Question

a pond snail’s shell may be narrow or round. each shape is better at protecting a snail against a different kind of predator. a narrow shell provides better protection against crayfish, which attack a snail at the opening of its shell. narrow shells have smaller openings, so snails with narrow shells are harder for crayfish to reach during an attack. a round shell provides better protection against carp, which crush shells with their teeth. round shells are harder for carp to crush. consider the population of pond snails over the time period previously shown. over this time period, snails with narrow shells were less likely to survive and reproduce than snails with round shells. this means that having narrow shells was less advantageous than having round shells. complete the following statements to construct the explanation that is best supported by the information above. having narrow shells may have been less advantageous than having round shells because snails with narrow shells were \boxed{} protected from predators. this may have been because the population’s environment had \boxed{} carp than crayfish.

Explanation:

Narrow shells protect against crayfish (which attack the shell opening, which is smaller on narrow shells), while round shells protect against carp (which crush shells, and round shells are harder for carp to crush). Since narrow-shelled snails were less likely to survive/reproduce, their shell type was less advantageous, meaning the environment had more carp (the predator they are less protected against) than crayfish.

Answer:

Having narrow shells may have been less advantageous than having round shells because snails with narrow shells were less protected from predators. This may have been because the population's environment had more carp than crayfish.