17.3 The Process of Speciation

1. 17.3The Process of Speciation

2. What is Speciation? • Speciation is the formation of new biological species, usually by the division of a single species into two or more genetically distinct one.

3. Four Types of Isolating Mechanisms • Reproductive Isolation • Behavioral Isolation • Temporal Isolation • Geographic Isolation

4. Reproductive Isolation • Reproductive Isolation is the separation of a species or population so that they no longer interbreed and evolve into two separate species. • Members of a certain species share a common gene pool. Over time, genes are shared by interbreeding. • Over time, isolated gene pools diverge into separate species.

5. Behavioral Isolation • Behavioral Isolation is a form of reproductive isolation in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding. • Example: Eastern and Western Meadowlark • The populations of the two subspecies overlap in the midwest.

6. Behavioral Isolation • Male birds sing a mating song that females like, East and West have different songs. Females only respond to their subspecies song.

7. Temporal Isolation • Temporal Isolation is a form of reproductive isolation in which two or more species reproduce at two separate times. • Example: Northern Leopard Frog & North American Bullfrog • Mates in April Mates in July

8. Geographic Isolation • Geographic Isolation is a form of reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains or bodies of water, leading to the foundation of two separate subspecies. • Example: 10,000 years ago the Colorado River separated two squirrel populations.

9. Geographic Isolation • Kaibab Squirrel Albert Squirrel • This resulted in a subspecies, but did not result in speciation because the two can still mate if brought together

10. Convergence • Convergence occurs when species evolve into a common phenotypic form due to a common need. • For example the diagram portrays a shark, ichthyosaurus, a penguin and a dolphin. These are fish, reptile. bird and mammal respectively . They all have a torpedo body shape, pectoral, caudal and dorsal fins. This is based on their common need to swim rapidly in an aquatic environment.

11. Divergent Evolution and Adaptive Radiation • Divergence occurs when species evolve in several directions away from a common ancestor. This happens usually to fill a vacant ecological niche. Also known as adaptive radiation.

12. Convergent or Divergent Evolution?

13. Convergent or Divergent Evolution?

14. What process is shown in diagram A? Explain • Divergent Evolution or Adaptive Radiation. It is because one ancestral species has given rise to many new species • Why do the animals in diagram A look different from each other? • They have evolved to fit different niches.

15. What process is shown in diagram B? Explain • Convergent Evolution. It is because the three organisms look similar but have been produced by separate evolutionary lines. • Why do the animals in Diagram B look similar to one another? • They have evolved to fit similar niches.