What is adaptation in biological terms?

Adaptation in biological terms refers to a process where organisms undergo changes that enhance their survival and reproductive success in a specific environment. This definition aligns closely with the correct answer, which focuses on the modification of beneficial features or functions that enable an organism to better suit its environment or fulfill its ecological niche.

For instance, the long neck of a giraffe is an adaptation that allows it to reach high leaves in trees, an example of how a change serves a practical purpose in the organism's life.

The other options don't quite capture the concept of adaptation as effectively. A permanent change in structure could suggest a variety of transformations, not necessarily ones that are beneficial or functional. A change in species implies a broader evolutionary process rather than a specific enhancement in individual organisms. Similarly, a change in the ecosystem refers to alterations in the community of living organisms or their environment, which is distinct from the idea of individual organisms adapting to their surroundings.