Predation Selection Predation selection act on both predator

Predation Selection Predation selection – act on both predator & prey • • behaviors camouflage & mimicry speed defenses (physical & chemical)

Physiological Selection Acting on body functions – – disease resistance physiology efficiency (using oxygen, food, water) biochemical versatility protection from injury HOT STUFF! Some fish had the variation of producing anti-freeze protein 5. 5 mya The Antarctic Ocean freezes over

Coevolution • Two or more species reciprocally affect each other’s evolution – predator-prey – competitive species – mutualism Copyright © 2008 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

Effects of Selection • Changes in the average trait of a population DIRECTIONAL SELECTION STABILIZING SELECTION giraffe neck human birth weight Copyright © 2008 Pearsonhorse Educationsize Inc. , publishing as Pearson Benjamin Cummings DISRUPTIVE SELECTION rock pocket mice

The Preservation of Genetic Variation • Various mechanisms help to preserve genetic variation in a population – Diploidy – Balancing selection – Heterozygote Advantage – Frequency-dependent selection – Neutral variation Copyright © 2008 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

Why Natural Selection Cannot Fashion Perfect Organisms 1. Selection can act only on existing variations 2. Evolution is limited by historical constraints 3. Adaptations are often compromises 4. Chance, natural selection, and the environment interact Copyright © 2008 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

The following question refers to this information: In the year 2500, five male space colonists and five female space colonists from Earth settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations

1. After many generations, the population on this planet has an unusually high frequency for the incidence of retinitis pigmentosa, relative to Earth's population. This is most likely due to A. the founder effect. B. sexual selection. C. the inheritance of acquired characteristics. D. mutations. E. the bottleneck effect.

2. A balanced polymorphism exists through diversifying selection in seedcracker finches from Cameroon in which small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If longterm climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population? A. B. C. D. E. diversifying selection. directional selection stabilizing selection sexual selection No selection would operate because the population is in Hardy-Weinberg equilibrium.

4. The bottleneck effect A. Eliminates traits whether they are beneficial or not. B. Increases the overall variability in the population. C. Amplifies the presence of traits that will eventually lead to extinction D. Increases the adaptability of a population E. Decreases the number weak organisms in the population.

5. Which of the following statements accurately describes genetic drift? A. It occurs when individuals in a population drift out due to emmigration B. It occurs when individuals drift in to a population due to immigration C. It refers to random changes in the gene frequencies in a population due to a drop in population size D. Mutations are the cause of genetic drift E. Natural selection is the cause of genetic drift.

1. In a random sample of a population of shorthorn cattle, 73 animals were red (CRCR), 63 were roan – a mixture of red and white (CRCr) – and 13 were white (Cr. Cr). Estimate the allele frequencies of CR and Cr, and determine whether the population is in Hardy. Weinberg equilibrium. – – – CR 5 0. 64, Cr 5 0. 36; because the population is large and a random sample was chosen, the population is in equilibrium. CR 5 0. 7, Cr 5 0. 3; the genotype ratio is not what would be predicted from these frequencies and the population is not in equilibrium. CR 5 0. 7, Cr 5 0. 3; the genotype ratio is what would be predicted from these frequencies and the population is in equilibrium. CR 5 1. 04, Cr 5 0. 44; the allele frequencies add up to greater than 1 and the population is not in equilibrium. You cannot estimate allele frequency from this information.

2. Genetic analysis of a large population of mink inhabiting an island in Michigan revealed an unusual number of loci where one allele was fixed. Which of the following is the most probable explanation for this genetic homogeneity? * A. The population exhibited nonrandom mating, producing homozygous genotypes. B. The gene pool of this population never experienced mutation or gene flow. C. A very small number of mink may have colonized this island, and this founder effect and subsequent genetic drift could have fixed many alleles. D. Natural selection has selected for and fixed the best adapted alleles at these loci. E. The colonizing population may have had much more genetic diversity, but genetic drift in the last year or two may have fixed these alleles by chance.

3. Which of the following statements is NOT true about genetic mutations? a. Genetic mutations are always harmful b. Mutations can occur when DNA molecules are copied c. Mutations are the ultimate source of all variations in a population d. Mutations that occur in the skin cells of parents can be passed to offspring e. Mutations are the raw material that drives evolution.

Base your answers to the following questions on the choices below: A. B. C. D. E. Founder effect Adaptive Radiation Gene Flow Genetic Drift Hardy-Weinberg Equilibrium 5. Occurs when a population undergoes a dramatic decrease in size. 6. Describes the introduction or removal of alleles when individuals enter or leave a population. 7. The term used to describe a theoretical, non evolving population.