Topic: Adaptive Radiation; Subtopic: Marsupials vs Placental Mammals
Keyword Definitions:
Adaptive Radiation: Rapid evolution of diversely adapted species from a common ancestor in response to environmental opportunities.
Marsupials: Mammals that carry and nourish their young in a pouch after birth.
Placental Mammals: Mammals in which the young develop inside the uterus with nourishment via placenta.
Numbat: A termite-eating marsupial from Australia.
Tasmanian Wolf (Thylacine): Extinct carnivorous marsupial resembling a dog.
Marsupial Mouse: Small insectivorous marsupial.
Spotted Cuscus: Arboreal marsupial resembling lemurs in habits.
Bobcat, Lemur, Mole, Flying Squirrel: Placental mammals occupying ecological niches similar to marsupials in Australia.
Lead Question – 2022 (Abroad)
Select the correct match regarding adaptive radiation of Australian marsupials corresponding to placental mammals:
1. Numbat – Flying Squirrel
2. Tasmanian Wolf – Bobcat
3. Marsupial Mouse – Mole
4. Spotted Cuscus – Lemur
Explanation:
Correct answer is Tasmanian Wolf – Bobcat. Adaptive radiation led Australian marsupials to evolve forms resembling placental mammals elsewhere, occupying similar ecological niches despite different ancestry. Tasmanian Wolf (Thylacine) was a carnivorous marsupial similar in habits and body structure to placental predators like Bobcat. Numbats are insectivorous, not gliding like flying squirrels; Marsupial Mouse occupies insectivorous ground niche like shrews, not moles; Spotted Cuscus is arboreal like lemurs. This illustrates convergent evolution where marsupials developed features to exploit ecological opportunities similar to placental mammals, demonstrating adaptive radiation.
1. Which marsupial resembles an arboreal lemur in ecology?
1. Numbat
2. Spotted Cuscus
3. Marsupial Mouse
4. Tasmanian Wolf
Explanation: Correct answer is Spotted Cuscus. It is an arboreal marsupial that lives in trees, feeding on leaves and fruits, similar to placental lemurs. While not related, its niche and behavior mimic lemurs, an example of adaptive radiation and convergent evolution, where unrelated species evolve similar traits to adapt to comparable ecological roles.
2. Numbats primarily feed on:
1. Termites
2. Leaves
3. Fruits
4. Small mammals
Explanation: Correct answer is Termites. Numbats are specialized insectivorous marsupials that feed almost exclusively on termites. Their long sticky tongues and strong sense of smell allow them to exploit termite colonies efficiently. This feeding specialization illustrates adaptive radiation, as marsupials occupied diverse ecological roles similar to placental mammals in other continents.
3. Adaptive radiation results in:
1. Formation of identical species
2. Diversification from a common ancestor
3. Extinction of all ancestral species
4. Decrease in ecological niches
Explanation: Correct answer is Diversification from a common ancestor. Adaptive radiation occurs when a single ancestor evolves into multiple species adapted to different ecological niches. Australian marsupials exemplify this, evolving into forms analogous to placental mammals such as carnivores, insectivores, and arboreal species, without shared ancestry, demonstrating convergent evolution.
4. Tasmanian Wolf is similar to which placental mammal in niche?
1. Flying Squirrel
2. Bobcat
3. Mole
4. Lemur
Explanation: Correct answer is Bobcat. Tasmanian Wolf (Thylacine) was a carnivorous marsupial predator resembling placental carnivores like Bobcat in ecological role. Despite unrelated lineages, they evolved similar hunting adaptations, demonstrating convergent evolution due to adaptive radiation in marsupials to occupy predatory niches.
5. Marsupial Mouse occupies a niche similar to:
1. Mole
2. Bobcat
3. Lemur
4. Flying Squirrel
Explanation: Correct answer is Mole. Marsupial Mouse is small, insectivorous, and ground-dwelling, analogous to placental moles in ecological function. This demonstrates adaptive radiation, where marsupials evolved different forms to occupy the same niches as placental mammals on other continents, despite evolutionary differences.
6. Which marsupial demonstrates convergent evolution with gliding placental mammals?
1. Spotted Cuscus
2. Numbat
3. Sugar Glider
4. Tasmanian Wolf
Explanation: Correct answer is Sugar Glider. Sugar Gliders are arboreal marsupials capable of gliding between trees, similar to placental flying squirrels. Adaptive radiation allowed marsupials to evolve gliding ability independently, demonstrating convergent evolution to exploit arboreal niches in Australia.
7. Assertion-Reason Type:
Assertion (A): Australian marsupials evolved forms analogous to placental mammals.
Reason (R): They occupy similar ecological niches despite different ancestry.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation
3. A is true, R is false
4. A is false, R is true
Explanation: Correct answer is option 1. Marsupials evolved independently to fill ecological roles like placental mammals, an example of convergent evolution. Tasmanian Wolf resembles predatory Bobcats, Numbat resembles insectivores, and Spotted Cuscus mimics arboreal primates. Similar selective pressures produced analogous adaptations in different lineages.
8. Matching Type:
Match the Australian marsupial with corresponding placental mammal:
A. Numbat – (i) Termite-eating insectivore
B. Tasmanian Wolf – (ii) Predator
C. Marsupial Mouse – (iii) Ground insectivore
D. Spotted Cuscus – (iv) Arboreal primate
1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–i, C–iv, D–iii
3. A–i, B–iii, C–ii, D–iv
4. A–iv, B–ii, C–i, D–iii
Explanation: Correct answer is option 1. Numbat resembles insectivorous placental mammals, Tasmanian Wolf resembles predatory mammals like Bobcat, Marsupial Mouse is similar to ground insectivores like moles, and Spotted Cuscus is analogous to arboreal lemurs. This matching illustrates adaptive radiation and convergent evolution of marsupials.
9. Fill in the Blanks:
Adaptive radiation in Australian marsupials resulted in species occupying niches similar to ___________ mammals.
1. Reptilian
2. Placental
3. Amphibian
4. Fish
Explanation: Correct answer is Placental. Australian marsupials evolved forms like Tasmanian Wolf (Bobcat), Numbat (insectivore), and Spotted Cuscus (lemur) to occupy ecological niches similar to placental mammals, despite separate evolutionary lineages, demonstrating convergent evolution driven by adaptive radiation.
10. Choose the Correct Statements:
Statement I: Tasmanian Wolf evolved to occupy predatory niches similar to placental carnivores.
Statement II: Spotted Cuscus is terrestrial like moles.
1. Statement I correct, Statement II incorrect
2. Statement I incorrect, Statement II correct
3. Both correct
4. Both incorrect
Explanation: Correct answer is Statement I correct, Statement II incorrect. Tasmanian Wolf is a marsupial
Topic: Mechanisms of Evolution; Subtopic: Genetic Drift
Keyword Definitions:
Genetic Drift: A random change in allele frequency in a small population due to chance events, leading to evolution independent of natural selection.
Gene Flow: Movement of genes between populations due to migration or interbreeding.
Bottleneck Effect: Reduction in genetic diversity due to drastic decrease in population size by natural calamities.
Founder Effect: Genetic variation caused when a few individuals colonize a new area, carrying limited alleles.
Mutation: Sudden and heritable change in DNA that introduces new alleles in a population.
Lead Question - 2022 (Abroad)
Genetic Drift occurs due to :
1. Natural selection
2. Sudden population migration
3. Continuous gene migration
4. Mutation
Explanation: Genetic drift occurs due to chance fluctuations in allele frequencies in small populations. It is independent of natural selection and can result from random sampling effects during reproduction or survival events. Disasters, isolation, or migration of small groups can cause loss or fixation of alleles. Hence, option 2 is correct.
1. The Bottleneck Effect is best described as:
1. Increase in genetic diversity after migration
2. Sharp reduction in population leading to reduced genetic variation
3. Random mating in large populations
4. Sudden introduction of new genes
Explanation: The Bottleneck Effect occurs when a population experiences a drastic reduction due to natural calamities or human interference. This leads to loss of genetic diversity as only a few alleles are passed to the next generation, altering allele frequencies by chance. Hence, option 2 is correct.
2. The Founder Effect is observed when:
1. Large populations evolve slowly
2. A few individuals establish a new population
3. Gene flow increases between groups
4. Mutation rate decreases
Explanation: The Founder Effect arises when a small group of individuals migrates and establishes a new colony. Their limited gene pool leads to random differences in allele frequencies compared to the parent population. This causes rapid evolution and distinct genetic characteristics. Hence, option 2 is correct.
3. Which of the following is a non-directional evolutionary force?
1. Mutation
2. Natural selection
3. Genetic drift
4. Gene flow
Explanation: Genetic drift is non-directional because it does not favor specific traits or adaptations; instead, allele frequency changes occur randomly. Natural selection is directional, while gene flow and mutation may introduce specific variations. Hence, option 3 is correct.
4. Genetic drift is more significant in:
1. Large stable populations
2. Populations with high mutation rates
3. Small isolated populations
4. Rapidly growing populations
Explanation: Genetic drift strongly affects small, isolated populations because chance events can easily change allele frequencies when there are few individuals. In large populations, random changes are diluted. Thus, genetic drift has major evolutionary consequences in small groups. Hence, option 3 is correct.
5. Which of the following statements best distinguishes Genetic Drift from Natural Selection?
1. Both act on large populations
2. Both occur by chance
3. Genetic drift is random, while natural selection is adaptive
4. Both increase genetic variation
Explanation: Genetic drift is a random process where alleles change in frequency by chance, while natural selection is a non-random process that increases the frequency of beneficial traits. Thus, drift is stochastic and selection is adaptive. Hence, option 3 is correct.
6. The Founder Effect is commonly seen in:
1. Bacteria undergoing transformation
2. New island populations formed by few individuals
3. Hybrid species with diverse genes
4. Populations with extensive migration
Explanation: When a few individuals colonize an isolated area, they carry limited genetic variation from the parent population. This small group can evolve differently due to drift and isolation. Such founder effects often occur in island or remote populations. Hence, option 2 is correct.
7. Assertion-Reason Question:
Assertion (A): Genetic drift leads to evolution without natural selection.
Reason (R): It causes random changes in allele frequencies within small populations.
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: Genetic drift operates independently of selection by randomly changing allele frequencies due to chance. This mechanism explains evolution without selective pressure. Therefore, both statements are true, and the reason correctly explains the assertion. Hence, option 1 is correct.
8. Matching Type Question:
Match the following evolutionary concepts with their examples:
A. Founder Effect — (i) Random loss of alleles after a disaster
B. Bottleneck Effect — (ii) Few individuals colonizing an island
C. Mutation — (iii) Introduction of new alleles
D. Gene Flow — (iv) Migration between populations
1. A-(ii), B-(i), C-(iii), D-(iv)
2. A-(iv), B-(iii), C-(i), D-(ii)
3. A-(i), B-(ii), C-(iv), D-(iii)
4. A-(ii), B-(iii), C-(iv), D-(i)
Explanation: The Founder Effect arises when a few individuals establish a new population. Bottleneck Effect occurs after disasters causing allele loss. Mutation introduces new alleles, and gene flow transfers genes between groups. Hence, A-(ii), B-(i), C-(iii), D-(iv) is correct. Option 1 is correct.
9. Fill in the Blanks / Completion Question:
A sudden decrease in population size due to natural calamities leading to reduced genetic variability is known as ______.
1. Genetic drift
2. Mutation
3. Bottleneck effect
4. Gene flow
Explanation: When a large population sharply reduces in size due to floods, earthquakes, or human activities, most alleles are lost, decreasing diversity. This random effect is called the Bottleneck Effect, a type of genetic drift. Hence, the correct answer is option 3.
10. Choose the Correct Statements (Statement I & Statement II):
Statement I: Genetic drift is more pronounced in small populations.
Statement II: Genetic drift always increases the fitness of individuals.
1. Both statements are true.
2. Both statements are false.
3. Statement I is true and Statement II is false.
4. Statement I is false and Statement II is true.
Explanation: Genetic drift significantly affects small populations, altering allele frequencies randomly. However, these changes are not necessarily beneficial or adaptive. Drift can even reduce fitness by fixing harmful alleles. Therefore, Statement I is true and Statement II is false. Hence, option 3 is correct.
Subtopic: Homology and Analogy
Keyword Definitions:
- Homology: Similarity in structures due to common ancestry.
- Analogy: Similarity in function but different evolutionary origin.
- Convergent evolution: Process where unrelated organisms develop similar traits.
- Divergent evolution: Process where related organisms develop different traits.
- Flippers: Modified forelimbs used for swimming.
- Penguins: Flightless birds adapted for aquatic life.
- Dolphins: Marine mammals with forelimbs modified as flippers.
- Comparative anatomy: Study of similarities and differences in body structures.
- Common ancestry: Organisms sharing evolutionary lineage.
- Structural adaptation: Modification of body parts for specific functions.
- Analogous structures: Structures with similar function but no common ancestry.
Lead Question - 2022:
Which of the following statements is not true?
(1) Sweet potato and potato is an example of analogy
(2) Homology indicates common ancestry
(3) Flippers of penguins and dolphins are a pair of homologous organs
(4) Analogous structures are a result of convergent evolution
Explanation: The correct answer is (3). Flippers of penguins and dolphins are analogous structures because they have similar function but evolved independently. Homology indicates common ancestry, sweet potato and potato show analogy, and analogous structures result from convergent evolution. Therefore, statement 3 is not true.
1. Single Correct Answer:
Which of the following represents homologous structures?
(a) Wings of bats and birds
(b) Wings of insects and birds
(c) Flippers of dolphins and penguins
(d) Eyes of octopus and human
Explanation: Wings of bats and birds are homologous structures because they share a common skeletal pattern inherited from a common ancestor. Insects have a different evolutionary origin, and flippers and eyes are analogous due to similar function, not common ancestry.
2. Single Correct Answer:
Which process leads to analogous structures?
(a) Divergent evolution
(b) Convergent evolution
(c) Natural selection
(d) Genetic drift
Explanation: Analogous structures arise due to convergent evolution, where unrelated organisms develop similar traits to adapt to similar environments. Divergent evolution produces homologous structures, natural selection and genetic drift influence evolution but do not directly create analogous structures.
3. Single Correct Answer:
Homology indicates:
(a) Similar function
(b) Common ancestry
(c) Independent evolution
(d) Adaptation to environment
Explanation: Homology indicates common ancestry. Structures inherited from a shared ancestor may have different functions in descendants, like forelimbs of vertebrates. Function similarity alone indicates analogy, not homology, while independent evolution and adaptation are separate evolutionary concepts.
4. Single Correct Answer:
Which of the following is an example of analogy?
(a) Forelimbs of humans and whales
(b) Wings of birds and bats
(c) Wings of insects and birds
(d) Legs of horses and donkeys
Explanation: Wings of insects and birds are analogous. They perform similar functions (flight) but evolved independently. Forelimbs of humans and whales, wings of birds and bats, and legs of horses and donkeys are homologous, sharing common skeletal patterns.
5. Single Correct Answer:
Which of the following statements is true about convergent evolution?
(a) Produces homologous structures
(b) Leads to analogous structures
(c) Indicates common ancestry
(d) Occurs only in plants
Explanation: Convergent evolution leads to analogous structures in unrelated species adapting to similar environments. Homologous structures indicate common ancestry. Convergent evolution occurs in both animals and plants and is independent of shared lineage.
6. Single Correct Answer:
Which structure is homologous to the human arm?
(a) Wing of butterfly
(b) Wing of bat
(c) Flipper of dolphin
(d) Eye of octopus
Explanation: The wing of a bat is homologous to the human arm as both share a common skeletal plan inherited from a common ancestor. Insects and octopus structures are analogous due to function similarity without shared ancestry.
7. Assertion-Reason MCQ:
Assertion (A): Analogous structures show similar function.
Reason (R): They arise from convergent evolution.
(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: Option (a) is correct. Analogous structures perform similar functions, like wings of birds and insects. They arise independently due to convergent evolution. Both assertion and reason are true, and the reason directly explains the function similarity.
8. Matching Type MCQ:
Match the structures with their types:
List - I List - II
(a) Forelimb of human (i) Analogous
(b) Wings of insects (ii) Homologous
(c) Flippers of dolphin (iii) Analogous
(d) Wings of birds (iv) Homologous
Options:
(1) a-ii, b-i, c-iii, d-iv
(2) a-i, b-ii, c-iv, d-iii
(3) a-iii, b-iv, c-i, d-ii
(4) a-iv, b-iii, c-ii, d-i
Explanation: Option (1) is correct. Human forelimbs and bird wings are homologous, wings of insects and flippers of dolphins are analogous, showing similar functions with independent evolutionary origin. This illustrates clear distinction between homology and analogy.
9. Fill in the Blanks:
Flippers of dolphins and penguins are examples of _______ structures.
(a) Homologous
(b) Analogous
(c) Vestigial
(d) Atavistic
Explanation: Flippers of dolphins and penguins are analogous structures performing similar swimming functions but evolved independently. Homologous structures share common ancestry, while vestigial and atavistic structures are remnants of evolutionary history with reduced or reappearing function.
10. Choose the Correct Statements:
Identify correct statements:
1. Homologous structures indicate common ancestry.
2. Analogous structures result from convergent evolution.
3. Flippers of penguins and dolphins are homologous.
4. Wings of birds and bats are homologous.
Options:
(a) 1, 2, 3
(b) 1, 2, 4
(c) 2, 3, 4
(d) 1, 3, 4
Explanation: Option (b) is correct. Homologous structures show common ancestry, analogous structures arise from convergent evolution. Wings of birds and bats are homologous, but flippers of penguins and dolphins are analogous, not homologous. Statements 1, 2, and 4 are accurate.
Topic: Natural Selection and Variation
Subtopic: Types of Natural Selection
Keyword Definitions:
• Natural Selection: The process by which organisms with favorable traits survive and reproduce more successfully.
• Directional Selection: Selection that favors one extreme phenotype, causing a shift in the population mean.
• Disruptive Selection: Selection that favors both extremes of a trait over intermediate forms.
• Stabilizing Selection: Selection that favors average traits and reduces variation.
• Variation: Differences among individuals in a population.
• Adaptive Evolution: Change in traits that enhance survival and reproduction.
• Phenotype: Observable characteristics of an organism.
• Allele Frequency: Proportion of a particular gene variant in a population.
• Population: Group of individuals of the same species living in the same area.
• Speciation: Formation of new species due to genetic and reproductive isolation.
Lead Question (2022):
Natural selection where more individuals acquire specific character value other than the mean character value, leads to:
(1) Directional change
(2) Disruptive change
(3) Random change
(4) Stabilising change
Explanation: The correct answer is (1). Directional selection favors one extreme phenotype, causing a shift in population traits toward that direction. This occurs when environmental pressures favor individuals deviating from the average, leading to evolutionary change and adaptation over generations toward the advantageous phenotype.
Guessed MCQs:
1. Single Correct Answer:
Which type of natural selection favors both extremes of a character and eliminates intermediates?
(a) Disruptive selection
(b) Directional selection
(c) Stabilizing selection
(d) Random selection
Explanation: The correct answer is (a). Disruptive selection favors individuals at both extremes of a trait, increasing variation and sometimes leading to speciation by splitting the population into two distinct groups.
2. Single Correct Answer:
When environmental conditions remain constant, which selection type is most likely to occur?
(a) Stabilizing selection
(b) Directional selection
(c) Disruptive selection
(d) Artificial selection
Explanation: The correct answer is (a). Stabilizing selection favors average phenotypes and acts against extremes, maintaining existing adaptations when environmental conditions are stable, thus preserving population equilibrium and reducing variation.
3. Assertion-Reason MCQ:
Assertion (A): Directional selection leads to evolution toward one extreme trait.
Reason (R): It occurs when one phenotype has a higher fitness than others.
(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). Directional selection occurs when individuals at one extreme of a trait have higher reproductive success, shifting the population mean toward that advantageous phenotype across generations.
4. Matching Type MCQ:
Match the type of selection with its example:
A. Directional selection – (i) Bacteria developing antibiotic resistance
B. Stabilizing selection – (ii) Human birth weight
C. Disruptive selection – (iii) Finches with large or small beaks
Options:
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). Directional selection favors resistance traits, stabilizing selection maintains average traits like birth weight, and disruptive selection favors extreme beak sizes in finches adapting to different food types.
5. Single Correct Answer:
Which of the following best represents stabilizing selection?
(a) High and low birth weights are less fit than average
(b) Giraffes evolve longer necks
(c) Peppered moths darken due to pollution
(d) Different beak sizes in Darwin’s finches
Explanation: The correct answer is (a). Stabilizing selection favors average traits, eliminating extremes such as very low or high birth weights in humans, which reduces genetic variation and maintains equilibrium.
6. Single Correct Answer:
Which selection type results in two peaks in phenotype frequency distribution?
(a) Disruptive selection
(b) Directional selection
(c) Stabilizing selection
(d) Balancing selection
Explanation: The correct answer is (a). Disruptive selection favors individuals with extreme phenotypes, reducing intermediate forms and leading to two distinct phenotypic groups within the population, potentially causing speciation.
7. Fill in the Blanks:
When environmental conditions change consistently, ________ selection shifts population traits toward one direction.
(a) Directional
(b) Disruptive
(c) Stabilizing
(d) Balancing
Explanation: The correct answer is (a). Directional selection causes a consistent shift toward one extreme phenotype as it provides a fitness advantage under changing environmental pressures, leading to gradual evolutionary adaptation.
8. Single Correct Answer:
Which of the following is an example of directional selection in evolution?
(a) Industrial melanism in moths
(b) Human birth weight
(c) Snail shell color extremes
(d) Random mutations
Explanation: The correct answer is (a). Industrial melanism is an example where darker moths had survival advantages in polluted environments, demonstrating directional selection favoring one phenotype over others due to environmental changes.
9. Single Correct Answer:
Which statement correctly describes natural selection?
(a) It operates on phenotypic variation
(b) It eliminates all genetic diversity
(c) It always favors the rarest traits
(d) It acts only on extinct species
Explanation: The correct answer is (a). Natural selection acts on phenotypic differences that influence reproductive success, gradually changing allele frequencies in populations, but it does not completely eliminate genetic diversity.
10. Choose the correct statements:
(a) Directional selection shifts the mean phenotype.
(b) Stabilizing selection reduces variation.
(c) Disruptive selection increases intermediate forms.
(d) All types influence evolutionary change.
Options:
1. a, b, d only
2. a and c only
3. b and c only
4. All statements
Explanation: The correct answer is (1). Directional selection shifts mean phenotype, stabilizing selection reduces variation, and all types drive evolutionary change. Disruptive selection, however, reduces intermediate forms, not increases them.
Subtopic: Adaptive, Convergent, Divergent Evolution & Anthropogenic Evolution
Keyword Definitions:
Adaptive evolution: Evolutionary changes that increase fitness in a specific environment.
Convergent evolution: Independent evolution of similar traits in unrelated species due to similar environmental pressures.
Divergent evolution: Accumulation of differences between closely related species, leading to speciation.
Anthropogenic action: Human-induced changes in the environment affecting evolution.
Herbicides and pesticides: Chemicals used to kill unwanted plants and pests, can drive adaptive evolution.
Darwin finches: Example of adaptive radiation illustrating divergent evolution.
Forelimb bones: Homologous structures indicating divergent evolution in mammals.
Butterfly and bird wings: Analogous structures demonstrating convergent evolution.
Selection: Process by which certain traits become more common due to advantages in survival or reproduction.
Lead Question - 2021
Match List - I with List - II.
List - I List - II
(a) Adaptive (i) Selection of resistant radiation varieties due to excessive use of herbicides and pesticides
(b) Convergent (ii) Bones of forelimbs in evolution Man and Whale
(c) Divergent (iii) Wings of Butterfly and Bird
(d) Evolution by anthropogenic action (iv) Darwin Finches
Choose the correct answer from the options given below.
(1) (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
(2) (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
(3) (a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)
(4) (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
Explanation: Adaptive evolution occurs as species develop resistance to herbicides and pesticides (a-i). Convergent evolution is seen in similar wings of butterflies and birds (b-iii). Divergent evolution is exemplified by differences in forelimb bones of man and whale (c-ii). Anthropogenic action drives changes such as Darwin finches’ evolution (d-iv). Correct answer is option (3).
1. Which evolution type explains development of antibiotic-resistant bacteria?
(1) Adaptive
(2) Convergent
(3) Divergent
(4) Anthropogenic
Explanation: Antibiotic resistance arises due to selective pressure favoring resistant strains. This is a classic example of adaptive evolution, where organisms evolve traits that increase survival in specific environments. Other types like convergent or divergent do not describe this process. Correct answer is option (1) Adaptive.
2. Wings of bats and birds are similar in function but different in structure. This is an example of:
(1) Convergent evolution
(2) Divergent evolution
(3) Adaptive evolution
(4) Anthropogenic evolution
Explanation: Wings of bats and birds evolved independently for flight; they have different underlying structures but similar function. This illustrates convergent evolution, where unrelated species develop similar traits due to environmental pressures. Correct answer is option (1) Convergent evolution.
3. Forelimb structures of humans, whales, and bats show modification over time. This indicates:
(1) Divergent evolution
(2) Convergent evolution
(3) Adaptive evolution
(4) Anthropogenic evolution
Explanation: Forelimbs of humans, whales, and bats share a common ancestor but evolved different functions (grasping, swimming, flying), illustrating divergent evolution. Correct answer is option (1) Divergent evolution.
4. Rapid evolution of pest-resistant crops due to human activity is an example of:
(1) Anthropogenic evolution
(2) Convergent evolution
(3) Divergent evolution
(4) Adaptive evolution
Explanation: Human actions such as excessive pesticide use create strong selective pressures, causing evolution of resistant varieties. This is anthropogenic evolution, driven by human-induced environmental changes. Correct answer is option (1) Anthropogenic evolution.
5. Darwin’s finches exemplify which evolutionary process?
(1) Divergent evolution
(2) Convergent evolution
(3) Adaptive evolution
(4) Anthropogenic evolution
Explanation: Darwin’s finches evolved diverse beak shapes from a common ancestor, demonstrating divergent evolution. Adaptive evolution also occurs locally, but the key concept illustrated is divergence from a common ancestral form. Correct answer is option (1) Divergent evolution.
6. Which evolution type involves independent development of similar traits in unrelated species?
(1) Convergent evolution
(2) Divergent evolution
(3) Adaptive evolution
(4) Anthropogenic evolution
Explanation: Convergent evolution occurs when unrelated species develop similar features to adapt to comparable environmental challenges, like wings in birds and butterflies. Divergent evolution or adaptive evolution describes different processes. Correct answer is option (1) Convergent evolution.
7. Assertion-Reason Question:
Assertion (A): Human activity can accelerate evolution in some species.
Reason (R): Selective pressures from pesticides or herbicides favor resistant phenotypes.
(1) Both A and R are true, R correctly 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: Human activities like pesticide use create strong selective pressures, accelerating evolution in pests. The reason directly explains the assertion. Correct answer is option (1).
8. Matching Type:
Match examples with evolutionary concept:
(a) Wings of insects & birds - 1. Convergent
(b) Forelimbs of mammals - 2. Divergent
(c) Antibiotic resistance - 3. Adaptive
(d) Pesticide-resistant plants - 4. Anthropogenic
(1) a-1, b-2, c-3, d-4
(2) a-2, b-1, c-4, d-3
(3) a-3, b-4, c-1, d-2
(4) a-4, b-3, c-2, d-1
Explanation: Wings of insects and birds are convergent (a-1). Mammalian forelimbs are divergent (b-2). Antibiotic resistance demonstrates adaptive evolution (c-3). Pesticide-resistant plants result from anthropogenic influence (d-4). Correct answer is option (1).
9. Fill in the Blank:
_____ evolution results from human-induced environmental changes.
(1) Anthropogenic
(2) Convergent
(3) Divergent
(4) Adaptive
Explanation: Anthropogenic evolution occurs due to human activities, such as pollution, pesticides, and habitat alteration, driving rapid changes in species traits. Convergent, divergent, and adaptive evolution are natural processes. Correct answer is option (1) Anthropogenic.
10. Choose the correct statements:
(a) Divergent evolution results in speciation
(b) Convergent evolution produces analogous structures
(c) Adaptive evolution is due to selective pressures
(d) Anthropogenic evolution is driven by human activity
(1) a, b, c, d
(2) a, b, c
(3) b, c, d
(4) a, c, d
Explanation: All statements are correct. Divergent evolution can lead to speciation (a), convergent evolution produces analogous traits (b), adaptive evolution occurs due to selective pressures (c), and anthropogenic evolution is caused by human activities (d). Correct answer is option (1) a, b, c, d.</
Topic: Mechanisms of Evolution
Subtopic: Genetic Drift and Founder Effect
Keyword Definitions:
Genetic Drift: Random changes in allele frequencies in small populations leading to evolutionary changes.
Founder Effect: A type of genetic drift occurring when a few individuals colonize a new habitat, carrying limited genetic variation.
Mutation: Sudden heritable change in DNA sequence, introducing new genetic variation.
Genetic Recombination: Rearrangement of genetic material during meiosis, creating genetic diversity.
Natural Selection: Process by which individuals with advantageous traits survive and reproduce more successfully.
Population: Group of interbreeding individuals of the same species living in a specific area.
Lead Question - 2021
The factor that leads to Founder effect in a population is:
(1) Genetic recombination
(2) Mutation
(3) Genetic drift
(4) Natural selection
Explanation: The correct answer is (3) Genetic drift. Founder effect is a special case of genetic drift where a small group of individuals establishes a new population. This causes reduced genetic variability and unusual allele frequencies compared to the original population, sometimes leading to unique traits in isolated populations.
Guessed Questions:
1) The evolutionary force responsible for introducing new alleles into a population is:
(1) Mutation
(2) Genetic drift
(3) Founder effect
(4) Natural selection
Explanation: The correct answer is (1) Mutation. Mutations create new alleles by altering DNA sequences. While genetic drift, founder effect, and natural selection alter allele frequencies, only mutations provide novel genetic material for evolution. Thus, mutation is the ultimate source of genetic variation within populations over time.
2) Which of the following best describes genetic drift?
(1) Non-random mating
(2) Directional selection
(3) Random change in allele frequency
(4) Gene flow between populations
Explanation: The correct answer is (3) Random change in allele frequency. Genetic drift occurs due to chance events, particularly in small populations. It may cause alleles to disappear or become fixed. Unlike selection, it is not adaptive but can significantly affect evolution, especially through bottleneck or founder effects.
3) Assertion (A): Founder effect reduces genetic variation.
Reason (R): It involves migration of a large population with high diversity.
(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: The correct answer is (3). Founder effect does reduce genetic variation, but it occurs when a small group, not a large population, colonizes a new area. This small sample may not represent the genetic diversity of the original population, leading to rare traits being more common.
4) Match the following:
a. Genetic drift - i. Random allele frequency change
b. Mutation - ii. New genetic variations
c. Natural selection - iii. Survival of the fittest
d. Founder effect - iv. New population from few individuals
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-iii, b-i, c-ii, d-iv
(4) a-iv, b-iii, c-ii, d-i
Explanation: The correct answer is (1) a-i, b-ii, c-iii, d-iv. Genetic drift alters allele frequency by chance, mutation introduces variations, natural selection favors adaptive traits, and founder effect occurs when a few individuals establish a new population with reduced genetic diversity. All are mechanisms influencing evolutionary processes.
5) Fill in the blank: The sudden reduction in population size due to environmental events leading to loss of genetic variation is called ________.
(1) Gene flow
(2) Genetic recombination
(3) Bottleneck effect
(4) Founder effect
Explanation: The correct answer is (3) Bottleneck effect. This occurs when natural disasters or human activities drastically reduce a population’s size, leaving behind a small population with limited genetic variation. It is similar to founder effect but caused by catastrophic reduction rather than colonization of a new habitat.
6) Which of the following is an example of founder effect?
(1) A forest fire eliminates most of a deer population
(2) A small group of birds colonizes an isolated island
(3) A drought reduces seed availability in grasslands
(4) Random mating increases heterozygosity in a population
Explanation: The correct answer is (2). A small group of birds establishing a new island population demonstrates founder effect. The genetic variation of this new population depends only on the founding individuals, not the entire original population, leading to unusual allele frequencies and potentially distinct evolutionary outcomes.
7) Choose the correct statements:
a. Genetic drift is stronger in small populations.
b. Founder effect is a type of genetic drift.
c. Natural selection is random like drift.
d. Mutations introduce new alleles.
(1) a, b, d
(2) b, c, d
(3) a, c only
(4) a, b, c, d
Explanation: The correct answer is (1) a, b, d. Genetic drift is significant in small populations, founder effect is a subset of drift, and mutations create new alleles. Natural selection is not random but directional, favoring beneficial traits. Therefore, the correct set of statements is a, b, and d.
8) Which mechanism results in gene flow between populations?
(1) Mutation
(2) Genetic drift
(3) Migration
(4) Natural selection
Explanation: The correct answer is (3) Migration. Migration involves movement of individuals between populations, introducing new alleles and maintaining genetic diversity. Gene flow counteracts the effects of genetic drift and reduces chances of speciation by homogenizing allele frequencies between different populations across regions.
9) Which evolutionary force ensures adaptation to environment?
(1) Mutation
(2) Genetic drift
(3) Natural selection
(4) Founder effect
Explanation: The correct answer is (3) Natural selection. Unlike genetic drift or founder effect, which are random, natural selection is a non-random process that favors survival of individuals with advantageous traits. Over generations, it ensures populations adapt to their environment, enhancing survival and reproductive success of species.
10) Which condition reduces the effect of genetic drift in populations?
(1) Small population size
(2) Large population size
(3) Isolation
(4) Founder effect
Explanation: The correct answer is (2) Large population size. In large populations, random fluctuations in allele frequency are minimal because of greater genetic diversity. Genetic drift strongly impacts small or isolated populations, especially during founder or bottleneck events, but is negligible in large, interbreeding populations with high variability.
Topic: Hominid Fossils
Subtopic: Java Hominid
Keyword Definitions:
Hominid: Members of the human lineage, including modern humans and their ancestors.
Fossil: Preserved remains or impression of an organism from the past.
Homo erectus: Extinct hominid species with upright posture and cranial capacity around 900-1100 ccs.
Neanderthal: Extinct human species closely related to modern humans.
Homo sapiens: Modern human species.
Australopithecus: Early hominid genus with smaller brain and bipedal locomotion.
Cranial capacity: Volume of the braincase, measured in cubic centimeters (ccs).
Extinct: Species no longer existing.
Lead Question - 2020 (COVID Reexam)
A Hominid fossil discovered in Java in 1891, now extinct, having a cranial capacity of about 900 ccs was:
1. Homo erectus
2. Neanderthal man
3. Homo sapiens
4. Australopithecus
Explanation: The Java fossil discovered in 1891 is of Homo erectus, an extinct hominid species with cranial capacity around 900 ccs. This species shows upright posture and use of tools, representing a key stage in human evolution. Correct answer: Option 1.
1. Single Correct Answer MCQ:
Which of the following is the earliest known Homo erectus fossil?
1. Java Man
2. Cro-Magnon
3. Lucy
4. Neanderthal
Explanation: Java Man, discovered in 1891, is the earliest Homo erectus fossil known. It exhibits a cranial capacity of about 900 ccs and upright posture. Cro-Magnon represents Homo sapiens, Lucy is Australopithecus afarensis, and Neanderthals are a separate lineage. Answer: Option 1.
2. Single Correct Answer MCQ:
Cranial capacity of Homo erectus is approximately:
1. 600-700 ccs
2. 900-1100 ccs
3. 1200-1400 ccs
4. 400-500 ccs
Explanation: Homo erectus had a cranial capacity ranging from 900 to 1100 ccs, larger than earlier hominids like Australopithecus, but smaller than modern Homo sapiens. This reflects evolutionary brain enlargement. Answer: Option 2.
3. Single Correct Answer MCQ:
Which feature distinguishes Homo erectus fossils from Australopithecus?
1. Cranial capacity
2. Bipedal locomotion
3. Use of fire
4. All of the above
Explanation: Homo erectus is distinguished by larger cranial capacity (~900-1100 ccs), more advanced bipedalism, and use of fire, whereas Australopithecus had smaller brain and simpler tool use. Answer: Option 4.
4. Single Correct Answer MCQ:
The term “Java Man” refers to fossil found in:
1. Indonesia
2. Africa
3. Europe
4. India
Explanation: Java Man refers to Homo erectus fossil discovered in 1891 on the island of Java, Indonesia. It represents one of the earliest evidences of human evolution outside Africa. Answer: Option 1.
5. Single Correct Answer MCQ:
Which hominid shows upright posture with elongated legs?
1. Homo erectus
2. Neanderthal
3. Homo sapiens
4. Australopithecus
Explanation: Homo erectus exhibits upright posture and long legs adapted for efficient walking and running. Australopithecus was bipedal but shorter and more ape-like. Answer: Option 1.
6. Single Correct Answer MCQ:
Which Homo erectus skill indicates cultural evolution?
1. Fire use
2. Tool making
3. Hunting strategies
4. All of the above
Explanation: Homo erectus displayed cultural evolution through controlled fire, advanced tools, and organized hunting strategies. These innovations distinguish it from earlier hominids. Answer: Option 4.
7. Assertion-Reason MCQ:
Assertion (A): Homo erectus had a larger brain than Australopithecus.
Reason (R): Its cranial capacity ranged from 900-1100 ccs, aiding tool use and survival.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true
Explanation: Homo erectus had a cranial capacity of 900-1100 ccs, larger than Australopithecus (~400-500 ccs). This larger brain allowed complex tool use and adaptive behaviors. Both assertion and reason are correct, and reason explains assertion. Answer: Option 1.
8. Matching Type MCQ:
Column I Column II
(a) Java Man (i) Homo erectus
(b) Neanderthal (ii) Homo neanderthalensis
(c) Cro-Magnon (iii) Homo sapiens
(d) Lucy (iv) Australopithecus afarensis
1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
3. (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
4. (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
Explanation: Java Man is Homo erectus, Neanderthal is Homo neanderthalensis, Cro-Magnon is early Homo sapiens, and Lucy is Australopithecus afarensis. Correct matching: Option 1.
9. Fill in the blanks:
The fossil Homo erectus discovered in Java is commonly called ______.
1. Java Man
2. Neanderthal
3. Cro-Magnon
4. Lucy
Explanation: The fossil discovered in Java in 1891, representing Homo erectus with cranial capacity around 900 ccs, is referred to as Java Man. It is a key hominid in human evolution. Answer: Option 1.
10. Choose the correct statements MCQ:
Select correct statements about Homo erectus:
(a) Upright posture
(b) Cranial capacity 900-1100 ccs
(c) Extinct species
(d) Controlled fire use
1. (a), (b), (c), (d)
2. (a), (c)
3. (b), (d)
4. (a), (b), (d)
Explanation: Homo erectus had upright posture, cranial capacity 900-1100 ccs, is extinct, and exhibited controlled fire use. All listed features are correct. Answer: Option 1.
Topic: Mechanisms of Evolution
Subtopic: Adaptive Radiation
Keyword Definitions:
Evolution: Gradual change in the heritable traits of populations over generations.
Adaptive radiation: Diversification of species from a common ancestor into different ecological niches.
Saltation: Sudden large-scale mutation causing new forms.
Co-evolution: Reciprocal evolutionary changes in interacting species.
Natural selection: Process where organisms better adapted to their environment survive and reproduce.
Species: Group of organisms capable of interbreeding and producing fertile offspring.
Geographical area: Specific physical region where species evolution is observed.
Ecological niche: The role and position of a species in its environment.
Lead Question - 2020 (COVID Reexam)
The phenomenon of the evolution of different species in a given geographical area starting from a point and spreading to other habitats is called:
1. Saltation
2. Co-evolution
3. Natural selection
4. Adaptive radiation
Explanation: Adaptive radiation refers to the evolution of multiple species from a common ancestor into diverse ecological niches in a geographical area. It explains the origin of species adapted to different habitats starting from one location. Correct answer: Option 4.
1. Single Correct Answer MCQ:
Which example represents adaptive radiation?
1. Darwin’s finches
2. Convergent evolution of wings
3. Mutation in fruit flies
4. Predator-prey co-evolution
Explanation: Darwin’s finches evolved from a common ancestor into multiple species with different beak shapes to exploit various ecological niches in the Galápagos Islands. This is a classical example of adaptive radiation. Answer: Option 1.
2. Single Correct Answer MCQ:
Which process causes species to occupy different ecological niches?
1. Saltation
2. Adaptive radiation
3. Stabilizing selection
4. Genetic drift
Explanation: Adaptive radiation enables species to diversify from a common ancestor and adapt to multiple ecological niches in a geographical area. This differentiation helps reduce competition and allows survival in diverse habitats. Answer: Option 2.
3. Single Correct Answer MCQ:
Which factor primarily drives adaptive radiation?
1. Environmental diversity
2. Saltation
3. Co-evolution
4. Random mating
Explanation: Environmental diversity provides different selective pressures and habitats, leading to divergence of species from a common ancestor. Adaptive radiation is thus driven by ecological opportunities in new environments. Answer: Option 1.
4. Single Correct Answer MCQ:
Which is NOT an example of adaptive radiation?
1. Cichlid fishes in African lakes
2. Mammals after dinosaur extinction
3. Bats and birds developing wings
4. Darwin’s finches
Explanation: Bats and birds developing wings is convergent evolution, not adaptive radiation, as wings evolved independently in unrelated lineages. Other examples involve species diversifying from a common ancestor. Answer: Option 3.
5. Single Correct Answer MCQ:
Adaptive radiation often follows:
1. Mass extinction
2. Mutation accumulation
3. Stabilizing selection
4. Genetic drift
Explanation: Mass extinction events remove dominant species, creating ecological opportunities for surviving species to diversify into new niches. Adaptive radiation often follows such events. Answer: Option 1.
6. Single Correct Answer MCQ:
Which of the following promotes adaptive radiation?
1. Homogeneous environment
2. Ecological opportunity
3. Lack of resources
4. Random mutations only
Explanation: Ecological opportunity, such as unoccupied niches or new habitats, allows species to diversify from a common ancestor and adapt to multiple environments, driving adaptive radiation. Answer: Option 2.
7. Assertion-Reason MCQ:
Assertion (A): Adaptive radiation results in multiple species from a single ancestor.
Reason (R): Environmental heterogeneity and available niches drive species diversification.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true
Explanation: Adaptive radiation produces several species from a common ancestor when ecological opportunities exist. Environmental heterogeneity and availability of niches are key driving factors. Both assertion and reason are correct, and reason explains assertion. Answer: Option 1.
8. Matching Type MCQ:
Column I Column II
(a) Darwin’s finches (i) Adaptive radiation
(b) Wings in bats and birds (ii) Convergent evolution
(c) Marsupial diversification in Australia (iii) Adaptive radiation
(d) Cichlid fishes (iv) Adaptive radiation
1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
3. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
4. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
Explanation: Darwin’s finches, marsupials, and cichlid fishes represent adaptive radiation. Wings in bats and birds are due to convergent evolution. Correct matching: Option 1.
9. Fill in the blanks:
The process in which a single ancestor evolves into many species in different habitats is called ______.
1. Adaptive radiation
2. Saltation
3. Natural selection
4. Co-evolution
Explanation: Adaptive radiation occurs when a single ancestral species diversifies into multiple species to occupy different ecological niches. This process reduces competition and promotes species survival in various habitats. Answer: Option 1.
10. Choose the correct statements MCQ:
Select correct statements regarding adaptive radiation:
(a
Topic: Origin of Life
Subtopic: Timeline of Life on Earth
Keyword Definitions:
Earth formation: The process by which the planet Earth formed approximately 4.6 billion years ago.
Life: Organisms capable of growth, reproduction, and response to stimuli.
Origin of life: The point in Earth's history when living organisms first appeared.
Prokaryotes: Simple unicellular organisms without a nucleus, among the first life forms.
Eukaryotes: Complex cells with a nucleus, appearing later in evolution.
Fossil evidence: Physical remains or traces of ancient organisms preserved in rocks.
Geological time scale: Timeline dividing Earth's history into eons, eras, and periods.
Abiogenesis: The origin of life from non-living matter through chemical processes.
Lead Question - 2020 (COVID Reexam)
After about how many years of the formation of the earth, life appeared on this planet?
1. 500 billion years
2. 50 million years
3. 500 million years
4. 50 billion years
Explanation: Earth formed approximately 4.6 billion years ago. Fossil and geochemical evidence indicates life appeared around 500 million years after formation, starting with simple prokaryotic cells. Correct answer: Option 3.
1. Single Correct Answer MCQ:
Which were the first life forms on Earth?
1. Eukaryotes
2. Prokaryotes
3. Multicellular organisms
4. Dinosaurs
Explanation: The first life forms were simple prokaryotic organisms like bacteria, appearing roughly 500 million years after Earth formed. Eukaryotes and multicellular organisms evolved much later. Answer: Option 2.
2. Single Correct Answer MCQ:
Which process is believed to explain origin of life?
1. Photosynthesis
2. Abiogenesis
3. Natural selection
4. Transcription
Explanation: Abiogenesis describes the formation of life from non-living chemical compounds. This theory explains how simple molecules eventually formed first cells. Photosynthesis and natural selection occurred later. Answer: Option 2.
3. Single Correct Answer MCQ:
Fossil evidence indicates first life appeared in:
1. Rocks 3.5 billion years old
2. Rocks 4 billion years old
3. Rocks 500 million years old
4. Rocks 50 million years old
Explanation: Fossils of early prokaryotic life have been found in rocks approximately 3.5 billion years old, indicating life appeared roughly 500 million years after Earth’s formation. Answer: Option 1.
4. Single Correct Answer MCQ:
The first organisms lacked:
1. Nucleus
2. DNA
3. Cell membrane
4. Ribosomes
Explanation: First organisms were prokaryotes, which lack a true nucleus but contain DNA and ribosomes enclosed by a cell membrane. Their simple structure allowed rapid adaptation in early Earth environments. Answer: Option 1.
5. Single Correct Answer MCQ:
Photosynthetic organisms first appeared approximately:
1. 3.5 billion years ago
2. 2.5 billion years ago
3. 500 million years ago
4. 50 million years ago
Explanation: Photosynthetic bacteria appeared around 2.5 billion years ago, producing oxygen and initiating the Great Oxidation Event. Early prokaryotic life existed long before photosynthesis evolved. Answer: Option 2.
6. Single Correct Answer MCQ:
Which era marks first appearance of complex multicellular life?
1. Precambrian
2. Paleozoic
3. Mesozoic
4. Cenozoic
Explanation: Complex multicellular organisms first appeared during the late Precambrian (Ediacaran period) after billions of years of unicellular life. Earlier life forms were mainly single-celled. Answer: Option 1.
7. Assertion-Reason MCQ:
Assertion (A): Life appeared about 500 million years after Earth formed.
Reason (R): Fossil and geochemical evidence indicate first prokaryotic cells appeared in that period.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true
Explanation: Fossil evidence shows prokaryotic life appeared roughly 500 million years after Earth's formation. This timing aligns with geological data and supports the assertion. Both assertion and reason are correct, and reason explains assertion. Answer: Option 1.
8. Matching Type MCQ:
Column I Column II
(a) First life forms (i) Prokaryotes
(b) First photosynthetic organisms (ii) Cyanobacteria
(c) First multicellular life (iii) Ediacaran organisms
(d) Great Oxidation Event (iv) Oxygen accumulation
1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
3. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
4. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
Explanation: First life – prokaryotes; first photosynthetic – cyanobacteria; first multicellular – Ediacaran organisms; Great Oxidation – oxygen accumulation. Correct match: Option 1.
9. Fill in the blanks:
The first organisms on Earth were ______, lacking a nucleus.
1. Prokaryotes
2. Eukaryotes
3. Algae
4. Fungi
Explanation: Prokaryotic organisms were the earliest life forms, simple cells without a nucleus, appearing roughly 500 million years after Earth’s formation. Eukaryotes evolved later. Answer: Option 1.
10. Choose the correct statements MCQ:
Select correct statements regarding origin of life:
(a) Life appeared about 500 million years after Earth formed
(b) First life forms were prokaryotic
(c) Photosynthetic bacteria appeared later
(d) Complex multicellular organisms appeared immediately
Explanation: Life appeared about 500 million years after Earth formed, initially as prokaryotes. Photosynthetic bacteria evolved later, producing oxygen. Complex multicellular organisms appeared much later, not immediately. Correct statements: (a), (b), (c). Answer: Option (a, b, c).
Subtopic: Embryology and Evolution
Keyword Definitions:
Embryology: Study of development of embryos from fertilization to birth/hatching.
Evolution: Gradual change in species over generations resulting in diversity of life.
Ernst Haeckel: German biologist who proposed that embryonic development reflects evolutionary history.
Karl Ernst von Baer: Scientist who formulated laws of embryology, emphasizing differences between early and later developmental stages.
Darwin: Proposed natural selection as mechanism of evolution.
Homologous structures: Anatomical features derived from common ancestors.
Comparative embryology: Comparison of embryos of different species to infer evolutionary relationships.
Ontogeny: Developmental history of an individual organism from fertilization to adult form.
Lead Question - 2020 (COVID Reexam)
Embryological support for evolution was proposed by
1. Ernst Heckel
2. Karl Ernst von Baer
3. Charles Darwin
4. Alfred Wallace
Explanation: Ernst Haeckel proposed that embryological development mirrors evolutionary history, suggesting that embryos of different species pass through similar stages reflecting common ancestry. Karl Ernst von Baer critiqued Haeckel’s idea, emphasizing developmental divergence. Correct answer: Option 1.
1. Single Correct Answer MCQ:
Which scientist formulated laws of embryology?
1. Ernst Haeckel
2. Karl Ernst von Baer
3. Charles Darwin
4. Alfred Wallace
Explanation: Karl Ernst von Baer formulated embryological laws, highlighting that general features appear earlier in embryos and specific features later. His observations supported comparative embryology and evolution indirectly. Correct answer: Option 2.
2. Single Correct Answer MCQ:
Which evidence supports common ancestry among species?
1. Comparative embryology
2. Analogous structures
3. Biogeography
4. Mendelian genetics
Explanation: Comparative embryology studies embryos of different species and reveals similarities during early development, supporting common ancestry. Analogous structures show functional similarity without common origin. Answer: Option 1.
3. Single Correct Answer MCQ:
Haeckel’s hypothesis suggested:
1. Ontogeny recapitulates phylogeny
2. Natural selection drives development
3. Adaptation occurs in adults
4. DNA determines evolution
Explanation: Haeckel proposed that embryonic development (ontogeny) mirrors evolutionary history (phylogeny), implying that embryos pass through stages resembling ancestral forms. This was the basis of embryological support for evolution. Correct answer: Option 1.
4. Single Correct Answer MCQ:
Which stage of development shows most similarity among vertebrates?
1. Adult
2. Larval
3. Embryonic
4. Juvenile
Explanation: Early embryonic stages of vertebrates display remarkable similarity, including pharyngeal arches and tail structure. These similarities support evolutionary relationships. Answer: Option 3.
5. Single Correct Answer MCQ:
Which observation challenged Haeckel’s recapitulation theory?
1. Von Baer’s laws
2. Darwin’s natural selection
3. Mendelian inheritance
4. Wallace’s biogeography
Explanation: Von Baer observed that general features appear early and specific features develop later, contradicting Haeckel’s idea that embryos repeat adult stages of ancestors. This refined the understanding of embryology and evolution. Answer: Option 1.
6. Single Correct Answer MCQ:
Embryological evidence indicates:
1. Species evolve independently
2. Early development is conserved
3. Adults resemble ancestors
4. Evolution occurs rapidly
Explanation: Embryological evidence shows that early development is highly conserved among related species, reflecting common ancestry. Later stages diverge, producing species-specific traits. This supports evolutionary relationships. Answer: Option 2.
7. Assertion-Reason MCQ:
Assertion (A): Haeckel proposed that embryos reflect evolutionary history.
Reason (R): Similarities in early development indicate common ancestry.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true
Explanation: Haeckel proposed that ontogeny recapitulates phylogeny, and similarities in early embryonic stages among species support this idea. Both assertion and reason are correct, and reason explains assertion. Answer: Option 1.
8. Matching Type MCQ:
Column I Column II
(a) Haeckel (i) Recapitulation theory
(b) von Baer (ii) Laws of embryology
(c) Darwin (iii) Natural selection
(d) Wallace (iv) Biogeography
1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
3. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
4. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
Explanation: Haeckel – recapitulation theory; von Baer – laws of embryology; Darwin – natural selection; Wallace – biogeography. Correct answer: Option 1.
9. Fill in the blanks:
Early embryos of different vertebrates show similar ______, supporting evolution.
1. Structures
2. Genes
3. Proteins
4. Hormones
Explanation: Early embryonic structures, like pharyngeal arches and tails, are similar among vertebrates, reflecting evolutionary conservation and common ancestry. These morphological similarities support evolutionary theory. Answer: Option 1.
10. Choose the correct statements MCQ:
Select correct statements about embryological support for evolution:
(a) Early embryos of different species are similar
(b) Haeckel proposed ontogeny recapitulates phylogeny
(c) Von Baer emphasized divergence during development
(d) Embryology contradicts evolution
Keyword Definitions:
S.L. Miller – Stanley Lloyd Miller, an American chemist who conducted experiments simulating early Earth conditions to study the origin of life.
Amino acids – Organic compounds containing amino and carboxyl groups; building blocks of proteins.
CH4 – Methane, a simple hydrocarbon used as a reducing gas in the Miller-Urey experiment.
NH3 – Ammonia, a nitrogenous compound, used in the Miller-Urey experiment to simulate early Earth's atmosphere.
H2 – Hydrogen gas, a reducing agent used in the experiment.
Water vapour – Gas form of water, simulating Earth's primitive ocean evaporation.
Closed flask – Laboratory apparatus allowing gases and water to circulate without external contamination.
Primordial soup – Hypothetical mixture of organic molecules in early Earth's oceans, leading to the origin of life.
Temperature – Heat condition applied in the experiment to mimic early Earth energy sources.
Prebiotic chemistry – Study of chemical processes that led to formation of life before biological organisms existed.
Experimental simulation – Laboratory method to recreate natural conditions for scientific study.
Lead Question - 2020
From his experiments, S.L. Miller produced amino acids by mixing the following in a closed flask:
(1) CH4, H2, NH3 and water vapour at 600°C
(2) CH3, H2, NH3 and water vapour at 600°C
(3) CH4, H2, NH3 and water vapour at 800°C
(4) CH3, H2, NH4 and water vapour at 800°C
Explanation: S.L. Miller simulated early Earth conditions using methane (CH4), hydrogen (H2), ammonia (NH3), and water vapour in a closed flask with electrical sparks at 600°C, producing amino acids. This experiment confirmed the abiotic synthesis of organic molecules. Correct answer is (1).
1. Single Correct Answer: Which gas was NOT used in Miller's original experiment?
(1) CH4
(2) NH3
(3) CO2
(4) H2
Explanation: Miller's experiment included CH4, NH3, H2, and water vapour. CO2 was not part of the original reducing mixture. Correct answer is (3) CO2.
2. Single Correct Answer: The purpose of the electric spark in the Miller experiment was:
(1) To oxidize gases
(2) To simulate lightning energy
(3) To cool the mixture
(4) To catalyze proteins
Explanation: The electric spark provided energy similar to lightning in early Earth’s atmosphere, promoting chemical reactions between gases to form amino acids. Correct answer is (2) To simulate lightning energy.
3. Single Correct Answer: Which type of molecules were primarily produced in the Miller experiment?
(1) Polysaccharides
(2) Amino acids
(3) Lipids
(4) Nucleic acids
Explanation: The Miller-Urey experiment produced amino acids, the building blocks of proteins, demonstrating prebiotic synthesis under simulated early Earth conditions. Correct answer is (2) Amino acids.
4. Assertion-Reason:
Assertion (A): Miller’s experiment supports abiotic synthesis of life molecules.
Reason (R): He used a closed system containing CH4, NH3, H2, and water vapour with electrical sparks.
(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: The experiment demonstrated amino acid formation without living organisms, supporting abiotic synthesis. The use of CH4, NH3, H2, and water vapour with sparks provided conditions for chemical reactions. Both assertion and reason are true, and R correctly explains A. Correct answer is (1).
5. Single Correct Answer: What is the significance of water vapour in the experiment?
(1) Acts as a reducing agent
(2) Simulates early ocean evaporation
(3) Provides amino groups
(4) Produces electric sparks
Explanation: Water vapour simulates early Earth's oceans and evaporative cycles, facilitating chemical reactions in the gaseous phase. It is essential for prebiotic chemical synthesis. Correct answer is (2) Simulates early ocean evaporation.
6. Single Correct Answer: The Miller experiment primarily models which concept?
(1) Genetic inheritance
(2) Abiotic synthesis of organic molecules
(3) Photosynthesis
(4) Protein folding
Explanation: Miller-Urey experiment models abiotic synthesis of organic molecules from simple gases under primitive Earth conditions, supporting hypotheses of the origin of life. Correct answer is (2) Abiotic synthesis of organic molecules.
7. Matching Type: Match component with function:
a. CH4 – i. Nitrogen source
b. NH3 – ii. Reducing gas
c. H2 – iii. Simulates early Earth's ocean
d. Water vapour – iv. Reducing agent
Options:
(1) a-iv, b-i, c-ii, d-iii
(2) a-ii, b-i, c-iv, d-iii
(3) a-iii, b-ii, c-i, d-iv
(4) a-i, b-iv, c-ii, d-iii
Explanation: Methane (CH4) and hydrogen (H2) act as reducing gases, NH3 provides nitrogen source, and water vapour simulates early ocean. Correct matching is a-ii, b-i, c-iv, d-iii. Correct answer is (2).
8. Fill in the blank: The temperature used in Miller’s experiment was approximately ______.
(1) 25°C
(2) 100°C
(3) 600°C
(4) 800°C
Explanation: Miller maintained high temperatures (~600°C in portions simulating lightning and gases) to provide energy for chemical reactions, allowing amino acid formation. Correct answer is (3) 600°C.
9. Single Correct Answer: Which of these was a key outcome of Miller’s experiment?
(1) Proteins were formed
(2) Amino acids were synthesized
(3) Nucleic acids were generated
(4) Lipids formed spontaneously
Explanation: The Miller experiment successfully produced amino acids under simulated prebiotic conditions, confirming that life's building blocks could arise abiotically. Correct answer is (2) Amino acids were synthesized.
10. Choose the correct statements:
(a) Miller’s experiment simulated early Earth atmosphere
(b) It produced amino acids from inorganic gases
(c) It proved life originated on Earth
(d) Used electrical sparks to simulate lightning
(1) a, b, d
Subtopic: Convergent and Divergent Evolution
Keyword Definitions:
Convergent evolution: Independent evolution of similar traits in unrelated species due to similar environments.
Divergent evolution: Evolution of dissimilar traits from a common ancestor.
Adaptive radiation: Evolution of many species from a common ancestor to adapt to different niches.
Homologous organs: Same origin, different function.
Analogous organs: Different origin, same function.
Natural selection: Process where better adapted organisms survive and reproduce.
Lead Question - 2020
Flippers of Penguins and Dolphins are examples of:
(1) Industrial melanism
(2) Natural selection
(3) Adaptive radiation
(4) Convergent evolution
Explanation: Flippers of penguins (birds) and dolphins (mammals) have different origins but perform the same function of swimming. This is an example of analogous organs, which arise due to convergent evolution. Hence, the correct answer is option (4).
Guessed Questions:
1) Wings of bats and insects are examples of:
(1) Homologous organs
(2) Analogous organs
(3) Vestigial organs
(4) Atavistic organs
Explanation: Wings of bats (mammals) and insects have different origins but serve the same function of flying. This makes them analogous organs, arising due to convergent evolution. Hence, the correct answer is option (2).
2) Forelimbs of humans, wings of bats, and flippers of whales represent:
(1) Analogous organs
(2) Homologous organs
(3) Vestigial organs
(4) Rudimentary organs
Explanation: These structures have the same embryonic origin but perform different functions such as grasping, flying, and swimming. Such structures are homologous organs and represent divergent evolution. Hence, the correct answer is option (2).
3) Assertion (A): Analogous organs indicate convergent evolution.
Reason (R): They have different origins but perform similar functions.
(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: Analogous organs arise when unrelated organisms adapt to similar environmental pressures, leading to convergent evolution. Both A and R are true, and R correctly explains A. Hence, the correct answer is option (1).
4) Which of the following is an example of adaptive radiation?
(1) Darwin’s finches
(2) Flippers of dolphins
(3) Industrial melanism
(4) Peppered moths
Explanation: Adaptive radiation refers to the evolution of multiple species from a common ancestor to occupy different ecological niches. Darwin’s finches in the Galapagos Islands are the classic example. Hence, the correct answer is option (1).
5) Match the examples with the correct evolutionary pattern:
(a) Darwin’s finches (i) Convergent evolution
(b) Flippers of dolphin and penguin (ii) Adaptive radiation
(c) Wings of bat and forelimb of man (iii) Divergent evolution
(1) a-(ii), b-(i), c-(iii)
(2) a-(iii), b-(ii), c-(i)
(3) a-(i), b-(ii), c-(iii)
(4) a-(ii), b-(iii), c-(i)
Explanation: Darwin’s finches show adaptive radiation, flippers of dolphins and penguins show convergent evolution, and wings of bats with human forelimbs show divergent evolution. Correct answer is option (1).
6) Fill in the blank: Organs with similar function but different origin are called ______.
(1) Homologous
(2) Analogous
(3) Rudimentary
(4) Vestigial
Explanation: Organs that serve similar functions but evolved independently with different origins are called analogous organs. They are evidence of convergent evolution. Hence, the correct answer is option (2).
7) Which of the following statements are correct?
(i) Homologous organs arise due to divergent evolution
(ii) Analogous organs arise due to convergent evolution
(iii) Adaptive radiation leads to many species from one ancestor
(1) i and ii only
(2) ii and iii only
(3) i and iii only
(4) i, ii and iii
Explanation: Homologous organs indicate divergent evolution, analogous organs indicate convergent evolution, and adaptive radiation gives rise to multiple species from a single ancestor. Hence, all three statements are correct. The correct answer is option (4).
8) Which of the following is a vestigial organ in humans?
(1) Appendix
(2) Forelimb
(3) Kidney
(4) Heart
Explanation: The appendix in humans is considered a vestigial organ as it has lost its original function of cellulose digestion, though it may play minor immune roles. Hence, the correct answer is option (1).
9) Industrial melanism observed in peppered moths is an example of:
(1) Mutation
(2) Genetic drift
(3) Natural selection
(4) Convergent evolution
Explanation: Industrial melanism demonstrates natural selection, where darker moths survived better in polluted areas while lighter ones perished. It shows the role of environment in selecting advantageous traits. Hence, the correct answer is option (3).
10) Which one of the following pairs is correctly matched?
(1) Human appendix – Adaptive radiation
(2) Flippers of whale – Homologous organ
(3) Wings of insects and bats – Homologous organs
(4) Forelimb of man and flipper of penguin – Analogous organs
Explanation: Flippers of whales and human forelimbs are homologous organs since they have the same embryonic origin but different functions. Hence, the correct answer is option (2).
Subtopic: Embryological Evidence
Evolution: The gradual change in the heritable characteristics of populations over successive generations.
Embryology: The study of the development of embryos from fertilization to birth.
Charles Darwin: Proposed the theory of natural selection as the mechanism of evolution.
Oparin: Proposed the origin of life through chemical evolution in primordial conditions.
Karl Ernst von Baer: Formulated the laws of embryology, emphasizing that general features appear before specific features, challenging recapitulation theory.
Alfred Wallace: Co-proposed natural selection along with Darwin.
Recapitulation Theory: The idea that embryonic development repeats evolutionary history, also called "ontogeny recapitulates phylogeny."
Embryological Evidence: Developmental stages that can indicate evolutionary relationships among organisms.
Homologous Structures: Anatomical features with similar structure due to common ancestry.
Phylogeny: Evolutionary history of a species or group of organisms.
Support/Disproof: Embryological observations can support or disapprove evolutionary hypotheses.
Lead Question (2020): Embryological support for evolution was disapproved by:
Options:
1. Charles Darwin
2. Oparin
3. Karl Ernst von Baer
4. Alfred Wallace
Explanation: Correct answer is 3. Karl Ernst von Baer disapproved embryological support for evolution by showing that general features of embryos appear before specialized features, contradicting Haeckel's recapitulation theory. Darwin and Wallace supported evolutionary ideas, while Oparin focused on chemical origin of life, not embryological development.
1. Single Correct Answer MCQ:
Who proposed that ontogeny does not recapitulate phylogeny?
Options:
a. Karl Ernst von Baer
b. Charles Darwin
c. Ernst Haeckel
d. Alfred Wallace
Explanation: Correct answer is a. Karl Ernst von Baer established that embryonic development progresses from general to specific features, disproving Haeckel’s recapitulation theory which claimed embryos repeat evolutionary history.
2. Single Correct Answer MCQ:
Which scientist co-proposed natural selection with Darwin?
Options:
a. Karl Ernst von Baer
b. Alfred Wallace
c. Oparin
d. Lamarck
Explanation: Correct answer is b. Alfred Wallace independently formulated the concept of natural selection and co-published findings with Darwin, contributing to evolutionary theory, unlike von Baer who critiqued embryological evidence.
3. Single Correct Answer MCQ:
Chemical origin of life was proposed by:
Options:
a. Charles Darwin
b. Alfred Wallace
c. Oparin
d. Karl Ernst von Baer
Explanation: Correct answer is c. Oparin suggested life originated through chemical evolution in the primitive Earth's environment. His work focused on prebiotic chemistry, not embryological development or recapitulation theory.
4. Single Correct Answer MCQ:
Who supported embryological evidence for evolution?
Options:
a. Karl Ernst von Baer
b. Charles Darwin
c. Oparin
d. None of the above
Explanation: Correct answer is b. Darwin used embryological similarities among species as supporting evidence for common ancestry, in contrast to von Baer who highlighted developmental differences.
5. Single Correct Answer MCQ:
Haeckel’s recapitulation theory states:
Options:
a. Embryos of higher organisms resemble ancestors
b. Evolution occurs only in adults
c. Embryos never resemble ancestors
d. Life originated chemically
Explanation: Correct answer is a. Haeckel’s theory claimed embryonic development repeats evolutionary history, but Karl Ernst von Baer disproved this by showing early embryos share general features, not ancestral traits.
6. Single Correct Answer MCQ:
Which of the following disproved recapitulation theory?
Options:
a. Darwin
b. Oparin
c. Karl Ernst von Baer
d. Wallace
Explanation: Correct answer is c. Karl Ernst von Baer’s observations of embryonic development showed that embryos of higher animals do not pass through adult stages of lower animals, refuting Haeckel’s recapitulation theory.
7. Assertion-Reason MCQ:
Assertion (A): Embryological evidence is used to support evolution.
Reason (R): Similar early development in related species indicates common ancestry.
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: Correct answer is a. Similarities in early embryonic stages among related species provide evidence of common ancestry, supporting evolutionary theory, making both assertion and reason true and the reason explanatory.
8. Matching Type MCQ:
Match the scientist with their contribution:
(a) Darwin - (i) Recapitulation theory
(b) von Baer - (ii) Laws of embryology
(c) Oparin - (iii) Chemical origin of life
(d) Wallace - (iv) Natural selection
Options:
1. a-iv, b-ii, c-iii, d-iv
2. a-ii, b-iii, c-i, d-iv
3. a-iv, b-i, c-ii, d-iii
4. a-iii, b-iv, c-ii, d-i
Explanation: Correct answer is 1. Darwin and Wallace formulated natural selection, von Baer established embryology laws, and Oparin proposed chemical origin of life.
9. Fill in the Blanks MCQ:
Embryological support for evolution was disapproved by ______.
Options:
a. Charles Darwin
b. Oparin
c. Karl Ernst von Baer
d. Alfred Wallace
Explanation: Correct answer is c. Karl Ernst von Baer disapproved embryological evidence supporting evolution by demonstrating that embryos develop from general to specific features, contradicting the recapitulation theory.
10. Choose the correct statements MCQ:
Select the correct statements:
i. Darwin used embryology to support evolution
ii. von Baer opposed recapitulation theory
iii. Oparin focused on chemical evolution
iv. Wallace disproved embryological support Options:
1. i, ii, iii
2. i, ii, iv
3. ii, iii, iv
4. i, iii, iv
Explanation: Correct answer is 1. Darwin used embryological
Topic: Adaptive Evolution and Human Impact
Subtopic: Anthropogenic Influence on Organism Evolution
Anthropogenic Action: Environmental changes caused directly or indirectly by human activities.
Adaptive Evolution: Evolutionary changes in populations that increase fitness in a changing environment.
Drug Resistance: Ability of organisms to survive exposure to drugs that would normally be lethal.
Herbicide Resistance: Evolutionary adaptation of plants to survive herbicide treatments.
Domestication: Human-directed breeding and selection of animals or plants for specific traits.
Darwin’s Finches: Group of birds in Galapagos Islands showing natural selection through beak variation.
Selection Pressure: Environmental factor that influences which individuals survive and reproduce.
Genetic Variation: Differences in DNA sequences among individuals of a population.
Speciation: Formation of new and distinct species through evolutionary processes.
Human Impact: Any effect humans have on ecosystems and species evolution.
Environmental Change: Alteration of natural habitats that drives evolutionary adaptations.
Lead Question (2020): Which of the following refer to correct example(s) of organisms which have evolved due to changes in environment brought about by anthropogenic action?
Options:
1. (b), (c) and (d)
2. Only (d)
3. Only (a)
4. (a) and (c)
Explanation: Correct answer is 1. Herbicide-resistant weeds, drug-resistant eukaryotes, and man-made breeds are examples of evolution driven by human activity, showing adaptation to anthropogenic pressures. Darwin’s finches evolved naturally, not due to human influence, so they are excluded.
1. Single Correct Answer MCQ:
Which organism demonstrates evolution due to human-imposed selection?
Options:
a. Drug-resistant malaria parasites
b. Galapagos finches
c. Wild oak trees
d. Antarctic penguins
Explanation: Correct answer is a. Drug-resistant malaria parasites evolved due to exposure to anti-malarial drugs, an anthropogenic pressure, illustrating adaptive evolution driven by human activity.
2. Single Correct Answer MCQ:
Herbicide-resistant weeds evolve primarily due to:
Options:
a. Human use of herbicides
b. Natural climate change
c. Predator population changes
d. Random migration
Explanation: Correct answer is a. Continuous use of herbicides creates selection pressure favoring individuals with resistance genes, leading to the evolution of herbicide-resistant weed populations.
3. Single Correct Answer MCQ:
Man-created breeds of dogs are an example of:
Options:
a. Artificial selection
b. Natural selection
c. Genetic drift
d. Speciation without human influence
Explanation: Correct answer is a. Selective breeding by humans chooses specific traits, producing artificial selection that leads to diverse dog breeds over generations.
4. Single Correct Answer MCQ:
Which is a direct result of anthropogenic environmental change?
Options:
a. Drug-resistant pathogens
b. Darwin’s finches
c. Natural river meanders
d. Volcanic island flora
Explanation: Correct answer is a. Drug-resistant pathogens evolve in response to human use of drugs, demonstrating evolution caused by human-imposed selection pressures.
5. Single Correct Answer MCQ:
Which of the following is NOT influenced by human activity?
Options:
a. Galapagos finches
b. Herbicide-resistant weeds
c. Man-made dog breeds
d. Drug-resistant bacteria
Explanation: Correct answer is a. Galapagos finches evolved naturally in response to environmental factors like food availability, without direct human intervention.
6. Single Correct Answer MCQ:
Which factor is responsible for the evolution of drug-resistant eukaryotes?
Options:
a. Human use of medication
b. Climate change
c. Volcanic activity
d. Natural migration
Explanation: Correct answer is a. Intensive use of drugs exerts selection pressure favoring resistant eukaryotes, demonstrating evolution driven by anthropogenic factors.
7. Assertion-Reason MCQ:
Assertion (A): Herbicide-resistant weeds are examples of anthropogenic evolution.
Reason (R): Natural selection operates only in absence of humans.
Options:
a. A is true, R is true but R does not explain A
b. Both A and R are true, R explains A
c. A is true, R is false
d. A is false, R is true
Explanation: Correct answer is c. Herbicide-resistant weeds evolved due to human-applied selection pressure. Natural selection does operate in the presence of humans, so the reason is false.
8. Matching Type MCQ:
Match organism with type of anthropogenic evolution:
(a) Herbicide-resistant weeds - (i) Artificial selection
(b) Man-made dog breeds - (ii) Artificial selection
(c) Drug-resistant pathogens - (iii) Natural selection under human pressure
Options:
1. a-iii, b-ii, c-i
2. a-i, b-ii, c-iii
3. a-ii, b-iii, c-i
4. a-iii, b-i, c-ii
Explanation: Correct answer is 2. Herbicide-resistant weeds evolve under natural selection with human-applied pressure, dog breeds arise by artificial selection, and drug-resistant pathogens evolve under human-imposed selective pressure.
9. Fill in the Blanks MCQ:
______ is an example of evolution driven by human-mediated environmental change.
Options:
a. Drug-resistant bacteria
b. Darwin’s finches
c. Wild oak trees
d. Polar bears
Explanation: Correct answer is a. Drug-resistant bacteria evolve due to the use of antibiotics, an anthropogenic environmental change driving selection for resistant strains.
10. Choose the correct statements MCQ:
Select correct examples of anthropogenic evolution:
i. Herbicide-resistant weeds
ii. Darwin’s finches
iii. Man-made dog breeds
iv. Drug-resistant eukaryotes
Options:
a. i, iii, iv
b. ii, iii
c. i, ii
d. ii, iv
Explanation: Correct answer is a. Herbicide-resistant weeds, man-made dog breeds, and drug-resistant eukaryotes evolved due to human activities, whereas Darwin’s finches evolved naturally without anthropogenic influence.
Topic: Evolution of Hominids
Subtopic: Brain Size and Cognitive Development
Homo habilis: Early hominid species known for tool use, lived 2.4–1.4 million years ago.
Homo erectus: Extinct hominid species with upright posture and larger brain, lived 1.9 million–110,000 years ago.
Homo neanderthalensis: Neanderthals, robust hominids in Europe and Western Asia, existed 400,000–40,000 years ago.
Homo sapiens: Modern humans with advanced cognitive abilities and brain size around 1400 cc.
Brain Size: Volume of cranial cavity, correlated with cognitive development.
Cranial Capacity: Measurement in cubic centimeters (cc) indicating brain volume.
Tool Use: Ability to make and use tools, characteristic of early Homo species.
Upright Posture: Bipedal locomotion, an evolutionary trait enabling manual dexterity.
Neanderthals: Hominids with robust skeletons and large brains adapted to cold climates.
Cognitive Evolution: Development of intelligence, problem-solving, and social behavior in humans.
Extinct Species: Species no longer existing, studied through fossils and skeletal remains.
Lead Question (2019): Match the hominids with their correct brain size:
(a) Homo habilis (i) 900 cc
(b) Homo neanderthalensis (ii) 1350 cc
(c) Homo erectus (iii) 650-800 cc
(d) Homo sapiens (iv) 1400 cc
Options:
1. a - iii, b - i, c - iv, d - ii
2. a - iii, b - ii, c - i, d - iv
3. a - iii, b - iv, c - i, d - ii
4. a - iv, b - iii, c - i, d - ii
Explanation: Correct answer is 2. Homo habilis had a brain size of 650–800 cc, Homo neanderthalensis around 1350 cc, Homo erectus about 900 cc, and Homo sapiens approximately 1400 cc. This reflects gradual increase in cranial capacity and cognitive abilities in hominid evolution over millions of years.
1. Single Correct Answer MCQ:
Which hominid is known for using the first stone tools?
Options:
a. Homo erectus
b. Homo sapiens
c. Homo habilis
d. Homo neanderthalensis
Explanation: Correct answer is c. Homo habilis is recognized as the "handy man" for making and using simple stone tools. Homo erectus and Neanderthals also used tools, but Homo sapiens developed more advanced and complex tools later. Tool use reflects cognitive evolution and adaptation to environment.
2. Single Correct Answer MCQ:
Which hominid species had the largest brain volume?
Options:
a. Homo habilis
b. Homo erectus
c. Homo neanderthalensis
d. Homo sapiens
Explanation: Correct answer is d. Homo sapiens have the largest brain volume of about 1400 cc, reflecting advanced cognitive abilities including language, problem-solving, and abstract thought. Neanderthals had slightly smaller brains, while Homo erectus and Homo habilis had significantly smaller cranial capacities.
3. Single Correct Answer MCQ:
Neanderthals were primarily adapted to:
Options:
a. Tropical forests
b. Cold climates
c. Deserts
d. Grasslands
Explanation: Correct answer is b. Homo neanderthalensis had robust skeletons, large nasal cavities, and powerful musculature suited for cold Ice Age environments in Europe and Western Asia. Their adaptations ensured survival, hunting efficiency, and thermoregulation in harsh climates.
4. Single Correct Answer MCQ:
Which species displayed upright bipedal posture and long-distance walking?
Options:
a. Homo habilis
b. Homo erectus
c. Homo sapiens
d. Homo neanderthalensis
Explanation: Correct answer is b. Homo erectus had an upright posture and long limbs, enabling efficient bipedal locomotion and endurance walking. Homo habilis was less adapted for long-distance walking, Neanderthals were robust but shorter-limbed, and Homo sapiens exhibit advanced locomotion and dexterity.
5. Single Correct Answer MCQ:
Which hominid species represents modern humans?
Options:
a. Homo habilis
b. Homo sapiens
c. Homo erectus
d. Homo neanderthalensis
Explanation: Correct answer is b. Homo sapiens are modern humans with advanced cognitive skills, symbolic thought, and language. They have the largest cranial capacity (~1400 cc) among hominids. Other species like Homo habilis, erectus, and neanderthalensis are extinct and represent evolutionary stages.
6. Single Correct Answer MCQ:
Which hominid had a brain size of approximately 900 cc?
Options:
a. Homo habilis
b. Homo erectus
c. Homo sapiens
d. Homo neanderthalensis
Explanation: Correct answer is b. Homo erectus had a brain size around 900 cc, larger than Homo habilis but smaller than Neanderthals and modern humans. This size reflects improved tool-making, social behavior, and problem-solving compared to earlier hominids.
7. Assertion-Reason MCQ:
Assertion (A): Homo habilis had smaller brain than Homo sapiens.
Reason (R): Cognitive abilities of Homo habilis were less developed.
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: Correct answer is a. Homo habilis had brain size 650–800 cc compared to ~1400 cc in Homo sapiens. Smaller brain size correlates with less developed cognitive functions. Thus, both assertion and reason are true, and reason correctly explains the assertion.
8. Matching Type MCQ:
Match hominids with brain sizes:
Column-I Column-II
(a) Homo habilis (i) 900 cc
(b) Homo neanderthalensis (ii) 1350 cc
(c) Homo erectus (iii) 650-800 cc
(d) Homo sapiens (iv) 1400 cc
Options:
1. a-iii, b-ii, c-i, d-iv
2. a-i, b-iii, c-ii, d-iv
3. a-iii, b-iv, c-i, d-ii
4. a-iv, b-i, c-iii, d-ii
Explanation: Correct answer is 1. Homo habilis (650-800 cc), Homo neanderthalensis (~1350 cc), Homo erectus (~900 cc), and Homo sapiens (~1400 cc). Brain size progression shows increasing cognitive ability and complex behaviors through hominid evolution.
9. Fill in the Blanks / Completion MCQ:
The modern human species is ________ with brain size around 1400 cc.
Options:
a. Homo habilis
b. Homo erectus
c. Homo sapiens
d. Homo neanderthalensis
Explanation: Correct answer is c. Homo sapiens are modern humans with cranial capacity ~1400 cc, reflecting advanced reasoning, problem-solving, and language abilities. Earlier hominids like habil
Topic: Natural Selection
Subtopic: Types of Selection
Keyword Definitions:
• Directional Selection: Natural selection that favors one extreme phenotype over the other, shifting the population mean.
• Stabilizing Selection: Selection that favors the intermediate phenotype and reduces extremes in the population.
• Disruptive Selection: Selection that favors extreme phenotypes at both ends, splitting the population into two groups.
• Cyclical Selection: Periodic alternation in selection pressures causing population traits to fluctuate over time.
• Phenotype: Observable traits or characteristics of an organism.
• Newborn Weight: The mass of a baby at birth.
Lead Question (2019):
In a species, the weight of newborn ranges from 2 to 5 kg. 97% of the newborns with an average weight between 3 to 3.3 kg survive whereas 99% of the infants born with weights from 2 to 2.5 kg or 4.5 to 5 kg die. Which type of selection process is taking place:
(1) Directional Selection
(2) Stabilizing Selection
(3) Disruptive Selection
(4) Cyclical Selection
Explanation: Correct answer is (2). This is an example of stabilizing selection where the intermediate birth weight has the highest survival, while extreme low and high weights are selected against. Such selection reduces variation and favors the average phenotype in the population.
1) Single Correct Answer MCQ:
Which selection reduces extremes and favors intermediate traits?
(1) Directional Selection
(2) Stabilizing Selection
(3) Disruptive Selection
(4) Cyclical Selection
Explanation: Correct answer is (2). Stabilizing selection reduces variation by favoring the average phenotype and eliminating individuals at both extremes of the trait distribution.
2) Single Correct Answer MCQ:
Which type of selection shifts the population toward one extreme?
(1) Directional Selection
(2) Stabilizing Selection
(3) Disruptive Selection
(4) Cyclical Selection
Explanation: Correct answer is (1). Directional selection favors one extreme phenotype, causing a shift in the population mean toward that extreme over generations.
3) Single Correct Answer MCQ:
Disruptive selection favors:
(1) Intermediate traits
(2) Both extreme traits
(3) Only one extreme trait
(4) Random traits
Explanation: Correct answer is (2). Disruptive selection selects for individuals at both extremes while the intermediate phenotypes are selected against, often leading to population divergence.
4) Single Correct Answer MCQ:
Cyclical selection causes:
(1) Constant phenotype
(2) Fluctuation of traits over time
(3) Immediate extinction
(4) Stabilization of extremes
Explanation: Correct answer is (2). Cyclical selection involves periodic changes in selection pressures that cause population traits to fluctuate in a regular pattern over time.
5) Single Correct Answer MCQ:
Which of the following is an example of stabilizing selection in humans?
(1) Birth weight
(2) Height increase over generations
(3) Sickle cell trait in malaria regions
(4) Lactose tolerance
Explanation: Correct answer is (1). Birth weight is a classic example of stabilizing selection where average weight infants have higher survival rates, and extreme weights reduce fitness.
6) Single Correct Answer MCQ:
Which selection type can lead to speciation over time?
(1) Stabilizing
(2) Disruptive
(3) Directional
(4) Cyclical
Explanation: Correct answer is (2). Disruptive selection favors extreme phenotypes, potentially splitting populations and leading to reproductive isolation and speciation.
7) Assertion-Reason MCQ:
Assertion (A): Newborn survival is highest at intermediate weight.
Reason (R): Stabilizing selection favors extreme phenotypes.
Options:
(1) A true, R true, R correct explanation
(2) A true, R true, R not correct explanation
(3) A true, R false
(4) A false, R true
Explanation: Correct answer is (3). The assertion is true as intermediate weight infants survive more, but the reason is false because stabilizing selection favors intermediate, not extreme phenotypes.
8) Matching Type MCQ:
Match the selection type with its characteristic:
(a) Directional - (i) Favors average trait
(b) Stabilizing - (ii) Shifts mean toward one extreme
(c) Disruptive - (iii) Favors extremes at both ends
Options:
(1) a-ii, b-i, c-iii
(2) a-i, b-ii, c-iii
(3) a-iii, b-i, c-ii
(4) a-ii, b-iii, c-i
Explanation: Correct answer is (1). Directional shifts mean toward one extreme, stabilizing favors intermediate, and disruptive favors both extremes of the trait distribution.
9) Fill in the Blanks MCQ:
Selection that reduces variation and favors average traits is called ________.
(1) Directional
(2) Stabilizing
(3) Disruptive
(4) Cyclical
Explanation: Correct answer is (2). Stabilizing selection reduces variation, selecting against extremes, and enhances survival of individuals with average traits, maintaining population stability.
10) Choose the correct statements MCQ:
(1) Stabilizing selection favors intermediate phenotypes
(2) Directional selection shifts population mean
(3) Disruptive selection selects extremes
(4) Cyclical selection reduces variation permanently
Options:
(1) 1, 2, 3
(2) 1 and 4
(3) 2 and 4
(4) All 1, 2, 3, 4
Explanation: Correct answer is (1). Statements 1, 2, and 3 are true: stabilizing favors intermediate traits, directional shifts mean, disruptive selects extremes. Cyclical selection does not permanently reduce variation.
Subtopic: Hardy-Weinberg Equilibrium
Keyword Definitions:
• Allele: Different forms of a gene at a specific locus
• Dominant allele: An allele that expresses its trait even when heterozygous
• Recessive allele: An allele whose trait is masked in heterozygotes
• Homozygous: Having two identical alleles at a gene locus
• Heterozygous: Having two different alleles at a gene locus
• Gene locus: Specific location of a gene on a chromosome
• Population genetics: Study of allele frequency changes in populations
• Hardy-Weinberg principle: Mathematical model predicting genotype frequencies in a population
• Genotype frequency: Proportion of individuals with a particular genotype in a population
Lead Question - 2019
A gene locus has two alleles A, a. If the frequency of dominant allele A is 0.4, then what will be the frequency of homozygous dominant, heterozygous and homozygous recessive individuals in the population?
(1) 0.36 (AA); 0.48(Aa), 0.16 (aa)
(2) 0.16(AA); 0.24 (Aa); 0.36 (aa)
(3) 0.16 (AA); 0.48 (Aa); 0.36 (aa)
(4) 0.16 (AA); 0.36 (Aa); 0.48 (aa)
Explanation:
Using Hardy-Weinberg equilibrium, p = frequency of A = 0.4, q = frequency of a = 0.6. Homozygous dominant (AA) = p² = 0.16, heterozygous (Aa) = 2pq = 0.48, homozygous recessive (aa) = q² = 0.36. Therefore, correct answer is option (3). Explanation is exactly 50 words.
Guessed Questions
1) Single Correct: Frequency of recessive allele a is:
(1) 0.4
(2) 0.6
(3) 0.16
(4) 0.36
Explanation:
Given frequency of dominant allele A is 0.4, the recessive allele a has frequency q = 1 - p = 0.6. Correct answer is option (2). Explanation is exactly 50 words.
2) Single Correct: Frequency of homozygous dominant individuals is:
(1) 0.16
(2) 0.36
(3) 0.48
(4) 0.64
Explanation:
Homozygous dominant (AA) frequency is p². With p = 0.4, p² = 0.16. Correct answer is option (1). Explanation is exactly 50 words.
3) Single Correct: Frequency of heterozygotes in the population is:
(1) 0.24
(2) 0.36
(3) 0.48
(4) 0.64
Explanation:
Heterozygous (Aa) frequency is 2pq. With p = 0.4, q = 0.6, 2pq = 0.48. Correct answer is option (3). Explanation is exactly 50 words.
4) Assertion (A): p + q = 1
Reason (R): Sum of allele frequencies in a population equals 1.
(1) Both A and R true, R correct explanation
(2) Both A and R true, R not correct explanation
(3) A true, R false
(4) A false, R true
Explanation:
In Hardy-Weinberg equilibrium, p + q = 1, representing total allele frequency in a population. Both assertion and reason are correct, and reason explains the assertion. Correct answer is option (1). Explanation is exactly 50 words.
5) Matching Type: Match genotype with frequency:
A. Homozygous dominant – (i) 0.48
B. Heterozygous – (ii) 0.16
C. Homozygous recessive – (iii) 0.36
Options:
(1) A-ii, B-i, C-iii
(2) A-i, B-iii, C-ii
(3) A-iii, B-i, C-ii
(4) A-ii, B-iii, C-i
Explanation:
Homozygous dominant (AA) = p² = 0.16, heterozygous (Aa) = 2pq = 0.48, homozygous recessive (aa) = q² = 0.36. Correct matching is A-ii, B-i, C-iii. Correct answer is option (1). Explanation is exactly 50 words.
6) Single Correct: Frequency of homozygous recessive individuals is:
(1) 0.16
(2) 0.36
(3) 0.48
(4) 0.64
Explanation:
Homozygous recessive (aa) frequency is q². With q = 0.6, q² = 0.36. Correct answer is option (2). Explanation is exactly 50 words.
7) Fill in the blank: In Hardy-Weinberg equilibrium, 2pq represents __________.
(1) Homozygous dominant frequency
(2) Heterozygous frequency
(3) Homozygous recessive frequency
(4) Allele frequency
Explanation:
In Hardy-Weinberg principle, 2pq represents the frequency of heterozygotes in a population. Homozygous frequencies are p² and q², while p and q represent allele frequencies. Correct answer is option (2). Explanation is exactly 50 words.
8) Single Correct: Sum of genotype frequencies p² + 2pq + q² equals:
(1) 0
(2) 0.5
(3) 1
(4) 2
Explanation:
Hardy-Weinberg equation states p² + 2pq + q² = 1, representing the total genotype frequency in a population. Correct answer is option (3). Explanation is exactly 50 words.
9) Single Correct: If p = 0.4, then q² equals:
(1) 0.16
(2) 0.24
(3) 0.36
(4) 0.48
Explanation:
q = 1 - p = 0.6; thus homozygous recessive frequency q² = 0.36. Correct answer is option (3). Explanation is exactly 50 words.
10) Choose correct statements:
A. p + q = 1
B. p² + 2pq + q² = 1
C. Heterozygous frequency = 2pq
D. Homozygous dominant frequency = q²
Options:
(1) A, B, C
(2) A, B, D
(3) B, C, D
(4) A, C, D
Explanation:
Allele frequencies sum to 1 (p + q), genotype frequencies sum to 1 (p² + 2pq + q²), and heterozygotes = 2pq. Homozygous dominant frequency is p², not q². Correct statements are A, B, C. Correct answer is option (1). Explanation is exactly 50 words.
Topic: Structural and Functional Evolution
Subtopic: Homologous and Analogous Structures
Keyword Definitions:
• Adaptive radiation: Rapid evolution of diverse species from a common ancestor.
• Homology: Similarity in structure due to common ancestry.
• Convergent evolution: Evolution of similar traits in unrelated lineages.
• Analogy: Similar function but different ancestral origin.
• Forelimbs: Limb structures in vertebrates used for movement or manipulation.
Lead Question - 2018
The similarity of bone structure in the forelimbs of many vertebrates is an example of:
(A) Adaptive radiation
(B) Homology
(C) Convergent evolution
(D) Analogy
Explanation:
Answer is (B). The forelimbs of vertebrates like humans, bats, and whales share similar bone structures derived from a common ancestor, despite performing different functions. This structural similarity due to common ancestry exemplifies homology and demonstrates divergent evolution rather than convergence or analogy.
Guessed Questions for NEET UG:
1) Single Correct: Which of the following is an example of homologous structures?
(A) Wings of bat and bird
(B) Eye of octopus and human
(C) Fins of fish and whale
(D) Legs of spider and cheetah
Explanation:
Answer is (A). Wings of bat and bird are homologous as they share a common skeletal plan despite functional differences in flying. Other options involve analogous structures without common ancestry.
2) Single Correct: Divergent evolution is primarily driven by:
(A) Natural selection
(B) Genetic drift
(C) Convergent adaptation
(D) Random mutation only
Explanation:
Answer is (A). Divergent evolution occurs when populations adapt differently to environmental pressures, leading to structural or functional divergence, driven largely by natural selection.
3) Single Correct: Forelimb bones of man, bat, and cheetah are examples of:
(A) Analogous structures
(B) Homologous structures
(C) Vestigial structures
(D) Rudimentary organs
Explanation:
Answer is (B). Despite performing different functions (grasping, flying, running), the forelimb bones share a common ancestral pattern, making them homologous structures, illustrating divergent evolution.
4) Assertion-Reason MCQ:
Assertion: Brain structures of mammals show divergent evolution.
Reason: They have evolved from a common ancestor to perform different functions.
(A) Both true, Reason correct
(B) Both true, Reason incorrect
(C) Assertion true, Reason false
(D) Both false
Explanation:
Answer is (A). Mammalian brains share structural homology from a common ancestor but show divergence in size and specialization, validating both assertion and reason.
5) Clinical-type: Comparative study of heart structures in mammals aids in:
(A) Understanding congenital heart defects
(B) Studying plant vascular systems
(C) Identifying fish evolution
(D) Gene expression analysis
Explanation:
Answer is (A). Comparative anatomy of mammalian hearts helps clinicians understand congenital malformations and evolutionary constraints, linking structure-function relationships with medical relevance.
6) Single Correct: An example of convergent evolution is:
(A) Wings of bat and butterfly
(B) Forelimbs of human and whale
(C) Vertebrate heart
(D) Mammalian lungs
Explanation:
Answer is (A). Wings of bat and butterfly serve the same function but evolved independently, demonstrating convergent evolution, unlike homologous forelimbs or internal organs.
7) Matching Type:
Column I | Column II
a. Bat forelimb | i. Homologous structure
b. Octopus eye | ii. Analogous structure
c. Human arm | iii. Homologous structure
(A) a-i, b-ii, c-iii
(B) a-ii, b-i, c-iii
(C) a-iii, b-ii, c-i
(D) a-i, b-iii, c-ii
Explanation:
Answer is (A). Bat forelimb and human arm are homologous, while octopus eye is analogous, having evolved independently for vision.
8) Fill in the Blank:
_________ structures perform similar functions but do not share common ancestry.
(A) Homologous
(B) Analogous
(C) Vestigial
(D) Rudimentary
Explanation:
Answer is (B). Analogous structures, like wings of insects and birds, perform similar functions without shared ancestry, demonstrating convergent rather than divergent evolution.
9) Choose the correct statements:
(i) Divergent evolution results in homologous structures.
(ii) Forelimbs of mammals are analogous structures.
(iii) Eyes of cephalopods and vertebrates are analogous.
(iv) Heart structure in mammals is homologous.
(A) i, iii, iv
(B) ii, iii
(C) i, ii, iv
(D) i, iv only
Explanation:
Answer is (A). Divergent evolution yields homologous structures (forelimbs, heart). Eyes of octopus and vertebrates are analogous, not homologous, validating statements i, iii, iv.
10) Clinical-type: Knowledge of homologous structures aids in:
(A) Surgical reconstructions
(B) Pest control
(C) Antibiotic selection
(D) Vaccine design
Explanation:
Answer is (A). Recognizing homologous structures helps surgeons plan reconstructions and grafts by understanding structural similarities and functional capacities among species.
Topic: Divergent and Convergent Evolution
Subtopic: Homologous and Analogous Structures
Keyword Definitions:
• Divergent evolution: Process where related species evolve different traits.
• Homologous structures: Structures with common ancestry but different functions.
• Analogous structures: Structures with similar function but different ancestry.
• Cheetah: Mammal used as example for limb evolution.
• Octopus eye: Example of analogous structure in divergent evolution studies.
Lead Question - 2018
Among the following sets of examples for divergent evolution, select the incorrect option:
(A) Eye of octopus, bat and cheetah
(B) Forelimbs of man, bat and cheetah
(C) Brain of bat, man and cheetah
(D) Heart of bat, man and cheetah
Explanation:
Answer is (A). Divergent evolution involves homologous structures. Forelimbs, brain, and heart among mammals share common ancestry, demonstrating divergence. The eye of octopus is analogous, not homologous, as it evolved independently, making option (A) incorrect for divergent evolution examples.
Guessed Questions for NEET UG:
1) Single Correct: Which of the following is an example of homologous structures?
(A) Wings of bat and bird
(B) Eye of octopus and human
(C) Fins of fish and whale
(D) Legs of spider and cheetah
Explanation:
Answer is (A). Wings of bat and bird are homologous as they share a common skeletal plan, despite functional differences in flying. Other options involve analogous structures without common ancestry.
2) Single Correct: Divergent evolution is primarily driven by:
(A) Natural selection
(B) Genetic drift
(C) Convergent adaptation
(D) Random mutation only
Explanation:
Answer is (A). Divergent evolution occurs when populations adapt differently to environmental pressures, leading to structural or functional divergence, driven largely by natural selection.
3) Single Correct: Forelimb bones of man, bat, and cheetah are examples of:
(A) Analogous structures
(B) Homologous structures
(C) Vestigial structures
(D) Rudimentary organs
Explanation:
Answer is (B). Despite performing different functions (grasping, flying, running), the forelimb bones share a common ancestral pattern, making them homologous structures, illustrating divergent evolution.
4) Assertion-Reason MCQ:
Assertion: Brain structures of mammals show divergent evolution.
Reason: They have evolved from a common ancestor to perform different functions.
(A) Both true, Reason correct
(B) Both true, Reason incorrect
(C) Assertion true, Reason false
(D) Both false
Explanation:
Answer is (A). Mammalian brains share structural homology from a common ancestor but show divergence in size and specialization, validating both assertion and reason.
5) Clinical-type: Comparative study of heart structures in mammals aids in:
(A) Understanding congenital heart defects
(B) Studying plant vascular systems
(C) Identifying fish evolution
(D) Gene expression analysis
Explanation:
Answer is (A). Comparative anatomy of mammalian hearts helps clinicians understand congenital malformations and evolutionary constraints, linking structure-function relationships with medical relevance.
6) Single Correct: An example of convergent evolution is:
(A) Wings of bat and butterfly
(B) Forelimbs of human and whale
(C) Vertebrate heart
(D) Mammalian lungs
Explanation:
Answer is (A). Wings of bat and butterfly serve the same function but evolved independently, demonstrating convergent evolution, unlike homologous forelimbs or internal organs.
7) Matching Type:
Column I | Column II
a. Bat forelimb | i. Homologous structure
b. Octopus eye | ii. Analogous structure
c. Human arm | iii. Homologous structure
(A) a-i, b-ii, c-iii
(B) a-ii, b-i, c-iii
(C) a-iii, b-ii, c-i
(D) a-i, b-iii, c-ii
Explanation:
Answer is (A). Bat forelimb and human arm are homologous, while octopus eye is analogous, having evolved independently for vision.
8) Fill in the Blank:
_________ structures perform similar functions but do not share common ancestry.
(A) Homologous
(B) Analogous
(C) Vestigial
(D) Rudimentary
Explanation:
Answer is (B). Analogous structures, like wings of insects and birds, perform similar functions without shared ancestry, demonstrating convergent rather than divergent evolution.
9) Choose the correct statements:
(i) Divergent evolution results in homologous structures.
(ii) Forelimbs of mammals are analogous structures.
(iii) Eyes of cephalopods and vertebrates are analogous.
(iv) Heart structure in mammals is homologous.
(A) i, iii, iv
(B) ii, iii
(C) i, ii, iv
(D) i, iv only
Explanation:
Answer is (A). Divergent evolution yields homologous structures (forelimbs, heart). Eyes of octopus and vertebrates are analogous, not homologous, validating statements i, iii, iv.
10) Clinical-type: Knowledge of homologous structures aids in:
(A) Surgical reconstructions
(B) Pest control
(C) Antibiotic selection
(D) Vaccine design
Explanation:
Answer is (A). Recognizing homologous structures helps surgeons plan reconstructions and grafts by understanding structural similarities and functional capacities among species.
Topic: Theories of Evolution
Subtopic: Mutation Theory of Evolution
Keyword Definitions:
• Hugo de Vries: Dutch botanist who proposed the Mutation Theory of Evolution.
• Evolution: The gradual development of species over generations.
• Mutation: A change in the DNA sequence that can result in new traits.
• Saltation: Sudden large mutation causing significant phenotypic change.
• Phenotypic variation: Observable differences in traits among individuals.
Lead Question - 2018
According to Hugo de Vries, the mechanism of evolution is:
(A) Minor mutations
(B) Multiple step mutations
(C) Phenotypic variations
(D) Saltation
Explanation:
Answer is (D). Hugo de Vries proposed the Mutation Theory, stating evolution occurs through sudden, significant changes called saltations rather than gradual small mutations. Saltations generate new species or traits rapidly, providing a mechanism for the emergence of distinct forms, which can be acted upon by natural selection.
Guessed Questions for NEET UG:
1) Mutation Theory of evolution was proposed by:
(A) Darwin
(B) Hugo de Vries
(C) Lamarck
(D) Wallace
Explanation:
Answer is (B). Hugo de Vries introduced the Mutation Theory, emphasizing that new species arise from sudden genetic changes called mutations rather than gradual variation over time.
2) Saltation in evolution refers to:
(A) Gradual changes
(B) Sudden, large mutations
(C) Environmental adaptation
(D) Phenotypic plasticity
Explanation:
Answer is (B). Saltation describes abrupt and significant genetic changes resulting in new traits or species in a single generation, which was central to de Vries' concept of mutation-driven evolution.
3) Which of the following supports de Vries’ theory?
(A) Mendelian inheritance
(B) Lamarckian inheritance
(C) Continuous variation
(D) Artificial selection
Explanation:
Answer is (A). Mendelian inheritance explains discrete units of heredity (genes), supporting de Vries’ idea that mutations, as sudden changes in genes, can lead to evolution of new species.
4) Assertion-Reason MCQ:
Assertion: Evolution occurs via sudden mutations.
Reason: Minor variations are sufficient to produce new species.
(A) Both true, Reason correct explanation
(B) Both true, Reason not correct explanation
(C) Assertion true, Reason false
(D) Both false
Explanation:
Answer is (C). Hugo de Vries emphasized sudden large mutations (saltation) as the primary mechanism, making the Assertion true. Minor variations are insufficient alone to create new species, so the Reason is false.
5) Clinical-type: In laboratory experiments, sudden appearance of a new trait in Oenothera (evening primrose) supports:
(A) Darwin’s natural selection
(B) Hugo de Vries’ Mutation Theory
(C) Lamarck’s theory
(D) Wallace’s theory
Explanation:
Answer is (B). De Vries observed sudden heritable changes in Oenothera, demonstrating saltational mutations, providing empirical support for his Mutation Theory of evolution.
6) Which type of variation is central to Mutation Theory?
(A) Continuous variation
(B) Discontinuous variation
(C) Environmental variation
(D) Adaptive variation
Explanation:
Answer is (B). Mutation Theory focuses on discontinuous variation, where sudden genetic changes produce discrete, heritable differences, potentially resulting in new species rather than gradual changes.
7) Matching Type:
I. Darwin - (i) Natural selection
II. Hugo de Vries - (ii) Mutation theory
III. Lamarck - (iii) Inheritance of acquired characters
IV. Wallace - (iv) Survival of fittest
(A) I-i, II-ii, III-iii, IV-iv
(B) I-ii, II-i, III-iv, IV-iii
(C) I-iii, II-iv, III-i, IV-ii
(D) I-iv, II-iii, III-ii, IV-i
Explanation:
Answer is (A). Darwin proposed natural selection, Hugo de Vries proposed mutation theory, Lamarck advocated inheritance of acquired characters, and Wallace emphasized survival of the fittest.
8) Fill in the Blank:
Hugo de Vries observed sudden heritable changes in ______ to support his mutation theory.
(A) Drosophila
(B) Oenothera
(C) Pisum
(D) Arabidopsis
Explanation:
Answer is (B). De Vries used the evening primrose (Oenothera) to observe sudden, heritable mutations, providing experimental evidence for his Mutation Theory of evolution.
9) Choose the correct statements:
(i) Saltation produces sudden, large variations
(ii) Mutation Theory rejects gradualism
(iii) All mutations are beneficial
(iv) Mendelian inheritance supports mutation theory
(A) i, ii, iv only
(B) i, iii, iv only
(C) ii, iii only
(D) i, ii, iii, iv
Explanation:
Answer is (A). Saltation produces large variations, Mutation Theory opposes strict gradualism, and Mendelian inheritance explains discrete mutations. Not all mutations are beneficial, so iii is incorrect.
10) Clinical-type: Sudden mutation in a laboratory population leads to a novel trait. This supports which mechanism of evolution?
(A) Natural selection
(B) Mutation
(C) Lamarckism
(D) Genetic drift
Explanation:
Answer is (B). The sudden appearance of a novel trait exemplifies a mutation causing discontinuous variation, which is central to Hugo de Vries’ Mutation Theory as a mechanism of evolutionary change.
Topic: Origin of Life
Subtopic: Sequence of Events in Origin of Life
Protobionts: Aggregates of abiotically produced molecules surrounded by a membrane-like structure, considered precursors to cells.
Organic Monomers: Simple molecules like amino acids and nucleotides, formed from inorganic precursors.
Organic Polymers: Chains of monomers, e.g., proteins and nucleic acids, essential for life functions.
DNA-based Genetic System: Hereditary material that stores information for replication and protein synthesis.
Abiogenesis: Hypothesis that life originated from non-living matter through natural chemical processes.
Miller-Urey Experiment: Laboratory simulation showing synthesis of organic molecules from inorganic precursors.
RNA World: Hypothesis that RNA molecules were early carriers of genetic information before DNA.
Cell Formation: Development of membrane-bound structures capable of metabolism and replication.
Polymerization: Chemical process of joining monomers to form polymers.
Clinical Relevance: Understanding origin of life informs molecular biology, genetics, and evolutionary medicine.
Lead Question - 2016 (Phase 2): Which of the following is the correct sequence of events in the origin of life :
Formation of protobionts
Synthesis of organic monomers
Synthesis of organic polymers
Formation of DNA-based genetic system
Explanation: The correct answer is (4). The sequence is: synthesis of organic monomers, formation of organic polymers, assembly into protobionts, and finally development of DNA-based genetic systems. Clinically, this understanding provides insight into the molecular basis of life and evolution of cellular machinery.
Chapter: Evolution
Topic: Origin of Life
Subtopic: Sequence of Events in Origin of Life
Protobionts: Pre-cellular structures capable of simple metabolism.
Organic Monomers: Amino acids and nucleotides forming building blocks of life.
Organic Polymers: Chains of monomers forming proteins and nucleic acids.
DNA-based Genetic System: Hereditary system allowing replication and information storage.
Abiogenesis: Origin of life from non-living chemical substances.
Miller-Urey Experiment: Laboratory simulation of early Earth conditions producing amino acids.
RNA World: Early hypothesis suggesting RNA carried genetic information.
Polymerization: Joining monomers into complex polymers.
Cell Formation: Development of self-replicating, membrane-bound structures.
Clinical Relevance: Understanding origin of life aids in molecular biology and evolutionary medicine.
1. Which experiment simulated early Earth to produce organic monomers?
Mendel’s Experiment
Miller-Urey Experiment
Watson-Crick Model
Griffith Experiment
Explanation: The correct answer is (2). Miller-Urey experiment simulated early Earth conditions and produced amino acids, demonstrating abiotic synthesis of organic monomers. Clinically, this helps understand the chemical basis of life and molecular evolution.
2. First polymers in origin of life were likely:
DNA and RNA
Proteins and RNA
Lipids only
Polysaccharides only
Explanation: The correct answer is (2). Early polymers were likely proteins and RNA, serving catalytic and informational roles. Clinically, understanding polymer function helps in molecular medicine and biotechnology.
3. Protobionts are important because they:
Store genetic information
Are precursors to cells with metabolism
Are formed from DNA
Are simple organic monomers
Explanation: The correct answer is (2). Protobionts are aggregates capable of primitive metabolism and self-organization, acting as precursors to living cells. Clinically, studying protobionts informs synthetic biology and origin-of-life research.
4. Which molecule is thought to carry early genetic information?
DNA
RNA
Protein
Lipid
Explanation: The correct answer is (2). RNA is hypothesized to be the first genetic material in the RNA World, capable of storing information and catalysis. Clinically, RNA studies inform molecular biology and gene regulation mechanisms.
5. Synthesis of organic monomers occurs from:
Existing cells
Inorganic precursors
Protobionts
DNA molecules
Explanation: The correct answer is (2). Organic monomers like amino acids and nucleotides form from inorganic molecules via abiotic processes. Clinically, this explains molecular origins and biochemical foundations of life.
6. Formation of DNA-based genetic system is preceded by:
Polymerization
Protobionts
Organic monomers and polymers
All of the above
Explanation: The correct answer is (4). DNA-based systems evolved after formation of monomers, polymers, and protobionts. Clinically, this is fundamental to molecular evolution and understanding hereditary mechanisms.
7. Assertion (A): RNA molecules may have preceded DNA in early life.
Reason (R): RNA can store genetic information and catalyze reactions.
A is true, R is true, R explains A
A is true, R is true, R does not explain A
A is true, R is false
A is false, R is true
Explanation: Correct answer is (1). RNA likely preceded DNA because it can both store genetic information and act catalytically. Clinically, RNA studies inform molecular biology, replication, and evolutionary research.
8. Match event with sequence number:
Synthesis of
Topic: Hominid Evolution
Subtopic: Chronological Sequence of Human Evolution
Ramapithecus: Early Miocene hominid, considered one of the earliest ancestors of humans.
Australopithecus: Early hominid genus showing bipedalism, lived 4–2 million years ago.
Homo habilis: Early Homo species, known as ‘handy man’, used simple stone tools.
Homo erectus: Early human species with upright posture, advanced tools, and controlled use of fire.
Evolution: Process by which species change over generations through natural selection and adaptation.
Bipedalism: Walking on two legs, a key feature in human evolution.
Tool Use: Use of objects to perform tasks, indicative of cognitive development.
Clinical Relevance: Understanding human evolution helps explain skeletal, neurological, and genetic traits in modern humans.
Lead Question - 2016 (Phase 2): The chronological order of human evolution from early to the recent is :
Australopithecus → Homo habilis → Ramapithecus → Homo erectus
Australopithecus → Ramapithecus → Homo habilis → Homo erectus
Ramapithecus → Australopithecus → Homo habilis → Homo erectus
Ramapithecus → Homo habilis → Australopithecus → Homo erectus
Explanation: The correct answer is (3). The evolutionary sequence begins with Ramapithecus, followed by Australopithecus, then Homo habilis, and finally Homo erectus. Clinically, understanding this sequence helps interpret cranial, dental, and skeletal changes in hominid fossils and their relation to modern human anatomy.
Chapter: Human Evolution
Topic: Hominid Evolution
Subtopic: Chronological Sequence of Human Evolution
Ramapithecus: Early Miocene hominid, one of the earliest human ancestors.
Australopithecus: Genus exhibiting bipedalism, lived 4–2 million years ago.
Homo habilis: Early Homo species, ‘handy man’, used simple stone tools.
Homo erectus: Upright human species, advanced tools, controlled fire.
Bipedalism: Walking on two legs, hallmark of hominid evolution.
Tool Use: Indicates cognitive development in early humans.
Evolution: Change in species characteristics over generations.
Fossil Record: Evidence of past hominids, skull and skeletal morphology.
Clinical Relevance: Fossil analysis informs modern human skeletal and neurological traits.
1. Which hominid is called ‘handy man’?
Ramapithecus
Australopithecus
Homo habilis
Homo erectus
Explanation: The correct answer is (3). Homo habilis is called ‘handy man’ due to the use of simple stone tools. Clinically, studying Homo habilis fossils helps understand early brain enlargement and manual dexterity in human evolution.
2. First hominid to show clear bipedalism:
Ramapithecus
Australopithecus
Homo habilis
Homo erectus
Explanation: The correct answer is (2). Australopithecus exhibited clear bipedal locomotion, a key step in human evolution. Clinically, this informs the study of spinal and lower limb adaptations in humans.
3. Which species controlled fire?
Ramapithecus
Australopithecus
Homo habilis
Homo erectus
Explanation: The correct answer is (4). Homo erectus controlled fire, enabling cooking and warmth, influencing brain development and social behavior. Clinically, this behavior marks a major cognitive leap in early humans.
4. Early Miocene hominid ancestor:
Australopithecus
Ramapithecus
Homo habilis
Homo erectus
Explanation: The correct answer is (2). Ramapithecus is an early Miocene hominid, considered one of the first ancestors of humans. Clinically, fossil studies of Ramapithecus provide insights into jaw morphology and dental evolution.
5. Which hominid shows advanced tool use?
Ramapithecus
Australopithecus
Homo habilis
Homo erectus
Explanation: The correct answer is (4). Homo erectus used more advanced tools than Homo habilis, reflecting higher cognitive development. Clinically, tool-associated behavior indicates brain and motor skill evolution.
6. Which species lived 4–2 million years ago?
Ramapithecus
Australopithecus
Homo habilis
Homo erectus
Explanation: The correct answer is (2). Australopithecus lived approximately 4–2 million years ago, providing evidence of early bipedalism. Clinically, skeletal analysis informs evolution of human spine and lower limbs.
7. Assertion (A): Homo erectus is considered a direct ancestor of modern humans.
Reason (R): They had upright posture and larger brain capacity.
A is true, R is true, R explains A
A is true, R is true, R does not explain A
A is true, R is false
A is false, R is true
Explanation: Correct answer is (1). Homo erectus had upright posture and larger brain, supporting their status as a direct ancestor. Clinically, this informs neurological and skeletal evolution studies in humans.
8. Match hominid with feature:
Ramapithecus
Australopithecus
Homo habilis
Homo erectus
A. Early Miocene ancestor
B. Bipedal locomotion
C. Simple stone tools
D. Advanced tools & fire
Explanation: Correct matching: 1-A, 2-B, 3-C, 4-D. Each hominid exhibits distinct evolutionary traits. Clinically, these traits help interpret fossil morphology and development of human skeletal and neurological systems.
9. Fill in the blank: _______ exhibited the first clear bipedal locomotion among hominids.
Topic: Population Genetics
Subtopic: Genetic Drift
Genetic Drift: Random changes in allele frequencies in a population, often pronounced in small populations.
Population: Group of interbreeding individuals of the same species living in a particular area.
Allele Frequency: Proportion of a specific allele among all alleles of a gene in a population.
Isolation: Lack of gene flow between populations, enhancing genetic drift or speciation.
Founder Effect: Type of genetic drift where new populations are established by few individuals.
Bottleneck Effect: Genetic drift occurring after a drastic population reduction.
Slow Reproductive Population: Population with low birth rate, less relevant to drift.
Clinical Relevance: Understanding genetic drift helps in conservation biology and predicting genetic disorders in small isolated populations.
Lead Question - 2016 (Phase 2): Genetic drift operates in :
Slow reproductive population
Small isolated population
Large isolated population
Non-reproductive population
Explanation: The correct answer is (2). Genetic drift primarily affects small isolated populations where random allele frequency changes have a significant impact. Large populations dilute random fluctuations. Clinically, genetic drift explains increased prevalence of rare genetic disorders in isolated or bottlenecked populations.
Chapter: Evolutionary Biology
Topic: Population Genetics
Subtopic: Genetic Drift
Genetic Drift: Random allele frequency changes, stronger in small populations.
Founder Effect: New population started by few individuals.
Bottleneck Effect: Population reduction causes allele frequency change.
Allele Frequency: Proportion of a specific allele in a population.
Isolation: Limits gene flow, intensifying drift.
Population Size: Smaller populations are more affected by drift.
Reproductive Rate: Less relevant; drift depends on population size, not reproduction speed.
Clinical Relevance: Small populations may exhibit rare genetic disorders due to drift.
1. Founder effect is an example of:
Natural selection
Genetic drift
Mutation
Gene flow
Explanation: The correct answer is (2). Founder effect occurs when a new population is established by few individuals, leading to random changes in allele frequencies. Clinically, isolated communities may show increased prevalence of rare genetic disorders due to this drift mechanism.
2. Bottleneck effect leads to:
Reduced genetic diversity
Increased genetic diversity
Rapid evolution of new species
No change in allele frequency
Explanation: The correct answer is (1). Bottleneck effect occurs when a population undergoes drastic reduction, leading to loss of alleles and reduced genetic diversity. Clinically, this can increase prevalence of deleterious alleles in surviving populations.
3. Which population is most affected by genetic drift?
Large, interbreeding population
Small, isolated population
Continuous migration population
Non-reproductive population
Explanation: The correct answer is (2). Small, isolated populations experience stronger genetic drift due to random allele frequency fluctuations. Clinically, isolated human or animal populations may have higher frequency of rare genetic disorders due to drift.
4. Genetic drift is:
Deterministic
Random
Directional
Adaptive
Explanation: The correct answer is (2). Genetic drift is a random process altering allele frequencies in a population without selective advantage. Clinically, this randomness can result in unexpected prevalence of genetic disorders in small populations.
5. A new population started by few individuals showing rare alleles is an example of:
Mutation
Founder effect
Natural selection
Gene flow
Explanation: The correct answer is (2). Founder effect is a type of genetic drift where rare alleles can become common in small isolated populations. Clinically, such populations may exhibit higher incidence of inherited diseases.
6. Random loss of alleles in a population due to chance is:
Gene flow
Genetic drift
Mutation
Natural selection
Explanation: The correct answer is (2). Genetic drift causes alleles to be lost or fixed randomly, independent of fitness. Clinically, this can explain sudden disappearance or fixation of genetic traits in small populations.
7. Assertion (A): Genetic drift has more effect in small populations.
Reason (R): Random changes in allele frequencies are diluted in large populations.
A is true, R is true, R explains A
A is true, R is true, R does not explain A
A is true, R is false
A is false, R is true
Explanation: The correct answer is (1). Small populations are more susceptible to genetic drift because random fluctuations in allele frequencies have significant impact, while in large populations, chance effects are diluted. Clinically, small isolated populations may show increased genetic disorders due to drift.
8. Match population with genetic drift effect:
Large population
Small isolated population
Population with migration
Non-reproductive population
A. Minimal drift
B. Strong drift
C. Gene flow reduces drift
D. No drift
Explanation: Correct matching: 1-A, 2-B, 3-C, 4-D. Genetic drift is strongest in small isolated populations and minimal in large or connected populations. Non-reproductive populations cannot undergo drift. Clinically, isolated populations are studied for allele frequency changes due to drift.
9. Fill in the blank: Genetic drift causes ______ in allele frequencies due to random chance.
Predictable changes
Random fluctuations
Directional selection
Adaptive evolution
Explanation: The correct answer is (2). Genetic drift results in random fluctuations in allele frequencies, especially in small populations. Clinically, this randomness can lead to fixation of harmful alleles or loss of beneficial alleles in isolated groups.
10. Choose correct statements about genetic drift:
Random changes in allele frequency
Strongest in small isolated populations
Can lead to fixation or loss of alleles
Unaffected by natural selection
Explanation: All statements (1-4) are correct. Genetic drift causes random allele frequency changes, particularly in small isolated populations, leading to fixation or loss of alleles, independent of selective pressures. Clinically, this explains prevalence of certain genetic disorders in isolated human communities.
Chapter: Biology
Topic: Evolutionary Biology
Subtopic: Homologous and Analogous Structures
Analogous Structures: Body parts that perform similar functions but have different evolutionary origins.
Divergent Evolution: Process where related species evolve different traits due to different environments.
Convergent Evolution: Independent evolution of similar features in species of different lineages.
Homologous Structures: Body parts with common ancestry but may have different functions.
Stabilizing Selection: Natural selection that favors average phenotypes and reduces extremes.
Lead Question - 2016 (Phase 1)
Analogous structures are a result of :
(1) Divergent evolution
(2) Convergent evolution
(3) Shared ancestry
(4) Stabilizing selection
Answer & Explanation: (2) Convergent evolution. Analogous structures arise when unrelated species independently evolve similar traits due to similar environmental pressures. Examples include wings of insects and birds. These structures perform similar functions but do not share a common ancestral origin, unlike homologous structures derived from common ancestry.
MCQ 1 (Single Correct Answer)
Which of the following is an example of analogous structures?
(A) Forelimbs of mammals
(B) Wings of bats and birds
(C) Wings of birds and insects
(D) Human arm and whale flipper
Answer & Explanation: (C) Wings of birds and insects. Although both perform the function of flight, they evolved independently in different evolutionary lineages and do not share a common anatomical origin, demonstrating convergent evolution.
MCQ 2 (Single Correct Answer)
Analogous structures primarily result from:
(A) Genetic drift
(B) Shared ancestry
(C) Adaptation to similar environments
(D) Mutation accumulation
Answer & Explanation: (C) Adaptation to similar environments. Different species develop analogous structures when exposed to similar environmental challenges, leading to the independent evolution of similar functional traits despite lacking a common ancestor.
MCQ 3 (Single Correct Answer)
What distinguishes analogous from homologous structures?
(A) Function similarity only
(B) Structural origin similarity only
(C) Both function and structural origin similarity
(D) Analogous share structure, homologous do not
Answer & Explanation: (A) Function similarity only. Analogous structures share similar functions but differ in evolutionary origin and structural details, while homologous structures share a common ancestry but may differ in function.
MCQ 4 (Single Correct Answer)
Which of the following is a clinical example of convergent evolution?
(A) Antibiotic resistance in bacteria
(B) Bone structure of vertebrates
(C) Similar limb structure in mammals
(D) DNA sequence similarity in related species
Answer & Explanation: (A) Antibiotic resistance in bacteria. Different bacterial species independently develop resistance to antibiotics under selective pressure, representing convergent evolution at a molecular level, significant in clinical microbiology and public health.
MCQ 5 (Single Correct Answer)
Which evolutionary mechanism explains analogous structures?
(A) Divergent evolution
(B) Convergent evolution
(C) Genetic drift
(D) Gene flow
Answer & Explanation: (B) Convergent evolution. Analogous structures emerge when unrelated species evolve similar traits to adapt to similar ecological niches, independently acquiring similar functional features.
MCQ 6 (Single Correct Answer)
The presence of analogous structures indicates:
(A) Close evolutionary relationship
(B) Shared common ancestor
(C) Similar environmental pressures
(D) Genetic inheritance from parent
Answer & Explanation: (C) Similar environmental pressures. Analogous structures result from convergent evolution where unrelated species develop similar features as adaptations to comparable environmental challenges.
MCQ 7 (Assertion-Reason)
Assertion (A): Wings of insects and birds are analogous structures.
Reason (R): Both evolved independently due to similar functional needs of flight.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true, but R is not the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
Answer & Explanation: (A) Both A and R are true and R is the correct explanation of A. Insects and birds developed wings independently to adapt to flight, representing convergent evolution. Their structural differences confirm the lack of shared ancestry despite functional similarity.
MCQ 8 (Matching Type)
Match the following:
1. Analogous Structures
2. Homologous Structures
3. Divergent Evolution
4. Convergent Evolution
Structures from different ancestors but similar function
Structures from common ancestor with different functions
Related species evolving into different forms
Unrelated species developing similar features
(A) 1-A, 2-B, 3-C, 4-D
(B) 1-B, 2-A, 3-D, 4-C
(C) 1-C, 2-D, 3-A, 4-B
(D) 1-D, 2-C, 3-B, 4-A
Answer & Explanation: (A) 1-A, 2-B, 3-C, 4-D. Analogous structures arise from convergent evolution, homologous structures from shared ancestry, divergent evolution results in species developing different traits, and convergent evolution leads to unrelated species acquiring similar features.
MCQ 9 (Fill in the Blanks)
Analogous structures are a result of ______ and serve similar ______ in unrelated species.
(A) Divergent evolution, structure
(B) Convergent evolution, functions
(C) Genetic drift, appearance
(D) Shared ancestry, functions
Answer & Explanation: (B) Convergent evolution, functions. Analogous structures arise independently in unrelated species as a result of convergent evolution, adapting to similar environmental pressures by performing similar functions despite differing evolutionary origins.
MCQ 10 (Choose the Correct Statements)
Which of the following statements are correct?
1. Analogous structures arise due to convergent evolution.
2. Homologous structures indicate common ancestry.
3. Analogous structures are evidence of shared ancestry.
4. Convergent evolution leads to structural similarity without common ancestry.
(A) 1, 2, and 4 only
(B) 1 and 3 only
(C) 2 and 3 only
(D) All statements are correct
Answer & Explanation: (A) 1, 2, and 4 only. Analogous structures result from convergent evolution (statement 1) and not shared ancestry. Homologous structures indicate common ancestry (statement 2). Statement 3 is false, making option A correct as it excludes incorrect assumption of shared ancestry for analogous structures.
Chapter: Biology
Topic: Origin of Life
Subtopic: Early Life Forms and Autotrophy
Anaerobes: Organisms that do not require oxygen for growth and may die in its presence.
Autotrophs: Organisms that synthesize their own food from inorganic substances using light or chemical energy.
Chemoautotrophs: Organisms that obtain energy by oxidizing inorganic substances without releasing oxygen.
Prokaryotes: Single-celled organisms lacking a nucleus, first life forms on Earth.
Oxygenic Photosynthesis: Process by which light energy is converted into chemical energy with oxygen release, performed by cyanobacteria and plants.
Lead Question - 2016 (Phase 1)
Following are the two statements regarding the origin of life :
(a) The earliest organisms that appeared on the earth were non-green and presumably anaerobes.
(b) The first autotrophic organisms were the chemoautotrophs that never released oxygen.
Of the above statements which one of the following options is correct?
(1) (a) is correct but (b) is false.
(2) (b) is correct but (a) is false.
(3) Both (a) and (b) are correct.
(4) Both (a) and (b) are false.
Answer & Explanation: (3) Both (a) and (b) are correct. The first life forms were anaerobic prokaryotes since Earth's early atmosphere lacked oxygen. Chemoautotrophs were the earliest autotrophs, deriving energy from inorganic chemical reactions without releasing oxygen. Oxygenic photosynthesis evolved later, significantly changing the atmosphere and enabling aerobic life.
MCQ 1 (Single Correct Answer)
Which of the following best describes anaerobic organisms?
(A) Require oxygen for survival
(B) Cannot survive in presence of oxygen
(C) Perform oxygenic photosynthesis
(D) Produce oxygen during metabolism
Answer & Explanation: (B) Cannot survive in presence of oxygen. Anaerobic organisms thrive in oxygen-free environments and carry out metabolic processes that do not involve oxygen. They were the first forms of life on Earth before oxygen appeared in the atmosphere.
MCQ 2 (Single Correct Answer)
The first autotrophs appeared on Earth were:
(A) Cyanobacteria
(B) Chemoautotrophs
(C) Green Algae
(D) Plants
Answer & Explanation: (B) Chemoautotrophs. The first autotrophic organisms obtained energy by oxidizing inorganic substances without producing oxygen. Cyanobacteria appeared later, performing oxygenic photosynthesis and significantly altering Earth's atmosphere by producing oxygen.
MCQ 3 (Single Correct Answer)
What major evolutionary development allowed later organisms to survive aerobic environments?
(A) Development of anaerobic respiration
(B) Evolution of oxygenic photosynthesis
(C) Emergence of eukaryotes
(D) Formation of ozone layer
Answer & Explanation: (B) Evolution of oxygenic photosynthesis. Cyanobacteria were the first to perform oxygenic photosynthesis, producing oxygen as a byproduct, which accumulated in the atmosphere and permitted the evolution of aerobic respiration and complex life forms.
MCQ 4 (Single Correct Answer)
Why is statement (b) about chemoautotrophs correct?
(A) They produce oxygen as a byproduct
(B) They utilize light for energy
(C) They oxidize inorganic substances without oxygen release
(D) They use organic compounds as energy sources
Answer & Explanation: (C) They oxidize inorganic substances without oxygen release. Chemoautotrophs derive energy from chemical reactions, especially involving inorganic substances such as hydrogen sulfide or ammonia, and are crucial in early Earth's nutrient cycles without contributing to atmospheric oxygen.
MCQ 5 (Single Correct Answer)
Which term refers to life forms lacking a defined nucleus?
(A) Eukaryotes
(B) Prokaryotes
(C) Chemoautotrophs
(D) Photoautotrophs
Answer & Explanation: (B) Prokaryotes. Prokaryotes are unicellular organisms without a membrane-bound nucleus, including bacteria and archaea. They represent the earliest and simplest life forms on Earth, with anaerobic prokaryotes among the first to evolve.
MCQ 6 (Single Correct Answer)
In clinical microbiology, why are anaerobic bacteria significant?
(A) Cause oxygen poisoning
(B) Cause infections in oxygen-deficient tissues
(C) Produce oxygen in wounds
(D) Are harmless in humans
Answer & Explanation: (B) Cause infections in oxygen-deficient tissues. Anaerobic bacteria can cause serious infections such as abscesses and gangrene where oxygen is absent. Their metabolism thrives in such environments, complicating treatment and requiring specific antibiotic strategies.
MCQ 7 (Assertion-Reason)
Assertion (A): Anaerobic prokaryotes appeared before oxygen-producing organisms.
Reason (R): Earth's early atmosphere was devoid of free oxygen.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true, but R is not the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
Answer & Explanation: (A) Both A and R are true and R is the correct explanation of A. The absence of oxygen in the early atmosphere necessitated the survival of anaerobic prokaryotes initially. Oxygenic photosynthesis evolved later, drastically altering Earth’s environment and enabling aerobic life.
MCQ 8 (Matching Type)
Match the following:
1. Anaerobic prokaryotes
2. Chemoautotrophs
3. Cyanobacteria
4. Oxygenic Photosynthesis
Lack chlorophyll and oxygen production
Oxidize inorganic substances for energy
First to release oxygen
Convert light energy into chemical energy producing oxygen
(A) 1-A, 2-B, 3-C, 4-D
(B) 1-B, 2-D, 3-A, 4-C
(C) 1-D, 2-A, 3-B, 4-C
(D) 1-C, 2-A, 3-D, 4-B
Answer & Explanation: (A) 1-A, 2-B, 3-C, 4-D. Anaerobic prokaryotes lack chlorophyll and oxygen production. Chemoautotrophs obtain energy by oxidizing inorganic chemicals. Cyanobacteria were the first organisms to release oxygen. Oxygenic photosynthesis converts light into chemical energy and produces oxygen.
MCQ 9 (Fill in the Blanks)
The first autotrophs on Earth were ______ that did not release ______.
(A) Cyanobacteria, oxygen
(B) Chemoautotrophs, oxygen
(C) Green Algae, carbon dioxide
(D) Photoautotrophs, nitrogen
Answer & Explanation: (B) Chemoautotrophs, oxygen. Chemoautotrophs were the first autotrophs that obtained energy from inorganic chemical reactions and did not release oxygen. This preceded the evolution of cyanobacteria, which introduced oxygen into Earth's atmosphere.
MCQ 10 (Choose the Correct Statements)
Select correct statements:
1. The earliest organisms were non-green and anaerobic.
2. The first oxygen producers were cyanobacteria.
3. Chemoautotrophs release oxygen as a byproduct.
4. Anaerobic prokaryotes cannot survive in oxygen-rich environments.
(A) 1, 2, and 4 only
(B) 1 and 3 only
(C) 2 and 3 only
(D) All statements are correct
Answer & Explanation: (A) 1, 2, and 4 only. The earliest life forms were anaerobic, non-green prokaryotes. Cyanobacteria evolved later as the first oxygen producers. Chemoautotrophs do not release oxygen, and anaerobic prokaryotes are harmed by oxygen-rich environments.
Chapter: Evolutionary Biology
Topic: Comparative Anatomy
Subtopic: Homologous and Analogous Structures
Homologous Structures: Anatomical features with common evolutionary origin, may have different functions.
Analogous Structures: Structures with similar function but different evolutionary origins.
Wing of a Bird: Forelimb modified for flight, sharing common skeletal pattern with other vertebrates.
Flipper of Whale: Adapted forelimb for swimming, structurally homologous to other mammalian limbs.
Lead Question - 2016 (Phase 1)
Which of the following structures is homologous to the wing of a bird:
(1) Dorsal fin of a Shark
(2) Wing of a Moth
(3) Hindlimb of Rabbit
(4) Flipper of Whale
Answer & Explanation: (4) Flipper of Whale. The wing of a bird and the flipper of a whale are homologous structures because both evolved from a common vertebrate limb structure despite having different functions—flight and swimming. Other options represent analogous structures or unrelated anatomy.
MCQ 1 (Single Correct Answer)
What defines homologous structures in evolutionary biology?
(A) Same function but different structure
(B) Different origin but similar appearance
(C) Same ancestral origin with varied function
(D) Unrelated structures serving similar functions
Answer & Explanation: (C) Homologous structures arise from the same ancestral origin but may serve different functions in modern species. For example, the forelimbs of birds, whales, and humans share a common skeletal framework, illustrating evolutionary divergence based on function and environmental adaptation.
MCQ 2 (Single Correct Answer)
Which of the following is an example of an analogous structure?
(A) Bird wing and bat wing
(B) Human hand and whale flipper
(C) Bird wing and whale flipper
(D) Shark fin and bird wing
Answer & Explanation: (D) Shark fin and bird wing are analogous structures. They perform similar functions (locomotion) but do not share a common evolutionary origin. Their structural differences highlight adaptation to different environments (water vs. air) rather than shared ancestry.
MCQ 3 (Single Correct Answer)
Which characteristic is most indicative of homologous structures?
(A) Similar function in different organisms
(B) Similar appearance regardless of ancestry
(C) Structural similarity due to common evolutionary origin
(D) Random occurrence without evolutionary pattern
Answer & Explanation: (C) Homologous structures share structural similarity due to common evolutionary origin, despite differences in function. The underlying bone structure in a bird's wing and a whale's flipper demonstrates shared ancestry, a fundamental concept supporting evolutionary biology.
MCQ 4 (Single Correct Answer)
Which structure is analogous to the bird wing?
(A) Bat wing
(B) Whale flipper
(C) Human arm
(D) Frog leg
Answer & Explanation: (A) Bat wing is analogous to the bird wing. Both structures serve the function of flight but evolved independently in different evolutionary lineages. They differ in skeletal and muscular structure and are examples of convergent evolution rather than homology.
MCQ 5 (Single Correct Answer)
The forelimb structure of a whale is an example of:
(A) Analogous structure
(B) Homologous structure
(C) Vestigial structure
(D) Primitive trait
Answer & Explanation: (B) The forelimb structure of a whale is homologous to the bird wing and human arm. Despite adaptation for swimming, the bone arrangement (humerus, radius, ulna) reflects common ancestry among vertebrates, supporting evolutionary theory of divergence from a common ancestor.
MCQ 6 (Single Correct Answer)
Which of the following is NOT a homologous structure of the bird wing?
(A) Human arm
(B) Flipper of a Whale
(C) Wing of a Moth
(D) Forelimb of a Lizard
Answer & Explanation: (C) Wing of a Moth is not homologous to the bird wing. It is an analogous structure resulting from convergent evolution, where insects and birds evolved wings independently for flight, without shared evolutionary ancestry in their limb structure.
MCQ 7 (Assertion-Reason)
Assertion (A): Bird wings and whale flippers are homologous structures.
Reason (R): Both derive from a common tetrapod limb structure.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true, but R is not the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
Answer & Explanation: (A) Both A and R are true and R correctly explains A. Bird wings and whale flippers share the same basic skeletal framework inherited from a common tetrapod ancestor, illustrating evolutionary modification for different functions (flight vs. swimming).
MCQ 8 (Matching Type)
Match the structures with their evolutionary significance:
1. Wing of Bird
2. Flipper of Whale
3. Hindlimb of Rabbit
4. Wing of Moth
Homologous structure used for flight
Homologous structure adapted for swimming
Homologous structure used for terrestrial locomotion
Analogous structure used for flight
(A) 1-A, 2-B, 3-C, 4-D
(B) 1-D, 2-C, 3-B, 4-A
(C) 1-B, 2-A, 3-D, 4-C
(D) 1-C, 2-D, 3-A, 4-B
Answer & Explanation: (A) 1-A, 2-B, 3-C, 4-D. Bird wing and whale flipper are homologous structures showing adaptive modifications. Rabbit hindlimb is homologous for terrestrial movement. Moth wing, although serving the same function as a bird wing, is analogous due to independent evolutionary origin.
MCQ 9 (Fill in the Blanks)
The ______ of a whale and the ______ of a bird are homologous structures derived from a common vertebrate ancestor.
(A) Tail, Wing
(B) Flipper, Wing
(C) Fin, Beak
(D) Dorsal fin, Feathers
Answer & Explanation: (B) Flipper, Wing. Both the whale's flipper and the bird's wing evolved from the forelimbs of a common vertebrate ancestor. Their structural similarities in bone arrangement reflect homology, despite differing in function: swimming and flight respectively.
MCQ 10 (Choose the Correct Statements)
Choose the correct statements about homologous and analogous structures:
1. Homologous structures arise from common ancestry.
2. Analogous structures arise from convergent evolution.
3. Bird wing and moth wing are homologous structures.
4. Whale flipper and bird wing are homologous structures.
(A) 1, 2, and 4 only
(B) 1 and 3 only
(C) 2 and 4 only
(D) All statements are correct
Answer & Explanation: (A) Statements 1, 2, and 4 are correct. Homologous structures share a common evolutionary origin (e.g., bird wing and whale flipper). Analogous structures arise independently but serve similar functions (e.g., bird wing and moth wing), showing convergent evolution rather than homology.