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Fig. 22-2

Linnaeus (classification). Hutton (gradual geologic change). Lamarck (species can change). Malthus (population limits). Fig. 22-2. Cuvier (fossils, extinction). Lyell (modern geology). Darwin (evolution, natural selection). Wallace (evolution, natural selection). American Revolution.

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Fig. 22-2

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  1. Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Fig. 22-2 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

  2. Argument from Design (Paley, 1802) In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that, for any thing I knew to the contrary, it had lain there for ever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given, that, for any thing I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? Why is it not as admissible in the second case, as in the first? For this reason, and for no other: that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose, e.g., that they are so formed and adjusted as to produce motion so regulated as to point out the hour of the day.

  3. Layers of deposited sediment Fig. 22-3 Younger stratum with more recent fossils Older stratum with older fossils

  4. What Were the Main Accomplishments of Charles Darwin and Alfred Wallace? • Descent with Modification and Mutability (vs. Great Chain of Being) • Darwin studied beetles in the Amazon, mockingbirds on Galapagos Islands, other fauna and fossils in South America • Darwin’s Origin of Species convinced most naturalists of evolution; added to earlier concepts of “transmutation” (Buffon, Lamarck, Chambers, Lyell) • Mutability of species: giant sloth and armadillo fossils; giant tortoise, marine iguana of Galapagos Islands suggested that species could be transformed • Adaptations • Darwin wrote about adaptations observed during voyage of HMS Beagle, and multiple functions of adaptations (ex., steamers using wings to row) • Wallace especially interested in cryptic coloration and mimicry (ex., stick insects) • Biogeography • Both noted similarities of island fauna to fauna of nearby continents • Natural Selection: proposed jointly as the main mechanism of change (“survival of the fittest” later coined by Herbert Spencer) • Both influenced by Thomas Malthus’ “Tragedy of the Commons” thesis • Darwin influenced by results of selective breeding (artificial selection) • Reigning paradigm: Inheritance of Acquired Characteristics (Jean Baptiste Lamarck); Darwin grudgingly accepted as the mechanism of inheritance; August Weismann (1888) disproved by cutting tails off mice


  6. GREAT BRITAIN Fig. 22-5 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

  7. Figure 22.12

  8. What are the Postulates of Darwin’s Theory? • Darwin’s Postulates (theory of natural selection as the major cause of evolution – each postulate can be tested; each potentially falsifiable) 1. Individuals within populations are variable 2. Variations among individuals are, at least in part, passed from parents to offspring (Darwin was not aware of genetic mechanisms) 3. In every generation, some individuals are more successful at surviving and reproducing than others • Most juveniles die before reproducing (note biotic potential) 4. The survival and reproduction of individuals are not random; instead, they are tied to the variation among individuals. The individuals with the most favorable variations, those who are better at surviving and reproducing, are naturally selected • Fitness: measurement of organism’s ability to survive and reproduce

  9. Original population Frequency of individuals Fig. 23-13 Phenotypes (fur color) Original population Evolved population (b) Disruptive selection (c) Stabilizing selection (a) Directional selection

  10. What Factors Cause Evolution? • Evolution (population genetics definition): change in gene frequencies in a population (changes in gene pool) • Factors that can change the nature of a gene pool: • Natural selection: a strong force in evolution • Migration: especially strong in island populations • Mutation: a weak force in evolution, but the ultimate source of novelty; mutations are generally mildly deleterious (due to second copy of gene) • Non-random mate choice: sexual selection generally involves female choice (among competing males) • Chance events: environmental changes and catas- trophes; “random” evolution called genetic drift

  11. What Evidence Supports the Modern Theory of Evolution? • Direct observations of change through time • Ex., changes in beak morphologies among Darwin’s finches (long-term study at Galapagos Islands) • Ex., change in beak lengths of soapberry bugs after introduction of golden rain trees in Florida • Vestigial traits: functionless or rudimentary version of functional feature in other, closely related species or subspecies • Examples: eye sockets in blind cave fishes; wings in flightless birds; pelvic and leg bones (and spurs) in snakes (similar situation with cetaceans); reduced tailbone (coccyx) and arrector pili muscles in humans ( goosebumps; lift hair in other mammals)

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

  13. What Evidence Supports the Modern Theory of Evolution? • Evidence from the fossil record • Extinction: in 1812, Cuvier provided strong evidence of extinction with analysis of fossils (mammoths, mastodons, and Irish elk) • Law of Succession: general pattern of correspondence between fossil and living forms from the same locale; supported from wide variety of locations and taxonomic groups (ex. marsupials of Australia) • Transitional forms: exhibit various characteristics seen in ancestral species and other characteristics seen in more recent descendents (the latter often including important novel features) • Examples: Archaeopteryx; Basilosaurus; transitional tetrapods

  14. 0 2 4 4 Bristolia insolens 6 4 8 Bristolia bristolensis 3 Fig. 22-15 10 12 Depth (meters) 3 Bristolia harringtoni 2 14 16 Bristolia mohavensis 18 1 2 Latham Shale dig site, San Bernardino County, California 1

  15. (a) Pakicetus (terrestrial) Fig. 22-16 (b) Rhodocetus (predominantly aquatic) Pelvis and hind limb (c) Dorudon (fully aquatic) Pelvis and hind limb (d) Balaena (recent whale ancestor)

  16. What Evidence Supports the Modern Theory of Evolution? • Homology: the study of likeness (modern meaning: similarity due to inheritance of traits from a common ancestor) • Structural and developmental homology • Ex., pattern of limb bones similar in all tetrapods • Ex., vertebrate embryos undergo similar developmental stages before acquiring group-specific features (first noted by Karl Ernst von Baer in 1828) • Molecular homology: shared genetic code for nearly all living organisms; genes for critical enzymes with few differences among groups; shared genetic flaws in related species • Thousands of lab, field, and in silico studies that document the importance of natural selection, sexual selection, mutation, and migration in the evolution of populations

  17. Humerus Fig. 22-17 Radius Ulna Carpals Metacarpals Phalanges Human Whale Bat Cat

  18. Fig. 22-18 Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo

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

  20. What are Adaptations? • Adaptation: a feature used for some function that has become prevalent or is maintained in a population because of natural selection for that function • Multiple functions of single traits: many traits have multiple uses (ex. functions of fish swim bladder include buoyancy, oxygen storage, and sound production) • Trade-offs: single traits may have off-setting benefits and detri- ments (ex. fish swim bladder provides buoyancy, but is a good target for dolphin echolocation) • Key innovations: traits that are associated with large gains in evolutionary success (ex. skeletal fin rays in bony fishes) • Preadaptation: a feature already present in a population that fortuitously serves a new function • Examples: wings in ancestral insects likely selected for surface- skimming performance; bird wings likely enabled uphill running, gliding, and/or thermoregulation before birds obtained flight

  21. What is the function of the hammerhead’s cephalofoil?

  22. How Does Speciation Occur? • The Biological Species Concept: species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups (Ernst Mayr, 1942); emphasizes reproductive isolation (lack of gene flow); later modified to account for existence of fertile animal hybrids (animal hybrids are rare, and are typically sterile or exhibit low fitness) • Mechanisms of Speciation • Speciation: origin of new species (process vs. event) • Allopatric Mechanisms (physical isolation triggers reproductive isolation) • Via dispersal and colonization (ex., islands, edge of range) • Via physical split of original range (ex., new mountain range or isthmus, change in river’s course) • Sympatric Mechanisms • Genetic mechanisms: polyploidy (ex., wheat), mutations in regulator genes • Behavioral mechanisms: temporal separation, courtship displays

  23. Fig. 24-5 (a) Allopatric speciation (b) Sympatric speciation

  24. Fig. 24-6 A. harrisi A. leucurus

  25. Mantellinae (Madagascar only): 100 species Rhacophorinae (India/Southeast Asia): 310 species Fig. 24-7 Other Indian/ Southeast Asian frogs 100 60 20 80 40 0 1 2 3 Millions of years ago (mya) 1 3 2 India Madagascar 56 mya 88 mya 65 mya

  26. Prezygotic barriers Postzygotic barriers Habitat Isolation Behavioral Isolation Temporal Isolation Mechanical Isolation Gametic Isolation Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Fig. 24-4 Individuals of different species Viable, fertile offspring Mating attempt Fertilization (c) (e) (f) (a) (g) (h) (l) (i) (d) (j) (b) (k)

  27. Prezygotic barriers Mechanical Isolation Habitat Isolation Temporal Isolation Behavioral Isolation Individuals of different species Mating attempt Fig. 24-4a (e) (f) (a) (c) (d) (b)

  28. Prezygotic barriers Postzygotic barriers Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Gametic Isolation Viable, fertile offspring Fertilization Fig. 24-4i (h) (g) (l) (i) (j) (k)

  29. What are Some Patterns of Macroevolution? • Adaptive Radiation: ancestral species evolves into multiple descendent species, with each exploiting a different available lifestyle in their respective environment • Darwin’s finches on Galapagos Islands • African cichlids (very diverse family of fishes in African Great Lakes) • Convergence: independent evolution of superficially similar traits (in response to similar selection pressures) • Streamlining in dolphins, penguins, tunas (reduces drag in water) • Echolocation in bats and dolphins (swarmed, patchy food sources) • Coevolution: reciprocal changes in two or more species in close association with each other • “Arms races” between predators and their prey • Adaptations for pollination (insects/hummingbirds/bats and flowering plants) • Gradualism: slow emergence of new species (Darwin emphasized) • Punctuated Equilibrium: long periods of stasis interrupted by sudden emergence of new species (Stephen J. Gould and Niles Eldridge, 1972)

  30. NORTH AMERICA Sugar glider Fig. 22-20 AUSTRALIA Flying squirrel

  31. Fig. 40-2 (a) Tuna (b) Penguin (c) Seal

  32. (a) Punctuated pattern Fig. 24-17 Time (b) Gradual pattern

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