Adaptation and Constraints
Adaptation Is Not Perfection
What adaptation means
An adaptation is a heritable trait that increases fitness in a particular environment. Adaptations arise because selection favors traits that work better in that environment.
Trade-offs
Many traits involve trade-offs. A feature that helps in one way may hurt in another. Evolution works with existing variation and past history, not from scratch.
Avoid teleology
Evolution has no goal or plan. Traits do not evolve because organisms 'need' them; they spread when they improve reproductive success.
Useful concepts
What is an adaptation?
An adaptation is a heritable trait that improves fitness in a particular setting.
Correct answer: A trait favored because it increases fitness in a given environment
Why are organisms not perfectly designed?
Natural selection improves traits relative to the environment, but it does not produce perfection.
Correct answer: Because evolution works with trade-offs, constraints, and existing history rather than from scratch.
What is an exaptation?
Exaptations are traits co-opted for a new function.
Correct answer: A trait that evolved for one use and later became useful for another