Chap 24: Population Genetics Supplemental Instruction Iowa State University Leader: Adam Course: Biology 211 Instructor: Dr. Holscher Date: The Hardy-Weinberg equation: p2 + 2pq+q2=1 p^2 & q^2 represents: the frequencies of the homozygous genotype 2pq represents: the frequency of the heterozygous genotype Question: Using the Hardy-Weinberg equation solve the following questions. What is the allele frequency of a population that is 74% homozygous dominant? What percent of the population is heterozygous P2 is .74 take the square root= .86=p 1-p=q Q=.14 1. Changes in allele frequency due to random chance describes what? Genetic drift 2. Describe bottleneck effect and founder effect i. (Bottleneck effect) -A sudden change in the environment may drastically reduce the size of the population ii. Founder effect) -Occurs when a few individuals become isolated from a larger population, this new group establish a new population whose gene pool differs from the source population 3. How does migration alter allele frequency between two different established populations? Decrease between pop, increase within pop 4. True or False: The smallest unit that can evolve is a population and thus is also the smallest unit that can be selected for by natural selection? False individuals selected for 5. Natural selection is different than all other agents of microevolution that change the gene pool because natural selection is… Adaptive 6. What are the three types of natural selection? Draw a curve that would represent each type. Directional: ind, at one extreme has more offspring Stabilizing: middle have more Diversifying/ disruptive: individual at both end have more offspring Supplemental Instruction 1060 Hixson-Lied Student Success Center 294-6624 www.si.iastate.edu 7. Which of the above types of natural selection can lead to speciation? Diversifying 8. Causes of Speciation: Reproductive Isolation: impedes two subspecies from producing fertile offspring 1. Prezygotic isolating mechanisms: (impede members of different species from mating) Before fetili What are the 5 types of prezygotic isolating mechanism called? Describe each. i. Habitat isolation ii. Temporal Isolation iii. Behavioral Isolation iv. Mechanical Isolation v. gametic isolation: gametes of diff. species raraly fuse to form zygote 2. Postzygotic isolating mechanism: (prevent the interspecies hybrid zygote from developing into a viable, fertile offspring) After fertil What are the 3 types of postzygotic isolating mechanism called? i. (Hybrid sterility) ii. (Hybrid inviability) iii. (hybrid breakdown) Mechanism of Speciation 1. Allopatric speciation: a. Occurs when some members of a species occupy a habitat…………………….. from other members Regions in which members of different species meet and mate, producing some offspring of mixed alleles is called? (hybrid zone) 3. Sympatric speciation a. Occurs in populations that live in _______ geographic area. (same) Patterns of Speciation: 1. Cladogenesis (Branching): Budding of one or more new species from a parent species that continues to exist. 2. Anagenesis: Transformation of an unbranched lineage to a new species different from ancestral population ???? which mechansism of speciation would be the most common cause of cladogenesis????