Mader: Biology 8 th Ed.

Population Genetics Genetic diversity in populations changes over generations Forces that cause populations to evolve Allele and genotype frequencies over generations Mader: Biology 8 th Ed.

Microevolution Change in gene frequencies between populations of a species over time Hardy-Weinberg Equilibrium Stable, non-evolving population Mader: Biology 8 th Ed.

The nitty-gritty: p292 of text Random mating No selection (no reproductive advantages) No mutation No migration Large population Mader: Biology 8 th Ed.

Migration aka GENE FLOW Amount depends on: – Distance between populations – Ability of individuals/gametes to move between populations – behavior No migration can result in reproductive isolation Mader: Biology 8 th Ed.

Genetic Drift: A result of small populations Chance events alter the gene pool Bottleneck effect Founder effect High level of inbreeding – loss of diversity in the population Mader: Biology 8 th Ed.

Figure 24.9 Ensatina eschscholtzii, a ring species

How do we define a “species”? Morphological species – Cryptic species Evolutionary species (fossils) Biological species Mader: Biology 8 th Ed.

Reproductive Isolation Incapable of interbreeding… – Formation of new species… SPECIATION Mader: Biology 8 th Ed.

Speciation The splitting of one species into two or more species. OR The transformation of one species into a new species over time.

Mader: Biology 8 th Ed. Modes of Speciation 1. Allopatric Speciation (Greek, different fatherland)—a population forms a new species while geographically separated from its parent population. reproductive isolation occurs. Examples: squirrels on either side of the Grand Canyon; pupfish in springs in the deserts of California and Nevada; adaptive radiation in island chains.

Mader: Biology 8 th Ed. Modes of Speciation continued 2. Sympatric Speciation (Greek, together, fatherland)—a population develops two or more reproductively isolated groups without prior geographic isolation. Usually a mutation erects a reproductive barrier between the mutants and the parent population. Best evidence is found among plants where it can occur by means of polyploidy or by hybridization between two species followed by doubling of the chromosome number. These new plants can no longer reproduce with the parent species.

Mader: Biology 8 th Ed. Figure 24.6 Two modes of speciation

Mader: Biology 8 th Ed. Figure 24.7 Allopatric speciation of squirrels in the Grand Canyon

Mader: Biology 8 th Ed. Figure 23.9 Geographic variation between isolated populations of house mice

Mader: Biology 8 th Ed. Figure 24.8 Has speciation occurred during geographic isolation?

Mader: Biology 8 th Ed. Figure Sympatric speciation by autopolyploidy in plants

Mader: Biology 8 th Ed. Figure One mechanism for allopolyploid speciation in plants

Mader: Biology 8 th Ed. Adaptive Radiation Is an example of allopatric speciation. The rapid development from a single ancestral species of many new species, which have spread out and become adapted to various ways of life. --as the parent population increases in size, daughter populations are subjected to the founder effect and the process of natural selection. --Examples: 13 species of Galapagos finches 20+ species of Hawaiian honeycreeper 500 species of Drosophila in Hawaii

Mader: Biology 8 th Ed.

Types of evolution Divergent Parallel Convergent Mader: Biology 8 th Ed.

Rates of Evolution Mader: Biology 8 th Ed.