1. Evolution Processes

2. As new species originate, they may go through different processes of evolution…
Divergent evolution
Convergent evolution
Coevolution
Adaptive radiation

3. Divergent evolution
Once related populations evolve independently of each other

4. Divergent evolution Causes: Geographic barriers
Small group colonizing new area

5. Divergent evolution Example – polar bear and brown bear
Scientists think that a long time ago a group of Brown Bears became geographically separated from the rest. This isolated group acquired new characteristics, such as blubber to keep warm in snowy weather and a white coat for camouflage. They slowly evolved into Polar Bears

6. Convergent evolution
Different, unrelated species develop similar characteristics

7. Convergent evolution
Cause – similar environments

8. Convergent evolution
Example – Shark and Dolphin

9. Modeling Convergent Evolution
Think of an invention that would make ____________________ better.

10. Modeling Convergent Evolution
Were any of your ideas the same or similar?
How does this activity illustrate convergent evolution?

11. Coevolution
Species adapt to one another

12. Coevolution Cause – close interaction Symbiotic Relationships
Predator and prey – one benefits
Mutualistic – both benefit

13. Coevolution
Example – hummingbird and flower

14. Adaptive radiation
Evolution of many diversely adapted species from one ancestor

15. Adaptive radiation
Example – Darwin’s finches

16. Populations show evolution
Each individual member exhibits unique characteristics, but the effect of natural selection (evolution) can only be measured as an entire population

17. Population genetics
The study of genetic traits and changes in populations

18. Gene pool
All the genetic material of all the members of a population

19. Allele frequencies
A fraction of all the genes for a particular trait

20. Genetic equilibrium
Allele frequencies stay constant

21. Hardy-Weinberg principle
If a population is not evolving then the allele frequencies remain constant
In 1908, two researchers came up with the same idea

22. Hardy-Weinberg principle
This principle will be maintained in nature only if all five of the following conditions are met:
a. Very large population
b. Isolation from other populations
c. No new mutations
d. Random mating
e. No natural selection

23. Genetic drift Random change in allele frequencies due to chance events
Natural disasters – volcanoes, earthquakes, forest fires, flooding…
Migration

24. Florida Panthers Hunted to protect homes and livestock
Cities built in their habitats
Fewer than 100
Less genetic variation means lower ability to adapt to changes
Texas cougars introduced to crossbreed

25. Population Genetics

26. A population showing variation in colour.

27. There is lots of food so your population survives and reproduces. Add 5.

28. The bright yellow of some of your offspring attracts predators
The bright yellow of some of your offspring attracts predators. All but two of them get eaten.

29. There’s lots of food and hiding places for the green and
red, but the blue ones can’t hide and get eaten.

31. Plenty of food and its spring so another 10 offspring are born, they are a variety of colours.

32. Plenty of food and its spring so another 10 offspring are born, they are a variety of colours.

33. It’s winter and 5 of your population die

35. Its mating time again, red and green mate and produce 5 green and 2 red offspring. A mutation also produces 2 blue offspring

37. There is lots of food, and all reproduce 2 offspring, but the white are better at finding water and hiding from predators so they produce 5 offspring

38. There is lots of food, and all reproduce 2 offspring, but the white are better at finding water and hiding from predators so they produce 5 offspring

39. The blue color attracts mosquitoes carrying a deadly disease
The blue color attracts mosquitoes carrying a deadly disease. They all die.

41. It is a particularly hot summer, red and green are poor temperature regulators; white and yellow, which reflect heat, are more likely to survive.

43. When food is plentiful again the remainder mate and produce 5 offspring some white and some yellow.

44. When food is plentiful again the remainder mate and produce 5 offspring some white and some yellow.

45. A scientist finds this population and reports that this species occurs in two colours. He says they have adapted to their habitat. What does he mean?
What is the population?
Has it changed?

47. In outline, Darwin stated the following:
Many more individuals are born than can possibly survive.
Individuals within a population vary slightly from one another.
There is a frequent recurring struggle for existence.
Some individuals will have a better chance of surviving than others (they will be naturally selected).
Any selected variety will tend to propagate its form.
Q.What did the individuals in our population compete for in the struggle to survive?
Q.Which individuals were naturally selected?

48. Distribution curves

49. Normal distribution Acts upon extremes and favors the intermediate
Number of
Individuals
Size of individuals
Small Large

50. Directional selection
Favors variants of one extreme
Number of
Individuals
Size of individuals
Small Large

51. Disruptive selection Favors variants of opposite extremes Number of
Individuals
Size of individuals
Small Large

52. Why does evolution matter now?

53. Why does evolution matter now?