Presentation on theme: "The Evidence for Evolution. Darwin’s Voyage – BBC 2009 shows/greatest- discoveries/videos/evolution.htm."— Presentation transcript:
The Evidence for Evolution
Darwin’s Voyage – BBC shows/greatest- discoveries/videos/evolution.htm
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
1. Biogeography + Darwin’s Observations
Reptiles, Birds, but No Mammals or Amphibians?
Key Observation from Galapagos Islands
Testing Darwin’s Hypotheses: Hawaiian Islands
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)
2. Homologous Features Structures with common evolutionary features which serve different functions in modern species. Example of Divergent Evolution Video on homology:
Homology: Similar structures for different functions
How many bones in the Human Neck?
How many bones in a Giraffe’s neck?
2. Analogous Features Structures that perform same function in two species but are not similar in origin or anatomy Convergent Evolution
Analogous: Same function, different structure
3. Vestigial Features Features that no longer serve the function they do in similar species / actually-do-something/ m0
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 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
moths.htm moths.htm 29
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 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 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