Topic: Earthworm Anatomy
Subtopic: External Structures and Functions
Keyword Definitions:
Prostomium: Lobe-like structure in front of the mouth of an earthworm, aiding in sensory functions and soil penetration.
Earthworm: Segmented annelid worm, important for soil aeration and nutrient cycling.
Sensory structures: Organs or body parts that detect environmental stimuli such as touch, light, or chemicals.
Body segment: Repeated structural units in annelids, each with specific functions.
Soil penetration: Ability of earthworms to move through soil using specialized body parts.
Mouth covering: Structures that protect or aid the function of the mouth opening.
Cracks in soil: Small gaps in soil facilitating earthworm movement and aeration.
Anterior segment: Front part of the body in annelids, usually containing prostomium.
Locomotion: Movement or ability to crawl, burrow, or navigate through the environment.
Soil aeration: Process by which earthworms enhance oxygen availability in soil.
Segmented body plan: Division of the body into repeated units, characteristic of annelids.
Lead Question - 2021
Following are the statements about prostomium of earthworm.
(a) It serves as a covering for mouth.
(b) It helps to open cracks in the soil into which it can crawl.
(c) It is one of the sensory structures.
(d) It is the first body segment.
Choose the correct answer from the options given below.
(1) (a), (b) and (d) are correct
(2) (a), (b), (c) and (d) are correct
(3) (b) and (c) are correct
(4) (a), (b) and (c) are correct
Explanation: The prostomium is the lobe in front of the mouth, acting as a covering (a), aiding in opening soil cracks (b), and serving as a sensory structure (c). It is not considered the first true body segment. Therefore, statements a, b, and c are correct. Correct answer is option (4).
1. Prostomium helps in:
(1) Digestion
(2) Soil penetration
(3) Excretion
(4) Circulation
Explanation: Prostomium assists the earthworm in penetrating soil by sensing cracks and soft areas to crawl through. It does not directly participate in digestion, excretion, or circulation. Correct answer is option (2) Soil penetration.
2. Sensory function of prostomium includes:
(1) Touch and chemical detection
(2) Blood pumping
(3) Soil digestion
(4) Locomotion only
Explanation: Prostomium contains sensory receptors to detect touch and chemical signals in the soil, helping the earthworm navigate and find food. It does not function in circulation, digestion, or movement directly. Correct answer is option (1) Touch and chemical detection.
3. The prostomium is located:
(1) Anterior to mouth
(2) Posterior to anus
(3) Middle body segment
(4) Along ventral surface
Explanation: The prostomium is the foremost lobe, anterior to the mouth, assisting in sensing and soil penetration. It is not located near the anus, middle body, or ventral surface specifically. Correct answer is option (1) Anterior to mouth.
4. Which is not a function of prostomium?
(1) Covering mouth
(2) Sensory detection
(3) Locomotion
(4) Opening soil cracks
Explanation: Prostomium covers the mouth, helps sense the environment, and aids soil penetration. It does not directly contribute to locomotion, which is driven by circular and longitudinal muscles along with setae. Correct answer is option (3) Locomotion.
5. Prostomium is made of:
(1) Epidermal tissue
(2) Muscular tissue only
(3) Nervous tissue only
(4) Cartilage
Explanation: Prostomium consists mainly of epidermal tissue with some sensory cells. It does not have cartilage or exclusively muscular or nervous tissue. Correct answer is option (1) Epidermal tissue.
6. Single Correct Answer:
Which body structure precedes the mouth in earthworm?
(1) Prostomium
(2) Clitellum
(3) Setae
(4) Anus
Explanation: Prostomium is located before the mouth at the anterior end, aiding in soil detection and entry. Clitellum, setae, and anus are located elsewhere in the segmented body. Correct answer is option (1) Prostomium.
7. Assertion-Reason:
Assertion (A): Prostomium is a sensory structure.
Reason (R): It detects touch and chemical signals in soil.
(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: Prostomium contains sensory cells that detect touch and chemical cues, explaining its role as a sensory structure. Correct answer is option (1).
8. Matching Type:
Match prostomium function with description:
(a) Mouth covering - 1. Protects oral opening
(b) Soil penetration - 2. Opens soil cracks
(c) Sensory detection - 3. Detects touch and chemicals
(1) a-1, b-2, c-3
(2) a-2, b-3, c-1
(3) a-3, b-1, c-2
(4) a-1, b-3, c-2
Explanation: Prostomium protects mouth (a-1), helps open soil cracks (b-2), and senses touch and chemicals (c-3). Correct answer is option (1).
9. Fill in the Blank:
_____ is the foremost lobe of an earthworm helping in soil detection.
(1) Prostomium
(2) Clitellum
(3) Setae
(4) Anus
Explanation: The prostomium is the front lobe of an earthworm, assisting in soil exploration and sensory detection. Clitellum, setae, and anus have different functions. Correct answer is option (1) Prostomium.
10. Choose the correct statements:
(a) Prostomium covers mouth
(b) It aids in soil penetration
(c) It is a sensory structure
(d) It is the first true body segment
(1) a, b, c
(2) a, b, d
(3) b, c, d
(4) a, c, d
Explanation: Prostomium functions as mouth covering (a), aids soil penetration (b), and is sensory (c). It is not the first true body segment (d). Correct answer is option (1) a, b, c.