1. Speciation and Time

2. Review
What is evolution?
What is natural selection?

3. Speciation
Speciation is the process by which new species come into existence

4. What is a species?
Species – organisms that are capable of breeding and produce fertile offspring

5. Are these the same species?
Cat
Dog

6. Are these the same species?
Great Dane
Golden retriever

7. Donkeys and horses can have offspring: Mules
Mules are not fertile
Thus they do not fit the definition of being the same species.

8. How are new species made?
Populations must become reproductively isolated from one another for speciation to occur
Reproductive isolation means that two populations are unable to mate together

9. If two populations stop mating with each other, natural selection can drive them to become different species

10. Geographic isolation Reproductive isolation due to geographic features
Can be caused by formation of new rivers or mountains

12. Behavioral isolation Reproductive isolation due to different behaviors
Birds have different songs and are only attracted to mates with the same song as them.

13. Reproductive isolation due to mating at different times
Temporal isolation
Reproductive isolation due to mating at different times
Ex. Morning glories and moonflowers

15. Why is reproductive isolation needed for speciation?
Review
What is a species?
Why is reproductive isolation needed for speciation?
A population of rabbits is separated by a river that they cannot cross and stop breeding with each other. What kind of isolation is this?

16. Is there enough time for evolution?
Speciation can take hundreds or thousands or years
Is it possible for all of life to have evolved in that time period?

17. How old is the Earth?

18. 4.54 Billion years

19. Evidence for an old Earth
Half-Life radioactive dating: Measuring how old something is based upon how much radiation is left in it.
Radioactive dating has placed the age of the world at approximately billion years.

20.
I have existed for less than % as long as the Earth
The United States has existed for % as long as the Earth
Humans have existed for % as long as the Earth