An organism's niche includes its habitat, its resource requirements, and its:

• A. role in the ecosystem
• B. population size
• C. genetic variation
• D. evolutionary history

Answer: (A)

Verified step by step guidance

1. Understand the concept of an organism's niche: A niche refers to the role an organism plays in its ecosystem, including its interactions with other organisms and its environment.
2. Break down the components of a niche: It includes the organism's habitat (where it lives), its resource requirements (what it needs to survive, such as food, water, and shelter), and its role in the ecosystem (how it contributes to the ecosystem, such as being a predator, prey, or decomposer).
3. Evaluate the options provided: 'Population size' refers to the number of individuals in a species, which is not directly part of the niche. 'Genetic variation' refers to the diversity of genes within a population, which is related to evolution but not directly part of the niche. 'Evolutionary history' refers to the organism's past adaptations, which influence its niche but are not part of the definition.
4. Focus on the correct answer: The role in the ecosystem is a fundamental part of an organism's niche because it defines how the organism interacts with other species and contributes to the ecosystem's functioning.
5. Conclude that the correct answer is 'role in the ecosystem,' as it aligns with the definition of an organism's niche and its ecological significance.