1. Evolution What does it mean to you?
Write what you think “evolution” means from a scientific point of view and then write what “evolution” means to you personally.

2. How do populations evolve?
What is a population?
A group of similar species that are capable of interbreeding with one another
What kinds of factors would cause this Apennine sheep population to change or evolve?

3. Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations.
Organisms descended with modifications from a common ancestor
Biological evolution is caused by changes in the allele frequency in a population from one generation to the next due to disturbing factors in the environment
The Hardy-Weinberg Theory: there are 5 factors that can contribute to changes in allele frequencies that can lead to evolution
Scientists believe that populations can evolve over time but not individual species
Charles Darwin: contributed to the theory of evolution

4. The Hardy Weinberg Theory STATES:
How realistic is it that NONE of the disturbing factors will occur in a population?
The frequency of alleles in a population will remain constant (in equilibrium) from one generation to the next in the absence of disturbing factors.
Disturbing factors:
Mutations- so NO genetic mutations can occur
gene flow- NO migration can occur
non-random mating- mating must be random
genetic drift- populations must be large so that alleles can’t drift in and out of a a population due to a random natural occurrence
natural selection- NO natural or sexual selection occurring
This means that a population does NOT evolve unless a factor is involved.
If a factor is involved, there could be a change in allele frequencies and evolution could occur

5. Genetics Review DNA is broken down into genes
Genes are made-up of alleles (one from each parent)
A: dominant allele
a: recessive allele
Genotypes:
AA or Aa or aa
Genetics Review
DNA
chromosomes
cells

6. AA: homozygous dominant aa: Aa:
Genetics Review
AA: homozygous dominant
aa:
Aa:
A genotype is the genetic make-up of the organism
A phenotype is the physical characteristics that describe the genotype
Hardy Weinberg GIZMO/ socks demo

7. Reflection: Did the allele frequencies change in the Hard-Weinberg demonstration or Gizmo? Explain.
Let’s see how the five factors can alter the frequency of alleles in a population

8. Evolution due to Natural Selection
Natural selection: Individuals who have the most favorable traits/variations are better adapted/suited to their environment, therefore surviving and reproducing more successfully
Nature selects against unfavorable phenotypes NOT genotypes
removes less successful alleles
Most fit VS “strongest”- what’s the difference?
As the environment changes, phenotypes become more or less favorable
NS leads to changes in allele frequencies which causes the population to EVOLVE!
Examples:
British peppered moths
Tusk-less elephants in Africa
Antibiotic resistant bacteria
NS is an example of microevolution: a change in the gene pool on a small scale

9. Natural Selection Examples

10. Evolution Due to Natural Selection
Gene Pool:
Ff, FF, Ff, ff in a warm environment Ff
Gene Pool:
Ff, FF, Ff, ____
in a cold and changing environment FF Ff ff
Nature selects against the phenotype: furless rabbits
Changes the frequencies of alleles in the gene population

11. What would cause this to happen?
Insects that are more FIT due to a mutation will survive, reproduce, and pass on the resistant gene to their offspring

13. A mode of natural selection: sexual selection
Sexual selection acts on an organism's ability to successfully copulate with a mate
Selection due to variation in reproductive success
How can they achieve reproductive opportunities?
Ex: larger females can carry more eggs
Ex: larger males can compete with other males for sex
nature is NOT selecting this time
Selection makes many organisms go to extreme lengths for sex
Male to male and female to female competition
Sexual selection can also be due to mate choice based on appearance
It is often powerful enough to produce features that are harmful to the individual's survival.
For example, extravagant and colorful tail feathers or fins are likely to attract predators as well as interested members of the opposite sex.

14. Natural Selection in humans (take notes)

15. Evolution due to Mutations
Mutations alter the DNA
Ex: DNA is deleted, the genes are deleted, and the alleles are removed from the gene pool
Causes changes in allele frequencies
Mutations of sex cells or gametes only, (sperm or egg) COULD cause a population to evolve
Some DNA doesn’t code for proteins- JUNK DNA- therefore some mutations do not alter phenotype
Silent mutation
Mutations do not create a significant change in allele frequencies but, can be more significant if a mutation occurs at more than one gene location
Can increase genetic diversity
More differences could result in speciation
Mutations are slow: estimated to occur 1 to 10 times for every 100,000 cell divisions
Remember: DNA polymerase enzyme
Causes of genetic mutations: carcinogens (tar), UV rays, genetics, food, viruses, etc

16. Evolution due to Mutations in gametes: sex cells
Deletion mutation: no gene, no alleles BB, Bb or bb
A gene for fur color= alleles (BB or Bb or bb)
Changes the frequency of alleles in the original gene pool

17. Evolution due to Non-Random Mating
Non random mating: the probability that two individuals in a population will mate is not the same for all possible pairs of individuals.
Very similar to sexual selection in by mating choices
Animal breeders essentially do the same thing
Intentionally try to improve varieties or create new ones
Select mates for their animals with desired traits
Hoping to increase the frequency of those traits in future generations
Leads to inbreeding or mating with relatives
This lowers the frequency of Aa and increases the proportion of homozygotes (aa/AA) in a population
decreases the genetic diversity in a population
Effect: a change in the allele frequencies of a population that leads to EVOLUTION.
This factor has the least effect on gene frequencies

18. Evolution due to non- random matingBB BB
If this black rabbit continues to choose black rabbits, over white rabbits the allele frequencies will change due to a loss of bb alleles in the gene pool BB Bb bb bb BB bb bb

19. Evolution due to Gene Flow
Gene flow: movement of alleles in or out of a population due to migration of individuals
Immigrants: new individuals bring new alleles into the
gene pool
Emigrants: individuals remove alleles from a gene pool
Results: a change in allele frequencies: EVOLUTION

20. Evolution due to migrationbb bb bb bb
As the rabbits with the bb allele emigrate, the frequency of the b allele decreases and the B allele increases resulting in evolution

21. Evolution due to Genetic Drift
Genetic drift is the result of a random occurrence that “drifts” the frequency of alleles in a population
Chance events like a hurricane, flood, volcanic eruption, or a tsunami that could remove individuals ( and their alleles) out of the gene pool
Causes changes in the allele frequency of a population
Small populations that are isolated or separated from one another as a result of genetic drift, their gene pools can differ greatly and results in speciation
Also leads to genetic uniformity in a small population
Genetic uniformity can lead to a decrease in disease resistance
Usually referred to as the “bottleneck effect”

22. Bottleneck Effect

23. Bottleneck Effect: results in changes in allele frequencies

24. Evolution Due to Genetic Driftbb bb bb bb
If a flood wiped out some of the bb individuals the frequency of the b allele decreases and the B allele increases resulting in evolution

25. Speciation
Speciation is a lineage-splitting event that produces two or more separate species. But why and how did it happen?
The scene: a population of wild fruit flies minding its own business on several bunches of rotting bananas, cheerfully laying their eggs in the mushy fruit...
Disaster strikes: A hurricane washes the bananas and the immature fruit flies they contain out to sea. The banana bunch eventually washes up on an island off the coast of the mainland. The fruit flies mature and emerge from their slimy nursery onto the lonely island. The two portions of the population, mainland and island, are now too far apart for gene flow to unite them. At this point, speciation has not occurred—any fruit flies that got back to the mainland could mate and produce healthy offspring with the mainland flies.

26. The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Morphology, food preferences, and courtship displays change over the course of many generations of natural selection.
So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. The lineage has split now that genes cannot flow between the populations.
This is a simplified model of speciation by geographic isolation, but it gives an idea of some of the processes that might be at work in speciation.

27. Reproductive Isolation is the driving force behind Speciation
Speciation is a lineage-splitting event that produces two or more separate species.
A new species will form when reproductive isolation occurs
Due to the absence of gene flow
Reproductive Isolation:
The existence of biological factors (barriers) that prevent two individuals of a species from mating and producing viable and fertile offspring
Factors or barriers:
Mating locations (river, mountain, etc.) barriers- geographic
Mating time (seasons/time of day)- temporal
Mating behaviors (courtship rituals)
Morphological differences: body development differences- mechanical
(habitat)