Question

Which of the following is/are necessary condition(s) for natural selection to shape limb lengths in a population?

• A. Individuals in a population vary in the length of their limbs.
• B. Limb length increases in individuals with repeated use.
• C. Offspring inherit the limb lengths of their parents.
• D. Limb length influences running speed and thus, their ability to survive and reproduce.

Hint:

Natural selection needs variation, heritability, and fitness differences.

Answer 1

The Correct Option is A, C, D

To understand which conditions are necessary for natural selection to influence limb lengths in a population, let's examine the key principles of natural selection:

1. Variation: There must be differences among individuals in a population. In this case, it's needed that individuals show variation in limb length. Without variation, there is no raw material for natural selection to act upon.
2. Inheritance: Traits must be heritable, meaning offspring inherit traits from their parents. For natural selection to affect limb lengths, offspring must inherit the limb lengths of their parents.
3. Differential Survival and Reproduction: The trait must influence an individual's ability to survive and reproduce. In this scenario, limb length affects running speed, thereby impacting survival and reproduction. This implies that individuals with advantageous limb lengths are more likely to survive and pass on these traits to the next generation.

We can now match these principles with the given options:

• Option: Individuals in a population vary in the length of their limbs.
  This matches the first condition, Variation. Thus, it is necessary.
• Option: Limb length increases in individuals with repeated use.
  This suggests a change due to use in an individual's lifetime, not inherited, which aligns with Lamarckism rather than Darwinism (Natural Selection). This is not necessary for natural selection.
• Option: Offspring inherit the limb lengths of their parents.
  This matches the Inheritance condition. Thus, it is necessary.
• Option: Limb length influences running speed and thus, their ability to survive and reproduce.
  This corresponds with the Differential Survival and Reproduction principle. Therefore, it is necessary.

Based on the above analysis, the necessary conditions for natural selection to act on limb lengths in a population are:

• Individuals in a population vary in the length of their limbs.
• Offspring inherit the limb lengths of their parents.
• Limb length influences running speed and thus, their ability to survive and reproduce.