1 / 31

Chapter 16

Chapter 16. Evolution of Populations. 16-1 Genes and Variation. 1856- 1863 Mendel breed garden peas to study inheritance 1859- Charles Darwin, On the Origin of Species. Gene pool- all genes that are present in a population.

metta
Download Presentation

Chapter 16

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 16 Evolution of Populations

  2. 16-1 Genes and Variation • 1856- 1863 Mendel breed garden peas to study inheritance • 1859- Charles Darwin, On the Origin of Species

  3. Gene pool- all genes that are present in a population

  4. Relative frequency- number of times that an allele occurs in a gene pool compared to other alleles. Homozygous Tall- 48% (TT) Heterozygous Tall- 16% (Tt) Homozygous Short- 36% (tt) In a population of 100 plants How many T alleles? How many t alleles?

  5. Relative frequency of T and t alleles Homozygous Tall- 48% (TT) Heterozygous Tall- 16% (Tt) Homozygous Short- 36% (tt) In a population of 100 plants How many T alleles? 48 are TT = 96 16 are Tt = 16 Total = 112 T alleles How many t alleles? 36 are tt = 72 16 are Tt = 16 Total = 88 t alleles

  6. Relative frequency of T and t alleles Homozygous Tall- 48% (TT) Heterozygous Tall- 16% (Tt) Homozygous Short- 36% (tt) In a population of 100 plants How many T alleles? Total = 112 T alleles How many t alleles? Total = 88 t alleles (112/200)= 56% T (88/200)= 44% t Is it possible to have a greater % of a recessive allele?

  7. Sources of genetic variation • Mutations- change in DNA • Can increase, decrease, or have no effect on fitness of an organism • Gene shuffling- sexual reproduction creates unique combinations of genes

  8. Single gene and polygenic traits • Normal distribution- bell-shaped curve on the graph for a polygenic trait

  9. 16-2 Evolution as Genetic Change Natural Selection on Single-Gene Traits leads to changes in allele frequency 10% 20% 70%

  10. 10% 20% 70% 20% 10% 70% 30% 0% 70% 45% 0% 55%

  11. Natural Selection on Polygenic Traits Directional Selection- occurs when individuals at one end of the curve have higher fitness Example: birds with bigger beaks can eat larger seeds. If the supply of small seeds decreases, those birds with larger beaks will be more fit

  12. Natural Selection on Polygenic Traits Stabilizing Selection- occurs when individuals at the middle of the curve have higher fitness Example: human baby birth weights. Large babies have difficulty being born. Small babies are usually less healthy.

  13. Natural Selection on Polygenic Traits Disruptive Selection- occurs when individuals at the both ends of the curve have higher fitness. This can create two distinct phenotypes. Ex: Middle size seeds become scare and birds with small beaks and large beaks are more fit.

  14. Genetic Drift • Genetic drift- random change in allele frequency • In small populations rare alleles may become more common.

  15. Genetic Drift • Founder effect- migration of a subgroup of organisms establishes a new colony • Ex: space ship travels to Mars with only 100 people aboard Amish community- poldactylism Fundamentalist Church of Latter Day Saints- fumarasedeficieny AshkenzaiJews- Tay-Sachs

  16. Evolution Versus Genetic Equilibrium • Hardy-Weinberg principle- allele frequency will remain constant unless a factor causes change • Genetic equilibrium- allele frequency remains constant 10% 20% 70%

  17. 5 Conditions needed for genetic equilibrium • Random mating • Large population • No movement into or out of population • No mutations • No natural selection

  18. 16-3 The Process of Speciation • Species- a group of organisms that can produce fertile offspring Isolating Mechanisms Reproductive isolation- when members of two populations cannot interbreed and produce fertile offspring

  19. Reproductive isolation • Behavioral isolation- two species are capable of interbreeding but have differences in reproductive behavior (courtship rituals) Ex: Western and Eastern meadowlarks use different mating songs

  20. Reproductive isolation • Geographic isolation- a physical barrier separates two species (rivers, mountains, bodies of water) Ex: Kaibab and Abert squirrel

  21. Reproductive isolation • Temporal isolation- two or more species reproduce at different times • Ex: orchids that release pollen only on one day, three similar orchids in a rain forest release pollen on different days

  22. Testing Natural Selection in Nature • Peter and Rosemary Grant • Studied Daphne Major finch on the Galapogos islands Large beak size became an advantage during drought

  23. Speciation in Darwin’s Finches

  24. Speciation in Darwin’s Finches • Founders arrive- came from S. America. • Finches do not normally travel over open water

  25. Speciation in Darwin’s Finches • Separation of populations • Separate gene pools established

  26. Speciation in Darwin’s Finches • Changes in the Gene Pool • Adaptations occur due to differences in food supply

  27. Speciation in Darwin’s Finches • Reproductive isolation • Finches prefer to mate with finches of a comparable beak size

  28. Speciation in Darwin’s Finches • Ecological Competition • Within an island finches compete for resources

  29. Speciation in Darwin’s Finches • Continued Evolution • 13 separate species created

  30. Studying Evolution Since Darwin • Darwin made bold assumptions • Heritable variation • Age of earth • Relationships between organisms

  31. Studying Evolution Since Darwin • Darwin made bold assumptions • Heritable variation (supported by genetics) • Age of earth (supported by geology and physics) • Relationships between organisms (supported by biochemistry)

More Related