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Arguments & evidence. How incredibly stupid not to have thought of that Thomas Huxley.

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Presentation on theme: "Arguments & evidence. How incredibly stupid not to have thought of that Thomas Huxley."— Presentation transcript:

1 Arguments & evidence

2 How incredibly stupid not to have thought of that Thomas Huxley

3 Arguments Blending inheritance Variability Isolation Age of the earth

4 Arguments Blending inheritance -new adaptations diluted with each generation Darwin’s reply: Favorable traits maintained if popln isolated Some traits ‘preponent’ Adaptive traits arise often Enhanced reproduction of favorable traits

5 Arguments Variability -Darwin confined natural selection to small, continuous variation How could new spp arise from small variations? -successive change through time How could small variations confer an advantage? -Darwin could not answer, later demonstrated How could selection act on a nonexistent trait? -preadaptation - new organ modified from another

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7 1% per generation change in anatomy < yrs

8 Arguments Isolation -how could a new spp evolve in close proximity to its parents Darwin did not emphasize isolation as a primary cause for evolution

9 Arguments Age of the earth -earth was not old enough to allow time for evolution 5,000 50,000 75, ,000,000 Biblical Newton Buffon Kelvin 4,500,000,000present

10 Arguments Blending inheritance Variability Isolation Age of the earth

11 Evidence Systematics Geographic distribution Comparative anatomy Embryology Fossils Artificial selection Direct observation

12 Evidence Systematics -gradation of species easily understood by evolutionary relationships

13 Evidence Geographic distribution -evolutionarily related organisms geographically connected

14 Evidence Geographic distribution -evolutionarily related organisms geographically connected marsupial radiation

15 Evidence Comparative anatomy homologous/analogous organs

16 Evidence Comparative anatomy homologous/analogous organs Darwin’s interpretation of homology has become the definition: similarity due to common ancestry

17 Evidence Comparative anatomy homologous/analogous organs

18 Organisms show curious similarities in structure and development unrelated to function

19 Evidence Comparative anatomy convergent evolution

20 Evidence Comparative anatomy vestigial organs

21 Evidence Comparative anatomy vestigial organs femur whale ancestor modern whale

22 Organisms have vestigial structural, developmental and molecular traits Vestigial structures are a manifestation of change through time

23 Evidence Embryology -remarkable similarity among diverse vertebrates

24 Evidence Fossils -vast majority of fossil forms differ from extant spp extinction succession transitional forms environmental changes

25 Evidence Fossils -vast majority of fossil forms differ from extant spp extinction The fact that many species have gone extinct suggests that Earth’s flora and fauna have changed over time

26 Evidence Fossils -vast majority of fossil forms differ from extant spp transitional forms

27 Evidence Fossils -vast majority of fossil forms differ from extant spp “living fossils”

28 Evidence Fossils -vast majority of fossil forms differ from extant spp extinction succession transitional forms environmental changes

29 Evidence Artificial selection -accelerated evolution based on human-favored traits

30 Evidence Artificial selection -accelerated evolution based on human-favored traits

31 Evidence Direct observation -natural selection can be observed in real time Observations on living organisms show that populations and species change over time

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