Question

evolution: gene flow

1. suggest how it was possible for this gene flow to occur between the two frog populations.
2. after many generations, population 2 has evolved so that all of the frogs are spotted. suggest how and why this happened.

Explanation:

For question 2, gene - flow could occur if the river level drops allowing frogs to cross, or if there are temporary land bridges. Also, if birds or other animals carry frogs or their eggs between the populations. For question 3, if the spotted trait was advantageous (e.g., better camouflage), natural selection would favor it. Frogs with the spotted trait would have higher survival and reproductive rates, passing on the genes for spotting. Over many generations, this led to all frogs in population 2 being spotted.

Answer:

1. The river level may drop, creating a land - bridge for frogs to move between populations. Birds or other animals may carry frogs or their eggs across the river.
2. The spotted trait was likely advantageous, perhaps for camouflage. Frogs with this trait had higher survival and reproductive success, passing on the spotting genes. Over generations, the frequency of the spotting genes increased until all frogs in population 2 were spotted.