Question

why do some stickleback populations lack pelvic spines?
select all that apply.
pelvic spines are homologous to legs in four - legged animals and freshwater sticklebacks don’t need hind limbs to move.
in freshwater, a marine stickleback sheds its spines.
freshwater fish have evolved different types of protective armor to keep them safe from predators.
in lakes with dragonfly larvae, pelvic spines can be disadvantageous, allowing the predatory larvae to grab the fish.
in lakes where there are no large predatory fish, there is no advantage to having pelvic spines.

Explanation:

Pelvic spines in sticklebacks are homologous to legs in four - legged animals. In freshwater environments, especially in lakes where there are no large predatory fish (or in lakes with dragonfly larvae where pelvic spines can be disadvantageous), having pelvic spines may not be beneficial. In the case of lakes with no large predatory fish, there is no advantage to having pelvic spines as the selective pressure (from large predatory fish) that would favor their presence (e.g., for protection) is absent. In lakes with dragonfly larvae, pelvic spines can be a disadvantage as they allow the predatory larvae to grab the fish.

Answer:

In lakes where there are no large predatory fish, there is no advantage to having pelvic spines. In lakes with dragonfly larvae, pelvic spines can be disadvantageous, allowing the predatory larvae to grab the fish.