Copyright Pearson Prentice Hall Variation and Gene Pools A population is a group of individuals of the same species that interbreed. A gene pool consists of all genes, including all the different alleles, that are present in a population.
Copyright Pearson Prentice Hall Sources of Genetic Variation The two main sources of genetic variation are mutations and the genetic shuffling that results from sexual reproduction. (**remember crossing over and independent assortment during meiosis)
Copyright Pearson Prentice Hall Natural Selection on Polygenic Traits Natural selection can affect the distributions of phenotypes in any of three ways: directional selection stabilizing selection disruptive selection
Copyright Pearson Prentice Hall Natural Selection on Polygenic Traits Directional Selection When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end, directional selection takes place.
Copyright Pearson Prentice Hall Natural Selection on Polygenic Traits Stabilizing Selection When individuals near the center of the curve have higher fitness than individuals at either end of the curve, stabilizing selection takes place.
Copyright Pearson Prentice Hall Natural Selection on Polygenic Traits Disruptive Selection When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle, disruptive selection takes place.
Copyright Pearson Prentice Hall Genetic Drift A random change in allele frequency Genetic drift may occur when a small group of individuals colonizes a new habitat.
Copyright Pearson Prentice Hall Genetic Drift
Copyright Pearson Prentice Hall Genetic Drift
Copyright Pearson Prentice Hall Genetic Drift Descendants Population A Population B When allele frequencies change due to migration of a small subgroup of a population it is known as the founder effect.
Copyright Pearson Prentice Hall Speciation is the formation of new species. A species is a group of organisms that breed with one another and produce fertile offspring. The gene pools of two populations must become separated for them to become new species
Copyright Pearson Prentice Hall Isolating Mechanisms When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred.
Copyright Pearson Prentice Hall Isolating Mechanisms Behavioral Isolation -when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.
Copyright Pearson Prentice Hall Isolating Mechanisms Geographic Isolation - when two populations are separated by geographic barriers such as rivers or mountains. Abert Kaibab
Copyright Pearson Prentice Hall Isolating Mechanisms Temporal Isolation - when two or more species reproduce at different times.
What are two patterns of macroevolution? adaptive radiation and convergent evolution.
Adaptive Radiation Adaptive radiation is an evolutionary process by which a single species or a small group of species evolves over a relatively short time into several different forms that live in different ways. (ex. Darwin’s finches) Also known as DIVERGENT EVOLUTION
Convergent Evolution Evolution produces similar structures and characteristics in distantly-related organisms through the process of convergent evolution.
Coevolution The process by which two species evolve in response to changes in each other over time is called coevolution. (ex. flowers and pollinators)