1. Darwin based his theory on his own observations and the writings of Thomas Malthus.
Malthus was a British social scientist who made these observations about humans:
KEY POINTS
People have more children than are able to survive.
There are built-in population checks: disease, famine, and war.

2. You will need your notebook a packet
from the welcome table.
You will have 5 minutes from the bell to get them cut out and tabs folded

3. You will need your notebook and each of these from the welcome table.
Please put your cell phone in the phone pouch.

4. The gradual change in a species over time.
Evolution is…
The gradual change in a species over time.

5. Things to keep in mind… Populations, not individuals, evolve.
It’s all about the genes!
Occurs over a LONG period of time.

6. Evidences of Evolution
Fossil Record
Biochemical - DNA
Comparative Anatomy
Biogeography
Observable Events

7. Mechanisms of Evolution How does evolution occur?

8. A mechanism for change in a population. Survival of the Fittest
Natural Selection is…
Fitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations.
A mechanism for change in a population.
Survival of the Fittest
Organisms with favorable genetic variation survive to reproduce and pass on their genes

9. Requirements for Natural Selection
Inherited Variation within the species
Production of more offspring than can survive
Finite (limited) supply of environmental resources
Competition for resources

10. Types of Natural Selection
Stabilizing
Directional
Disruptive

11. Stabilizing Selection:
When the average is favored over either of the extremes in a population.

12. Stabilizing Selection:

13. Directional Selection:
This happens when one of the “extremes” is favored in an environment over the other extreme or the old average.

14. Directional Selection:

15. Disruptive Selection:
This situation happens when either extreme is favored over the average.

16. Disruptive Selection:

17. The alteration of allelic frequencies by chance events.
Genetic Drift
The alteration of allelic frequencies by chance events.

18. Genetic Drift

19. Bottleneck Effect
An event that kills off a large number of members of a species randomly by chance therefore reducing the genetic diversity.

20. Bottleneck Effect

21. Founder Effect
is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

22. Founder Effect

23. Founder Effect

24. Random genetic changes that occur in a populations DNA.
Mutations
Random genetic changes that occur in a populations DNA.

25. Mutations
Most mutations either silent and do not affect the organism or are harmful
Some are advantageous

26. Mutations

27. Gene Flow
The transfer of alleles from one population to another population through immigration or emigration of individuals.

28. Gene Flow

29. Gene Flow

30. How are new species made? Speciation: the evolution of a new species

31. How are new species made? Speciation is always caused by isolation
Types of isolation:
Geographic
Reproductive

32. Types of Isolation Geographic Isolation
A single species can become two different species because they are isolated by mountains, rivers, canyons, etc.

33. Types of Isolation 2. Reproductive Isolation
Animals in different areas of the country may develop different actions and behaviors.
These different behaviors can cause groups to separate from each other and become different species.

34. Types of Isolation 2. Reproductive Isolation
Organisms may develop different mating seasons which do not correspond to one another

35. Individuals die, species go extinct
Extinction
Individuals die, species go extinct
Photo – National Park Service – Dinosaur National Monument

36. Extinction
As the environment changes, organisms must have variations that allow them to survive (adapt) to those changes or die
If an entire population of a species cannot adapt, that species becomes extinct.
Photo – National Park Service – Dinosaur National Monument

37. Mass Extinction
There have been at least 5 MASS extinctions during Earth’s history where a huge % of the living species were destroyed
At least one of these has been attributed to meteor impact and its consequences.
For an article on mass extinctions and the % of loss, see
Photo courtesy of Donald E. Davis, also in public domain from NASA.

38. Mass Extinction
For an article on mass extinctions and the % of loss, see
Photo courtesy of Donald E. Davis, also in public domain from NASA.