Chapter 9

1. Chapter 9 Where Did We Come From? The Evidence for Evolution

2. Chapter 9 Section 1 What is Evolution?

3. 9.1 What is Evolution? What is Evolution? • Two different ways scientists think of evolution • The Process of Evolution • The Theory of Evolution

4. 9.1 What is Evolution? The Process of Evolution • Biological evolution – change in the characteristics of a population of organisms that occurs of over the course of generations. • Evolutionary changes are inherited via genes • Other changes may take place because of environmental changes and are not necessarily evolutionary.

5. 9.1 What is Evolution? Definitions • Species = a group of individuals that: • Can regularly breed together • Can produce fertile offspring • Are distinct from other species in appearance or behavior. • Population = a group of individuals of a species that are separated by geography.

6. 9.1 What is Evolution? - The Process of Evolution Example • Pesticide resistant lice are an example of biological evolution. Figure 9.1

7. 9.1 What is Evolution? -The Process of Evolution Populations evolve, NOT individuals. • In the lice example, the genetic structure of the population of lice changed. • Individuals without a gene for resistance died • But individuals with resistance survived to breed again • Over time, the population changed to mostly resistant individuals

8. 9.1 What is Evolution? -The Process of Evolution Why do populations evolve? • Natural selection= the differential survival and reproduction of individuals in a population. • Process by which populations adapt to changing environments • Examples: • Pesticide resistance in crop-eating insects • Antibiotic resistance in infectious bacteria

9. How Natural Selection Works 1. Offspring have different traits, some of which are inheritable.  2. Some traits are beneficial, and help the individual to survive, whereas others are harmful.  3. Organisms produce more young than can survive.  4. Organisms with beneficial traits have a better chance of surviving and passing on their characteristics to the next generation than those with harmful traits.  5. Therefore, over time, beneficial traits are perpetuated in the lineage, while harmful traits disappear.

10. 9.1 What is Evolution? Two different scales of evolution • Microevolution – changes that occur within a species due to changing characteristics of a population. • Easily observed, relatively non-controversial. • Macroevolution – changes that occur, as a result of microevolution, over long periods of time and result in the origin of new species. • Controversial among non-biologists.

11. 9.1 What is Evolution? Theory of Evolution The Theory of Evolution has Two Parts • All species present on earth today: • Represent the product of millions of years of accumulated evolutionary changes. • Are descendants of a single common ancestor • Aka the theory of common descent

12. 9.1 What is Evolution? The Theory of Common Descent Figure 9.2

13. 9.1 What is Evolution? Why is it controversial? • Ambiguity of the word “theory” • Everyday usage: theory = best guess, or tentative explanation • Scientific usage: theory = body of accepted general principles, supported by many lines of evidence. • Examples: atomic theory, gravity, germ theory.

14. End Chapter 9 Section 1 What is Evolution?

15. Chapter 9 Section 2 Charles Darwin and the Theory of Evolution

16. 9.2 Charles Darwin and the Theory of Evolution • Theory of Evolution is sometimes called “Darwinism” because Charles Darwin is largely credited with introducing the concept to mainstream science.

17. 9.2 Charles Darwin Early Views of Evolution • Charles Darwin did not “invent” the idea of evolution. Many philosophers of science had notions of organisms changing over time. • Fossils had caused people to propose animals evolved • Anaximander – Greek philosopher (611-546 BC) who first suggested that humans evolved from fish that had moved onto land • Jean Baptiste Lamarck – published ideas about inheritance of acquired traits in 1809

18. 9.2 Charles DarwinThe Voyage of the Beagle • In 1831 at age 22, Darwin set sail as ship’s naturalist aboard the HMS Beagle on a five year long trip to map S. America. • Darwin’s job was to collect and observe “anything worth to be noted for natural history.”

19. 9.2 Charles Darwin &Theory of EvolutionThe Voyage of the Beagle • The following had influences on Darwin during the voyage: • Darwin had a book by Lyell, Principles of Geology, which postulated earth was old and changes occurred over long periods of time. • Rainforests of Brazil • Fossils that he collected • Birds and reptiles of the Galapagos Islands

20. 9.2 Charles Darwin & the Theory of Evolution The Voyage of the Beagle Galapagos islands tortoises vary with their environments. Figure 9.5

21. 9.2 Charles Darwin & the Theory of Evolution Developing the Hypothesis of Common Descent • Darwin returned to England in 1836, but did not publish his ideas immediately. • Spent about 20 years refining his ideas • Learned about animal husbandry (selective breeding) • Finally published On the Origin of Speciesin 1858

22. End Chapter 9 Section 2 Charles Darwin and the Theory of Evolution

23. Chapter 9 Section 3 Examining the Evidence for Evolution

24. 9.3 Examining the Evidence for Evolution • Evolution versus Creation • Intelligent Design and Creation • God created organisms during 6 days as described in Genesis • Life has not significantly changed since then • Some claim creation occurred recently, within the past 10,000 years • Science can NOT test hypothesis based upon supernatural forces • But physical aspects can be tested

25. 9.3 Examining the Evidence for Evolution • Four Proposed explanations for life on earth • Static model hypothesis (creation or intelligent design) • Transformation hypothesis

26. 9.3 Examining the Evidence for Evolution • Four Proposed explanations for life on earth • Separate Types Hypothesis • Theory of Common Origin (theory of evolution)

27. 9.3 Examining the Evidence for Evolution An Overview of Evidence for Evolution • Several lines of biological evidence point to a common ancestor: • Biological classification • Anatomical similarities between organisms • Useless traits in modern species • Shared developmental pathways • DNA similarities • Distribution of organisms on earth (biogeography) • Fossil evidence

28. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution • Biological classification implies common ancestry. • Carl Linnaeus • 1707-1778. Figure 9.8

29. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution Humerus Radiusand ulna Carpals Metacarpals Phalanges Human Bat Lion Chimpanzee Sea lion • Anatomical similarities between organisms. Mammalian forelimbs have the same set of bones. The underlying structure is similar despite the very different functions. Figure 9.9

30. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution • Vestigial & useless traits in modern species. • Tail bones in humans

31. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution • Shared developmental pathways. Similarity among chordate embryos. Figure 9.11

32. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution • DNA similarities. Birds in same genus have DNA that is more similar to one another, while distantly-classified birds have DNA that is less similar. Figure 9.12

33. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution Biogeography • Distribution of organisms on earth. • Different species of mockingbird found on Galapagos all resemble another species found on the mainland. Figure 9.13

34. 9.3 Examining the Evidence for Evolution - An Overview of Evidence for Evolution • Fossil evidence. • Horse fossils provide a good sequence of evolutionary change within a lineage. Figure 9.14

35. 9.3 Examining the Evidence for Evolution PLAY Animation—Principles of Evolution

36. End Chapter 9 Section 3 Examining the Evidence for Evolution

37. Chapter 9 Section 4 Part A Are Alternatives to the Theory of Evolution Equally Valid?

38. 9.4 Are Alternatives to the Theory of Evolution Equally Valid? • Weighing the Alternatives Static model Transformation Separate types Common descent Rejected Rejected Rejected Supported by a widevariety of evidence,including comparativeanatomy, DNAsequences, and thefossil record. Evidence of relationshipsamong organisms abound. Earth is far older than10,000 years, andspecies have clearlychanged over time. Universality of DNA,genetic code, and cellcomponents areevidence of a singleorigin of all life. Figure 9.27

39. 9.4 Are Alternatives to the Theory of Evolution Equally Valid? Static Model • Predicts earth is less than 10,000 years old • Radiometric dating proves earth is far older • Predicts all species arose individually and have not changed • Fossil evidence proves organisms have changed over time Figure 9.27

40. 9.4 Are Alternatives to the Theory of Evolution Equally Valid? Transformation Model • Predicts species arose separately and then evolved, but no new species • No reason to expect different species would share structures • Especially vestigial structures • No reason to expect similarities in DNA sequences • Predicts little evidence of relatedness • Abundant evidence of species relatedness Figure 9.27

41. 9.4 Are Alternatives to the Theory of Evolution Equally Valid? Separate Types Model • Predicts that different groups arose separately and then evolved new species • No reason to expect genetic code to be universal • But genetic code is universal • Method for translating genes into proteins is universal • EXP: Genes from bacteria can be put into plants, which then make bacterial proteins Figure 9.27

42. 9.4 Are Alternatives to the Theory of Evolution Equally Valid? Common Descent Model • Predicts that species evolved from common ancestor • Supported by: • Biological classification • Anatomical homology • Vestigial traits • Biogeography • Homology of development • Homology of DNA • Fossil Record Figure 9.27

43. Chapter 9 Section 4 End Part A Are Alternatives to the Theory of Evolution Equally Valid?

44. Chapter 9 Section 4 Part B How Did Life Begin?

45. 9.4 The Origin of Life The Origin of Life • Evolution is the study of how life changes • It doesn’t address how life first began

46. 9.4 The Origin of Life A Hypothesis for Origin of Life from Nonliving Precursors • Simple molecules present early in earth’s history (CH4, NH3, H2O, H2) assembled into more complex molecules (such as nucleotides & amino acids) • These molecules assembled into chains that could store information (nucleic acids & proteins) • These more complex molecules became organized into self-replicating “cells”

47. 9.4 Experiment evidence does give some clues about beginnings of life Origin of life • The Miller-Urey experiment in 1953 demonstrated that complex molecules can spontaneously form from simple chemicals. Figure 9.29

48. 9.4 Experiment evidence does give some clues about beginnings of life Origin of life • The Miller-Urey experiment demonstrated that complex molecules can spontaneously form from simple chemicals. • Later experiments showed that simple precursors spontaneously form polymers to form proteins, DNA and RNA when put into contact with hot sand, clay or rock Figure 9.29

49. 9.4 Experiment evidence does give some clues about beginnings of life • In 1980 scientists showed RNA, which carries genetic info., could copy itself • Demonstrated capacity for self-replication • Phospholipids put into water spontaneously form cell like lipid bilayers Conclusions • These experiments suggest life could have started spontaneously in earths early environment • No one has been able to create life as we know it in the lab

50. 9.4 Importance of The Theory of Evolution Importance of The Theory of Evolution • Evolutionary theory informs all aspects of modern biology. • It is important because it helps scientists grapple with modern issues. • Examples: • To understand the function of human genes • To understanding species interactions • For predicting the biological consequences of climate change