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Evolution - constancy & change. Modern Evidence for Natural Selection 1.fossil records – organisms change over time 2.biogeography – related organisms.

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Presentation on theme: "Evolution - constancy & change. Modern Evidence for Natural Selection 1.fossil records – organisms change over time 2.biogeography – related organisms."— Presentation transcript:

1 Evolution - constancy & change

2 Modern Evidence for Natural Selection 1.fossil records – organisms change over time 2.biogeography – related organisms in same area 3.comparative anatomy – homologous structures 4.comparative embryology – similar embryos 5.molecular biology – similarities in DNA, proteins 6.artificial selection – selective breeding

3 Phylogeny & Molecular Systematics Phylogeny – study of evolutionary relationships Molecular Systematics – study of molecular structures (DNA, protein) to determine evolutionary relationships *animals, including humans, and fungi, are more closely related to each other than either are to plants

4 Occam’s Razor (law of parsimony) - "All other things being equal, the simplest solution is the best." Used to justify a phylogenetic tree that represents the smallest number of evolutionary changes Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Occam’s Razor & Parsimony

5 Comparison of hemoglobin Cladogram (phylogeny) - shows ancestral relationships

6 Cladogram - primate DNA comparisons

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8 Molecular Clocks DNA or protein comparisons to estimate the length of time that two species have been evolving independently Molecular Systematics

9 Primate evolution Humans have 99.99% similarity Humans and chimps have 98% similarity

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11 “Ontogeny recapitulates Phylogeny" The embryonic development of a species (ontogeny) is a replay of its evolutionary history (phylogeny). - 1866 Ernst Haeckel

12 Comparative Embryology (faked)

13 Drawings vs. photographs

14 Comparative Anatomy

15 Animal developmental characteristics p.371 body plan symmetry body cavity digestive tract segmentation

16 mono-, para-, or polyphyletic monophyletic – all descendants paraphyletic - not all descendants polyphyletic - last common ancestor is NOT within group

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18 Monophyletic includes the most recent common ancestor of a group of organisms and all of its descendants Polyphyletic does not include the common ancestor Paraphyletic includes most recent common ancestor, but not all of its descendants

19 Restriction Maps 17 13 10 4 3 1.G ibbon is least similar; chimp is most similar.

20 Skull Morphology human deer catdogbeargorilla brain size teeth types brain to face ratio meat-eaters mammals herbivore

21 Skull Morphology human deer catdogbeargorilla brain size teeth types brain to face ratio meat-eaters mammals herbivore

22 Restriction Maps 2.Changes will go back and forth as environment changes. 3.Neutral changes will accumulate. 4.Advantageous changes will accumulate more often. 5.Two closely related organisms will have fewer genetic differences.

23 Animal Development & Phylogeny

24 Animal developmental characteristics p.371 body plan symmetry body cavity digestive tract segmentation

25 Tissue Organization 1. no tissue - no specialized fxn 2. tissue - specialization

26 Body Symmetry 1. radial - looks same cut from any side at top 2. bilateral - looks same cut from 1 side at top

27 Body Cavity 1. acoelomate - no body cavity, digestive tube connected to muscle 2. pseudocoelomate - partial cavity 3. coelomate - digestive tube separated from muscles

28 Digestive Tract 1. protostome - spiral cleavage - blastopore-->mouth 2. deuterostome - radial cleavage - blastopore-->anus http://www.mun.ca/biology/scarr/141993_Protostome_vs_Deuterostome.jpg..jpg

29 Comparative Embryology closely related organisms go through similar stages in their embryonic development *all vertebrate embryos have gill slits: –gill slits in fish form gills –human gill slits form the Eustachian tubes connecting the middle ear with the throat

30 Comparative Anatomy

31 Vestigial Structures – pelvic bones in whale - eye sockets in blind salamanders

32 Convergent Evolution -similar solutions to similar “problems” Analogous structures similar functions, no evolutionary relationship; different internal structure & development *flight - bird vs bat vs insect *reproduction - marsupials vs placentals *aquatic vertebrates - dolphins vs fish

33 Artificial selection breeding

34 Artificial selection pesticide resistance antibiotic resistance

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36 Natural Selection “survival of the fittest”?

37 Charles Darwin (1809-1882) British naturalist 1831-1836 Voyage on HMS Beagle collected specimens of fossils as well as living; observed the various adaptations of plants and animals breeding experiments 1859 “On the Origin of Species by Means of Natural Selection”

38 “Origin of Species” Key Points 1. descent with modification all species evolved from ancestral species and were not specially created; diverse modifications accumulated over millions of years 2. natural selection mechanism of evolution; a consequence of interactions between individual organisms and their environment

39 Natural Selection Requires… 1.Variation - individuals within a population show variation in their characteristics 2.Overproduction / competition - environmental resources are limited 3.Survival / reproduction – only those best suited to environment will survive to reproduce and pass on favorable variations

40 Historical Views of Origin of Life Creationism (Judeo–Christian): Earth is ~6000 years old and was populated by unchanging life forms made by the Creator during a single week Greek philosophy (Aristotle ~350 BC): scala naturae (scale of increasing complexity) – species were fixed in form, did not evolve

41 Carolus Linnaeus (1707 – 1778) Swedish physician, botanist father of taxonomy — developed the binomial nomenclature system organized organisms into categories based on similar physical features

42 James Hutton (1726-1797) Scottish geologist proposed geological gradualism – change is the cumulative product of slow, continuous processes *canyons are formed by erosion from rivers

43 Georges Cuvier (1769-1832) French anatomist founder of paleontology – study of fossils proposed catastrophism – periodic catastrophes result in mass extinctions; migrating species repopulate the area

44 Charles Lyell (1797-1875) geologist “Principles of Geology” proposed uniformitarianism – geological processes are uniform and balanced throughout Earth *processes that build mountains are eventually balanced by the erosion of mountains by wind and water

45 Jean Baptiste Lamarck (1744-1829) naturalist evolution is driven towards complexity and perfection (organisms became better adapted to their environments) 1809 proposed inheritance of acquired characteristics: –use and disuse *giraffes

46 Reverend Thomas Malthus 1.all species over-produce 2.competition for resources 3.only a fraction survive to reproduce 4.eventually populations reach carrying capacity (1766-1834) studied human overpopulation:

47 Stephen Gould 1972 proposed theory of punctuated equilibrium - based on fossil record: little change occurs, then rapid localized speciation occurs exaptation – shifts in function of a trait during evolution *mammalian limb

48 Michael Behe 1992 irreducible complexity (argument for intelligent design) – biological systems are too complex to have evolved through natural selection – evolutionary pathways may contain one or more unselected steps

49 The Subtleties of Natural Selection individuals do not evolve; populations do only heritable variations can be changed an adaptation to a set of conditions may be useful or detrimental, under different circumstances

50 Modern Examples of Natural Selection Kettlewell - observed peppered moths Grants on the island of Daphne Major - observed shifts in the frequency of beak sizes over short periods of time Antibiotic resistance in bacteria How do genetic variations arise in nature?

51 Industrial Melanism – Peppered Moths 1848 Kettlewell’s observations – moths are darker in polluted areas

52 1973 Grant - change in finch beak size


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