Question

two populations of the same species of sea urchin, one with mostly long spines and the other with mostly short spines, are separated by the narrow strip of land that connects north and south america. a canal is built through this isthmus and connects the two urchin populations. neither has a reproductive advantage over the other. which of the following outcomes are likely to result after the new canal? correct answer(s) over time, the short-spine dominated population will come to have more long-spine individuals. long-spine sea urchin individuals will be less frequent in the short-spine population. the spines of the long-spine population will become longer. over time, the long-spine dominated population will come to have more short-spine individuals.

Explanation:

When the two populations are connected, gene flow occurs. Since neither has a reproductive advantage, the short - spine population will gain long - spine genes (so more long - spine individuals over time) and the long - spine population will gain short - spine genes (so more short - spine individuals over time). The option about spines becoming longer is wrong as no selection pressure for longer spines. The option about long - spine individuals being less frequent in short - spine population is wrong (they should become more frequent due to gene flow).

Answer:

• Over time, the short - spine dominated population will come to have more long - spine individuals.
• Over time, the long - spine dominated population will come to have more short - spine individuals.