1. Chapter 10 Darwin’s Theory of Evolution

2. Life’s Diversity
What scientific explanation can account for the diversity of life?
Evolution is the change over time in a population where modern organisms have descended from an ancient organism

3. Charles Darwin Summary of Darwin’s Theory:
Individual organisms differ, and some variation is heritable
Organisms produce more offspring than can survive, and many that survive may not reproduce
Organisms compete for limited resources
Each organism has different advantages and disadvantages in the struggle for existence, those that are better suited for environment will survive and reproduce those that aren’t will die off
Species today descended with modification from ancestral species

4. HMS Beagle How did Darwin’s views take shape?
In 1831, Darwin began his journey on the HMS Beagle
- Primary purpose of the mission was to map and explore little known territories along South American coastline
- His travel around the world led to many observations and collected evidence that would become the theory of evolution
- Most influential stop was the Galapagos Islands in which organisms existed no where else like the ones on the various islands
*differences even existed between animals on each of these close islands

5. Darwin’s Views Darwin’s views are thought to be revolutionary because…
At that time scientists thought the Earth was only a few thousand years old.
Also, plants and living species were fixed and unchanging.
Catastrophic events were believed to be the only cause of change of existence of species
Beginning in the Eighteenth and Nineteenth century scientific thought changed it’s views

6. Influences of Evolution
James Hutton proposed that the Earth was shaped by geological forces that had occurred over millions of years
Thomas Malthus predicted human population would grow faster and exceed the space and food needed to sustain life
* applied to mass reproduction in plants and some animals explained the competition for limited resources
Jean Baptiste Lamarck – proposed use and disuse of body parts, tendency toward perfection, and inherited acquired traits
*Most of theories were found to be incorrect, but incorporated early mechanisms of evolution
Charles Lyell – proposed that processes of the Earth presently shaping it were the same processes that have always taken place

7. Origin of Species
In 1859 Darwin published his work in a book titled “Origin of Species.”
- proposed the mechanism of evolution as natural selection of species
- almost had ideas presented before publishing the book by Alfred Wallace
- changed the face of biology and other scientific disciplines

8. Contents of His Book
Artificial variation – farmers and ranchers have selective breed desired characteristics for livestock in a short time
Created variation of modern species much different in genotype and phenotype from ancestors
If it could be done artificially in little time could it happen naturally over a long period of time?

9. Natural Selection
Struggle for existence – created from limited resources causing organisms to regularly compete for food, living space, and necessities of life
Survival of the Fittest – organism’s ability to survive and reproduce are a result of adaptations it has made to fit an environment
*Successful adaptations means organism are better suited for the environment and will continue to be successful as they pass those traits to offspring

10. Natural Selection
In natural selection only certain individuals produce offspring
Over time, natural selection results in changes in the inherited characteristics of a population
Those changes increase a species’ fitness in the environment
Can not be directly seen, but can be observed by changes in a population over successive generations

11. Descent with Modification
Descent with modification means that organisms have descended, with changes, from other species over time
- different structures, different niches, different habitats
- different appearance from distant ancestor

12. Evidence of Evolution
How could Darwin prove his theory about the Earth being millions of years old?
Evidence existed in:
1. Fossil record
2. Geographic distribution of species
3. Homologous structures
4. Embryology

13. Evidence
Different organisms in similar environments have features of anatomy and behavior in common
Homologous structures – structures that are different in mature form but come from the same type of cells and embryonic tissues
- common purpose of the structures
- different organisms with similar structure and function of these vestiges
- Vestigial organs – resemble miniature structures like arms, legs, or tails that have no real function or use.