Question

Select the correct answer. A certain widely distributed mammalian species remained unchanged for about 30 million years. Most members of this species lived on a fertile plain, but some members (that were less well adapted) survived in low numbers in the surrounding mountains. They adapted and evolved to this area and became significantly different from their relatives on the plain. A sudden meteorite attack struck the plain and destroyed the plain population. The mountain population was unaffected and as the plain environment recovered moved to the plain. In the absence of competitors, they underwent a very rapid population explosion. Which mode of evolution does this example explain? A. Gradualism B. Punctuated equilibrium C. Microevolution

Answer 1

The mode of evolution illustrated by the example is punctuated equilibrium, which occurs when long periods of little change are interrupted by bursts of rapid change due to environmental events like a meteorite strike. Therefore, the correct option is B.

Step-by-step explanation:

The mode of evolution that is explained by the scenario where a mammalian species remained unchanged for about 30 million years and then underwent rapid change after a meteorite event is known as punctuated equilibrium. In this case, a stable population on a plain lived without much change until a sudden environmental event killed them off. The members of the species that lived in the mountains, which were less well-adapted but survived the disaster, moved to the plain and quickly filled the open niches, leading to a rapid population explosion and evolution.

Punctuated equilibrium is characterized by long periods of stasis interrupted by bursts of rapid change, which is supported by the fossil record more than gradualism. This model suggests that environmental changes can create opportunities for rapid evolutionary changes. Gradual change over time, or gradualism, is another mode of evolution where species diverge at a slow, steady pace as traits change incrementally, typically when living in a stable climate.