Question

sometimes rare diseases are introduced on islands when nonnative species are introduced. what if a rare fungal disease that only killed brown anoles was inadvertently brought to an invaded island by researchers who were studying the anoles? using the data provided and what you know about natural selection, which one of the following predictions is most supported by evidence? ○ a. the brown anole population size would decrease overall because of the disease. there would there would be no impact on the green anoles population characteristics because there is no causal relationship between the two. ○ b. the brown anole population would not decrease because they would become immune to the disease and still be the stronger lizard species. this would mean that the introduction of this disease would have no impact on the green anoles population characteristics. ○ c. the brown anole population size would decrease overall, which would result in less competition for resources for the green anoles. the green anoles would be able to survive and reproduce equally well at different perching heights. after one generation, the green anole population would be back to how it was before the brown anoles were introduced. ○ d. the brown anole population size would decrease, which would result in less competition for resources for the green anoles. the green anoles would be able to survive and reproduce equally well at different perching heights. without large footpads being selected for, there would be an increase in green anoles with normal footpads over time.

Explanation:

• Option A: Ignores the ecological relationship (competition) between brown and green anoles. If brown anoles (competitors) decline, it will impact green anoles.
• Option B: There is no indication that brown anoles would become immune to the disease quickly. Also, it disregards the principle of natural selection acting on the population in the face of a new selective pressure (the disease).
• Option C: Evolutionary changes (like the change in footpad size in green anoles due to competition with brown anoles) do not reverse in one generation. Traits are passed on over multiple generations based on selective pressures.
• Option D: When the brown anole population (a competitor) decreases, green anoles face less competition. If the selective pressure (need for large footpads to out - compete brown anoles for perching sites) is removed, natural selection will no longer favor large footpads. Over time, the frequency of green anoles with normal footpads (which were likely the ancestral state before the brown anole invasion) will increase as there is no disadvantage to having normal footpads anymore.

Answer:

D. The brown anole population size would decrease, which would result in less competition for resources for the green anoles. The green anoles would be able to survive and reproduce equally well at different perching heights. Without large footpads being selected for, there would be an increase in green anoles with normal footpads over time.