1. Evolution of A new Species
Genetic Variation

2. Sources of Genetic Variety
The two main sources of genetic variation in a population are mutations and sexual reproduction
Sexual reproduction shuffles parent genes/DNA through meiosis(CROSSING OVER)
Mutations create constant random variety that sometimes makes an organism more fit for its environment. EX: A mutation that gave brown bears white fur in the polar regions making white polar bears more fit for survival.

3. Mutations=Variety

5. Lethal Alleles
How are lethal alleles maintained in a population? Shouldn’t natural selection remove these?
Alleles that are lethal in a homozygous individual may be carried in a heterozygous individual.

6. For example: If two parents are carriers of a bad allele and an individual inherits both bad alleles they will get the lethal disease.

7. Gene Pool-
consists of all genes, including all the different alleles, that are present in a population.

8. Allele Frequency number of times an allele occurs in a gene pool
EX: How many in this class have at least one dominant allele for brown eyes
Sexual reproduction produces different phenotypes, but it does not change the relative frequency of alleles in a population.

9. Allele frequency
If the environment changes(which they always do, and it now favors the red petal phenotype, what do you expect to happen to the frequency of the R=red and r=white alleles in the population?

10. Gene Pool for Fur Color in Mice

11. How is evolution defined in genetic terms?
In genetic terms, evolution is any change in the relative frequency of alleles in a population.

12. What is Speciation Speciation is the formation of a new species
Speciation is caused by reproductive isolation
Reproductive Isolation is when two members of a population cannot mate. There are 3 types of reproductive isolation.

13. Reproductive Isolation Causes Speciation

14. Reproductive Isolation
#1. Behavioral Isolation is when genetically similar populations are able to breed but don’t due to differing mating rituals.

15. Reproductive Isolation
#2. Geographic Isolation is when two members of a population are separated by barriers such as mountains, canyons, bodies of water, etc.
EX: Squirrels on opposite sides of the Grand Canyon

16. Reproductive Isolation
#3. Temporal Isolation is when members of a population mate at different times of the year.
EX: Different frogs mate in different months

17. Equilibrium Theoretical model of a population 5 Conditions:
1) No net mutations
2) NO immigration/Emigration
3) VERY large population
4) Individuals mate randomly
5)Selection doesn’t occur

18. The Equation Hardy-Weinberg equilibrium=predict population genotypes
p=dominant allele (A) q= recessive allele (a)
The sum of p+q=1,then solve p2 + 2pq + q2 = 1

19. p=dominant allele (A) q= recessive allele (a)
p=dominant allele (A) q= recessive allele (a) The sum of p+q=1,then solve p2 + 2pq + q2 = 1
Use the equation to solve this problem
What is p if q = 30%
p =1
p=.70
In this population what percent of individuals are homozygous dominant (AA)?
p2= .72=.49=49%
In this population what percent of individuals are heterozygous (Aa)?
2pq= 2(.7)(.3)= .42= 42%

20. Use the equation to solve this problem
What is p if q = 30%
p =1
p=.70
In this population what percent of individuals are homozygous dominant (AA)?
p2= .72=.49=49%
In this population what percent of individuals are heterozygous (Aa)?
2pq= 2(.7)(.3)= .42= 42%
-PRACTICE

21. Disrupting Equilibrium
1) Mutations- a change in DNA changes allele frequencies
2) Gene flow- genes move in and out of the population due to immigration and emigration
3) Genetic drift is a change in allele frequencies
Genetic drift operates most strongly in small populations
4) Non random mating- whenever individuals may choose partners. Sexual selection occurs when certain traits increase an individual’s success at mating
5) 3 types of selection

22. Genetic Drift
A random change in allele frequency (can be caused by fire, flood, etc)
In small populations, individuals that carry a particular allele may leave more descendants than other individuals do, just by chance.

23. Genetic Drift Genetic Drift
In small populations, individuals that carry a particular allele may have more descendants than other individuals. Over time, a series of chance occurrences of this type can cause an allele to become more common in a population. This model demonstrates how two small groups from a large, diverse population could produce new populations that differ from the original group.

24. Genetic drift
Active art
Code cbp-5162

25. Genetic Drift
Descendants
Population A
Population B

26. Founder effect Founder effect
When allele frequencies change as the result of the migration of a small subgroup of a population.

27. How does genetic drift differ from natural selection in the way it changes the genetic makeup/allele frequency of a species over time?

28. Stabilizing Selection
Favors the formation of average/intermediate traits.

29. Disruptive Selection
Favors extreme traits rather than average traits

30. Directional Selection
Favors the formation of a more-extreme trait.

33. Does Natural Selection act on the phenotype or genotype of a species?
Phenotype – predators can only see the outside physical appearance of an individual making them less fit or suited for their environment.