1. Lecture #30
Darwin and Evolution

2. Question????
How did life go from the first single cell to the existence of millions of types (species) of organisms?
In others words, where did all this diversity come from????????????????

3. Historical Perspective

4. Lamarckian Evolution
This theory of “Acquired Characteristics” is not valid.

6. Artificial Selection
Artificial Selection proves that species can change.
Darwin knew this.

7. Evolution: Descent with Modification.
Charles Darwin
Evolution: Descent with Modification.

8. Origin of Species by Means of Natural Selection………Doc Cam
Two basic messages from the Book:
All species come from pre-existing species.
Natural Selection is the mechanism of evolution.

9. Darwin’s Observations
Overproduction (but stable population size)
Struggle for Existence (Limited Resources)
Variation (must be inheritable)
Survival of the Fittest

10. Survival of the Fittest
Individuals that possess the most favorable combination of characteristics……..
…..are most likely to survive and reproduce…
…. thus passing heritable traits on to the next generation.

11. Natural Selection
Natural selection causes an increase in the frequency of favorable traits…
…and a decrease in the frequency of unfavorable traits within a population.

12. Successful Reproduction is the key to Natural Selection:
The “fittest” individuals are those that reproduce most successfully.

13. Evidence for Evolution
The Theory of Evolution is the string that ties all of Biology together. It explains how all of the diversity on earth has occurred.
What is the Evidence for Evolution?

14. The Evidence for Evolution
Fossils
Biogeography
Comparative Anatomy
Comparative Embryology
Molecular Biology

15. Fossils
Fossil Record – ordered array, fossils in layers (strata) of sedimentary rock.
Each layer represents sample of local organisms that lived when sediment was deposited. Younger fossils over older.
Position of fossil in strata reveal relative age.
Show gradual changes that led to many species.

16. Formation of Fossils

17. Comparative Embryology
Study of structures that appear during the development of different organisms.
Closely related organisms often have similar stages in embryonic development.

18. Biogeography*
The geographical distribution of organisms suggested to Darwin that organisms evolved from common ancestors.
Why???????

20. Comparative Anatomy
Anatomical similarities among many species gives signs of common descent.
Homologous /Analogous structures.
Evolution is a remodeling process.

21. Homologous Structures

22. Convergent Evolution
Structures are Analogous

23. Mimicry in Stoneplants

24. Molecular Biology
Comparing Gene Sequences
Or Amino Acid Sequences.