A scientist studies a population of lizards isolated on a tropical island over many years. During the study, several rats are accidentally introduced to the island. The rats prey on the lizards. The scientist notices that the lizards with the longest legs run the fastest and are more likely to outrun the rats. Over several more generations, the scientists finds that while the range of leg lengths in the lizards changes little, the average leg length has increased.

Question

Which ,begin emphasis,two,end emphasis, statements explain the scientist's observations?

Answer options with 5 options
A.
Lizards needed to run faster to escape the rats, so they developed longer legs.

B.
By running faster to escape the rats, the lizards made their legs slowly grow longer over time.

C.
Predation by rats caused new mutations in the lizards, which caused their legs to grow longer.

D.
Lizards with longer legs are more likely to survive and reproduce than lizards with shorter legs.

E.
There was already variation in the genes controlling leg length in the lizard population before the rats arrived.

Answer 1

The two statements that explain the scientist's observations are:

D. Lizards with longer legs are more likely to survive and reproduce than lizards with shorter legs.

E. There was already variation in the genes controlling leg length in the lizard population before the rats arrived.

These statements highlight that natural selection favored lizards with longer legs (statement D), and that there was genetic diversity in the population that allowed for this change (statement E).