McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved

The Processes of Evolution  What are species?  What are the processes of evolution?  How do these processes interact to bring about evolution as we understand it today?

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Species: The Units of Evolution  Evolution takes place in populations of organisms, and the basic population in nature is the species.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved definitions  Niche  The environment of an organism and its adaptive response to that environment.  Taxonomists  Scientists who classify and name living organisms.  Gene Frequency  The percentage of times a particular allele appears in a population.  Allele Frequency  Another name, and the preferred term, for gene frequency.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Mutations: Necessary Errors  Mutations are the price living things pay for the process of evolution.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved definitions  Point Mutations  Mutations of a single base of a codon.  Chromosomal Mutations  Mutations of a whole chromosome or a large portion of a chromosome.  Gene Pool  All the alleles in a population.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Natural Selection: The Prime Mover of Evolution  Natural selection selects phenotypes for reproductive success based on their adaptive relationship with the environment.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Gene Flow: Mixing Populations’ Genes  When members of different breeding populations interbreed, new genetic combinations are produced in the offspring.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved definitions  Breeding Populations  Populations within a species that are genetically isolated to some degree from other populations.  Gene Flow  The exchange of genes among populations through interbreeding.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Genetic Drift: Random Evolution  Fission, the founder effect, and gene flow are particularly important in the evolution of our species.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved definitions  Sampling Error  When a sample chosen for study does not accurately represent the population from which the sample was taken.  Fission  Here, the splitting up of a population to form new populations.  Founder Effect  Genetic differences between populations produced by the fact that genetically different individuals established (founded) those populations.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved definitions  Bottleneck  A severe reduction in the size of a population or the founding of a new population by a small percentage of the parent population that results in only some genes surviving and characterizing the descendant population.  Gamete Sampling  The genetic change caused when genes are passed to new generations in frequencies unlike those of the parental generation. An example of sampling error.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Sickle Cell Anemia: Evolutionary Processes in Action  Sickle cell anemia is the result of a mutation.  The connection between sickle cell and African Americans is an example of the founder effect.

McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All Rights Reserved The Processes of Evolution  Summary  The processes of evolution are  Mutation  Natural selection  Gene flow  Genetic drift