Chapter 16 Evolution Of Population

16-1 I. Genetic variation is studied in populations A. A population is a group of individuals of the same species that interbreed

B. Gene Pool 1. All the alleles in a population a. combined genetic info. of all the members of a population How often alleles occur in gene pool (expressed as a percentage) 2. Relative Frequency =

Gene Pool for Fur Color in Mice Page 394 3. Evolution is any change in the relative frequency of alleles in a population

II. Sources of Genetic Variation A. Mutations 1. Any change in sequence of DNA 2. result of radiation or chemicals in the environment 3. does not always affect organism’s phenotype/fitness

B. Gene Shuffling 1. Responsible for heritable differences due to crossing over 2. Sexual reproduction produces different phenotypes = does not change relative frequency

EXAMPLE Genes and Variation Sexual Reproduction Remember…an organism is successful if it reproduces Can produce many phenotypes, BUT the relative frequency will stay the same Think of a deck of cards 52 different cards Chance of an Ace off the top – 1/13 (4/52) Many combinations, BUT the frequency stays the same

C. Single-gene and Polygenic traits 1. Phenotypes for a given trait depends the # of genes controlling the trait Single-gene Polygenic -controlled by one gene -controlled by many genes -only 2 possible phenotypes -many possible phenotypes -ex. Widow’s peak, tongue roll, freckles -ex. Height, eye color

16-2 I. Evolution as Genetic Change A. Natural selection affects which individuals survive and reproduce and which do not B. individual dies without reproducing = does not contribute alleles to gene pool C. individual produces offspring = alleles stay in the gene pool D. Populations, not individual organisms, can evolve over time

II. Natural Selection on Single Gene Traits A. Can change relative frequency  evolution Example: lizard color  mutation caused red and black color: red seen easily = eaten and disappear / black beneficial = increase in numbers Page 397

Page 398 III. Natural Selection on Polygenic traits A. can affect the phenotypes in 3 ways 1. Directional Selection Page 398 a. individuals at one end of the curve have higher fitness

Page 399 2. Stabilizing Selection a. individuals near the center of the curve have higher fitness

Page 399 3. Disruptive Selection a. individuals at the upper and lower ends of the curve have higher fitness

16-2 Evolution as Genetic Change

Page 400 IV. Genetic Drift A. Random change in relative frequency B. May occur when small group colonizes a new habitat C. Founder effect = migration (Hawaiian fruit flies) Page 400

V. Hardy-Weinberg Principle A. Allele frequency will remain constant unless 1 or more factors change B. No evolution = Genetic Equilibrium C. 5 conditions to maintain genetic equilibrium 1. Random mating = equal chance to pass alleles 2. Population very large = less genetic drift 3. No movement in/out of population = separate gene pool 4. No mutations = no new alleles 5. No natural selection = no phenotypic advantage

16-3 I. Process of Speciation (formation of new species) A. Isolating Mechanisms new species cannot interbreed 1. Reproductive isolation = 2. Behavioral = Differences in courtship or other behaviors (page 404) 3. Geographic = Separated by barriers (rivers/mountain) (page 405) 2 or more species reproduce at different times 4. Temporal =

B. Speciation of Galapagos Finches (Page 409) 1. Founders arrive – finches from S.A. to Galapagos 2. Geographic Isolation– part of group A goes to other island 3. Changes in Gene Pool – population adapt to environment = changes 4. Reproductive Isolation – pop. B goes back to first island  A and B cannot interbreed 5. Ecological Competition – A and B compete for available seeds continue to evolve = species C 6. Continued Evolution – repeated over and over again

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16-1 Which of the following statements is TRUE? A. The relative frequency of an allele is not related to whether the allele is dominant or recessive. B. Mutations always affect an organism's phenotype. C. Crossing-over decreases the number of different genotypes that appear in an offspring. D. Evolution does not affect the frequency of genes in a gene pool.

16-1 Most inheritable differences are a result of A. gene shuffling. B. frequency of alleles. C. mutations. D. DNA replication.

16-1 The main sources of inherited variation are A. gene shuffling and mutations. B. gene pools and frequencies. C. single-gene and polygenic traits. D. genotypes and phenotypes.

16-1 A widow's peak in humans is an example of a(an) A. invariable trait. B. single-gene trait. C. polygenic trait. D. mutation.

16-1 A graph of the length of the little finger on the left hand versus the number of people having fingers of a particular length is a bell-shaped curve. This indicates that finger length is a A. single-gene trait. B. polygenic trait. C. randomly inherited trait. D. strongly selected trait.

16-2 Which of the following patterns of natural selection on polygenic traits favors both extremes of a bell curve? A. stabilizing selection B. disruptive selection C. directional selection D. genetic drift

16-2 Which of the following events could lead to genetic drift? A. A few new individuals move into a large, diverse population. B. A few individuals from a large, diverse population leave and establish a new population. C. Two large populations come back together after a few years of separation. D. The mutation rate in a large population increases due to pollution.

16-2 The situation in which allele frequencies remain constant in a population is known as A. genetic drift. B. the founder effect. C. genetic equilibrium. D. natural selection.

16-2 Which of the following conditions is required to maintain genetic equilibrium in a population? A. movement in or out of the population B. random mating C. natural selection D. small population

16-2 According to the Hardy-Weinberg principle, no evolution will take place if all five of the Hardy-Weinberg conditions are met. B. any one of the Hardy-Weinberg conditions is met. C. at least three of the Hardy-Weinberg conditions are met. D. none of the Hardy-Weinberg conditions are met.

16-3 When two species do not reproduce because of differences in mating rituals, the situation is referred to as A. temporal isolation. B. geographic isolation. C. behavioral isolation. D. reproductive isolation.

16-3 The most important factor involved in the evolution of the Kaibab and Abert squirrels of the American Southwest appears to be A. temporal isolation. B. geographic isolation. C. behavioral isolation. D. different food sources.

16-3 One finding of the Grants' research on generations of Galápagos finches was that A. natural selection did not occur in the finch B. natural selection can take place often and very rapidly. C. beak size had no effect on survival rate of the finches. D. natural selection was slow and permanent.

16-3 All of the following played a role in speciation of Galápagos finches EXCEPT A. no changes in the gene pool. B. separation of populations. C. reproductive isolation. D. natural selection.

16-3 Beak size in the various groups of Galápagos finches changed primarily in response to A. climate. B. mating preference. C. food source. D. availability of water.