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Varieties of life forms

Varieties of life forms. Figure 1.4C-F. Clown, Fool, or Well Adapted?. All organisms have evolutionary adaptations Inherited characteristics that enhance their ability to survive and reproduce blue-footed booby Large, webbed feet help propel the bird through water at high speeds.

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Varieties of life forms

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  1. Varieties of life forms Figure 1.4C-F

  2. Clown, Fool, or Well Adapted? • All organisms have evolutionary adaptations • Inherited characteristics that enhance their ability to survive and reproduce • blue-footed booby • Large, webbed feet help propel the bird throughwater at high speeds

  3. Specialized salt-secreting glands manage salt intake while at sea • A streamlined shape, large tail, and nostrils that close are useful for diving

  4. Evolution explains the unity and diversity of life • Charles Darwin synthesized the Theory of Evolution by natural selection • Theory vs hypothesis • Evolution is the core theme of biology Figure 1.6A

  5. 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 Figure 13.1B

  6. Prevalent ideas at Darwin’s time • species are fixed • Earth is about 6,ooo yrs old

  7. New ideas proposed • Fossils indicated the earth was very old • Lyell, a geologist, argued that land forms changed constantly. • Lamarck proposed that organisms changed and these changes were passed to progeny.

  8. Mex. marine snail shells on high mtns • Darwin became convinced that the Earth was old and continually changing • He concluded that living things also change, or evolve over generations • He also stated that living species descended from earlier life-forms: descent with modification

  9. Darwin proposed natural selection as the mechanism of evolution • Darwin observed that • organisms produce more offspring than the environment can support • organisms vary in many characteristics • these variations can be inherited

  10. natural selection explains the mechanism of evolution (1) Population with varied inherited traits Pesticide-resistant insects Antibiotic-resistant bacteria (2) Elimination of individuals with certain traits (3) Reproduction of survivors Figure 1.6B

  11. Alfred Wallace • Charles Darwin, 1874 Figure 13.1x2

  12. Darwin cartoon Figure 13.1x3

  13. Evolution happens when populations of organisms with inherited variations are exposed to environmental factors that favor the reproductive success of some individuals over others • Natural selection is the editing mechanism • Evolution is based on adaptations Figure 1.6C

  14. Fossils provide strong evidence for evolution • Hominid skull • Petrified trees Figure 13.2A, B

  15. Ammonite casts • Fossilized organic matter in a leaf Figure 13.2C, D

  16. Scorpion in amber • “Ice Man” • acid bogs Figure 13.2E, F

  17. Mammoth tusks Figure 13.2x4

  18. fossils show that organisms have appeared in a historical sequence • Many fossils link early extinct species with species living today • hind leg bones of fossil whales Figure 13.2G, H

  19. Other evidence for evolution • Biogeography • Comparative anatomy • Comparative embryology Human Cat Whale Bat Figure 13.3A

  20. Molecular biology - protein “clocks” Human Rhesus monkey Mouse Chicken Frog Lamprey Last commonancestor lived26 million yearsago (MYA),based onfossil evidence 80 MYA 275 MYA 330 MYA 450 MYA Figure 13.3B

  21. Populations are the units of evolution Figure 13.6

  22. What is evolving? gene pool, microevolution Four agents of evolution 3. Types of natural selection

  23. Populations are the units of evolution • A population is a group of interbreeding individuals • A species is a group of populations whose individuals can interbreed and produce fertile offspring Figure 13.6

  24. What is evolving? • gene pool = total collection of genes in a population at any one time • Microevolution is a change in the relative frequencies of alleles in a gene pool

  25. Four agents of microevolution 1. Mutation changes alleles 2. Genetic drift = random changes in allele frequency Bottleneck Founder effect

  26. Genetic drift - effects of population size: LARGE POPULATION = 10,000 SMALL POPULATION = 10 1,000 10,000 1 10 allele frequency = = 10% allele frequency = = 10% 50% of population survives, including 450 allele carriers 50% of population survives, with no allele carrier among them 0 5 450 5,000 allele frequency = = 0% allele frequency = = 9% little change in allele frequency (no alleles lost) dramatic change in allele frequency (potential to lose one allele)

  27. Bottleneck effect Founder effect Figure 13.11B, C

  28. Gene flow can change a gene pool due to the movement of genes into or out of a population ex. Migration • Natural selection leads to differential reproductive success Nonrandom mating changes genotype frequency but not allele frequency.

  29. Natural selection - results in the accumulation of traits that adapt a population to its environment - the only agent of evolution that results in adaptation.

  30. What is an organism’s evolutionary fitness? • Darwinian fitness is an individual’s contribution to the gene pool of the next generation compared to other individuals; i.e., number of progeny • Production of fertile offspring is the only score that counts in natural selection

  31. There are three general outcomes of natural selection Originalpopulation Frequency ofindividuals Phenotypes (fur color) Originalpopulation Evolvedpopulation Stabilizing selection Directional selection Diversifying selection Figure 13.19

  32. 80 beak depth 1976 60 40 Number of individuals Average beak depth, 1976 20 Average beak depth, 1978 1978 0 5 6 7 8 9 10 11 12 13 14 Beak depth (mm) Shift of average beak depth during drought

  33. 20 70 Infant deaths Infant births 60 15 50 Percent of infant deaths Percent of births in population 40 10 30 20 5 10 0 0 2 3 4 5 6 7 8 8 8 9 10 11 Birth weight in pounds Natural selection tends to reduce variability in populations.

  34. Why doesn’t natural selection eliminate all genetic variation in populations? • The diploid condition preserves variation by “hiding” recessive alleles (Bb) • Balanced polymorphism (2+ phenotypes stable in population) may result from: a. heterozygote advantage Aa > aa and AA b. frequency-dependent selection c. variation of environment for a population

  35. Many populations exhibit polymorphism and geographic variation Figure 13.13

  36. Not all genetic variation may be subject to natural selection 3. Some variations may be neutral, providing no apparent advantage or disadvantage • Example: human fingerprint patterns Figure 13.16

  37. Endangered species often have reduced variation • Low genetic variability may reduce their capacity to survive as humans continue to alter the environment • cheetah populations have extreme genetic uniformity Figure 13.17

  38. Why do male and female animals differ in appearance? • Sexual selection leads to the evolution of secondary sexual characteristics • Sexual selection may produce sexual dimorphism Figure 13.20A, B

  39. Natural selection cannot fashion perfect organisms • This is due to: • historical constraints • adaptive compromises • chance events • availability of variations

  40. What is a species? • appearance alone does not always define a species • Example: eastern and western meadowlarks Figure 14.1A

  41. What is a species? • Naturally interbreeding populations - potentially interbreeding - reproductively isolated from other species What about asexually reproducing organisms? Extinct species? Shy species?

  42. MECHANISMS OF SPECIATION When does speciation occur? • When geographically isolated, species evolution may occur • gene pool then changes to cause reproductive isolation = allopatric speciation Figure 14.3

  43. A ring species may illustrate the process of speciation 1 OREGON POPULATION SierraNevada 2 Yellow-blotched Yellow-eyed INLANDPOPULATIONS COASTALPOPULATIONS Gap in ring Large-blotched Monterey 3 Figure 14.1C

  44. Reproductive barriers between species • Habitat - different locations • Timing - mating, flowering • Behavioral - mating rituals, no attraction • Mechanical - structural differences • Gametic - fail to unite • Hybrid weak or infertile

  45. A horse and a donkey may produce a hybrid offspring, a mule • Mules are sterile • Hybrid sterility is one type of postzygotic barrier Figure 14.2C

  46. Sympatric speciation • No geographical isolation • Mutation creates reproductive isolation • Polyploidization • Hybridization

  47. When does speciation occur? • Specialists - Galapagos finches • Generalists - horseshoe crabs, cockroaches • New environments - ecological niche

  48. Adaptive radiation on an island chain - specialization for different niches 1 Species Afrom mainland 2 B A B 3 B B 4 C C C C D C D 5 Figure 14.4B

  49. Cactusground finch Smalltree finch Mediumtree finch Woodpeckerfinch Mediumground finch Smallground finch Large cactusground finch Vegetarianfinch Largetree finch Mangrovefinch Greenwarbler finch Graywarbler finch Largeground finch Sharp-beakedground finch Budeaters Seedeaters Cactus flowereaters Insecteaters Ground finches Tree finches Warbler finches Common ancestor fromSouth America mainland Figure 15.9

  50. No predestined goal of evolution Figure 15.8

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