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Evolution of Populations

Evolution of Populations. II. Evolution of Populations. A. Genes and Variation. 1. Gene Pool - combined genetic information of all members of a particular population. 2. Sources of Genetic Variation - biologist have discovered two main sources.

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Evolution of Populations

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  1. Evolution of Populations

  2. II. Evolution of Populations • A. Genes and Variation • 1. Gene Pool- combined genetic information of all members of a particular population

  3. 2. Sources of Genetic Variation- biologist have discovered two main sources • a. Mutations- change in a sequence of DNA. May affect an organisms fitness(it’s ability to survive and reproduce in its environment) • b. Gene shuffling- most caused during production of gametes. (sexual reproduction major source of variation within many populations)

  4. 3. Natural selection does not act directly on genes. It acts on phenotypes. (it can change the relative frequencies of alleles in the population over time)

  5. 4. Genetic Drift- may occur when a small group of individuals colonizes a new habitat. Individuals may carry alleles in different relative frequencies than the original larger population.

  6. Genetic drift has been observed in some small human populations that have become isolated due to reasons such as religious practices and belief systems. For example, in Lancaster County, Pennsylvania, there is an Amish population of about 12,000 people who have a unique lifestyle and marry other members of their community. By chance, at least one of the original 30 Amish settlers in this community carried a recessive allele that results in short arms and legs and extra fingers and toes in offspring. Because of small gene pool, many individuals inherited the recessive allele over time. Today, the frequency of this allele among the Amish is high (1 in 14 rather than 1 in 1000 in the larger population of the U.S.)

  7. B. Evolution Versus Genetic Equilibrium • Hardy-Weinberg Principle- states that allele frequencies in population will remain constant unless one or more factors cause those frequencies to change. • There are 5 conditions to maintain genetic equilibrium otherwise populations will evolve

  8. a. Random mating- populations breed randomly (mates not chosen as with humans) • b. Large populations- genetic drift has less affect • c. No migrations (in or out) gene pool kept together • d. No mutations- if genes mutate from one form into another, new alleles may be introduced- changing frequencies of alleles • e. No natural selection- no phenotype can have selective advantage over another.

  9. C. The Process of Speciation(formation of a new species) • 1. Isolating mechanisms • a. Reproductive isolation- can develop in variety of ways- behavioral isolation, geographic isolation, temporal isolation The Eastern and Western Meadowlark have overlapping ranges but do not interbreed, because they have different mating songs

  10. b. Behavioral isolation- don’t interbreed because of differences in courtship rituals or other types of behavior • c. Geographic isolation- two populations separated by geographic barriers (rivers, mountains, bodies of water) • d. Temporal isolation- when two species reproduce at different times

  11. Chapter 16 TheEvolution Of Populations

  12. Natural selection acts directly on a. alleles. b. genes. c. phenotypes. d. mutations.

  13. Natural selection acts directly on a. alleles. b. genes. c. phenotypes. d. mutations.

  14. Interbreeding among members of a population a. alters the relative frequencies of alleles in the gene pool. b. alters the different types of alleles in the gene pool. c. does not alter the different types of alleles in the gene pool. d. does not alter genetic variation in the population.

  15. Interbreeding among members of a population a. alters the relative frequencies of alleles in the gene pool. b. alters the different types of alleles in the gene pool. c. does not alter the different types of alleles in the gene pool. d. does not alter genetic variation in the population.

  16. In genetic drift, allele frequencies change because of a. mutation. b. chance. c. natural selection. d. genetic equilibrium.

  17. In genetic drift, allele frequencies change because of a. mutation. b. chance. c. natural selection. d. genetic equilibrium.

  18. Mutations do NOT always affect a. genotype. b. phenotype. c. only single-gene traits. d. only polygenic traits.

  19. Mutations do NOT always affect a. genotype. b. phenotype. c. only single-gene traits. d. only polygenic traits.

  20. Populations are separated by barriers such as rivers, mountains, or bodies of water in a. temporal isolation. b. geographic isolation. c. behavioral isolation. d. natural selection.

  21. Populations are separated by barriers such as rivers, mountains, or bodies of water in a. temporal isolation. b. geographic isolation. c. behavioral isolation. d. natural selection.

  22. One of the conditions required to maintain genetic equilibrium is a. natural selection. b. mutations. c. nonrandom mating. d. no movement into or out of the population.

  23. One of the conditions required to maintain genetic equilibrium is a. natural selection. b. mutations. c. nonrandom mating. d. no movement into or out of the population.

  24. The genetic equilibrium of a population can be disturbed by each of the following EXCEPT a. nonrandom mating. b. movement into and out of the population. c. a large population size. d. mutations.

  25. The genetic equilibrium of a population can be disturbed by each of the following EXCEPT a. nonrandom mating. b. movement into and out of the population. c. a large population size. d. mutations.

  26. An example of a polygenic trait in humans is a. widow's peak. b. absence of widow's peak. c. height. d. ABO blood type.

  27. An example of a polygenic trait in humans is a. widow's peak. b. absence of widow's peak. c. height. d. ABO blood type.

  28. All members of a population a. are temporally isolated. b. are geographically isolated. c. are able to interbreed. d. have identical genes.

  29. All members of a population a. are temporally isolated. b. are geographically isolated. c. are able to interbreed. d. have identical genes.

  30. Most inheritable differences are due to a. mutation. b. chemicals in the environment. c. gene shuffling. d. radiation.

  31. Most inheritable differences are due to a. mutation. b. chemicals in the environment. c. gene shuffling. d. radiation.

  32. The combined genetic information of all members of a population is the population's a. relative frequency. b. phenotype. c. genotype. d. gene pool.

  33. The combined genetic information of all members of a population is the population's a. relative frequency. b. phenotype. c. genotype. d. gene pool.

  34. The situation in which allele frequencies remain constant is called a. evolution. b. genetic drift. c. genetic equilibrium. d. natural selection.

  35. The situation in which allele frequencies remain constant is called a. evolution. b. genetic drift. c. genetic equilibrium. d. natural selection.

  36. A change in a sequence of DNA is a a. recombination. b. polygenic trait. c. single-gene trait. d. mutation. .

  37. A change in a sequence of DNA is a a. recombination. b. polygenic trait. c. single-gene trait. d. mutation. .

  38. The actual distribution of phenotypes for a typical polygenic trait a. is best expressed as a bar graph. b. forms a bell-shaped curve. c. exactly matches Mendelian ratios. d. is similar to the distribution of phenotypes of a single-gene trait. .

  39. The actual distribution of phenotypes for a typical polygenic trait a. is best expressed as a bar graph. b. forms a bell-shaped curve. c. exactly matches Mendelian ratios. d. is similar to the distribution of phenotypes of a single-gene trait. .

  40. Gene shuffling includes the independent movement of chromosomes and a. the expression of polygenic traits. b. the expression of single-gene traits. c. crossing over. d. mutation.

  41. Gene shuffling includes the independent movement of chromosomes and a. the expression of polygenic traits. b. the expression of single-gene traits. c. crossing over. d. mutation.

  42. According to the Hardy-Weinberg principle, genetic equilibrium would be encouraged in a population of deer mice, Peromyscus maniculatus, if a. the population size decreases. b. mutation rates within the population rise. c. no natural selection occurs. d. frequent movement both into and out of the population occurs.

  43. According to the Hardy-Weinberg principle, genetic equilibrium would be encouraged in a population of deer mice, Peromyscus maniculatus, if a. the population size decreases. b. mutation rates within the population rise. c. no natural selection occurs. d. frequent movement both into and out of the population occurs.

  44. Which factor would most likely cause evolution in a large population? a. the production of large numbers of offspring within the population b. the occurrence of nonrandom mating within the population c. the absence of movement into and out of the population d. the absence of mutations within the population

  45. Which factor would most likely cause evolution in a large population? a. the production of large numbers of offspring within the population b. the occurrence of nonrandom mating within the population c. the absence of movement into and out of the population d. the absence of mutations within the population

  46. Genetic drift tends to occur a. in very large populations. b. in small populations. c. only in new species. d. following stabilizing selection.

  47. Genetic drift tends to occur a. in very large populations. b. in small populations. c. only in new species. d. following stabilizing selection.

  48. Which factor most favors speciation? a. ecological competition b. geographic isolation c. gene pool stability d. a halt in evolution

  49. Which factor most favors speciation? a. ecological competition b. geographic isolation c. gene pool stability d. a halt in evolution

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