1. Descent with Modification: A Darwinian View of Life

2. Charles Darwin
5 year voyage on the HMS Beagle that included time on the Galapagos Islands
He kept extensive journals of observations of his natural surroundings
This journey led him to question many of the beliefs of the time

3. Charles Darwin Darwin’s direct observations included:
Fossils that were specific to the region and similar to (but not same as) current species
Species that were similar, but had specific adaptations that made them different
Species similarities were directly related to where they lived

4. Charles Darwin
In 1838, Darwin hypothesized on Natural Selection, but this was not published until 1858
Alfred Russel Wallace came to the same conclusion at that time and they decided to publish jointly
Darwin published the book On the Origin of Species by Means of Natural Selection (1859)
Used the phrase “descent with modification”

5. Natural Selection
Natural Selection is the mechanism for descent with modification; aka ‘Survival of the Fittest’
A process in which individuals that have certain heritable characteristics survive and reproduce at a higher rate than other individuals

6. Natural Selection Reasoning Included:
Overproduction – Populations have more offspring than will survive to increase chance of survival of species
Genetic Variation – Different traits occur within a population
Struggle to Survive – Individuals must compete (food, space, mates, etc.) to survive, some will not succeed.
Differential Reproduction – Individuals that survive and better attract mates will be more likely to reproduce, thus giving their traits to the next generation.

7. Natural Selection Isn’t…
Evolution/Natural Selection acts on a population not on an individual

8. Darwin’s Finches – Divergent Evolution

9. Evidence of Evolution
There are several key factors that provide strong evidence for evolution
Direct observation of evolutionary change
Fossil record
Homology
Biogeography

10. Evidence of Evolution
Scientists have documented many studies that show evolutionary change through direct observation
Guppy coloration
Coloration is directly related to the level of predation.
Those populations under greater threat of predation tend to be more drab in color; less predation means brighter colors
Drug-resistant HIV
Those HIV that survive treatments can go on to reproduce those traits that allowed them to survive
Similar to pests building resistance to pesticides

11. Evidence of Evolution Fossil Record
Scientists are able to age fossils using carbon dating
Fossils are also found in the rock layers according to time periods which gives us another option for aging
Fossil record also shows a gradual sequence of changes in a species over time (transitional species)

12. Evidence of Evolution Anatomy and Embryology are homologous
Body structures of different animals are homologous
Forelimbs of humans, penguins and bats are homologous
Embryonic development is extremely similar between species

13. Evidence of Evolution Biological Molecules
Comparative analysis of DNA and RNA can show relationships between closely related species and those species that are only distantly related
Can determine what genes caused the divergence and what proteins were involved
Can help with regard to time lines of divergence of different species

14. Evidence of Evolution Biogeography
Distribution of organisms of similar adaptations based on geography
Australia has marsupial mammals that are related based on a common ancestor
Cannot be confused with convergent evolution where similar species arise based on adaptations needed for a specific environment and niche