Chapter 3: Evolution and Genetics

 Learning Objectives- After reading this chapter and coming to class you should be able to: 
1.	Know the key dimensions of Charles Darwin’s and Alfred Russel Wallace’s theory of evolution by natural selection. Consider the influence of the geologic principle of uniformitarianism on Darwin’s work and subsequent research in human evolution and other fields. Compare and contrast the other perspectives on the origin of life that existed in Darwin’s time and exist today.  
2.	Know the importance of Gregor Mendel’s experiments and their implications for evolution. Identify the key contributions of Mendelian genetics to the study of hereditary traits.  
3. 	Understand the significance for evolution of the functions of DNA, the two primary types of cell division, the process of crossing over, and instances of genetic mutation. 
4.	Be familiar with the subject matter of population genetics. 
5.	Be able to discriminate between the key mechanisms of genetic evolution and understand the role each mechanism plays in evolution. 
6. 	Know the significance of the modern evolutionary synthesis and the three kinds of evolutionary change in the contemporary study of biological evolution. 

Terms-  You should understand these terms and be ready to identify them: 
adaptive Favored by natural selection in a particular environment. 
allele A biochemical variant of a particular gene. 
balanced polymorphism Two or more forms, such as alleles of the same gene, that maintain a constant frequency in a population from generation to generation. 
chromosomes Basic genetic units, occurring in matching (homologous) pairs; lengths of DNA made up of multiple genes.
crossing over During meiosis, the process by which homologous chromosomes intertwine and exchange segments of their DNA.
dominant Allele that masks another allele in a heterozygote.
evolution Belief that species arose from others through a long and gradual process of transformation, or descent with modification.
gene Area in a chromosome pair that determines, wholly or partially, a particular biological trait, such as whether one's blood type is A, B, or O.
gene flow Exchange of genetic material between populations of the same species through direct or indirect interbreeding.
gene pool All the alleles, genes, chromosomes, and genotypes within a breeding population—the "pool" of genetic material available.
genetic evolution Change in gene frequency within a breeding population.
genotype An organism's hereditary makeup.
heterozygous Having dissimilar alleles of a given gene.
homozygous Possessing identical alleles of a particular gene.
independent assortment Mendel's law of; chromosomes are inherited independently of one another.
meiosis Special process by which sex cells are produced; four cells are produced from one, each with half the genetic material of the original cell.
mitosis Ordinary cell division; DNA molecules copy themselves, creating two identical cells out of one.
mutation Change in the DNA molecules of which genes and chromosomes are built.
natural selection The process by which the forms most fit to survive and reproduce in a given environment do so in greater numbers than others in the same population; more than survival of the fittest, natural selection is differential reproductive success.
phenotype An organism's evident traits, its "manifest biology"—anatomy and physiology.
population genetics Field that studies causes of genetic variation, maintenance, and change in breeding populations.
punctuated equilibrium Evolutionary theory that long periods of stasis (stability), during which species change little, are interrupted (punctuated) by evolutionary leaps.
random genetic drift Change in gene frequency that results not from natural selection but from chance; most evident in small populations.
recessive Genetic trait masked by a dominant trait.
sexual selection Based on differential success in mating, the process in which certain traits of one sex (e.g., color in male birds) are selected because of advantages they confer in winning mates.
speciation Formation of new species; occurs when subgroups of the same species are separated for a sufficient length of time.
species Population whose members can interbreed to produce offspring that can live and reproduce.
uniformitarianism Belief that explanations for past events should be sought in ordinary forces that continue to work today.