1. Evolution

2. Sickle Cell Passage
Transcribe and translate the normal and mutated DNA. What type of mutation causes sickle cell? How is the phenotype affected?
Explain how the sickle cell mutation can be considered an adaptation.
In which populations is the sickle cell gene more common? Why?
Explain why some mutations spread through a population while other mutations “die out” quickly.

3. Mutations
We have been looking at mutations as disadvantages… and many are.
Some mutations actually are advantageous to an organism
These are more likely to be passed down to offspring
Theory of natural selection
Example: sickle cell anemia

4. Adaptations
Adaptation: a feature that allows an organism to survive better in its environment
Leads to changes in a population over time

5. Evolution
Evolution is the biological process by which descendants come to differ from their ancestors
Microevolution vs. macroevolution
Microevolution is small changes over a shorter period of time
Resistance to drugs/pesticides (mosquitoes and DDT)
Size of sparrows in North America (larger in colder climates)
Macroevolution refers to large-scale changes over a long period of time
Horses
Dinosaurs to birds?

6. Jean-Baptiste Lamarck
Proposed that all organisms evolve toward more perfect and complex forms
Environmental changes lead to behavioral changes… organisms may have to use certain structures more or less.
These structures become larger or smaller and these changes are passed down to offspring
Example: giraffe necks lengthened over time as giraffes had to reach for leaves higher in the trees
Inheritance of acquired characteristics

7. Darwin
1831
Set sail in the HMS Beagle to map the coast of South America and the Pacific Islands
Observed many species in his travels
Noticed a great variation of traits, especially in the Galapagos Islands
Wrote about his theory of natural
selection in a book entitled
On the Origin of Species

8. Adaptations
Darwin realized that species must be able to adapt to their surroundings
For example, he noticed many species of finches with different types of beaks
Adapted to best fit their diet

9. Natural Selection
Humans selectively breed plants and animals to take advantage of certain traits
Larger pigs, higher corn
This process occurs naturally
Natural selection: “survival of the fittest”
Fitness is defined as an organism’s ability to reproduce and pass along genes

10. Evidence of Evolution Several sources of evidence Fossils Geography
Carbon dating
Geography
Embryology
Anatomy
Genetics

11. Fossils Fossil record shows evidence of changes over time
Also shows how the land has changed
Marine fossils found in land locked areas

12. Fossil records can help us date organisms by looking at stratification of rock layers
Which organisms are the oldest?

13. Radiometric Dating
Scientists can use radiometric dating to get more precise ages of fossils or rocks
This involves using the rate of decay of unstable isotopes to calculate age
Half life- the amount of time it takes for half of an isotope in a sample to decay into a different element

14. Radiocarbon Dating
Carbon-14 (14C) is often used for radiometric dating
14C has a half-life of 5700 years
After 5700 years, half of the 14C will have decayed
We measure this by comparing the ratio of 14C to 12C

15. Geography Island species resembled species from mainland
When populations become isolated (cannot interbreed) new traits develop
Example: Darwin’s finches

16. Embryology Embryology- the study of the development of organisms
Some organisms do not resemble each other as adults but go through very similar stages of development
Example: humans and chickens

17. Anatomy
Different species physically resemble each other, suggesting common descent
Just like you might look like your family members

18. Homologous Structures
Similar structure
Different functions
Evidence of common descent

19. Analogous Structures Similar functions but not similar in structure
Evolved separately

20. Vestigial Structures
Structures that no longer have a use or are underdeveloped
Remnants of structures from earlier ancestors
Examples: human appendix, kiwi and ostrich wings

21. Genetic and Molecular Evidence
We have tools available today that Darwin did not have
DNA sequence analysis and cellular comparisons can reveal relationships between species
Sometimes have surprising results
Similarity between cells in worms and in vertebrate eyes
This relationship could not have been predicted by physical traits alone

22. Convergent vs. Divergent Evolution
Divergent evolution- related species become increasingly different over time
Elephant and wooly mammoth
Convergent evolution- unrelated species develop similar characteristics over time
Birds and bats
Sharks and dolphins

23. Theories of Geologic Change
Three principles of geologic change help shape the theory of evolution
Catastrophism
Gradualism
Uniformitarianism

24. Catastrophism
Natural disasters have occurred often during the history of Earth
Shaped landforms
Mass extinctions

25. Gradualism Slow changes occur over a long period of time
Shapes landforms
Gradual changes in species

26. Uniformitarianism Builds on gradualism
Changes occur as a result of slow processes over time
Geologic processes that shape Earth are uniform over time
We can still see them happening today
Example: layers of sediment