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The Evidence for Evolution. Darwin’s Voyage – BBC 2009 shows/greatest- discoveries/videos/evolution.htm.

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Presentation on theme: "The Evidence for Evolution. Darwin’s Voyage – BBC 2009 shows/greatest- discoveries/videos/evolution.htm."— Presentation transcript:

1 The Evidence for Evolution

2 Darwin’s Voyage – BBC 2009 shows/greatest- discoveries/videos/evolution.htm

3 Evidence for Evolution Types of evidence Darwin used to support his theory: – 1. Biogeography – 2. Homologous and Analogous features – 3. Vestigial features – 4. Competition within populations

4 1. Biogeography + Darwin’s Observations



7 Reptiles, Birds, but No Mammals or Amphibians?

8 Key Observation from Galapagos Islands

9 Testing Darwin’s Hypotheses: Hawaiian Islands

10 Testing Darwin’s Hypotheses When non-native mammals and amphibians introduced to islands, they have been able to thrive. This eliminates the possibility that they can’t survive on remote islands. Dodo Bird Extinction within 175 years – Mauritius Islands (Indian Ocean)

11 2. Homologous Features Structures with common evolutionary features which serve different functions in modern species. Example of Divergent Evolution Video on homology:

12 Homology: Similar structures for different functions

13 How many bones in the Human Neck?

14 How many bones in a Giraffe’s neck?


16 Embryological Homology

17 2. Analogous Features Structures that perform same function in two species but are not similar in origin or anatomy Convergent Evolution


19 Analogous: Same function, different structure

20 3. Vestigial Features Features that no longer serve the function they do in similar species / actually-do-something/ m0






26 4. Competition Within Populations Thomas Malthus (Principle of Population) showed that all population are limited in size by the environment (food supply) Darwin’s thoughts: All species produce more offspring than can survive to reproduce This results in competition for resources between members of the same species Environment might be favouring certain individuals


28 28 J.W. Tutt hypothesized that light-colored moths declined because of predation Light moths were easily seen by birds on darkened (sooty) trees Evidence of Natural Selection

29 moths.htm moths.htm 29

30 30 Evidence of Natural Selection Bernard Kettlewell tested the hypothesis – Dark tree trunks = more dark-colored moths survived – Light tree trunks = more light-colored moths survived When environmental conditions reverse, so does selection pressure

31 31 Industrial melanism: phenomenon in which darker individuals come to predominate over lighter ones Pollution control resulted in lichen growing on trees and bark color being lighter again Light-colored peppered moths now are dominant in the population Evidence of Natural Selection

32 32 The agent of selection may be difficult to pin down Could poisoning by pollution be the agent of natural selection? Selection against melanism Evidence of Natural Selection

33 Homework Page 303 # 1,2,4-7

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