1. What is Evolution Changing?

2. Evolution acts on populations not individuals
Individual organisms do not improve themselves
Nature selects the best of the members of a population to survive and produce the next generation

3. Mutations may produce such unique features but selection enhances them
Evolution does not produce new adaptations!
It amplifies (increases) or diminishes (decreases) variations that are already present
Mutations may produce such unique features but selection enhances them

4. Gene Pools
All of the alleles for all of the traits for all of the members of a population
Only organisms that can mate together can share alleles and produce offspring
So only members of the same species are found in a gene pool

5. Evolution Changes the Alleles in a Gene Pool
All of the alleles for all of the traits for all of the members of a population

6. More long ear alleles (LL) in the next generation
If natural selection chooses certain traits in an organism, in reality it is really choosing particular alleles that code for the trait
long ear alleles (LL) survives Babies with L
short ear alleles (ll) dies No Babies 
More long ear alleles (LL) in the next generation LL LL LL LL ll LL LL

7. So What Changed in the Population?
The proportion of certain alleles!
more long ear alleles (LL) in the next generation
When natural selection occurs, the number of certain alleles in a population changes

8. This is the smiley face bug of the great paisley forest
There are four variations in color, due to four alleles:
R = red allele B = blue allele Y = yellow allele G = green allele
Which color do you think would survive the best?
What allele will increase in proportion in the next generation?

9. A New Definition for Evolution:
Evolution is any change in the proportion (frequency) of alleles in a population, from one generation to the next
It’s all about Passing on your awesome alleles!

10. Mechanisms for Evolution
Mutations
Non-random mating
Migration
Small population size
Natural Selection

11. Mutations
Tadpoles go through metamorphosis changing into frogs caused by a particular hormone

12. Axolotl injected with missing hormone
Axolotl external gills
External gills due to a mutation
Lost the ability to make the hormone that causes metamorphosis
So he lives his whole life in the water!
Axolotl injected with missing hormone
Completes the metamorphosis into a salamander
Clearly, a mutation can cause alleles to change and even create a new organism

13. Such sorting out in mating affects the proportion of certain alleles
Nonrandom Mating
Blister beetles sort themselves out for mating by size
Snow geese tend to mate by color.
Such sorting out in mating affects the proportion of certain alleles

14. Nonrandom mating in humans

15. Migration allows alleles to move into or out of
a gene pool

16. (The Bottleneck Effect)
Small Population Size
(The Bottleneck Effect)
If some event caused most of the members of species to die, the surviving population will now have a different proportion of alleles

17. Different allele frequency!
Event which nearly wipes out the population.
Different allele frequency!

18. Limited alleles within a gene pool leaves an unhealthy population
The Cheetah
Two species whose numbers got so low that many alleles were lost from the gene pool
Hey Baby!
Wanta come over to my
place and see my sea shell collection?
Limited alleles within a gene pool leaves an unhealthy population
Northern Elephant Seals

19. Small Population (The Founder Effect)
Ellis-Van Creveld Syndrome
Shortened limbs
6 fingers
Lancaster Pennsylvania Amish Community

20. But the biggest, baddest, meanest factor in changing the alleles in a population (evolution) is: drum roll please
Natural Selection

21. More long ear alleles (LL) in the next generation
If natural selection selects against certain traits in an organism, in reality it is really selecting against particular alleles that code for the trait
long ear alleles (LL) survives Babies with L
short ear alleles (ll) dies No Babies 
More long ear alleles (LL) in the next generation LL LL LL LL ll LL LL

22. Natural Selection Changes the Proportion of Certain Alleles
more long ear alleles (LL) in the next generation

23. More Fit Population Less Fit
Natural Selection
More Fit
More Fit
More Fit
More Fit
The better adapted organism (with better set of alleles) passes those on to the next generation – more of them so become more popular!
BETTER TRAITHIGHER REPRODUCTIVE RATECHANGE IN ALLELE FREQUENCY OF THE POPULATION
More Fit
More Fit
More Fit
More Fit
Positive Trait
More Fit
Population
More Fit
Negative Trait
Less Fit
Less Fit
Less Fit
Less Fit

24. Types of (Natural) Selection

25. Disruptive Selection
Favors the extremes in population at the expense of the intermediate (middle) phenotypes
original population
evolved population

26. Disruptive selection results in two very different types of males in the coho salmon
coho hooknose male coho jack male
coho female

27. Directional Selection
Favors one extreme of the range of phenotypes
original population
original population
evolved
population

28. Directional Selection in Galapagos Finches
In a drought the larger beak size is where it’s at!

29. Stabilizing Selection
Favors the intermediate (middle) individuals in a range of phenotypes
original population
evolved
population

30. An example of stabilizing selection is clutch size in birds
A clutch of eggs
An example of stabilizing selection is clutch size in birds
Few eggs (1-2) = fewer offspring 
Many eggs (6-8) = too many mouths to feed 
Intermediate number (3-5) = just right
to have the most surviving offspring

31. Sexual Selection Intersexual Selection Intrasexual Selection
one sex exerts selective pressures on the other sex by selecting mates based on a specific trait
members of the same sex compete for the chance of mating
Long-tailed widow bird
Rams!

32. So What is Evolution Changing?
Allele Frequencies in the Gene Pool of the Population!