Question

pond snails live in freshwater environments such as ponds, lakes, and rivers. a pond snail’s shell may be narrow or round.
(right)
a narrow shell (left) and a round shell
the table below describes a possible population of pond snails over a time period long enough for natural selection to occur. the table shows shell shape in the population at the start and end of this period.
data about a population of pond snails
point in time\tpercentage with narrow shells\tpercentage with round shells
start\t55.6%\t44.4%
end\t36.3%\t63.7%
complete the following statements to construct the hypothesis that is best supported by the data.
over this time period, snails with narrow shells were
likely to survive and reproduce than snails with round shells. this means that having narrow shells was
advantageous than having round shells.

Explanation:

Step1: Analyze percentage change (narrow)

Start: $55.6\%$, End: $36.3\%$. Change: $36.3 - 55.6 = -19.3\%$

Step2: Analyze percentage change (round)

Start: $44.4\%$, End: $63.7\%$. Change: $63.7 - 44.4 = +19.3\%$

Step3: Infer survival/reproduction likelihood

Narrow shells decreased, so they are less likely to survive/reproduce.

Step4: Infer adaptive advantage

Round shells increased, so narrow shells are less advantageous.

Answer:

1. (Completed table logic: the missing cells are the given values, so the full table is:

Point in time	Percentage with narrow shells	Percentage with round shells
End	36.3%	63.7%	)

1. 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.