Evolution may lead to speciation：練習題

Which of the following best describes sympatric speciation?

A researcher studied a population of mice on a small, isolated island. Over ten years, the frequency of an allele for light-colored fur increased significantly, even though the environment favored dark-colored fur for camouflage.

Which process most likely caused this change in allele frequency?

A population of butterflies exists in an area with a high frequency of two distinct color phenotypes: bright orange and dark brown. Predation by birds is heavy on butterflies with intermediate (medium brown) wing colors, while the extreme phenotypes have a survival advantage.

What type of selection is occurring in this population?

Which of the following is the defining characteristic of allopatric speciation?

A population of an insect species was separated into two isolated groups by a volcanic eruption that created a lava flow barrier. After many generations, the lava flow weathered away, allowing the two groups to inhabit the same area again. However, it was observed that the two groups no longer interbred.

Which of the following processes most accurately describes how allopatric speciation resulted in this outcome?

Two populations of a wildflower species are separated by a wide river, leading to allopatric speciation.
Describe how the selection pressures in different environments lead to the accumulation of genetic differences between these populations.

A population of rare orchids is found in a small, isolated valley. Over several decades, a specific allele for petal spots increases in frequency from 0.05 to 0.40, despite having no apparent effect on pollinator attraction or plant survival.
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}State the most likely process responsible for this change and explain why its effect is particularly significant in this specific scenario.

Genetic variation and isolation are key drivers of speciation.

a) Describe the process of allopatric speciation, starting from a single population of a species.
b) Explain the role of natural selection and reproductive isolation in this process.
c) How does genetic drift differ from natural selection, and why is its effect more pronounced in small populations?