Biological Evolution

1. Biological Evolution

2. What is Biological Evolution?andWho first proposed that “life changes over time”?

3. Not Darwin…. Charles Darwin 1809-1882

4. It was Greek philosopherssuch as Anaximander, 2600 years ago!

5. Before going into details, let’s cover some basics first and clarify some confusion that frequently exists. In your head: Do you believe in God or some type of Supreme Being or Force? Do you believe in cells…that they are the fundament units of life? Are these the same sort of beliefs?

6. As a scientist, I do NOTbelieve that cells are the fundamental units of life (part of Cell Theory). I also DO NOT believe that the planets orbit about our sun (part of Heliocentric Theory). I simply CONCLUDE (or think) that Cell Theory and Heliocentric Theory are powerful and very well supported explanations of how our world works.

7. I also do not BELIEVE in evolution. I simply find it to be one of the most powerful theoriesin all of science… ….supported by many independent lines of evidence…which we will review briefly. If someone in the future proposes a theory that explains all that evolution explains and more, science must be willing to consider that theory instead. Such is the TENTATIVE nature of science.

8. But evolution is “just a theory”… right?

9. Heliocentric Theory:That the planets orbit the sun… is just a theory too.

10. Cell Theory:All life is made of cells...…is just a theory too.

11. Theory of Inheritance:How DNA codes for life……is just a theory too.

12. Germ Theory:Many diseases result from viral and bacterial infections……is just a theory too. COLD VIRUSES HIV - the cause of AIDS

13. Atomic Theory:…the structure of the atom…is just a theory too.

14. Theories are the strongest, most well supported explanations in all of science. There is NO term that we use in science with greater confidence. Science is VERY CONFIDENT that evolution occurs. https://www.youtube.com/watch?v=85diEXbJBIk&list=PL5270149AB732F0FB

15. So you have to wonder… • Can people just choose which scientific theories to accept or reject? • Or do we trust in the process of science….

16. In many textbooks, there is confusion about some terminology. Many elementary and high school textbooks use the word “Development” instead of “Evolution”. These two terms mean completely different things.

17. Development addresses the changes that occur within an individual’s lifetime.

18. Evolution addresses the changes that occur in species over time.

19. And… “What is a Species?” For organisms that reproduce sexually…which is by far most animals… Dr. Ernst Mayr proposed the Biological Species Concept: A species is: “a group of interbreeding natural populations that are reproductively isolated from other such groups.”

20. What are we speaking about, when we talk about “Evolution”? • Fact - That evolution occurs… • That life has changed over time, • That life continues to change over time, and • That all life has a common ancestry. Course / Ancestry - Who gave rise to whom and who is most closely related to who…are matters of ancestry and are still greatly explored & debated. “the family tree” Mechanism - Darwin & Wallace proposed Natural Selection as the mechanism. Although Natural Selection clearly occurs, it is still debated in science whether or not there are other mechanisms of evolution working too.

21. Chapter 15 History & the People who Studied evolution

22. Jean-Baptiste Lamark-180915-2 pg 376 • Organisms strive to improve themselves • Most used body structures develop • “Use it or lose it” • Used modification is inherited by offspring Ex: giraffe necks & muscle builders

24. August Weisman- 1883 • Uses mice to disprove Lamark • Cuts tails off of mice, didn’t lead to tailless mice • “cut off the tails of 901 young white mice in 19 successive generations, yet each new generation was born with a full-length tail. The final generation, he reported, had tails as long as those originally measured on the first”

25. Now on with the story of Charles Darwin and his contributions to science. • -Entered & left medical school • -Entered & left ministry • -Cambridge-meets John Henslow • Studies geology & biology

26. 15-1At the age of 22, Darwin began a 5 year voyage around the world on HMS Beagle

27. -5 year, global voyage -Goal was to make maps of S. America

28. Galapagos Islands- Darwin notices that many groups of animals represent variations on a theme.

29. Similar by DESIGN….

30. Similar because of shared ancestry.

31. Similar because of sharedancestry.

32. Similar because of shared ancestry

33. For more than 2500 years, people noticed natural groups

34. Was all of life related…and thus similarbecause of shared ancestry?

35. Into this world Darwin offered 5 theories, in his major work, On the Origin of Species…

36. 1) Evolution occurs: The world is not constant. - Instead, it is changing, and organisms change over time.

37. 2) Common Descent:Every group of organisms is descended from a common ancestor.

38. 3. Natural Selection: Evolution occurs through 1) the production of genetic variety and 2) the subsequent advantages that result from certain combinations.

39. 4. Gradualism: Evolution occurs through gradual change instead of the sudden appearance of new forms. Gradualismas proposed by Charles Darwin Punctuated Equilibrium- proposed by scientists working after Darwin

40. 5) Multiplication of species: a) Species multiply by splitting into daughter species or b) by geographic isolation of a founder population. Darwin titled his book “On the Origin of Species…” because he saw this part of his idea as one of the most important contributions of his ideas. HOW SPECIES FORM.

41. Summarizing Darwin’s main ideas: Natural Selection • There is variation within populations • Some variations are favorable • More offspring are produced than can survive • Favorable variations = survival • Change over time leads to population change

42. Lamarkvs Darwin • Both theorized that: • Life changed gradually over time and was still changing • that living things change to be better suited and adapted to their environments • all organisms are related

43. 15-3 Publication • Alfred Russel Wallace-makes similar voyage, but his notes were destroyed • Wants to publish findings • So…..Darwin publishes 1858 “On the Origin of Species”

44. A note about the phrase “survival of the fittest” Darwin referred to evolution as “Descent with Modification” The phrase “survival of the fittest” originated with another scientist, Herbert Spencer, after reading Darwin’s book Origin of Species. In the 6th Edition of Orgin of Species, Darwin Retitled Chapter IV, “Natural Selection; or the Survival of the Fittest.” Today we know that this phrase is circular. To be fit includes the ability to survive. Thus the phrase means “survival of the survivors!”. So the phrase “survival of the fittest” is not commonly used by scientists.

45. EVIDENCE FOR EVOLUTION • Multiple Lines of Evidence Increases Confidence • http://learn.genetics.utah.edu/content/variation/related/

46. Anatomical Studies • Homologous- modified structure seen among different groups • Similar in structure & function • Ex: forelimbs-reptiles, mammals, birds

48. 2. Analogous- similar in function, different structure ex: insect vs bird wing 3. Vestigial- structure once used but not now ex: appendix in humans eyes of sightless species

49. 16.1 Populations • All individuals of the same species that live in the same environment & interbreed

50. Features of populations: • 1. Population size- # of individuals • Small is bad- interbreeding, natural disasters • 2. Population density- # of individuals in an area • Spaced widely apart= no mating • 3. Dispersion- random, even, or clumped