NATURAL SELECTION AND GENE FREQUENCYBY WOLFGANG

WHAT IS THAT?

• Natural selection is a key mechanism of

evolution.

• It is the process in which individuals with

certain heritable traits survive and reproduce

at higher rates than other individuals without

those traits.

• These traits allow them to adapt to various

environmental pressures, favoring their

survival and passing on of those suitable traits

to succeeding generations, thereby altering

allele frequencies.

• Gene frequency demonstrates the

occurrence of an allele compared to other

alleles of the same gene in a population.

• The Hardy-Weinberg Principle states allele

frequencies will remain the same through

generations in a population: with

extremely large in size, that randomly

mates, and with the absence of mutations,

gene flow, and natural selection.

Purpose:

The natural selection lab aims to simulate the process

by which biological traits become more or less

prevalent in a population that has a changing

environment. The natural selection lab will also attempt

to show the relationship between predators and prey.

Hypothesis:

We predict that the predator will naturally pick out the

prey that is most contrasting in color to its

environment. The species that blends in the most to its

environment in color will thrive and reproduce to make

more generations of offspring.

The Natural Selection Experiment The Hardy Weinberg Experiment

Purpose:

To create a population and demonstrate how

consistent Hardy-Weinberg's principle really is.

To observe the survival rates in genotypes and

phenotypes of a population over a span of 6

generations.

Hypothesis:

Since there are mutations, certain allele frequencies

will decrease dramatically due to the circumstances of

the mutation standards. For other cases of mutation,

new species will emerge.

Specimens:

• 40 small colored paper dots which

represent the prey

• One clawed and double clawed

predators that kill the species.

Specimens:

• Red, white, and black beads which represented

alleles.

Materials:

• Red beads were used to represent red alleles.

• Black beads were used to represent black alleles.

• White beads were used to represent white alleles.

• 6 cups to place different allele combination in.

• 1 petri dish lid used to place allele combinations

in.

The Natural Selection Experiment The Hardy Weinberg Experiment

Materials:

• 1 plastic cup for the “dead” dots

• 2 distinct fabric mats which

represented different environments for

your dots

• A computer to record results on excel

SPECIMENS & MATERIALS

NATURAL SELECTION METHODS

1. Provided by the instructor, obtain one of the bottles of colored

dots and gather 40 paper colored dots of one color per each

individual in your group.

2. The instructor will then provide a fabric board that will serve as

an “environment” for your species.

3. Place your colored species around the board in any order. Next,

designate a predator for each group and send them to another

environment where they will simulate the killing of a species by

“eating them” for an allotted time set by the instructor.

4. After the event has occurred, calculate how many could survive,

and add in the offspring produced in that generation to the

population .

5. Repeat this process with multiple claws, environments, and

various conditions in order to simulate natural selection.

NATURAL SELECTION RESULTS

The different colored dots represented the genetic variation

between species. We predicted that those species that stood

out from their environment were less likely to survive. Those

species that adapted to their environment over time had a

better chance at survival.

• Predators play a role in enforcing evolution and natural selection because they choose which populations

survive and which do not. Those species newly introduced thrive because the predators are not yet familiar

with them as shown in the previous slide the newly introduced dark green dots thrived more than any of

the other populations.

• When a population is brought into a new environment their survival may be affected. Those that once were

able to successfully survive in the old environment may not be able to adjust so quickly to the new

environment because they have not yet adapted.

NATURAL SELECTION ANALYSIS

Case 1-2

1. Gather all materials and count out 50 white beads and 50 red beads.

2. Put the red and white beads into a single cup so that the beads will mix.

3. Have 3 separate cups available for your RR, Rw, and ww bead combinations.

4. Have a member of the group randomly grab two beads at a time and put the

appropriate bead combinations into its corresponding cup.

5. Once the team member has randomly picked all the beads, have someone

count and record on your excel document how many of each combination was

acquired.

6. Depending on which case you’re doing have a team member calculate the

amount of white beads that should be eliminated from the next generation.

7. Repeat steps 2-6 until you have reached generation 6.

8. For cases 3-4 repeat steps from case 1-2 but with different beads and

different mutation standards.

HARDY WEINBERG METHODS

GENE FREQUENCY RESULTS: Mutation Effects

GENE FREQUENCY RESULTS: Population Percent

• In this population, the red allele is dominant while the white allele is recessive. The dominant phenotype of red is

selected for, represented by the homozygous dominant RR and heterozygous dominant Rw. This favored trait is

passed on to more offspring, increasing its allele frequency.

• In both cases of 67% survival and 0% survival of the white allele, its frequency decreased dramatically over

time. However, we see that it is almost impossible to eliminate the recessive alleles because of the heterozygous

Rw genotype that codes for the favored phenotype.

• Unsuccessful genotypes leads to unsuccessful phenotypes resulting in the decline of allele frequency over time.

And natural selection consistently increases the allele frequencies of of favorable phenotypes over time, leading

to adaptive evolution.

GENE FREQUENCY ANALYSIS

Our hypotheses were validated because the mutations affected

allele frequencies significantly. The positive mutations led to an

increase in population % whereas the negative mutations lead

to a decrease in population %. Also, new species emerged with

the introduction of the dominant black allele producing favored

phenotypes of black and dark red.

• Natural selection can increase the frequencies of alleles if they are

advantageous to a species survival and reproductive abilities. If

they somehow produce a phenotype that is not a selective

advantage, their frequency will decrease.

• The change in allele frequencies is one way of defining evolution. A

population evolves as “better” alleles increase in frequency in the

gene pool.

• This means that gene frequency and natural selection go hand in

hand. They affect one another directly because the frequency of a

gene makes it better suited for natural selection, while

simultaneously, natural selection chooses which genes are going to

be selected against.

HOW ARE THEY RELATED?

Campbell, Neil A., and Jane B. Reece. Campbell Biology. San Francisco, CA:

Benjamin Cummings, 2011. Print.

Darwin, Charles. "On The Origin of Species." The Origin of Species by Charles

Darwin. Usenet Newsgroup, n.d. Web. 17 Feb. 2015.

Darwin’s Finches:

http://www1.northbrook28.net/~pamendelson/Mrs._Mendelsons_Site/Natural_Selection_Classification_files/shapeimage_3.png

Colorful Chromosomes: http://genetics.thetech.org/sites/default/files/KaryColor.gif

Natural Selection Banner: http://i.ytimg.com/vi/aTftyFboC_M/maxresdefault.jpg

Hardy Weinberg Penguins: http://i.ytimg.com/vi/oG7ob-MtO8c/maxresdefault.jpg

NS Cartoon Fish: http://media-cache-ak0.pinimg.com/736x/1d/d1/34/1dd13452486e4fd130930d50d2acbb53.jpg

Gene Frequency Goats: http://farm7.staticflickr.com/6128/5916685986_f891ba6255.jpg

Natural Selection Birds and Beetles: http://uedata.berkeley.edu//media/3/52571_evo_resources_resource_image_380_original.gif

All other photography were done by SCC Biology 3 Students

WORKS CITED

Photo Credits