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?

Embryological Homology

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

Homework Page 303 # 1,2,4-7