Biology

dylan roscover biology two first hour 21 09 2006 chapter 23 1. define + explain 1. Population genetics: The study of genetic variations in populations and the importance of quantitative characteristics. 2. Modern synthesis: A comprehensive theory of evolution emphasizing natural selection, gradualism, and populations as the fundament units of evolutionary change. Essentially, new Darwinism. 3. Population: A group of individuals of once species that live in an area. 4. Gene Pool: A pool consisting of an entire populations alleles and gene loci at a given time. 5. Hardy-Weinberg theorem: An axiom maintaining that the sexual shuffling of genes alone cannot alter the overall genetic make up of a population. 6. Hardy-Weinberg equilibrium: The base number of locus in a HW equation is considered the equilibrium. If an equilibrium is not begun with, it can be achieved after one generation. 7. Mutations: A change in an organisms DNA. 8. Duplication: N/a 9. Genetic Drift: changes in the gene pool of a small population due to chance. 10. Bottleneck effect: Disasters, natural or human, that will cause a massive decline in the size of a population. 11. Founder effect: Genetic drift in a new colony, very often in isolated areas such as islands. 11. Gene flow: Notice how I have two elevens? Neat. Anyway, the method by which a population gains or loses alleles. 12. Phenotypic Polymorphism: The coexistence of two or more distinct forms of individuals in the same population. 13. Genetic polymorphism: …The book does not distinguish this from phenotypic. 14. Average heterozygosity: N/a 15. Geographic Variation: difference in genetic structure between populations. 16. cline: A graded change in some trait along a geographic axis. It may represent a graded region of overlap where individuals of neighboring populations are interbreeding. 17. fitness: The measure that is critical to selection is the relative contribution an individual makes to the greater gene pool of the next generation / species. 18. relative fitness: The contribution of a genotype to the next generation compared to the contributions of alternatives genotypes for the same locus. 19. directional selection: Most common during periods of environmental change or when members of a population migrate to some new habitat with different environmental conditions. It shifts the frequency curve for variations in some phenotypic character in one direction or the other by favoring what are initially relatively rare individuals that deviate from the average for that character. 20. disruptive selection: 21. stabilizing selection: Acts against extreme phenotypes and favors the more common intermediate variants. 22. balancing selection: N/a :P

23. balanced polymorphism: The ability of natural selection to maintain diversity in a population. Essentially, a preservation of variation. 24. heterozygote advantage: One of the mechanisms for the preservation of variation. If individuals who are heterozygous at a particular locus have greater survivorship and reproductive success than any type of homozygote, then two or more alleles will be maintained at that locus by natural selection. 25. frequency-dependent selection: Another cause of balanced polymorphism. The reproductive success of any one morph declines if that phenotypic form becomes too common in the population. A good example is 26. neutral variation: Confers that there is no selective advantage for some individuals over others. Much of the protein variation detectable by electrophoresis may represent chemical "fingerprints" that are neutral in their adaptive qualities. 27. pseudogenes: N/a :P 28. sexual selection: A separate selection process which leads to sexual dimorphism. Many sex features do not seem to be adaptive in the general sense. But if such accouterments give the individual an edge in gaining a mate, however, they will be favored for reproductive success. 29. sexual dimorphism: The distinction that males and females of man animal species exhibit marked differences in addition to the differences in the reproductive organs that define the sexes. In other words, between the secondary sex characteristics of males and females. 30. intrasexual selection: N/a :P 31. intersexual selection: N/a :P 3. p is the frequency of the homozygous dominant genotype. q is the frequency of the homozygous recessive genotype. In a 500 wild flower population, 80% (0.8) have the C allele and 20% (0.2) have the c allele. Why? Well, there will be 320 CC, 160 Cc, and 20 cc, each out of 500 total. After taking the number of alleles in the gene pool, including doubling the total number and adding the Cc to both the CC and cc, you arrive at allele frequencies of 0.8 and 0.2. That's how. 5. Natural selection is the differential success in reproduction. It results in alleles being passed along to the next generation in numbers disproportionate to their relative frequencies in the present generation. Genetic drift is the culmination of changes in the gene pool of a small population due to chance. Only luck could result in random drift improving the population's adaptiveness to its environment. The bottleneck effect is the result that the genetic makeup of the small surviving population is unlikely to be a representative of the makeup of the original population. The founder effect is is genetic drift in a new colony. It has contributed to the evolutionary divergence of Darwin's finches. Gene flow is genetic exchange due to the migration of fertile individuals or gametes between populations. This tends to reduce differences between populations that have accumulated because of natural selection or genetic drift. 7. Polymorphisms occur when when two or more distinct morphs, or contrasting physical forms, are each represented in high enough frequencies to be readily noticeable. It is extensive in human populations. Phenotypic is a physical trait (ie, wings) and genotypical is a genetic trait (ie, Ww). Geographic variation is the difference in genetic structure between populations.