Darwin’s Theory of Evolution

1. Darwin’s Theory of Evolution Science’s Answer to the Question: “Where Did Life on Earth Come From?”

2. Charles Darwin (12 Feb. 1809 – 14 April 1882) • Robert Darwin, father, and Erasmus Darwin, grandfather - both physicians and Unitarian free thinkers. • Quit physician training to become a minister. Most naturalists in 1800’s were ministers who studied “natural theology,” which sought to discover the Creator’s plan and purpose for all creatures. • Voyage of the HSM Beagle (1831-1836). • Charles enlisted specialists (ornithologists, botanists, geologists to help him wade through his data • On the Origin of Species (1859)

3. England EUROPE NORTH AMERICA ATLANTIC OCEAN PACIFIC OCEAN Galápagos Islands HMS Beagle in port AFRICA SOUTH AMERICA Darwin in 1840, after his return AUSTRALIA Cape of Good Hope Andes Tasmania Cape Horn New Zealand Tierra del Fuego Voyage of the HMS Beagle 1831 - 1836 In 1839 he published his “Journey on the Beagle”

4. Alfred Russel Wallace(8 Jan. 1823 – 7 Nov 1913)

6. Wallace was a British naturalist, explorer, geographer, anthropologist, and biologist. He is best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858. This prompted Darwin to publish his own ideas in On the Origin of Species. Wallace did extensive fieldwork, first in the Amazon River basin and then in the Malay Archipelago, where he identified the faunal divide now termed the Wallace Line, which separates the Indonesian archipelago into two distinct parts: a western portion in which the animals are largely of Asian origin, and an eastern portion where the fauna reflect Australasia. He was considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography". Wallace was one of the leading evolutionary thinkers of the 19th century and made many other contributions to the development of evolutionary theory besides being co-discoverer of natural selection. These included the concept of warning colouration in animals, and the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridisation. http://en.wikipedia.org/wiki/Alfred_Russel_Wallace

7. In 1844, Darwin wrote a long essay on the origin of species and natural selection…- But he was reluctant to introduce his theory publicly, anticipating the uproar it would cause. -At the time, most people believed that the Earth was 6,000 years old and that all species had been created by the Creator all at once. His theory of evolution is incompatible with this view. - In June 1858 Darwin received a manuscript from Alfred Russell Wallace (in Indonesia) who had developed the theory of natural selection independently of Darwin.Darwin quickly finished The Origin of Species and published it the next year, 16 years after he had written it.

8. - Darwin collected many plant and animal specimens from the Galapagos Islands off South America. - He studied his finch collections, especially the differences in their beaks, when he got home and began to make connections between adaptations and how new species originated (speciation). (which is why The Origin of Species became his book title…)

9. Natural selection works on individuals, but populations/speciesevolve • Geospiza fortis (Galapagos ground finch of Daphne Major) • In 1977, 180 of 1200 individuals survived a drought. • Larger harder-shelled seeds survived the drought and so did the bird with the deepest and larger beaks. • Evolution occurred - allele frequencies change in a population

10. How do Populations and Species change?2 Primary Sources of Genetic Variation • Mutations – creates variation • Sex - shuffles the deck and spreads mutations around…..

11. Three basic mechanisms of evolutionary change • 1. Natural Selection • 2. Genetic Drift • 3. Migration (Gene Flow or Gene Migration)

12. Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier (fossils, extinction) Lyell (modern geology – Earth is old Darwin (evolution, nutural selection) Mendel (inheritance) Wallace (evolution, natural selection) American Revolution French Revolution U.S. Civil War 1800 1850 1900 1750 1795 Hutton proposes his theory of gradualism. 1798 Malthus publishes “Essay on the Principle of Population.” 1809 Lamarck publishes his theory of evolution. 1830 Lyell publishes Principles of Geology. Darwin travels around the world on HMS Beagle. 1831–1836 1837 Darwin begins his notebooks on the origin of species. 1844 Darwin writes his essay on the origin of species. 1858 Wallace sends his theory to Darwin. TheOrigin of Species is published. 1859 1865 Mendel publishes inheritance papers. • The historical context of Darwin’s life and ideas

13. Artificial Selection – selective breeding by farmers changes species over time

14. Darwin connected and built on others’ ideas • If the Earth is very old and has gradually changed over time…and if plants and animals have also changed over great periods of time… and if animals can be artificially bred to change…and if there is competition for survival… • He connected the dots between Cuvier, Lamarck, Hutton, Lyell, Malthus, and what he saw with selective breeding of plants and animals (artificial selection) ….

15. NATURAL SELECTION • Darwin made the connection that individuals in all species compete for survival, that successful individuals survive and pass on their genes, and in this way the entire species adapts to its environment. • Over time, these adaptations can accumulate to create new species. • He called this process natural selection. He did not coin the term “survival of the fittest.” • How do “successful” individuals get their “good” genes?

16. Darwin’s Observations • 1) Variation heritable differences exists among individuals within species. • 2) Overproduction, all offspring do not survive to become reproducing adults, the environment cannot support all progeny. • 3) Adaptation, organisms must be able to survive a changing environment for their offspring to be able to find mates and produce more offspring. • 4) Descent with modification, organisms will change to better fit their environment as time progresses.

17. Darwin’s Inferences Inference 1: The organisms whose variations best fit them to the environment are the ones who are most likely to survive, reproduce, and pass those desirable variations on to the next generation. Inference 2: Unequal survival and reproduction will lead to favored traits that may become inherited by future generations.

18. Darwin developed two main ideas • Natural selection – mechanism by which fit individuals survive and pass on their genes. Unfit individuals do not. • Evolution -natural selection causes change over time, or evolution. This explains life’s unity and diversity – all life on earth descended from a common ancestor (life’s unity) and then evolved into all the diversity that has ever existed on Earth (99% of which is already extinct!) **Natural selection is the mechanism; evolution is the result* • He used the phrase descent with modificationto capture both ideas. Descent captured his idea of a common ancestor from which all life descended • Modification captured his idea of adaptations leading to diversity.

19. Population - same species, same place, same time • Species - members of the same population that can interbreed and produce fertile offspring.. Reproductive compatibility is key. • Gene pool - the collection of all of the genes within a population. • Populations evolve. Individuals do not!

20. “Fitness” Darwin called the ability of an organism to survive and reproduce in its specific environment “fitness.”

22. Fitness is NOT just the strongest or the fastest! • Can be the sneakiest! Or best camouflaged…. • And you have to reproduce or its all for nothing evolutionarily speaking….

23. Descent with Modification = Theory of Evolution The characteristics of new species are not entirely new, but rather modified versions of ancestor characteristics. ….. Evolution is a process of remodeling, not inventing. Mother Nature can only work with the material she has. …..

24. Cladograms Phylogenetic tree Both phylogenetic trees and cladograms help show the relationships between different organisms, but only phylogenetic trees have branches that represent evolutionary time and amount of change.

25. Each group has to write up and submit to Dr. Spence the reasoning for the arrangement of their groups. • Common ancestor • Shared derived trait • Homology • Convergent structure (convergent evolution) • Compare your cladogram with the other groups. • As a group, defend your arrangement.

26. Nurse young Vertebra Internal skeleton Bilateral symmetry

27. What is the Evidence for Evolution?

28. Evidence for Evolution: Outline • Research Interventions…biotechnology • Homology – Evidence of Remodeling of body designs • Anatomical Homology • Vestigial Structures (snake pelvis, appendix) • Embryological Homologies • Molecular Homologies • The Fossil Record Corroborates Evolution • Transitional Fossils – • Biogeography - bears, marsupials and placentals

29. Homologous Structures - structures that have the same ancestral origin and develop from same embryonic tissue, but have evolved to fit their environment and have different mature forms in different species. - Not separately engineered – remodeled by natural selection…Mother Nature can only work with the material she has!

30. Forelimbs Up Close

31. Can you think of other homologous structures?

33. Evolution.berkeley.edu

34. Vestigial Structures Structures that no longer have a use Remnants of structures that were once useful…. Examples in humans: wisdom teeth, coccyx, appendix, Darwin’s Tubercle What was the ancestral purpose of these structures? Why do we still have them?

35. Embryology • Embryonic stages reveal anatomical homologies that disappear in adult organisms • In vertebrates, the same groups of embryonic cells develop in the same order and in similar patterns • The embryo “is the animal in its less modified state,” which “reveals the structure of its progenitor”

36. Embryology  "ontogeny recapitulates phylogeny“ Ernst Haeckel 1892 http://ncse.com/book/export/html/11831

37. Figure 22.18 Transitional Fossils: Evolutionary transitions have left signs in the fossil record • Fossilized whales have traits that link today’s whales to their terrestrial ancestors. Fossilized leg bones of Basilosaurus and Ambulocetus show the hind limbs of whale ancestors

38. Human Transitional Fossil:Australopithecus Afarensis

39. Molecular Homologies Because the genetic code is universal in all living things, molecular biology can now explore evolutionary relationships between very different species (plants, animals, fungus, bacteria…) If two species have some gene and protein sequences that match closely, the sequences have probably come from a common ancestor More on this when we discuss classification systems…

40. Biogeography • The distribution of species • Gave Darwin his first clue about evolution: Similar species live near each other because they have descended from a common ancestor. • Islands are showcases for biogeopraphic evidence because they are isolated

41. Australian Marsupials are closely related - all evolved from a common ancestor- therefore have common characteristics

42. Convergence: Evolution’s Wild Card Not all similarity represents common ancestry! Species from different evolutionary branches may resemble each other because they evolved similar adaptations in similar environments….in other words, by coincidence This is called convergent evolution and the similar traits are called analogies (not homologies!)

43. Sugar Gliders and Flying Squirrels

44. Dolphins and Sharks Convergence:

45. Sharks and Dolphins Dolphins are aquatic mammals Sharks are cartilaginous fish (along with rays and skates) They separately evolved similar traits as aquatic predators: Dorsal fins, fusiform body shape, coloration These are analogous traits

46. Sea Lions and Seals

47. Convergence • Sealions and seals have a very distant common ancestor. Sealions are more closely related to bears and seals are more closely related to otters. • They have converged on a form. It is a co-incidence. • Their structures are analogous to each other.

48. Prehistoric Convergence

50. Reznick and Endler transplanted guppies from pike-cichlid pools to killifish pools and measured the average age and size of guppies at maturity over an 11-year period (30 to 60 generations). Pools with killifish, but not guppies prior to transplant Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools” Figure 22.12 Evolution Research Example:Reznick and Endler, 1982 Paper