1. E. Dilemmas
1. Evolution of complex traits

2. E. Dilemmas
1. Evolution of complex traits

3. ? E. Dilemmas 1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms? X X X ? X X X

4. E. Dilemmas
1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms?
the fossil record is incomplete – not all species leave a fossil
Keep looking…

5. E. Dilemmas
1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms?
1861:
Archeopteryx Lithographica

6. E. Dilemmas
1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms?
3. What is the source of heritable variation???

7. E. Dilemmas
1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms?
3. What is the source of heritable variation???
- Natural selection should “weed out” poorly adapted forms over time, making the organisms in the population more similar (less variation).
Why is there still so much variation in natural populations?

8. E. Dilemmas
1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms?
3. What is the source of heritable variation???
- selection should eliminated variation
- and if heredity is governed by blending traits, then how is variation produced generation after generation?

9. E. Dilemmas
1. Evolution of complex traits
2. Where are the continuous sequences of transitional forms?
3. What is the source of heritable variation???
- selection should eliminated variation
- and if heredity is governed by blending traits, then how is variation produced generation after generation?
- Darwin’s explanation - Lamarckian “use and disuse”, and ‘gemmules’…

10. F. Darwinian Evolution
1. Darwin’s Model
Sources of Variation Causes of Change
????????????????  VARIATION  NATURAL SELECTION
(use and disuse??)