Exam 13: How Populations Evolve

Desert pupfish live in springs of the American Southwest. Today, there are about 30 species of pupfish, but they all evolved from a common Pleistocene ancestor. The southwestern United States was once much wetter than it is now, and the Pleistocene pupfish flourished over a wide geographic area. Over thousands of years, however, the Sierra Nevada mountain range was pushed upward by geological forces, blocking rainfall from the Pacific Ocean. As the large lakes dried up, small groups of pupfish remained in springs and pools fed by groundwater seepage. Now, although many of these small springs still have pupfish, each population, through evolution, has become very different from populations of pupfish in other springs. -Which of the following statements represents a probable explanation for differences among pupfish populations?

The ultimate source of all new alleles is

The core theme of biology, which explains both the unity and diversity of life, is

The recessive allele of a gene causes cystic fibrosis. For this gene among Caucasians, p = 0.98. If a Caucasian population is in Hardy-Weinberg equilibrium with respect to this gene, what proportion of babies is born homozygous recessive and therefore suffers cystic fibrosis?

Which of the following conditions would tend to make the Hardy-Weinberg equation more accurate for predicting the genotype frequencies of future generations in a population of a sexually reproducing species?

Which of the following best expresses the concept of natural selection?

An elk herd is observed over many generations. Most of the full-grown bull elk have antlers of nearly the same size, although a few have antlers that are significantly larger or smaller than this average size. The average antler size remains constant over the generations. Which of the following effects probably accounts for this situation?