A rain forest primate called an aye-aye has an extremely long middle finger that it uses to probe for insects in cracks and crevices in tree bark. This connection between structure and function developed gradually over time as a result of ...

The correct answer is - natural selection.

Explanation:

Natural selection is the process in which an organism adapted according to environmental changes for its survival and increase there number by reproduction.

Charles Darwin was first to explain its activities and now it's established as the major process behind the evolution.

Aye aye, primate adapted according to the environment and develop a character for its survival over a period of time. Natural selection is the connection between structure and function.

Thus, the correct answer is - natural selection.