Match List-I with List-II:

Choose the correct answer from the options given below:

List–I (Type of Interaction)	List–II (General Nature of Interaction)

(A) Parasitism

(I) Species A benefits while species B remains unaffected

(B) Mutualism

(II) Both species A and B negatively affected in the interaction

(C) Commensalism

(III) Species A generally smaller than species B

(D) Competition

(IV) Both species A and B positively affected in a positive and obligatory interaction

Correct option is B

Introduction

Species interactions are a central concept in ecology. These interactions—such as parasitism, mutualism, commensalism, and competition—define how species coexist and impact each other's survival and fitness.

Information Booster:

• A. Parasitism → Both negatively affected (II):
  In competition, both species suffer due to the struggle for limited resources like food, space, or light.
  Example: Plants competing for sunlight in a dense forest.

B. Mutualism → Both species A and B positively affected (IV):
Mutualism is an interaction where both species benefit, and in some cases, the relationship is obligatory, meaning they can't survive without each other.
Example: Pollination between bees and flowers.

• C. Commensalism → Species A benefits, B unaffected (I):
  In commensalism, one species benefits while the other is neither helped nor harmed.
  Example: Barnacles on whales.
• D. Competition → Species A generally smaller than species B (III):
  In parasitism, one organism (parasite) benefits by living on or in another organism (host), causing harm. The parasite is usually smaller and dependent on the host for survival.

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