BIOL 101 1nd Edition Exam 3 Study Guide Lectures 22 24 Review Hardy Weinberg Things to think about Are you given allele or genotype frequency Which equation will you use Will you need to use both equations Remember if an organism SHOWS the trait and the trait is recessive then they have 2 recessive alleles and you are given their genotypic frequency 1 In a population with two alleles B and b the allele frequency of B is 0 7 What would the frequency of heterozygotes be if the population is in Hardy Weinberg equilibrium B2 2Bb b2 49 09 58 42 2 In a population that is in Hardy Weinberg equilibrium 16 of the individuals show the recessive trait What is the frequency of the dominant allele in the population 2688 The Origin of Species Class Discussion I Concepts of Species A Ernst Mayr s Biological Species Concept a group of populations whose Individuals have the potential to mate and produce viable fertile offspring B Alternative definitions are needed Why Ecological morphological we cant always tell if species interbreed and produce fertile offspring For organisms that are extinct and for organisms that reproduce asexually C Reproductive Barriers why can t related species mate 1 Five pre zygotic Barriers and examples a Mechanical isolation differences in physical structures prevent successful mating b Habitat Isolation live in same area but different habitats so don t encounter each other c Temporal isolation species breed at different times of the day or different seasons d Behavioral isolation different courtship rituals or other behaviors prevent mate recognition between species e Gametic isolation male and female gametes of different species fail to unite fertilization did not occur 2 Three post zygotic Barriers and examples a Reduced Hybrid Viability the development or survival of hybrids is impaired b Reduced Hybrid Fertility hybrids fail to produce functional gametes c Hybrid Breakdown offspring of hybrids are feeble or infertile Two populations must have gene flow blocked with or without a physical barrier once this form of microevolution is blocked natural selection mutation and genetic drift make two different species that eventually cannot interbreed II How do reproductive barriers form When gene flow is blocked between two populations A Speciation 1 Two species from one ancestral species divergent chimp human head common ancestors where they intersect four spots Co speciation hypothesis human head and chimp lice lineages diverged at the same time that hominins and ancestral chimps diverged New niche hypothesis human pubic and head lice lineages diverged because hominins lost their body hair and developed two hair niches 2 A burst of divergences from a single ancestor that leads to many new species each adapted to a new habitat or using new resources adaptive radiation Phylogenetjc studies of lice suggest that hominins acquired a second species of louse 3 4 million years ago does not correlate with humans losing body hair Body louse arose less than 72 000 years ago correlates with clothing These studies are inconclusive Types of Species Concepts 1 2 3 4 biological species concept morphological ecological phylogenetic Phylogeny the study of evolutionary relationships B Allopatric Speciation when you have a geographic barrier impeding gene flow
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