Learning goal 1: Select the best definition of an adaptation.A physical feature of the body that can be passed down to offspringAn increase in the frequency of a genetic trait over many generationsA challenge that affects an organism's ability to survive and reproduceA genetic trait that helps an organism survive and reproduce

The best definition of an adaptation is: A genetic trait that helps an organism survive and reproduce.

Here's why:

An adaptation in biology is essentially a trait with a current functional role in the life of an organism that is maintained and evolved by means of natural selection. It is a genetic variation that is favorable in a specific environment, which causes this trait to become common in a population because it increases the probability of survival and reproduction.

While the other options have elements of truth, they do not fully encompass the definition of an adaptation.

• A physical feature of the body that can be passed down to offspring: This could potentially be an adaptation if it aids survival and reproduction, but not all inherited physical features are adaptations. For example, eye color is a physical feature that is inherited, but it does not aid in survival or reproduction.

• An increase in the frequency of a genetic trait over many generations: This is a result of adaptation, not the definition of adaptation itself.

• A challenge that affects an organism's ability to survive and reproduce: This is more related to the concept of natural selection, where challenges in the environment can lead to certain traits being favored (adaptations), but the challenge itself is not an adaptation.