BIOL 101 1nd EditionExam # 3 Study Guide Lectures: 22 - 24Review 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 equilibriumB2 + 2Bb + b2 .49 .09 .58, .422. 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?.2688The Origin of Species Class DiscussionI. Concepts of SpeciesA. 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 matingb. Habitat Isolation – live in same area but different habitats so don’t encounter each otherc. Temporal isolation – species breed at different times of the day or different seasonsd. Behavioral isolation – different courtship rituals or other behaviors prevent mate recognition between speciese. Gametic isolation – male and female gametes of different species fail tounite, fertilization did not occur2. Three post-zygotic Barriers and examples:a. Reduced Hybrid Viability – the development or survival of hybrids is impairedb. Reduced Hybrid Fertility – hybrids fail to produce functional gametesc. Hybrid Breakdown – offspring of hybrids are feeble or infertileTwo 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 populationsA. Speciation-1. Two species from one ancestral species = divergentchimp, human headcommon 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 divergedNew niche hypothesis – human pubic and head lice lineages diverged becausehominins lost their body hair and developed two hair niches2. 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 radiationPhylogenetjc 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) biological species concept2) morphological3) ecological4) phylogeneticPhylogeny – the study of evolutionary relationshipsB. Allopatric Speciation – when you have a geographic barrier impeding gene
View Full Document
Unlocking...