1. Theory explaining how species form
Speciation
Theory explaining how species form

3. What is a species? A species is a group of organisms that
Can interbreed
Produce fertile offspring
Mate in nature

4. What do you get when you breed a donkey and a horse?
A MULE!!!
Does the mule fit the definition of a species?

5. Why does a MULE NOT fit the definition of a species??
Can interbreed
X Produce fertile offspring
Do so in nature

6. What do get when you breed a tiger and a lion?
A LIGER!!!
Does the liger fit the definition
of a species?

7. Why does a LIGER NOT fit the definition of a species??
Can interbreed
X Produce fertile offspring
X Do so in nature

8. Speciation is the evolution of a new species.

9. Reproductive isolation
When formerly interbreeding organisms are prevented from mating and producing fertile offspring.

10. Extinction
The loss of a species

11. Speciation occurs when
Formerly interbreeding organisms are prevented from mating and producing fertile offspring.
This is called reproductive isolation.

12. Reproductive isolation can lead to speciation (3 ways):
Geographical Isolation
Temporal Isolation
Behavioral Isolation

13. Geographical Isolation
Occurs if a physical barrier separates a population into groups.

14. Geographical Isolation

15. Geographical isolation can be created by any type of physical barrier—mountains, rivers, even highways and roads.

16. Temporal Isolation Temporal means “time”
Occurs when timing prevents reproduction between populations

17. EX: Seasonal differences in mating habits—one mates in the spring, the other in the fall.

18. Behavioral Isolation
Caused by differences in courtship or mating rituals

20. Talk to a Partner

21. Speciation can occur slowly or quickly.

22. Gradualism
Slow and steady change.

23. Gradualism
Takes several generations.
Supported by the fossil record.

24. Punctuated Equilibrium
Stable periods interrupted by rapid changes.

25. Punctuated Equilibrium
Caused by change in environmental conditions.
Also supported by fossil evidence.

26. Which is which??

27. Stasis

28. Species will diversify when introduced to a new environment.

29. Adaptive Radiation
Ancestral species develops into two or more distinct species.
Due to natural selection.

32. Convergent Evolution
The pattern of evolution in which unrelated organisms evolve similar traits.
Due to similar environments and similar selection pressures.

33. An Example:
Dolphins and fish
Streamlined body for life in water