While natural selection arises from beneficial mutations that increase survival or the ability to reproduce, genetic drift is a random change in the genetic distribution of a population. This can occur due to things like the bottleneck effect (a change in population due to a disease epidemic or natural disaster) or the founder effect (where a small group forms a new colony). Gene flow or gene migration is the exchange of DNA between two populations via migration or cross-pollination. Genetic diversity can be quantified by average heterozygosity and nucleotide variation. This diversity is maintained by heterozygote advantage, diploidy, geographic variation, frequency-dependent selection, and outbreeding. The Hardy-Weinberg equilibrium and equation describe populations when natural selection is not occurring and certain conditions are met.
Evolution is a change in the
genetic composition of a population over time. Natural selection is
one mechanism for evolution.
Genetic drift is the change in
allele frequency due random chance and usually occurs in small
populations. The founder effect and the bottleneck effect are
examples of genetic drift.
The movement of alleles into or
out of a population is called gene flow and can result in a change
in the frequency of alleles.
The Hardy-Weinberg Equation, p2
+ 2pq + q2 = 1, can be used to predict the frequencies of alleles
and genotypes in populations that meet the following conditions:
Mating is random
No mutations occur
No natural selection is
The population is large.
There is no immigration or
Population Genetic and Evolution
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
The book and CD package include two full length practice exams that are presented with all questions answered and explained. The author also presents detailed reviews of all test topics and includes multiple-choice and free-response questions with answers at the end of each topic's chapter.
This book includes a review of the AP Biology exam format and scoring, proven strategies for answering multiple-choice questions, and hints for tackling the essay questions. The practice tests include answers and explanations and there is also proven test-taking strategies for both the multiple choice and essay parts.