chapter 16: evolution of populations

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Chapter 16: Evolution of Populations. HOMEWORK. Chapter 16 Section Assessments: Due Fri . 5/2 Chapter 16.1 SA: p. 396 (1-5) Chapter 16.2 SA: p. 402 (1-5) Chapter 16.3 SA: p. 410 (1-2) Chapter 16 Assessment: p. 413 (1-10, 12, 17, 18, 19). - PowerPoint PPT Presentation


Chapter 15: Darwins Theory of Evolution

Chapter 16: Evolution of Populations

HOMEWORKChapter 16 Section Assessments: Due Fri. 5/2Chapter 16.1 SA: p. 396 (1-5)Chapter 16.2 SA: p. 402 (1-5)Chapter 16.3 SA: p. 410 (1-2)Chapter 16 Assessment: p. 413 (1-10, 12, 17, 18, 19) VOCABULARY (DUE FRI. 5/2)Provide the glossary definition and etymology for the following terms: Gene poolRelative FrequencySingle-gene traitPolygenic traitDirectional selectionStabilizing selectionDisruptive selectionGenetic driftFounder effectHardy-Weinberg principleGenetic equilibriumSpeciationReproductive isolationBehavioral isolationGeographic isolationTemporal isolation16.1: Genes and VariationA weakness in Darwins theory stemmed from his lack of understanding in genetic variation.In the 1930s, evolutionary biologists combined Mendels work with that of Darwins to support evolutionary change, specifically the process of natural selection.How do you think Mendel would have felt about that? 416.1 Variation and Gene PoolsPopulation: a group of individuals of the same species that interbreed.Gene pool: consists of all genes, including all the different alleles, that are present in a population.Relative frequency: the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur. (Fig. 16-2)Key Concept: In genetic terms, evolution is any change in the relative frequency of alleles in a population.16.1 Sources of Genetic VariationKey Concept: The two main sources of genetic variation are mutations and the genetic shuffling that results from sexual reproduction. Remember mutations are changes in the genetic code. Some are expressed, some remain silent. Some mutations can affect an organisms fitness, while others have not effect. Crossing over and independent assortment during gamete formation leads to genetic variation. (23 pairs of chromosomes can have 8.4 million different combinations of genes!)616.2 Evolution as Genetic Change16.2 Natural Selection on Single-Gene TraitsKey Concept: Natural selection on single-gene traits can lead to changes in allele frequencies and thus to evolution. (Fig. 16-5)Remember: Evolution is change over time in the relative frequencies of alleles in a population, therefore it is populations that can evolve, not individual organisms.

16.2 Natural Selection on Polygenic TraitsKey Concept: Natural selection can affect the distributions of phenotypes in any of three ways: Directional Selection: when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. (Fig. 16-6)Stabilizing Selection: center curve has higher fitness (Fig. 16-7)Disruptive Selection: upper and lower ends have high fitness (Fig. 16-8)9Natural Selection and Normal DistributionOne extreme favoredAverage favoredBoth extremes favored16.2 Genetic DriftKey Concept: In small populations, individuals that carry a particular allele may leave more descendants that other individuals, just by chance. Over time, a series of chance occurrences of this type can cause an allele to become common in a population. (Fig. 16-9)Genetic Drift: Random change in allele frequencies that occurs in small populationsFounder Effect: A situation in which allele frequencies change as a result of the migration of a small subgroup of a population

1116.2 Hardy-Weinberg and Genetic EquilibriumGenetic Equilibrium: A situation in which allele frequencies remain constant.Key Concept: Five conditions are required to maintain genetic equilibrium from generation to generation:Random matingLarge population sizeNo movement into or out of the populationNo mutationsNo natural selection1216.2 Hardy-Weinberg Equation (p. 401-402)p + q = 1p = dominant allele frequency (A)q = recessive allele frequency (a)p2 + 2pq + q2 = 1p2: frequency of AA homozygous2pq: frequency of Aa heterozygousq2: frequency of aa homozygous1: sum of frequencies for all genotypes (100%)Extra Credit Assignment!! Due Fri. 5/213Bio Warm-Up April 28, 2014 (Do Not Copy)List and describe three types of natural selection that occur in a population. Draw a distribution curve for the population before and after selection.The inability to taste PTC paper (t) is recessive to being able to taste it (T). At UC Academy, 135 out of the 450 students are unable to taste PTC paper. Calculate the frequency for the following:homozygous dominant individualsheterozygous individualshomozygous recessive individualsfrequencies of the T and t alleles in our school population.

Bio Warm-Up April 29, 2014 (Do Not Copy)Having mid-digital hair (hair on the skin of the second bone in your finger) is dominant to not having hair there. At Chaffey College, 7350 out of the 15,000 students have no mid-digital hair. Calculate the frequency of the following individuals who are: homozygous recessiveheterozygoushomozygous dominantdominant mid-digital hair allele (H) recessive no mid-digital hair allele (h). When individuals at only one end of a bell-shaped curve of phenotype frequencies have high fitness, the result is ___________ selection.

16.3 The Process of Speciation16.3 Isolating MechanismsSpeciation: formation of new speciesKey Concept: As new species evolve, populations become reproductively isolated from each other.Reproductive Isolation: When members of two populations cannot interbreed and produce fertile offspring. They now have separate gene pools.1716.3 Isolating MechanismsBehavioral Isolation: capable of interbreeding, but have different courtship rituals or other reproductive behaviors.Geographic Isolation: separated by physical barriers (i.e. rivers, mountains, etc)Temporal Isolation: reproduce at different times.Is the definition of species constant? Can vs. Will

Causes of reproductive isolation:

1816.3 Testing Natural Selection in NaturePeter and Rosemary Grant have spent more than 20 years observing collecting data on Galapagos finches.They found variation in physical characteristics.They observed natural selection occurring during drought seasons.

1916.3 Speciation in Darwins FinchesKey Concept: Speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in the new populations gene pool, reproductive isolation, and ecological competition.

2016.3 Studying Evolution Since DarwinRead: Unanswered Questions (p. 410)New data from genetics, physics, and biochemistry could have proved him wrong on many counts. They didnt.while the Grants observed changes in the size of the finches beaks, they did not observe the formation of a new species.Why is understanding evolution important? 21