Define adaptation in evolutionary terms.

• A. A learned behavior that helps survival
• B. A non-heritable trait that changes with environment
• C. A trait that evolves due to mutation but is always beneficial
• D. A heritable trait that increases an organism's fitness in a given environment.

Answer: (D)

Adaptation in evolution means a heritable trait that increases an organism’s fitness in a given environment. This means the trait is passed from parents to offspring and helps individuals with it leave more offspring than those without it, so it becomes more common over generations through natural selection. It isn’t something learned during a life (that would be A) and it isn’t just a non-heritable response to surroundings (that would be phenotypic plasticity, B). Also, not every mutation produces an adaptation or is always beneficial in all conditions (C is too absolute). The key idea is that the trait enhances reproductive success in the environment, making it a true evolutionary adaptation.