Charles Darwin

2. Charles Darwin • 1859 – “Origin of Species”published • Argued from evidence that species inhabiting Earth today descended from ancestral species • Proposed a mechanism for evolution  Natural Selection • Many scientists helped pave the way for Darwin’s Theory

3. Fig. 22-2 Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier (fossils, extinction) Lyell (modern geology) Darwin (evolution, natural selection) Wallace (evolution, natural selection) American Revolution French Revolution U.S. Civil War 1800 1900 1750 1850 1795 Hutton proposes his theory of gradualism. Malthus publishes “Essay on the Principle of Population.” 1798 1809 Lamarck publishes his hypothesis of evolution. Lyell publishes Principles of Geology. 1830 Darwin travels around the world on HMS Beagle. 1831–1836 1837 1837 Darwin begins his notebooks. 1844 Darwin writes essay on descent with modification. Wallace sends his hypothesis to Darwin. 1858 The Origin of Species is published. 1859

4. Lamarck’s Hypothesis of Evolution • Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics • The mechanisms he proposed are unsupported by evidence

5. Charles Darwin had a consuming interest in nature • First studied medicine (unsuccessfully), and then theology at Cambridge University • After graduating, he took an unpaid position as naturalist and companion to Captain Robert FitzRoy for a 5-year around the world voyage on the Beagle GREAT BRITAIN EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands AFRICA Pinta Genovesa Equator Marchena SOUTH AMERICA Santiago Daphne Islands AUSTRALIA Pinzón Fernandina PACIFIC OCEAN Cape of Good Hope Andes Isabela Santa Cruz Santa Fe San Cristobal Tasmania Florenza Española Cape Horn New Zealand Tierra del Fuego • During his travels on the Beagle, Darwin collected specimens of South American plants and animals • He observed adaptations of plants and animals that inhabited many diverse environments

6. The most influential stop on the voyage was to the Galápagos Islands • Darwin noticed that many of the birds and reptiles were unique to specific islands in the Galápagos archipelago • These included tortoises…

8. Fig. 22-6 (a) Cactus-eater (c) Seed-eater (b) Insect-eater

9. In the Darwinian view, the history of life is like a tree with branches representing life’s diversity • Darwin’s theory meshed well with the hierarchy of Linnaeus

10. Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection Darwin then described four observations of nature and from these drew two inferences Artificial Selection, Natural Selection, and Adaptation

12. Fig. 22-9 Terminal bud Lateral buds Cabbage Brussels sprouts Flower clusters Leaves Kale Cauliflower Stem Wild mustard Flowers and stems Broccoli Kohlrabi

13. Observation #1: Members of a population often vary greatly in their traits

14. Observation #2: Traits are inherited from parents to offspring • Observation #3: All species are capable of producing more offspring than the environment can support • Observation #4: Owing to lack of food or other resources, many of these offspring do not survive

16. An example of the process of evolution: • Some populations of head lice won’t be killed by the chemical permethrin, a common treatment • Studies have shown that this evolution occurred after only about 30 months (40 generations of lice)

17. The Process of Evolution • Individuals DO NOT evolve • One louse did not, all of a sudden, have the ability to stay alive when permethrin was in the environment • The resistance that developed was genetic, passed on from one generation to the next

18. Fig. 22-12 (a)A flower mantid in Malaysia (b)A stick mantid in Africa

19. Direct Observations of Evolutionary Change • New discoveries continue to fill the gaps identified by Darwin in The Origin of Species • Examples provide evidence for natural selection: • the effect of differential predation on guppy populations • evolution of drug-resistant HIV • Antibiotic resistance in bacteria • Pesticide resistance in insects

20. Fig. 22-13 EXPERIMENT Predator: Killifish; preys mainly on juvenile guppies (which do not express the color genes) Experimental transplant of guppies Pools with killifish, but no guppies prior to transplant Guppies: Adult males have brighter colors than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on adult guppies Guppies: Adult males are more drab in color than those in “killifish pools” RESULTS 12 12 10 10 8 8 Area of colored spots (mm2) Number of colored spots 6 6 4 4 2 2 0 0 Source population Source population Transplanted population Transplanted population

22. Fig. 22-14 100 Patient No. 1 Patient No. 2 75 Percent of HIV resistant to 3TC 50 Patient No. 3 25 0 2 0 4 6 8 10 12 Weeks

24. Fig. 22-UN2 Insecticide Resistance

25. Natural selection does not create new traits, but edits or selects for traits already present in the population The local environment determines which traits will be selected for or selected against in any specific population

26. There are 5 major pieces of evidence that supports the theory of evolution 1. The Fossil Record • The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time (a) Pakicetus (terrestrial) (b) Rhodocetus (predominantly aquatic) (c) Dorudon (fully aquatic) (d) Balaena (recent whale ancestor)

28. Fig. 22-8 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium Barytherium Deinotherium Mammut Platybelodon Stegodon Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 34 5.5 104 0 24 2 Millions of years ago Years ago

29. 2. Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor Fig. 22-17 Humerus Radius Ulna Carpals Metacarpals Phalanges Human Whale Bat Cat

30. Homologous Structures

31. 3. Biochemical Evidence • Molecular level  genes shared among organisms inherited from a common ancestor

32. Fig. 22-18 Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo 4. Comparative embryology reveals anatomical homologies not visible in adult organisms

33. 5. Vestigial structures are remnants of features that served important functions in the organism’s ancestors

35. Convergent Evolution • Convergent evolution is the evolution of similar, or analogous,features in distantly related groups • Analogous traits arise when groups independently adapt to similar environments in similar ways • Convergent evolution does not provide information about ancestry Sugar glider Flying squirrel

36. Fig. 22-19 Branch point (common ancestor) Lungfishes Amphibians 1 Tetrapods Mammals 2 Tetrapod limbs Amniotes Lizards and snakes 3 Amnion 4 Crocodiles Homologous characteristic 5 Ostriches Birds 6 Feathers Hawks and other birds

37. The genetic structure of a population is defined by its allele and genotype frequencies Hardy Weinberg Theorem describes non-evolving populations The 5 causes of microevolution are: Genetic drift Gene flow Mutation Nonrandom mating Natural selection Population Genetics

38. Genetic drift • Changes in the gene pool of a small population due to chance • The larger the population = less drift

39. 2 situations which result in populations small enough for genetic drift to be important are: • Bottleneck effect (population is reduced by natural disasters) (ex. Cheetah) • Founder effect ( few individuals colonize new habitat) (ex. Amish)

40. The Bottleneck Effect • The bottleneck effect is a sudden reduction in population size due to a change in the environment • The resulting gene pool may no longer be reflective of the original population’s gene pool • If the population remains small, it may be further affected by genetic drift

41. The Founder Effect • The founder effect occurs when a few individuals become isolated from a larger population • Allele frequencies in the small founder population can be different from those in the larger parent population

43. Case Study: Impact of Genetic Drift on the Greater Prairie Chicken Post-bottleneck (Illinois, 1993) Pre-bottleneck (Illinois, 1820) Researchers used DNA from museum specimens to compare genetic variation in the population before and after the bottleneck The results showed a loss of alleles at several loci Researchers introduced greater prairie chickens from population in other states and were successful in introducing new alleles and increasing the egg hatch rate to 90% Loss of prairie habitat caused a severe reduction in the population of greater prairie chickens in Illinois The surviving birds had low levels of genetic variation, and only 50% of their eggs hatched Range of greater prairie chicken (a) Percentage of eggs hatched Number of alleles per locus Population size Location Illinois 5.2 3.7 93 <50 1930–1960s 1,000–25,000 <50 1993 Kansas, 1998     (no bottleneck) 750,000 5.8 99 Nebraska, 1998     (no bottleneck) 75,000– 200,000 5.8 96 Minnesota, 1998     (no bottleneck) 5.3 85 4,000 (b)

44. Effects of Genetic Drift: A Summary • Genetic drift is significant in small populations • Genetic drift causes allele frequencies to change at random • Genetic drift can lead to a loss of genetic variation within populations • Genetic drift can cause harmful alleles to become fixed

45. Gene Flow • Alleles can be transferred through the movement of fertile individuals or gametes (for example, pollen) • Gene flow tends to reduce differences between populations over time • Gene flow is more likely than mutation to alter allele frequencies directly • Effects of GMO’s on environment?

46. Gene flow can decrease the fitness of a population • In bent grass, alleles for copper tolerance are beneficial in populations near copper mines, but harmful to populations in other soils • Windblown pollen moves these alleles between populations • The movement of unfavorable alleles into a population results in a decrease in fit between organism and environment 70 MINE SOIL NON- MINE SOIL NON- MINE SOIL 60 50 Prevailing wind direction Index of copper tolerance 40 30 20 10 0 20 0 20 120 160 20 0 40 80 140 60 100 Distance from mine edge (meters)

47. Gene flow can increase the fitness of a population • Insecticides have been used to target mosquitoes that carry West Nile virus and malaria • Alleles have evolved in some populations that confer insecticide resistance to these mosquitoes • The flow of insecticide resistance alleles into a population can cause an increase in fitness

48. Mutations • A new mutation that is transmitted in gametes can change the gene pool by substituting one allele for another • Does not have a quantitative effect • Is the original source of variation

49. Mate Choice

50. Intrasexual selection is competition among individuals of one sex (often males) for mates of the opposite sex • Intersexual selection, often called mate choice,occurs when individuals of one sex (usually females) are choosy in selecting their mates • Male showiness due to mate choice can increase a male’s chances of attracting a female, while decreasing his chances of survival (sexual dimorphism)