1. Evolution
Mr. Wright, 2011

2. The Work of Charles Darwin
Sections 15.1 & 15.2

3. Evolutionary Theory Evolution – change over time
How modern organisms descended from their ancestors.
Theory – a well-supported testable explanation for something

4. Evolutionary Theory
The main person behind evolutionary theory was Charles Darwin.
Darwin sailed around the world, recording his observations as he travelled.
These observations led to him proposing the idea of evolution.

5. Darwin’s Observations
Darwin was most influence by what he saw on the Galapagos Islands.
Each island had a unique climate:
Some were dry and barren
Some were moist and diverse
Others were inbetween

6. Galapagos Tortoises
Darwin found tortoises on each island, but they looked different from those on other islands.
How are they different, and what might this mean?

7. Galapagos Finches Darwin also studied finches on each island.
How are they different? What might this mean?

8. Adaptations
An adaptation is any inherited characteristic that increases an organism’s chance of survival.
These are key for outcompeting other organisms.
Let’s look at a few examples and figure out what purpose they serve.

9. Adaptation - Porcupine

10. Adaptation - Hare

11. Adaptation – Walking Stick

12. Adaptation - Giraffe

13. Adaptation - Whale

14. Natural Selection
Section 15.3

15. Variation is heritable.
The variations that evolve over time can be passed on to offspring if an individual manages to reproduce.

16. Artificial Selection
Artificial Selection is when breeders select for certain desirable traits over time.

17. The Struggle for Existence
All organisms compete with each other to survive.
Evolution selects for “better” organisms that have a greater chance at making it.

18. Fitness
Fitness – the ability of an organism to survive and reproduce in its environment

19. Survival of the Fittest
The organisms that are the most fit are the ones who survive. The weak will perish.

20. Relation to Natural Selection
Nature selects for the most fit individuals over time – only the fit live to reproduce and pass on their traits!

21. Common Descent

22. Homologous Structures
Structures with different forms that develop from the same embryonic tissue.
Typically, the more similar two structures are, the closer they are related.

23. Embryology
Embryos are very similar to one another from species to species – suggests a common ancestor?

24. Darwin’s Theory - Summary
Individuals differ, and variation is heritable.
Organisms produce more offspring than will survive, and not all will reproduce.
Organisms compete for limited resources.
Survival of the fittest!
All species share a common ancestor they descended from.

25. Genes and Variation
Section 16.1

26. Genes and Variation
In the 1930’s, biologists began to connect Darwin and Mendel’s work to each other.
Evolution is controlled by gene frequencies.

27. Variation and Gene Pools
Genetic variation is studied in whole populations.
Population – group of individuals that can interbreed.
Gene pool – ALL the different alleles that occur in a population

28. Variation and Gene Pools
Relative Frequency – the number of times that an allele occurs in a gene pool compared to the total number of alleles
Evolution is any change in the relative frequencies of alleles over time.

29. Variation and Gene Pools
Relative Frequency of the Green Allele = 12/15 = 4/5
Relative Frequency of the Purple Allele = 2/15
Relative Frequency of the Red Allele = 1/15

30. Sources of Genetic Variation
Mutations
Changes to the genetic sequence of an organism
“Gene Shuffling”
Remember that meiosis produces gametes that are all genetically unique
Produces many different combinations of alleles but DOES NOT change their relative frequencies in a population.

31. Single-Gene Traits
Variation for a trait can be caused by a single gene – you either have the trait, or you don’t.

32. Polygenic Traits
Many traits are controlled by several genes together – polygenic traits.
Depending on how the genes combine, you can have several different phenotypes.
Generally forms a bell-curve.

33. Evolution as Genetic Change
Section 16.2

34. Review Concepts
Fitness – an organism’s success at passing on its genes
Adaptation – a genetically controlled trait that increases an individual’s fitness
Natural selection determines what individuals survive and reproduces – an organism either passes on ALL genes, or none at all.

35. Natural Selection on Single-Gene Traits
A forest lizard can appear in 3 colors: brown, red (mutant), or black (mutant)
What do you think might happen to the red allele over time?
What do you think might happen to the black allele over time?

36. Natural Selection on Single-Gene Traits
Due to natural selection, over time…
If an allele increases fitness, it’s relative frequency will increase.
If an allele decreases fitness, it’s relative frequency will decrease.
If an allele has no effect on fitness, it will not be affected by natural selection.

37. Natural Selection on Polygenic Traits
Remember that polygenic traits often form a bell curve.
The fitness of individuals close to each other on the curve is similar, but can vary over great distances.
Can be affected in three ways:

38. Directional Selection
When individuals at one sight of the curve are more fit than the other side, directional selection occurs.

39. Stabilizing Selection
When individuals at the center of the curve have the highest fitness stabilizing selection occurs.

40. Disruptive Selection
When the extremes have more fitness than the individuals in the middle, disruptive selection occurs.

41. Genetic Drift
Sometimes allele frequency changes simply due to chance – this is called genetic drift.
Most common in small populations.

42. Founder Effect
Genetic drift can also occur when a small group goes off and colonizes a new habitat.
This is known as the founder effect.

43. The Hardy-Weinberg Principle
Section 16.2

44. Overview
In order to study how evolution takes place, it can be useful to study a situation where NO CHANGE takes place.
When allele frequencies remain constant it is called genetic equilibrium. No evolution occurs.
This is called the Hardy-Weinberg Principle, and is made up of the following five rules.

45. Random Mating
All members of the population must have an equal opportunity to produce offspring.
All alleles have an equal chance of being passed on.

46. Large Population
Genetic drift has less of an affect on a large population.

47. No Immigration
Immigrating individuals can either bring genes into or out of the population.

48. No Mutations
Mutations can affect the allele frequencies in a population.

49. No Natural Selection
All genotypes must have an equal chance of surviving and reproducing.

50. The Process of Speciation
Section 16.3

51. Speciation Speciation – the formation of a new species
Species – group of organisms that can breed and produce fertile offspring
Speciation is a product of evolution.
As species evolve, populations become reproductively isolated and can no longer interbreed.
3 ways that this can happen.

52. Behavioral Isolation
When two populations are capable of interbreeding but do not due to different reproductive behaviors.
Example: Bird songs

53. Geographic Isolation
When a species is split into two new species by geological events it is geographic isolation
Example: separation by mountains

54. Temporal Isolation
When two species do not reproduce due to time differences it is called temporal isolation.
Example: rain forest orchids

55. Example of Speciation - Assignment
You will create a diagram showing the process of speciation in an organism of your choosing. The diagram should be at least 6 steps long.
There is a good example of what I am looking for on pages in your book.
The book uses finches as their example – you must use something different. Tigers, turtles, dung beetles, aardvarks, whatever floats your boat.