Which type of evidence is most important when determining whether a trait is an adaptation?

• A. Evidence that the trait is genetically inherited
• B. Evidence that the trait is present in all individuals of the species
• C. Evidence that the trait is unique to a single population
• D. Evidence that the trait increases the organism's fitness in its environment

Answer: (D)

Verified step by step guidance

1. Understand the concept of adaptation: An adaptation is a trait that has evolved through natural selection because it increases an organism's fitness, which refers to its ability to survive and reproduce in a specific environment.
2. Clarify the term 'fitness': Fitness is a measure of how well an organism can pass on its genes to the next generation. Traits that improve survival, reproduction, or both are considered to increase fitness.
3. Evaluate the importance of genetic inheritance: While genetic inheritance is necessary for a trait to be passed down, it alone does not confirm that the trait is an adaptation. The trait must also provide a fitness advantage.
4. Analyze the presence of the trait in all individuals of a species: A trait being present in all individuals does not necessarily mean it is an adaptation. It could be a neutral trait or one that does not affect fitness.
5. Focus on evidence of increased fitness: The most important evidence for determining whether a trait is an adaptation is whether it increases the organism's fitness in its environment. This can be assessed through studies showing improved survival or reproductive success in individuals with the trait compared to those without it.