Natural Selection & Evolution Slides

1. Evolution and Natural Selection

2. Theory of Evolution • Proposed by Charles Darwin • Process by which organisms that are best suited to environment survive and pass genetic traits on to offspring • Based of the idea that all species are related and gradually change over time • Adaptation – organisms with the most suited traits will survive • Evolution – change in a species over time (not a single individual, but the group)

3. Natural Selection • Adaptation – organisms with the most suited traits will survive • The traits that help an organism survive in a particular environment are “selected” in natural selection. • Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase species fitness (survival rate).

4. Conditions required for Natural Selection • There is variation in traits.For example, some beetles are green and some are brown. • There is differential reproduction. Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown (camouflage with the bark of trees) beetles do. • There is heredity. The surviving brown beetles have brown baby beetles because this trait has a genetic basis. • End resultThe advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. Eventually, all individuals in the population will be brown.

5. Natural Selection and Mutation • As mutations occur, natural selection decides which mutations will live on and which ones will die out. ... If the mutation is beneficial, the mutated organism survives to reproduce, and the mutation gets passed on to its offspring.

9. Practice Question

10. Evidence of Evolution • Evidence of Evolution exist fossils, molecular biology, embryology, comparative anatomy, biogeography.

11. Evidence of Evolution: Fossils • Fossils document the existence of now-extinct past species that are related to present-day species. • May appear in rocks, ice, and amber; when fossils are arranged in order of their age, the fossil record provides a series of changes that occurred over time; comparison of anatomical characteristics reveals shared ancestry/common ancestry

12. Evidence of Evolution: Molecular Biology • DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are. • Comparing DNA/gene or protein sequences from organisms (closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences). This also gives evidence of a common ancestor

13. Evidence of Evolution: Embryology • Embryos of different vertebrates look alike in their early stages, giving the superficial appearance of a relationship

14. Evidence of Evolution: Comparative Anatomy • Species may share similar physical features because the feature was present in a common ancestor (homologous structures). • Homologous structures - structures (body parts/anatomy) which are similar in different species because the species have common descent. They may or may not perform the same function. An example is the forelimb structure shared by cats and whales. • Vestigial structures are anatomical features that are still present in an organism (although often reduced in size) even though they no longer serve a function. Whales, which evolved from land mammals, have vestigial hind leg bones in their body

15. Evidence of Evolution: Biogeopraphy • The global distribution of organisms and the unique features of island species reflect evolution and geological change. • Patterns of past evolution are found in the natural geographic distribution of related species, similarity of endemic island species to nearby mainland species.

16. Evidence of Evolution

17. Practice Question

18. Trends in Hominid Evolution • Hominids are the family of organisms that includes humans. • Trends in Hominid Evolution: • Bipedalism (walk on two legs) • Increase in brain size • Smaller teeth and jaw • Tool usage • Language development

19. Using your paper, describe what happened to 3 of the trends of hominids.

20. Practice Question

21. Bellwork • Explain how mutations are related to natural selection • Explain ONE of the five evidence of evolution (Fossils, Molecular Biology, Embryology, Comparative Anatomy, or Biogeography)

22. Mechanisms of Evolutionary Change

23. Mechanism of Evolutionary Change: Mutation • Mutation is the change in DNA. • Since all cells in our body contain DNA, there are lots of places for mutations to occur; however, not all mutations matter for evolution. • Somatic mutations occur in non-reproductive cells and won't be passed onto offspring only those in germ cells/gametes.

24. Mechanism of Evolutionary Change: Mutation

25. Mechanism of Evolutionary Change: Gene Flow/ Migration • Any movement of genes from one population to another. • Gene flow includes lots of different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries. • If genes are carried to a population where those genes previously did not exist, gene flow can be a very important source of genetic variation which could potentially lead to the evolution of the species in that population.

26. Mechanism of Evolutionary Change: Gene Flow/ Migration

27. Mechanism of Evolutionary Change: Genetic Drift • Along with natural selection, mutation, and migration - is one of the basic mechanisms of evolution… Genetic drift. • In each generation, some individuals may, just by chance, leave behind a few more descendants (and genes, of course!) than other individuals. • The genes of the next generation will be the genes of the "lucky" individuals, not necessarily the healthier or "better" individuals

28. Mechanism of Evolutionary Change: Genetic Drift

29. Mechanism of Evolutionary Change: Nonrandom Mating • Mating that has not occurred due to chance (arranged marriages).

30. Practice Question

31. Exit Slip Explain one of the mechanisms of evolution IN YOUR OWN WORDS and specify one mechanism you are still confused about.

32. Bellwork In 3-5 sentences what is the difference between a law and a theory?

33. Random Notes • Scientific theories (like the Theory of Evolution) cannot become Laws. Additionally, laws cannot become scientific theories. • Regardless of the mechanisms, individuals do not evolve, populations do. • Meiosis • Independent assortment of chromosomes during Metaphase I and II increased genetic variation (aka genetic recombination) • Genetic recombination and mutation increase genetic variation

34. Conditions required for Natural Selection • There is variation in traits.For example, some beetles are green and some are brown. • There is differential reproduction. Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown (camouflage with the bark of trees) beetles do. • There is heredity. The surviving brown beetles have brown baby beetles because this trait has a genetic basis. • End resultThe advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. Eventually, all individuals in the population will be brown.

35. What is differential reproduction success? • This is when one group has more viable offspring than another. • If two populations are similar but one has a variation that leads to fewer births and more deaths you will see differential reproductive success between the population • Differential reproduction success is a result of • Overproduction of offspring • Inherited Variation • Struggle to Survive

36. 1. Overproduction of Offspring In ANY given generation, populations tend to create more progeny than can survive to reproductive age.

37. 2. Inherited Variation • Variation of genomes between members of species, or between groups of species thriving in different parts of the world as a result of genetic mutation.

38. Struggle to Survive • To remain alive or in existence • To carry on despite hardships or trauma (perseverance) • To remain functional or usable Reasons: Not enough resources (food, water, shelter, mate, etc.)

39. Practice Question 1 Over time, the climate of an island became drier, which resulted in changes to the populations of various island finch species. Finch populations with a certain beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations to occur? A. fewer mutations B. limited food resources C. limited beak variations D. overproduction of offspring

40. Practice Question 1 Over time, the climate of an island became drier, which resulted in changes to the populations of various island finch species. Finch populations with a certain beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations to occur? A. fewer mutations B. limited food resources C. limited beak variations D. overproduction of offspring Limited resources are a major driving factor for natural selection. Since there was not enough food for all of the finches, the finches that had beaks which allowed them to get food more easily were more likely to survive and reproduce.

41. Exit Slip Explain two of the three causes for differential reproduction success