1. Theories of Evolution

2. 1) Lamarck French scientist Late 1700’s- early 1800’s
“acquired traits” (use it or lose it) theory
traits are not determined by genes but by “need”
EX: giraffe necks grow longer because they stretch to reach the leaves higher up.

4. 2) Charles Darwin English scientist
Developed his theory of “natural selection” in the mid 1800’s
Was a naturalist on the HMS Beagle (traveled around the world, mostly the southern hemisphere) for 5 years.

6. Voyage of the HMS Beagle

7. Darwin
Noticed organisms had some similarities even when they lived far apart.
* Darwin’s Finches
Kept records & collected specimens
Published “The Origin of Species…”

8. Darwin’s Finches

9. Darwin read other published works and was influenced by:
1) Lamarck’s Theory
2) Lyell’s book on Geology
3) Malthus’ book on human population & economics

10. Natural Selection
Nature selects those that are best adapted to survive.
“Survival of the Fittest”
Adaptive advantage = a favorable trait

11. What is fitness?
“Measure of a trait’s relative contribution to the following generation” Ability of a trait to lead to reproductive success…more babies = more “fit”.

12. Darwin’s Theory of Natural Selection has 4 principles
Individuals in a population have differences
The differences of individuals are inherited
Organisms have more offspring than can survive
Differences that increase reproductive success are more likely to stay in a population

13. Patterns of Evolution

14. 1) Coevolution
2 species in close association evolving together. ( or a species evolving as a result of evolution in another species)
These organisms may depend exclusively on each other & be highly specialized!

16. 2) Convergent Evolution
unrelated species becoming more similar over time.
EX: Dolphin (mammal) and fish.

18. 3) Divergent Evolution
related species becoming more different over time.

20. Can be the result of:
1) artificial selection – humans selecting the traits and breeding for those traits (purebred dogs)
2) adaptive radiation – many species evolve from one species (Darwin’s finches)

21. The Peppered Moth – an example of how human’s can affect a species

22. Which colored moth has the advantage?

23. Genetic Equilibrium

24. What is genetic equilibrium?
A balance of alleles within a population
Genetic equilibrium does not exist!

25. 5 reason genetic equilibrium does not exist…
Mutations – random mutations alter genetic information
Sometimes new traits can develop.
Harmful traits are usually eliminated over time.

26. 2) Migration Immigration – movement INTO a population
Emigration – movement out of a population
When individual organisms move in or out of a population their genes go with them!

28. 3) Genetic Drift
Changes in a population that are caused by chance or random events.
EX: large volcano, fire, flood, disease
Genetic drift will have more effect on a small population more than on a large population.

30. 4) Non-random Mating
Non-random mating would lead to less “selection” and all alleles would have an equal chance of being passed on.
Some populations do have random mating, many animals do not.

31. 5) Natural selection
“Bad” traits are usually eliminated from a population as a result of natural selection.

32. 3 ways natural selection affects populations & their traits
1) Stabilizing selection – the “middle” trait is the most favorable. There will be few organisms at the extremes.

33. 2) Directional selection
One of the “extreme” versions of a trait is the most favorable. Most individuals will have that trait.

34. 3) Disruptive selection
Both “extreme” traits are favorable, but the “middle” trait is not.

35. Hardy - Weinberg Shows genetic equilibrium p2 + pq + q2 = 1
(p = dominant allele, q = recessive allele)