1. Patterns of Evolution & Speciationpp

2. Convergent Evolution
Occurs when different organisms that live in similar environments develop similar characteristics.
The environment selects similar adaptations in unrelated species.
Organisms develop analogous structures (same function, but different internal anatomy).
Examples: - Bird wings/insect wings
- Shark fins/dolphin fins

4. More examples: Placental Mammals: top row
Marsupial Mammals: bottom row

6. Divergent Evolution
The process by which related organisms become less alike
Organisms become adapted to different environmental conditions
Caused by isolation of part of a population due to migration or geographic barriers

7. Also known as adaptive radiation.
Can cause speciation
Examples:
Darwin’s Finches.
Brown bears and polar bears

8. Divergent Evolution

9. Speciation
Sometimes evolutionary changes within a population are so great that organisms can no longer interbreed with the original species
= reproductive isolation
When this happens it is called SPECIATION
Remember: A species is a group of organisms which can breed with each other & producing fertile offspring.

10. Evidence of Evolution Homologous Structure
Parts of the body that are similar in skeletal structure but have different functions

11. 2. Vestigial organs
Organs or parts that seem to have no useful function

12. 3. Biochemical Evidence similar RNA & DNA; same amino acids
More similarities are found in species that are more closely related
Human & gorilla hemoglobin differ by one amino acid
Human & frog hemoglobin differ by 67 amino acids

14. 4. Embryological Development
Embryos of different species develop in almost identical ways
Indicate common ancestry

16. 5. Fossil record Give us a time scale
Shows similarities between extinct animals and animals alive today
Debate about the speed of evolution because of gaps in the fossil record

18. Speed of Evolution

19. Option 1: Gradualism
A model of evolution in which one species slowly & steadily evolves into another
Proposed by Darwin

20. Option 2: Punctuated Equilibrium
A model of evolution in which one species suddenly changes into another after a long stable period
Occurs when niches are opened through:
Mass extinction
Migration into new environments
Isolation of small populations