Science Assessment

The brown anole is a long-legged species of lizards that lives in the lower limbs and trunks of trees. Scientists know that having long legs allows anoles to sprint faster, but they wondered whether having shorter legs could also give anoles a survival advantage in certain environments. To test this, scientists took brown anoles from their natural environment and placed them on small islands where there were bushes with thin branches and no trees. Each year, the scientists returned to measure the leg length of individuals from each generation of the brown anole lizards. They also measured the diameter of the branches the anoles were resting on.

The graph below shows the average diameter of resting places for anoles in both natural and experimental habitats.

How could changes in the diameter of resting places affect the distribution of leg-length in future generations of anoles born in the experimental habitat?

1. The change in resting place diameter could cause new leg length variations to arise in the experimental habitats. These leg length variations did not exist in the anole population when they were in their natural habitat.
2. The change in resting place diameter could affect the survival advantage of anoles with different leg lengths. These variations in leg length already existed in the anole population when they were in the natural habitat.
3. The change in resting place diameter could cause natural selection to begin acting on leg length in the experimental habitat. Natural selection was not acting on the anole population when they were in the natural habitat.
4. The change in resting place diameter could create a need for individual anoles to change the length of their legs and pass these changes on to their offspring. The anoles did not have this need when they were in their natural habitat.