Theories for Evolution

1. Theories for Evolution Mr. Young

3. Evolution • The process of change within a living system over a period of time • Genotype changes vs. Phenotype changes • Micro vs. Macro Evolution • Many different scientists have proposed theories about this process….…

4. Microevolution: Small-scale evolutionary changes, usually on the molecular level, that occur over the span of a few generations and can therefore be detected in living populations.

5. Macroevolution: Large scale evolutionary changes, speciation events, that may require many hundreds of generations and are usually only detectable in the fossil record

6. Natural Selection: The differential reproductive success of certain phenotypes within a given environment “Survival of the Fittest”

7. Jean Lamarck1744-1829 “Acquired Traits” • Theory of use and disuse • If an organ is used , it becomes stronger and better developed • If an organ is not used, it becomes weaker and withers away

8. Lamarck • An organism acquires traits from its experience (not genes) and those traits are passed down, or inherited by their offspring • Example: Lamarck believed that giraffes stretched their necks to reach food. Their offspring and later generations inherited the resulting long necks.

9. To Lamarck this means… • If you have a nose job, your kids will inherit the new nose! • In real life, what nose will your kids get? (the old one or the new one?) • Answer: the old one!

10. Is this logical? • What determines that traits are passed to their children? • DNA • If you change your appearance, will your children inherit the new appearance • No, because your DNA did not change

11. Natural Selection • Environmental Selection • Role of the Environment • Acquired traits???? (Lamarck)

12. Who’s Your Daddy? • Charles Darwin • Theory-descent w/ modification • Theory-natural selection-main principles:

13. Charles Darwin1809 - 1882 • A naturalist (studied and preserved biological specimens that he collected) • 5 year voyage around the world aboard the HMSBeagle

14. Charles Darwin • Theory of evolution by natural selection • Nature will select the organisms that have variations that allow them to better survive (survival of the fittest) • Descent by Modification • Darwin collected different species that were very similar and hypothesized that they shared a common ancestor

15. insects finches

16. Darwin’s Book:Origin of Species by Natural Selection • Described his theory of evolution • Caused a lot of controversy and angered the church • The church initially believed that evolution is a sin against God • Before Darwin died, the church accepted his theory and he was buried in a famous church in England

17. Charles Darwin • Darwin’s theories are accepted today as the most accurate explanation for evolution

18. Darwin explains why giraffes have longer necks than their ancestors • Overproduction – too many giraffes • Struggle or compete for food • Variation in length of neck exists naturally • Longer neck…reach food...survive • Longer necked giraffes survive and reproduce to eventually originate a new species of giraffes

20. Hugo De Vries • Added the concept that mutations in DNA are what cause organisms to change or have variations • Evolution is changes in DNA that is then inherited (microevolution)

21. Each species has organisms with varying characteristics for example: some are taller some have bigger feet some run faster some have better vision some smell better Variations in organisms

22. Struggle for existence • Overproduction of a species causes competition for resources to survive • food • water • shelter • space

23. Survival of the fittest by means of natural selection • Variations may give certain organisms advantages to survive, while other organisms died • Nature selects those organisms that will die or survive

24. Evidence for Darwin's theory • Fossil record • Biogeography • Comparative Anatomy • Embryology • Biochemistry

25. Evidence for EvolutionHomologous structures • Similar shape • Different function • Shared origin • Example: arms of human, wings of bats, wings of penguins, arms of alligators • Divergent evolution

28. Evidence for EvolutionAnalogous structures • Different shape • Similar function • Different origins • Example: wings of a humming bird and wings of a moth, both allow the organism to hover • Convergent evolution

31. Vestigial Structures • A structure that had a use in an ancestor but has no use in a particular organism • Examples: • Appendix in humans • Tail bones in humans… we have no tails • Tiny leg bones in snakes…they have no legs • Wings in penguins…they do not fly • Nipples on boys…they do not produce milk

32. Embryology • The study of an organism from creation to birth • Embryos have • tails that vanish into their spines • gill slits, like fish to breath that vanish into ears • coats of hair that fall off at birth

34. Embryos go through stages of heart development • 2 chambers like fish hearts • 3 chambers like reptiles • 4 chambers like birds and mammals

36. Adaptations • A trait that increases an organisms chances of survival

37. What forces cause evolution? • Mutation • Migration (gene flow) • Genetic drift • Random events • Small populations • Non-random mating • Natural selection-4 types;

38. Types of natural selection • Stabilizing • Directional • Disruptive • Aka diversifying • sexual

39. Natural Selection? • What leads to these changes? • Random mutations • Organisms w/ shorter generation times have higher mutation rates & so evolve quicker than animals w/ longer generation times • Examples: • Industrial Revolution vs. Peppered Moth

40. Natural selection results from Selection Pressures • those aspects of the environment that can have a notable impact on the reproduction of members of a particular species over evolutionary time. • adaptations

41. Defense Mechanism • Different ways for organisms to defend themselves • Example: thorns on rose bush

42. Mimicry • Copying the appearance of another, more dangerous specie • Example, the fat bumble bees do not sting, but they copy the yellow/black appearance of thin bumble bees that do sting

43. Camouflage • The ability of an organism to blend into their environment • Example, fish have pale bottoms and dark tops • Frogs are shades of green

44. Let’s play name that adaptation!!!