Week 1 Notes (January 21-23)
Week 1 Notes (January 21-23) 24010
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This 2 page Class Notes was uploaded by Amalia Cristiano on Friday January 23, 2015. The Class Notes belongs to 24010 at San Diego State University taught by Berta in Spring2015. Since its upload, it has received 48 views. For similar materials see Biology 204 in Biology at San Diego State University.
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Date Created: 01/23/15
Biology 204 January 23rd 2014 Speciation Evolution by natural selection resulting in new species Arti cial Selection Selection of desired species by humans analogy to natural selection Adaptation A trait with a current functional role in the life of the history of an organism that is maintained and evolved by natural selection Can be beneficial to the survival of the organismspecies Morphological Adaptation An example would be harder beaks for birds to be able to better reach seeds Camou age Protective resemblance Mimicry Deceptive resemblance of a different organism so that the mimic benefits from the mistaken identity as seeming to be unpalatable or harmful Ex Larva resembling snakes misleading structures owersorchids Symbiosis Two species living in close contact Three types 1 Mutualism Both species benefit 2 Communalism One benefits one neutral moss 3 Parasitism One harmed one neutral moss Mutation can lead to coadaptation and coevolution Chapter 23 Microevolution Evolution of population level change in allele frequencies over generations Descent with Modification Descent pattern of DNA Genetics Dealing with heredity or transmission of and organism s traits Ultimate source of inheritable variation is a change in DNA Changes in DNA can be caused by mutation and genetic recombination Mutations Change in genotype other than recombination Three types 1 Point Change in DNA nucleotide 2 Chromosome Rearrangement of large piece of chromosomes gain loss inversion 3 Change in Chromosome Number Anaploidy change in chromosome number or less than the entire genome 2n62 Trisomy additional chromosome 21 results in Down Syndrome Polyploidy Evolution of chromosome number which doubles chromosome number 2n12 to 2n24 Genetic Recombination Natural shuf ing of all genes with meiosis and sexual reproduction Independent Assortment Aa and AA to AA to Aa Crossing Over Exchange of DNA between chromatid segments during meiosis Genetic Variation Source of most variation in sexual organisms new alleles combine Mutations Ultimate source of variation new genes and alleles Fitness Population or individual Measure of relative contributions of a given genotype to next generation allele genotype frequency in future generations divided by allele genotype frequency in previous generations First Generation 25 AA X 50 Aa X 25 aa 25 550 50 Second Generation 36 AA 48 Aa 36 54560 Fitness 6050l2 HardyWeinberg Equilibrium Frequency of geneallele does not change over time Aa gt AA Aa aa Pfrequency A qfreq a Pql 100 The HardyWeinberg Equilibrium is never met which leads to evolution Would only be possible with no mutations no migrations large population size etc Population Bottleneck Population crashes unique to individuals Founder Effect One or two individuals gone from large population Mating is random 1 harem breeding or 2 assortment All genotypes equally adaptive