest, and wildlife acts address other environmental aspects. Option a is correct.

6. Single Correct Answer: Which is the most dangerous pollutant in urban air for human health?

a) PM2.5

b) Ozone

c) CO2

d) Nitrogen

Explanation: PM2.5 penetrates deep lungs causing cardiovascular and respiratory diseases. CO2 and nitrogen are not directly harmful in ambient concentrations. Ozone is harmful but PM2.5 is most critical. Option a is correct.

7. Assertion-Reason:

Assertion (A): PM2.5 is more harmful than PM10.

Reason (R): Smaller particles penetrate alveoli and bloodstream.

a) Both A and R true, R explains A

b) Both A and R true, R does not explain A

c) A true, R false

d) A false, R true

Explanation: PM2.5 penetrates deeper into lungs and enters circulation, causing greater health risk than PM10. Both assertion and reason are correct, and reason explains assertion. Option a is correct.

8. Matching Type: Match particle size with deposition site:

Column I: a) PM10, b) PM2.5

Column II: i) Upper respiratory tract, ii) Alveoli

Options:

1. a-i, b-ii

2. a-ii, b-i

3. a-i, b-i

4. a-ii, b-ii

Explanation: PM10 deposits in upper respiratory tract, while PM2.5 penetrates alveoli and bloodstream. Correct match is option 1.

9. Fill in the Blanks: PM2.5 can cause _______ and _______ diseases.

a) Respiratory, cardiovascular

b) Skin, hair

c) Digestive, liver

d) Eye, nail

Explanation: Fine particulates (PM2.5) penetrate lungs, causing respiratory and cardiovascular issues. Other organs are less affected. Option a is correct.

10. Choose the correct statements:

1) PM2.5 is ≤2.5 micrometers