Evolution—The Theory and Its Supporting Evidence

1. Biology 821 Evolution—The Theory and Its Supporting Evidence

2. I. Evolution is a theory (subject to revision and change) • In Biology a theory is an overarching principle, supported by evidence • Evolution provides the framework for modern biology • A hot topic long before Darwin and Wallace suggested a mechanism

3. II. Evolution is change over time • It occurs in populations, not in individuals • It explains how new organisms are created

4. III. History • Greek philosopher Anaximander (~2,500 years ago) – simpler life forms gave rise to complex life forms • Aristotle – species were fixed and did not change • Judeo-Christian culture - species were created by the Divine Creator

5. Georges Buffon • Fossils were ancient forms of modern organisms (1766) • Earth is more than 6000 years old

6. Studied fossils scientifically (1800s) • Comparisons of fossils among rock strata led him to believe natural catastrophes periodically wiped out existing species Georges Cuvier

7. Fossils suggested that life forms change (1809) • Current organisms evolved from past ones • Organisms respond to changes in their environment by developing or changing their structure • wrongly thought acquired characteristics could be inherited Jean Baptiste de Lamarck

8. IV. Darwin • 1859 - Charles Darwin published Origin of Species. • Proposed a different mechanism to account for changes in a species • Natural Selection

9. A sea voyage (1831-6) helped Darwin frame his theory of evolution 1874 Charles Darwin, 1859

10. H.M.S. Beagle cruise 1831-1836 www.rit.edu/~rhrsbi/GalapagosPages/Darwin.html

11. Author of “Principles of Geology” • Geologic changes occur slowly through natural forces, bringing about changes in the earth’s surface Charles Lyell

12. similarities between living and fossil organisms • the diversity of life on the Galápagos Islands, such as blue-footed boobies and giant tortoises • While on the voyage of the HMS Beagle in the 1830s, Charles Darwin observed

13. Darwin became convinced that the Earth was old and continually changing • Concluded living things also change, or evolve over generations • Living species descended from earlier life-forms: “descent with modification”

14. Darwin’s Journey • Joined the H.M.S Beagle as naturalist • Found fossils of marine animals in the mountains • Observed many new plants and animals in S. America • Read Charles Lyell’s Principles of Geology -- described the ancient world of plants and animals as one in flux. • Compared species in Galapagos with those in S. America – must be related • Collected much data, but didn’t publish for 20 years.

15. The voyage of the Beagle Great Britain Europe NorthAmerica PacificOcean AtlanticOcean Africa GalápagosIslands Equator SouthAmerica Australia Andes Cape ofGood Hope Tasmania Cape Horn NewZealand Tierra del Fuego

16. British naturalist working in Indonesia came up independently with a theory similar to Darwin’s theory Alfred Russell Wallace

17. The Origin of Species frontispiece

18. Darwin cartoon

19. V. Natural Selection • Arrived at independently by Darwin and Alfred Russell Wallace (Darwin published first!) • Darwin did not know about genetics • Contrast with Lamarck, who was right about organisms evolving from ancient forms, but wrong about inheriting acquired characteristics

20. VI. Darwin’s Theory of Evolution by Natural Selection • Variation exists within species • Traits vary among individuals of the same species • All organisms compete for limited natural resources • Some will get more, some less (Thomas Malthus) • Organisms produce more offspring than can survive, leads to competition

21. Thomas Robert Malthus

22. The environment selects organisms with beneficial traits • Organisms with traits well suited to the environment survive and reproduce in greater numbers than those less well suited. They pass these traits to their offspring • Darwinian fitness = an organism’s genetic contribution to the next generation • Over time the population becomes better adapted to the environment

23. VII. Key Points • Evolution is not the same as natural selection: Natural Selection is the process by which evolution occurs. • Darwin made two main points in The Origin of Species • Organisms inhabiting Earth today descended from ancestral species • Natural selection was the mechanism for descent with modification

24. VIII. Evidence of Evolution • Paleontology (Fossils) • Comparative anatomy/morphology • Comparative embryology • Biogeography and adaptive radiation • Direct observation of natural selection • Genetics and molecular biology

25. 1. Paleontology or Fossil Record • Fossils • Relates past organisms to living ones • Fossil record is incomplete • Are preserved remnants or impressions left by organisms that lived in the past • Are often found in sedimentary rocks

26. Rivers bring sediment to the ocean. Sedimentary rocks containing fossils form on the ocean floor. 1 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion by rivers reveals strata; deeper strata contain older fossils. Over time, additional strata are added, containing foss- -ils from each time period. Younger stratum with more recent fossils Older stratum with older fossils • The fossil record shows that organisms have appeared in a historical sequence

27. The study of fossils provides strong evidence for evolution • Fossils and the fossil record strongly support the theory of evolution • Hominid skull • Fossil perch • Petrified trees and bones

28. Ammonite casts • Tracks, footprints and impressions • Fossilized organic matter in a leaf

29. Scorpion in amber • “Ice Man”

30. Many fossils link early extinct species with species living today • These fossilized hind leg bones link living whales with their land-dwelling ancestors

31. 2. Comparative Anatomy/morphology • Homologous Structures • Parts of different organisms, often quite dissimilar, that developed from the same ancestral body parts

32. Homologous Structures • Forelimbs of the following types of organisms are made up of the same bones but serve different functions • This similarity in bone structure indicates a fairly recent common ancestor between these types of organisms

33. Analogous Structures • Wings of insects and bats serve the same function but differ considerably in structure and embryological development. This indicates a remote ancestry between these three types of organisms.

34. Vestigial Structures • Organs, structures, or parts that are incomplete or have no apparent function -- remaining parts of once functioning organs. • Examples: • Human tail bones • Whale leg bones • Snake pelvic bones • Human appendix • Horse splint bones (ancient side toes)

35. Vestigial Structures • Why do dogs have tiny, functionless toes on their feet? • Ancestral dogs had five toes on each foot • As they evolved they became toe-walkers with only four toes on the ground • Big toes and thumbs were lost or reduced to their present state

36. Remnants of Toes in Horses • Normally a horse’s back foot has only one functional toe, the third • Splints are small remnants of toes 2 and 4 that remain as vestiges

37. 3. Comparative Embryology • Early stages of vertebrate embryos are very similar • Gill slits • Long tail • Similar developmental stages may reflect common ancestry

38. Embryonic History (Ontogeny) Fish Rabbit Gorilla Bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html

39. 4. Biogeography • Study of the geographical distribution of species • First suggested to Darwin today’s “closely allied” organisms locally evolved from ancestral forms • Many examples of biogeography theory support evolution Marsupials in Australia Darwin’s finches on the Galapagos Old world vs. new world monkeys Lemurs in Madagascar

40. Closely allied species tend to be found on the same continent ex. Marsupials in Australia Australia Koala Kangaroo

41. Adaptive Radiation • Many new species can arise from a single species • Ex: Darwin’s finches • On the Galapagos -- similar appearance, but each species has a distinct beak shape and feeding habit • All closely related -- arose from a single type of finch in S. America • On the Galapagos, many different food sources, evolved into different species

42. Adaptive radiation in Darwin’s finches

43. Adaptive radiation in Hawaiian honeycreepers

44. Scientists can observe natural selection in action • Evolutionary adaptations have been observed in populations of birds, insects, and many other organisms • Example: camouflage adaptations of mantids that live in different environments

45. The result of natural selection is evolutionary adaptation (b) A Trinidad tree mantid that mimics dead leaves (a) A flower mantid in Malaysia (c) A leaf mantid in Costa Rica

46. 6. Direct Observation of Natural Selection • Ground finches on the island of Daphne Major in the Galapagos -- “The Laboratory of Evolution” • Artificial selection (vegetables, domestic animals) • Microbial resistance to antibiotics and pesticides

47. Darwin also saw that when humans choose organisms with specific characteristics as breeding stock, they are performing the role of the environment • This is called artificial selection • Example of artificial selection in plants: five vegetables derived from wild mustard

48. These five canine species evolved from a common ancestor through natural selection Jackal African wilddog Fox Wolf Coyote Thousands tomillions of yearsof natural selection Ancestral canine

49. Example of artificial selection in animals: dog breeding English springerspaniel German shepherd Yorkshire terrier Golden retriever Mini-dachshund Hundreds tothousands of yearsof breeding(artificial selection) Ancestral dog

50. The evolution of antibiotic resistance in bacteria is a serious public health concern • The excessive use of antibiotics is leading to the evolution of antibiotic-resistant bacteria • Example: Mycobacterium tuberculosis