1. Chapter 22, Descent with Modification
Big Idea 1: The process of evolution drives the diversity and unity of life. Unit 1:Evolution
Chapter 22, Descent with Modification

2. 22.1 Quick Evolution Review:
Who are these people what did they contribute to biology/evolution?
Aristotle – Scala of Nature. Organisms are unchanging.
Linnaeus – Taxonomy, grouping of organisms.
Cuvier – Paleontology, catastrophism.
Hutton – Gradualism.
Lyell – Uniformitarianism (gradual at the same rate)
Lamark – Theory of Use and disuse. Inherited traits versus acquired traits.

3. 22.2, In The Origin of the Species, Darwin Proposed that species change through Natural Selection
A. Darwin’s Research
1. The Voyage of the Beagle
a. Darwin left in 1831 and returned in 1836.
b. The Galapagos Islands strongly influenced Darwin’s thoughts.
i. Darwin’s Finches – similar but different species.
2. Darwin’s focused on adaptations
a. Adaptations are specific to environments… Natural Selection
b Darwin wrote an essay on origin of species and natural selection.

4. 22.2, In The Origin of the Species, Darwin Proposed that species change through Natural Selection
B. The Origin of Species
1. Descent with Modifications
a. The idea that organism are related through descent from an ancestor that lived in the remote past. As the descendants of ancestral organisms spilled into various habitats over millions of years they accumulated diverse modifications, or adaptations that fit to their specific environment.
b. History of Life is like a tree. Each branch representing a different ancestor.

7. 2. Natural Selection and Adaptation
22.2, In The Origin of the Species, Darwin Proposed that species change through Natural Selection
2. Natural Selection and Adaptation
a. Natural Selection result from the struggle to survive in which organism tend to overproduce.
b. Overproduction with limited resources lead to a struggle to survive.
c. Organism with traits favored by the environment tend to produce more offspring. Increases in the frequencies of favored traits in a population are an important source of evolutionary modification.

9. 22.2, In The Origin of the Species, Darwin Proposed that species change through Natural Selection
3. Artificial Selection
a. Selective breeding by humans have resulted in plants and animals bearing little resemblance to their ancestors.
i. Humans select and breed organisms that possess desired traits (artificial selection).
ii. Examples:

11. 4. Natural Selection Summary
22.2, In The Origin of the Species, Darwin Proposed that species change through Natural Selection
4. Natural Selection Summary
a. Differences emerge as organisms interact with their environment (over long periods of time).
b. Over time, natural selection can increase the adaptation of organisms to their environment.
c. If an environment changes over time or species move to a new environment natural selection may result in adaptations to these new conditions and may give rise to new species (speciation).

12. 22.2, In The Origin of the Species, Darwin Proposed that species change through Natural Selection
d. Populations evolve NOT individuals.
e. Evolution by natural selection.
f. Evolution can be measured by heritable variations in a population over time.
g. Natural Selection can amplify or diminish only heritable trait (not acquired).
i. Example:
h. A trait favorable in one environment may not be favorable in another.
i. example:
i. Life evolves through gradual accumulation of small changes…natural selection is always operating.

13. 22.3, Darwin’s theory explains a wide variety of observations.
A. Natural Selection in Action
1. Differential Predation and Guppy populations

15. 22.3, Darwin’s theory explains a wide variety of observations.
The Evolution of Drug Resistant HIV

16. 22.3, Darwin’s theory explains a wide variety of observations.
3. Two Main Points of these Natural Selection Examples
a. Natural selection is more of a process of editing rather than a creative mechanism.
b. Natural selection depends on a time and place (a situation in nature).

17. 22.3, Darwin’s theory explains a wide variety of observations.
B. Homology, Biogeography and the Fossil Record (evidence of evolution) 
1. Homology
a. Anatomical Homologies or homologous structures
i. Structures that have underlying similarities but different functions

19. 22.3, Darwin’s theory explains a wide variety of observations.
2.Comparative Embryology
a. Anatomical similarities of different organism at early stages of embryonic development

21. 22.3, Darwin’s theory explains a wide variety of observations.
3.Vestigial Structures
a. Remnants of structures that served an important function in its ancestor but are not unnecessary.

22. 22.3, Darwin’s theory explains a wide variety of observations.
Molecular Homology
Same genetic code. DNA, RNA and genes…

24. 22.3, Darwin’s theory explains a wide variety of observations.
C. Biogeography
1. Biogeography is the geographic distribution of species.
2. Closely related species can be found in the same geographic region, but same ecological niches in different regions are occupied by different species.
3. Sugar Glider versus Flying Squirrel.
a. Also an example of convergent evolution.
4. The sugar glider is endemic to Australia.

26. 22.3, Darwin’s theory explains a wide variety of observations.
D. The Fossil Record
1. The fossil record is consistent with inferences from the evolutionary tree of life.
2. Birds descending from reptiles (Archaeopteryx).
3. Aquatic Mammal link to terrestrial mammal (Basilosaurus)

28. 22.3, Darwin’s theory explains a wide variety of observations.
E. What is Theoretical about Darwinian View of Life?
1. What is a theory?
a. Many observations and data explain a great deal of phenomena.
b. Just a theory?
c. Hypothesis versus Theory in everyday language.

29. Summary of Chapter 22
Self Quiz pages,
Written Summary