Topic 5: Evolution

1. Topic 5: Evolution • Topic 5: Evolution and Biodiversity • Topic 10.3 Gene Pools and Speciation • Intro: Why does evolution matter now? • http://ca.pbslearningmedia.org/resource/tdc02.sci.life.evo.whymatters/evolving-ideas-why-does-evolution-matter-now/

2. Evolution • Evolution: The cumulative change in the heritable characteristics of a population (the change over time of the genetic composition of populations) • Natural selection: differential reproductive success of members of a population with particular inherited characteristics • individual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits • This changes the allele frequency of the population • Evolutionary adaptations: inherited characteristics that enhance organisms’ survival and reproduction November 24, 1859

3. Natural Selection-- I • Observations: • 1- Populations tend to produce more offspring than the environment can support. (There are limited resources) • 2- Natural population sizes are stable. • 3- Individuals in a species show variation • 4- This variation is heritable

4. Discussion: What causes variation between individuals in a species? • Mutation • Meiosis • Sexual Reproduction

5. Sexual Reproduction and variation • Explain how sexual reproduction promotes variation in a species… • Meiosis • Independent assortment • Crossing over • Random fertilization

6. Natural Selection-- II • 3 Inferences: • 1- There is a struggle for survival because of the overproduction of offspring. • 2- Non-random survival • 3- Natural selection occurs because of the differential success in reproduction of members of a pop. • This results in genetic change in the population as a whole b/c certain genes are passed on at a higher rate. • How does evolution work? http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

7. Examples of Evolution in response to environmental change • Antibiotic resistance in bacteria MRSA, methicillin-resistant staphylococcus aureus

8. Galapagos finches

9. Application: Changes in beaks of finches on Daphne Major. Example of natural selection in response to climate (El Niño, for example) • Wetter years -- all sizes of seeds are available in large numbers • smaller birds with smaller beak sizes eat more efficiently/ reproduce more. • Dryer years-- smaller seeds are quickly consumed, leaving only larger, harder seeds • larger birds with larger beak sizes eat more efficiently/ reproduce more Daphne Major = one of the Galapagos islands

10. Industrial melanism

11. Heavy- metal tolerance in plants • i.e. mercury , lead etc.

12. Pesticide resistance in insects

13. Video Clips • http://ca.pbslearningmedia.org/resource/tdc02.sci.life.gen.mutationstory/a-mutation-story/ A mutation story (sickle cell anemia) • HIV Immunity • http://www.pbs.org/wgbh/evolution/library/10/4/l_104_06.html • Double immunity etc. • http://ca.pbslearningmedia.org/resource/tdc02.sci.life.gen.doubleimmunity/double-immunity/ • Article with more detail on connection to plagues (perhaps not bubonic): https://www.sciencedaily.com/releases/2005/03/050325234239.htm • Discuss: • Explain why mutation is vital to the process of evolution. • Discuss the connection between evolution and molecular biology.

14. Some of the following info is from 10.3 (Gene pools and speciation)

15. There are three types of Natural Selection: • Stabilizing Selection • Directional Selection • Disruptive Selection

16. Stabilizing Selection • Type of selection in which… • average individuals are favored (selected for) • Extreme forms of a trait are selected against.

17. Example of Stabilizing Selection: Spiders • Large spiders are easily seen and eaten by birds • Small spiders can’t compete for food • Medium size spiders are selected for

18. Directional Selection • Type of selection in which… • one extreme form of a trait is favored (selected for).

19. Example of Directional Selection: Woodpeckers • A type of insect lives deep within the bark of trees • Woodpeckers with short or average-size beaks can’t get to these insects • Long-beaked woodpeckers are selected for

20. Disruptive Selection • Type of selection in which… • BOTH extreme forms of a trait are favored (selected for) • Average individuals are selected against.

21. Example of Disruptive Selection: Limpets • Limpets are snails that live attached to rocks in the tidepools • Limpets range in color from white to tan to dark brown • White colored limpets have the advantage on light-colored rocks • Dark brown limpets have the advantage on dark-colored rocks

22. Which type of natural selection is shown in each graph? 1 2 3

23. For the following videos, determine which type of natural selection is occuring. Justify your conclusion. • HIV and Natural Selection • https://www.youtube.com/watch?v=34GeUa7RzvY skip first 35 seconds (Evolution and AIDS) • Toxic Newts: • http://www.pbslearningmedia.org/resource/tdc02.sci.life.evo.toxicnewts/toxic-newts/

24. Gene Pools and Allele Frequencies • A gene pool consists of all the genes and their different alleles, present in an interbreeding population. • Evolution requires that allele frequencies change with time in populations.

25. Macroevolution and Speciation • Populations of a species can gradually diverge into separate species by evolution. • Speciation: the evolution of new species (REPRODUCTIVE ISOLATION = THE KEY!!) • Reproductive Isolation: • Occurs when formerly interbreeding organisms can no longer mate & produce fertile offspring

26. Causes of Reproductive isolation: • a. Geographic isolation: physical barrier divides a population (ex. Islands, mountains, rivers, canyons etc.) • IB note: Continuous variation across the geographical range of related populations matches the concept of gradual divergence. • http://video.pbs.org/video/1300397304/ Salamander Speciation • If speciation occurs because of geographic isolation, it is known as allopatric speciation Example: mountain range or body of water dividing a population

27. Causes of Reproductive isolation: b. Temporal (seasonal) isolation: breed at different times c. behavioral isolation: different courtship behaviors/signals http://www.youtube.com/watch?v=kwbGCmpa0Ck Albatross dance d. mechanical isolation:physical incompatibility e. changes in chromosome number (see next slide) If speciation occurs within the same geographic area, it is called sympatric speciation

28. Reproductive Isolation,cont’d: • Change in chromosome numbers • example: donkey (64) and horse (62) create mule (63) which is sterile • Polyploidy: having multiple sets of chromosomes (common in plants) • Utilization: Many crop species have been created to be polyploid. Polyploidy increases allelic diversity and permits novel phenotypes to be generated. It also leads to hybrid vigour. mule

29. Skill: Comparison of allele frequencies of geographically isolated populations. See page 459-460 for practice

30. Application: Speciation in the genus Allium by polyploidy • Nondisjunction resulting in different chromosome numbers • Ex. Allium angulosum (2n=16) but Allium oleraceum (2n =32)

31. Speciation due to divergence of isolated populations can be gradual. • gradualism—slow, gradual build-up of adaptations • Speciation can occur abruptly. • punctuated equilibrium— evolution occurs in fast bursts followed by long periods of genetic equilibrium.

32. Theory of knowledge: • Punctuated equilibrium was long considered an alternative theory of evolution and a challenge to the long established paradigm of Darwinian gradualism. How do paradigm shifts proceed in science and what factors are involved in their success?

33. Evolution Evidence • Selective Breeding • Shows that artificial selection can cause evolution • Examples (read article) http://www.learner.org/courses/essential/life/session5/closer1.html http://www.youtube.com/watch?v=EoB0pdhxfZs Silver fox experiment http://www.youtube.com/watch?v=0jFGNQScRNY

34. Evolution evidence: The Fossil Record • Succession of forms over time– inferred from layering of fossils in sedimentary rock. • Transitional links-- fossils that appear to be intermediates between species. • Order of appearance in fossil record aligns with predictions • Ex. Single-celled organisms  invertebrates  Fishes amphibiansreptiles birds  placental mammals • Transitional tetrapod fossil or fish with fingers • http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_49.html

35. Evolution evidence: Comparative Anatomy • Homologous structures (homology)– • Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function. • Analogous structures– structures that have similar functions but are unrelated in structure (i.e. bird wings vs. butterfly wings.) • Vestigial Structures • Ex: whale/snake hindlimbs; wings on flightless birds Alligator Application: Comparison of the pentadactyl (5 digit) limb of mammals, birds, amphibians and reptiles with different methods of locomotion. Human Cat Bird Bat Whale

36. End of IB

37. Evolution evidence: Molecular Biology • Similarities in DNA, RNA and Proteins • Common genetic code http://www.pbs.org/wgbh/evolution/library/03/4/l_034_04.html Genetic tool kit http://www.pbs.org/wgbh/evolution/library/04/4/l_044_02.html Common genetic Code

38. Explain how biochemistry/ molecular biology may provide evidence for evolution.   Describe the biochemical evidence discussed in the videos and the inferences derived from this evidence in a chart like this: 

39. Evolution evidence: Biogeography • Geographical distribution of species • Examples: Islands vs. Mainland Australia vs. other Continents

40. Evolution evidence: Comparative Embryology • Pharyngeal pouches (gill slits), ‘tails’ as embryos • Ernst Haeckel (“ontogeny recapitulates phylogeny” = discredited)

41. Evolutionary history • Linnaeus: taxonomy • Hutton: gradualism • Lamarck: evolution (inheritance of acquired characteristics) • Malthus: populations (An Essay on the Principle of Population) • Cuvier: paleontology • Lyell: uniformitarianism • Darwin: evolution • Mendel: inheritance • Wallace: evolution