Question

Which is an example of anisogamy?

1) Male red deer have large antlers, but females do not have antlers at all.
2) Female jacanas are larger in size than the males.
3) Female fiddler crabs have two small claws, but males have one small claw and one huge claw.
4) The eggs of a female kiwi are large, but the sperm of the males are small.
5) All of the above.
6) None of the above.

Answer 1

Option 4, where the female kiwi's eggs are large and the male's sperm are small, is an example of anisogamy. The other options describe sexual dimorphism, which is related to differences in physical traits rather than gamete size.

Step-by-step explanation:

Anisogamy refers to a form of sexual reproduction involving the fusion of two distinctly different gametes, typically an immobile, nutrient-rich egg and a smaller, mobile sperm. In the context of the examples provided, anisogamy is best demonstrated by option 4: The eggs of a female kiwi are large, but the sperm of the males are small. This represents the fundamental aspect of anisogamy, where female gametes (eggs) are generally larger and male gametes (sperm) are much smaller.

Sexual dimorphism, on the other hand, involves distinct differences between the sexes of a species in terms of size, coloration, and other physical traits, which is not directly related to the size of the gametes but rather to sexual selection pressures. Examples of sexual dimorphism are seen in male red deer having large antlers, female jacanas being larger in size than males, and male fiddler crabs having one huge claw compared to their two small claws. These represent instances where physical traits are selected to improve mating success, not cases of anisogamy.