Q1.
With reference to ecological interactions, consider the following statements:
- In mutualism, both interacting species derive benefit from the association.
- In commensalism, one species benefits while the other is neither harmed nor benefited.
- In parasitism, the host is always killed by the parasite.
How many of the statements given above are correct?
A. Only One
B. Only Two
C. Only Three
D. None
Correct Answer: B
Explanation:
- Statement 1 – Correct
- Mutualism is a (+ , +) interaction where both species benefit (e.g., lichen: algae + fungus).
- Statement 2 – Correct
- Commensalism is a (+ , 0) interaction where one benefits and the other is unaffected (e.g., cattle egret and grazing cattle).
- Statement 3 – Incorrect
- In parasitism, the host is harmed but usually not killed; killing the host would eliminate the parasite’s own survival niche.
Q2.
Which of the following interactions is best represented by the notation (– , –)?
A. Predation
B. Amensalism
C. Competition
D. Parasitism
Correct Answer: C
Explanation:
- Competition is a (– , –) interaction because both species suffer reduced fitness due to shared limited resources.
- Predation and parasitism are (+ , –) interactions, while amensalism is (0 , –).
Q3. Match List I (Interaction) with List II (Example):
| List I | List II |
| A. Mutualism | 1. Cattle egret and grazing cattle |
| B. Commensalism | 2. Lichen |
| C. Predation | 3. Snake feeding on frog |
| D. Amensalism | 4. Tall tree suppressing grass |
Select the correct answer.
A. A-1, B-2, C-3, D-4
B. A-2, B-1, C-3, D-4
C. A-3, B-2, C-1, D-4
D. A-2, B-3, C-1, D-4
Correct Answer: B
Explanation:
- Mutualism → Lichen (algae + fungus both benefit)
- Commensalism → Cattle egret and cattle
- Predation → Snake feeding on frog
- Amensalism → Tall tree suppressing grass (allelopathy/shading)
Q4.
Assertion (A): Predation plays a crucial role in maintaining ecosystem stability.
Reason (R): Predators regulate prey populations and prevent competitive exclusion.
Choose the correct answer.
A. Both A and R are correct and R explains A
B. Both A and R are correct but R does not explain A
C. A is correct but R is incorrect
D. A is incorrect but R is correct
Correct Answer: A
Explanation:
- Assertion – Correct: Predation helps maintain species diversity and population balance.
- Reason – Correct: By controlling prey populations, predators prevent dominance of a single species, reducing competitive exclusion.
- R correctly explains A, making option A correct.
Q5.
Which of the following interactions is NOT an example of symbiosis?
A. Mutualism
B. Commensalism
C. Parasitism
D. Predation
Correct Answer: D
Explanation:
- Symbiosis refers to long-term, close biological interactions between species.
- Mutualism, commensalism, and parasitism are all forms of symbiosis.
- Predation is a short-term interaction involving killing of prey, not long-term association.
