To be successful today… Pick up Warm-up sheet Pull out Mechanisms of Evolution Notes Pull out Mechanisms of Evolution WS BYOD Color of the day is Phones are in put away in backpacks

Warm-Up Mon1/23 What are the three main mechanisms that cause evolution? 2) Provide a definition for each.

To be successful today… Pick up graded work from blue table in lab (2) Turn in Gizmo Add to TOC & set up NOTES: Hardy-Weinberg Principle BYOD Color of the day is Phones are in put away in backpacks

Evolution of Populations

Is this population evolving? What do you think? Is this population evolving?

This population is NOT evolving Genetic Equilibrium - Population in which allele frequencies (p & q) do NOT change over generations p is the dominant allele q is the recessive allele

To maintain Genetic Equilibrium, 5 conditions must be met Random Mating: All members of the population must have an equal opportunity to produce offspring Large Population: To prevent genetic drift No Migration: No alleles can enter or leave the population No Mutations: No new alleles can enter the gene pool No Natural Selection: All traits must equally aid in survival Referred to as the Hardy-Weinberg Equilibrium

Do you think the 5 Hardy-Weinberg conditions exist in nature??

Real Populations rarely meet all 5 conditions H-W serves as a valuable model in evolutionary biology Populations NOT in H-W Equilibrium ARE evolving (allele frequencies p & q are changing) By determining which of the 5 conditions is/are being violated, scientists can understand HOW evolution is occurring

Using H-W Model to calculate dominant & recessive allele frequencies EX 1: In a certain population, 640 of the 1000 possible alleles are dominant. Calculate the dominant (A) and recessive (a) allele frequencies.

Let p and q represent the frequencies of A and a. According to H-W model, p + q = 1.0 Calculate p & q

You try it!!!! EX 2: In the gene pool containing 100 alleles, 19 are recessive, what is the frequency of both the dominant & recessive allele?

Let p = _________ ; q = ____ _______. Recall… p + q =___

You try it!!!!! EX 3: Within a population of butterflies, the color brown (B) is dominant over the color white (b). And, 40% of all the butterfly alleles in the population are white. Calculate the frequency of both brown & white alleles.

H-W model can also be used to calculate genotype frequencies When populations are in H-W equilibrium, allele frequencies and therefore genotype frequencies do not change from generation to generation This means the allele frequencies can be used to calculate genotype frequencies

Consider a cross between two heterozygous individuals

To calculate genotypic frequencies using H-W

Hardy-Weinberg Principle p2 + 2pq + q2 = 1 p2 = frequency of homozygous dominant individuals q2 = frequency of homozygous recessive individuals 2pq = frequency of heterozygous individuals 

EX 4: In a certain species of beetles, green body color is dominant to brown body color. In a population of beetles, 66% have the dominant allele. Calculate the frequency of homozygous dominant, homozygous recessive, and heterozygous individuals.

Step 1: Calculate p & q Step 2: Using p2 + 2pq + q2 = 1; Calculate genotypic frequencies

EX 5: A very large population of randomly-mating laboratory mice contains 35% white alleles. White coloring is caused by the double recessive genotype. Calculate allelic and genotypic frequencies for this population.

Putting it together… Most practice problems will give you the percentage or frequency of the recessive genotype (q2 ) Take the square root of (q2 ) to get q Use p + q = 1; to get allele frequencies Use p2 + 2pq + q2 = 1; to calculate genotypic frequencies

Practice Problem #1 You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 21%. Calculate the following:

PROBLEM #1 (aa) is 21%. a) The frequency of the "aa" genotype. b) The frequency of the "a" allele. c) The frequency of the "A" allele. d) The frequencies of the genotypes "AA" and "Aa."

Practice Problem #2 In humans, tongue rolling is dominant to non-rolling. In a population of 1000 individuals, 910 can roll their tongues while 90 cannot. Based on these facts, calculate all the expected genotype frequencies.

Problem #2

Practice Problem #3 In a population of 1000 fish, 640 have a forked tail, and 360 have a smooth tail. Tail fin shape is determined by two alleles. A is dominant for forked; and a is recessive for smooth. Determine allele and genotype frequencies.

Practice Problem #3

Practice Problem #4 A very large population of randomly-mating laboratory mice contains 25% white mice. White coloring is recessive to yellow. Calculate allelic and genotypic frequencies for this population.

Practice Problem #4

Practice Problem #5 Within a population of butterflies, the color brown (B) is dominant over the color white (b). 40% of all butterflies are white. Calculate the following:

Practice Problem #5 a) The percentage of butterflies in the population that are heterozygous. b) The frequency of homozygous dominant individuals.

Problem #4, cont. c) After mating and reproducing, there are 1200 butterflies in the population. Calculate the number of individuals that are homozygous dominant, heterozygous and homozygous recessive.

You try it!!!! 1) In cats, all-white color is dominant over not all-white. In a population of 100 cats, 41 are all-white cats. Assuming that the population is in H-W equilibrium, calculate the allele and genotype frequencies.

2) In a certain species of beetles, green body color is dominant to brown body color. In a population of 800 beetles, 216 are brown. Calculate the frequency of homozygous dominant, homozygous recessive, and heterozygous individuals.

If the next generation contains 2040 beetles, how many would be expected to be brown?