LEQ: What is the importance of genetic variation?

1. LEQ: What is the importance of genetic variation?

2. Variation is extensive in most populations… • Traits controlled by genes alone • Blood Type – determined by the genes that produce antigens which are present on your Red Blood Cells • Traits controlled by both genes and the environment • Height in humans – determined by polygenic inheritances and influenced by your environment (proper nutrition, etc…) Heritable Variation Nonheritable Variation

3. Variation is extensive in most populations… • Referring to a population in which two or more physical forms are present in readily noticeable frequencies • Garter snakes living in the same field can have several different body colorations. The behavior of each form correlates to the body coloration. Spotted snake blends in, doesn’t flee when approached. Stripped snake flees rapidly – stripes make it difficult to judge speed of motion. Example

4. Variation is extensive in most populations… • A gradation in an inherited trait along a geographic continuum; variation in a population's phenotypic features that parallels an environmental gradient • Body size of many birds and mammals tends to increase with increasing latitude in North America. Large size in colder latitudes reduces the ratio of body surface area to volume and helps conserve heat. Cline Example

5. Mutation and Sexual Recombination generation variation… • Changes to DNA in gametes can be passed to offspring and potentially impact a populations gene pool • Can be helpful, harmful or neutral • Occur often in bacteria • Variation that results from • crossing over (during prophase 1 of meiosis) • independent assortment of homologous chromosomes ( during metaphase 1 of meiosis) • Segregation of alleles (during anaphase 1 of meiosis) • random fertilization Mutation Sexual Recombination

6. Genetic Variation • http://www.pbs.org/wgbh/evolution/library/01/2/quicktime/l_012_02.html • http://www.pbs.org/wgbh/evolution/library/01/5/quicktime/l_015_03.html