1. Evolutionary Theory: Chapter 22

2. Evolution Evolution is change in a population over time
The mechanism by which evolution occurs is natural selection

3. The World Before Darwin
Darwin published “On the Origin of Species” in 1859, which challenged the root of Western culture
People thought the world was only a few thousand years old and that the living things on Earth were those that were created during the 6-day creation period.
Many STILL DO & THAT IS FINE!! Remember this is theory!

4. The World Before Darwin: Jean Baptiste Lamarck
Lamarck observed that there was change in organisms over time and proposed a theory with 3 parts:
All organisms strive to survive.
This striving improves some body parts more than others
The modifications that an organism acquires during its lifetime are passed along to its offspring.
Examples: blacksmith’s arms, giraffe’s necks

5. Charles Darwin: The Man
Born in England in 1809; dropped out of medical school
Went to divinity school
Sailed from Great Britain to South America with the H.M.S. Beagle in 1831
Mission was to chart poorly known parts of the South American coastline
Darwin spent much of his time looking at the flora and fauna of South America, which differed greatly from that of Europe

6. Galapagos Islands
Darwin noticed that the plants and animals on the island archipelago resembled those in South America, but they were slightly different
Finches on different islands had different beaks, depending on the available food supply
Giant tortoises

7. Darwin’s Theory of Evolution by Natural Selection
There are heritable variations within populations.
Some variations are favorable.
Each year, more offspring are produced than can survive. Competition results!
Those that survive & reproduce are those who possess the favorable traits. (“survival of the fittest”)
Over thousands of years, the favorable traits become more common in the population and the unfavorable traits disappear.

8. Evidence for Evolution
There are many pieces of scientific evidence that evolution has occurred
The Fossil Record
Biogeography
Comparative Anatomy
Comparative Embryology
Molecular Biology

9. The Fossil Record
A fossil is a preserved remnant or impression left by an organism that lived in the past
Organisms are compressed by deposits (sand, silt, etc.) and the “hard parts” (teeth, bones, etc.) may be preserved as fossils

10. The Fossil Record
The idea that all species were made/created at the same time is NOT supported by the fossil record
With time comes increasing complexity of life
Georges Cuvier developed the field of paleontology (the study of fossils)
Each stratum (layer) of rock is characterized by a unique group of fossil species

11. The Fossil Record Relative Dating of Fossils:
Fossils can be dated in relation to what is found around them
Wallpaper analogy
Absolute Dating of Fossils:
Since radioactive isotopes have fixed rates of decay, they can be used to date a specimen in years
Carbon-14 is used for relatively young fossils (half life of 5600 years)

12. Biogeography Biogeography is the geographical distribution of species
For example, species found on islands are found only there, but are closely related to species of the nearest mainland or island

13. Comparative Anatomy
Similar body structures are evidence that two organisms have a common ancestor
Homology
Similarity in characteristics resulting from having a common ancestor: Divergent Evolution.
Homologous structures:
Anatomical signs of evolution
Vestigial structures:
“leftover” structures that have little to no use to an organism, like the human appendix

14. Comparative Embryology
Closely related organisms go through similar stages in their embryonic development
“Ontogeny recapitulates phylogeny”
The development of an individual organism (ontogeny) is a replay of the evolutionary history of the species (phylogeny)

16. All Chordates share the following characteristics:
1. Rod shaped notochord for support
2. Dorsal, hollow nerve cord
3. Pharyngeal gill slits at some point in development.
4. Post-anal tail at some point in development.

17. Molecular Biology
There is much similarity among all living things in our DNA sequences
There is a common genetic code for all living things (ie. UUU codes for phenylalanine in humans AND bacteria)
Even relatively unrelated organisms (like bacteria and humans) have some amino acid sequences/proteins in common