UCSB EEMB 2 - Lec #11 EEMB 2 SM17 1S (Adaptation-Variation) (15 pages)

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Lec #11 EEMB 2 SM17 1S (Adaptation-Variation)



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Lec #11 EEMB 2 SM17 1S (Adaptation-Variation)

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Pages:
15
School:
University of California, Santa Barbara
Course:
Eemb 2 - Introductory Biology III

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Adaptation and Variation The Evolutionary process 1 Variation 2 Natural Selection 3 Genetic Divergence 4 Reproductive Isolation 5 Speciation Variation Natural Selection Genetic Divergence Reproductive isolation Speciation Populations evolve not individuals Populations have variation in traits among individuals Microevolution The change in allele frequencies in a population over generations Adaptation and Variation Features that characterize a population 1 Morphological traits Form 2 Physiological traits Function 3 Ethological traits Behavior In reproducing species there is variation in most traits in individuals Individuals of a population vary in their traits Discrete characters either or basis 2 or more distinct forms Quantitative characters vary along a continuum Adaptation and Variation Variation Traits may be positive negative or neutral to individuals in a population survival and reproduction Adaptation Adjustment or change to meet environmental conditions 1 Adaptive Traits form of trait that is an advantage in terms of survival reproduction 2 Maladaptive Traits form of trait that is a disadvantage in terms of survival reproduction 3 Neutral Traits 0 form of trait that is neither a disadvantage or advantage in terms of survival and reproduction Almost every trait or every species is variable Adaptation and Variation Variation Where does variation come from Information about heritable traits occurs in genes Gene Hereditary unit of DNA that codes for specific traits Alleles 2 or more different molecular forms of a gene alternate form of a gene dominant recessive incomplete dominance Gene Pool All the genes in a population pool of genetic resources Genome All the genes in a species Genotype Individuals inherit different combinations of alleles genetic expression Phenotype Individuals express different details of traits physical expression Adaptation and Variation Variation Individuals inherit different combinations of alleles which leads to variation in phenotype Which alleles end up in a given gamete and individual 5 events 1 Gene mutation produces new alleles 2 Crossing over at meiosis I puts novel combinations of alleles in chromosomes 3 Independent assortment at meiosis I puts mixes of maternal and paternal chromosomes into gametes 4 Fertilization combines alleles from two parents 5 Change in chromosome number or structure the loss duplication or repositioning of genes Ex Each human gamete 10600 possible allelic combinations Adaptation and Variation Phenotypic Frequencies The abundance of phenotype in a population Ex Eye color gross simplification Brown 25 BB Brown 25 50 X 100 50 Blue 40 20 50 X 100 Green 3 50 X 100 6 Hazel 2 50 X 100 4 100 Blue 20 bb Green 3 Hazel 2 Phenotype Frequency Each genotype has a distinct phenotype Adaptation and Variation Allele Frequencies The abundance of each kind of allele in a population Ex Wildflowers Flower color incomplete dominance 2 alleles A a Red White Pink Pop Size 320 AA AA Aa aa Aa 20 aa 320 X 2



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