1. Evolution
March 23, 2009

2. Jean-Baptiste Lamarck
First scientist to propose a mechanism for how organisms change (1809)
Theory of Acquired Traits
Through time, a generation would use an organ more than previously, and would pass those traits on to their offspring.

3. Charles Darwin English naturalist
Sailed around the world on the ‘Beagle’
His observations lead to theory of evolution

4. Why did some species survive while others became extinct?

5. Evolution = Change over time
In Biology evolution is the change in a species over time
How do species change?

6. Evolution - Fact vs. Theory
Evolution is the change in the genetic make up of populations over time.
All living things change. Evolution is a fact.
Populations evolve, not individuals.
The mechanism for evolution (how it happens) is a theory.

7. Theory of Natural Selection
Within a population, there are natural variations.
Farmers improved their plants and animals through selective breeding.

8. Farmers bred the plants or animals with most desired traits.
This process of humans allowing only the best organisms to reproduce is called artificial selection.

9. “Survival of the Fittest”
In nature, fitness is the ability of an organism to survive and reproduce in its environment.
Individuals with characteristics best suited to environment survive the struggle for existence.
This principle is called survival of the fittest.

10. Natural Selection
The process by which nature allows only the organisms best suited to their environment to reproduce is called natural selection.
I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.
   —Charles Darwin from "The Origin of Species"

11. Natural Selection in Action
Two variations of peppered moths (light and dark).
Tree trunks light colored.
Who will survive?

12. Light populations grew.
Industrial revolution released soot into air - tree trunks darken…
Now who will survive?
Example of microevolution

13. Microevolution Small changes between generations Allele frequency
Leads to macroevolution

14. Macroevolution Large scale changes over long periods of times
Eliminate/create species

15. Mechanisms of Microevolution
Mutation
Migration
Genetic drift
Natural selection

16. Mutation Allele is changed by random mutation
Mutation present in offspring and may be passed to next generation

17. Migration
New individuals emigrate into population.

18. Genetic Drift
By random chance, individuals mate and increase allele frequency

19. Natural Selection Survival of the fittest.
Some individuals have traits making them more adapted to their environment.

20. Evidence for Microevolution
Pesticide resistant insects
Gene for pesticide resistance passed on through ‘fit’ survivors

21. Evidence for Macroevolution
Fossil record
Biochemistry & Molecular Biology
Anatomy
Vestigal structures
Comparitive embryology

22. Fossil Record Fossils are the remains of ancient life.
When fossils are arranged according to their age, a progressive series of changes are seen.

23. How Fossils are Formed
Petrification - Organic material replaced by minerals
Mold & Cast - Form of organism after rots away
Carbonization - All element except carbon removed
Unaltered Preservation - Original state (amber)

24. Law of Superposition
Each layer of rock is older than the layer above it.
Fossils arranged by age relative to each other
Radioactive Dating
Used to date layers in which fossils occur.
Allows time frame of when fossil was formed

26. Biochemistry & Molecular Biology
All organisms from bacteria to humans share many of the same biochemical details.
The genetic code for protein-coding genes
All organisms use ATP
Plasma membranes of all organisms are structurally similar (phospholipid bi-layer)

28. Anatomy
Homologous structures are parts of different organisms, often quite dissimilar, that develop from the same ancestral part.

30. Analogous Structures
Analogous structures have similar form & function, but are structurally quite different

31. Vestigial Structures Traces of structures no longer used by organism.
May be reduced version of homologous structures in other species.

32. Comparative Embryology
Embryos of many animals with backbones look so similar they are hard to tell apart.

33. Human Embryo Characteristics
Early in their development, embryos posses gill slits like those of fish.
Later in development, the embryos develop a tail.
Human fetuses have a fine fur (lanugo) during the fifth month of development

35. So far… Darwin & Natural Selection
How species evolve between generations
Evidence for evolution
How do we get new species?

36. Speciation Changes leading to formation of new species.
Populations evolve and become reproductively isolated from each other (members of two populations cannot interbreed)
Behavioral isolation
Geographic isolation

37. Behavioral Isolation
Capable of interbreeding, but have different courtship rituals.

38. Geographical Isolation
Populations separated by geographic barriers (rivers, mountains, bodies of water, etc.)
Doesn’t always lead to new species.

39. Patterns of Evolution Adaptive Radiation
Small group of species evolve into different forms that live in different ways.

40. Patterns of Evolution Convergent Evolution
Unrelated organisms begin to resemble each other.
Similar environmental demands

41. Patterns of Evolution Coevolution
Two species evolve in response to changes in each other.

42. Summary