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 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 Lamarck 1744-1829 “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 Darwin 1809 - 1882 A naturalist (studied and preserved biological specimens that he collected) 5 year voyage around the world aboard the HMS Beagle

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. Variations in organisms 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

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 Evolution Homologous 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 Evolution Analogous 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? 1.Mutation 2.Migration (gene flow) 3.Genetic drift –Random events –Small populations 4.Non-random mating 5.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!!!