1. Aim: How does geographic & reproductive isolation lead to speciation?

2. Master and commander

3. Speciation
Evolution has lead to the formation of new species from different ancient organisms.
Species- a group of organisms that share certain characteristics & can mate with one another, producing fertile offspring.
Population- all the individuals of a single species that live in a specific area

4. What was Darwin’s explanation for evolution?2
NATURAL SELECTION
HOW DOES EVOLUTION REALLY WORK?

5. Natural Selection2
According to Darwin, nature controls evolution, the environment selects the characteristics best suited for survival in a particular area.

6. Geographic Isolation3
When part of a population of a species becomes geographically isolated from the remainder, it may (over time) evolve characteristics different from the original population.
Physical barriers
Mountain Ranges
Large bodies of water
Deserts
Great Wall of China

7. Movie: Elements of biology: agents of evolution

8. How does Geographic isolation lead to Speciation?
Those who have an adaptive variation will survive & reproduce in the different environments. This leads to different species with different variations.

9. Darwin’s Finches (An Example of Geographic Isolation)5
All came from a common ancestor. Due to different environments on each island, new species evolved that were adapted to their particular environment

11. Adaptive Radiation6
Evolution of many species from one common ancestor due to natural selection

12. Adaptive Radiation
Each group of finches adapted to its new environment, and through the process of natural selection, became different enough that interbreeding became impossible.

13. Reproductive Isolation:7
A reproductive barrier keeps similar species from interbreeding.
Timing- two similar species may have different breeding seasons.
Behavior- two similar species may have different courtship or mating behaviors.

14. How long does evolution take?8
Evolution takes a long time, but if the environment changes suddenly, evolution will be faster

15. Patterns Of Change
Species with SHORT reproductive cycles that produce MANY offspring tend to evolve more quickly than species with LONG life spans and FEW offspring.
Types:
Gradualism – evolution occurs steadily through time (Slow & Continuous) .
Punctuated Equilibrium- species stay the same for long periods of time and then change rapidly.
No Change
No Change
No Change