NATURAL SELECTION AND GENE FREQUENCY

BY 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 1-21. 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.pngColorful Chromosomes: http://genetics.thetech.org/sites/default/files/KaryColor.gifNatural Selection Banner: http://i.ytimg.com/vi/aTftyFboC_M/maxresdefault.jpgHardy Weinberg Penguins: http://i.ytimg.com/vi/oG7ob-MtO8c/maxresdefault.jpgNS Cartoon Fish: http://media-cache-ak0.pinimg.com/736x/1d/d1/34/1dd13452486e4fd130930d50d2acbb53.jpgGene Frequency Goats: http://farm7.staticflickr.com/6128/5916685986_f891ba6255.jpgNatural Selection Birds and Beetles: http://uedata.berkeley.edu//media/3/52571_evo_resources_resource_image_380_original.gifAll other photography were done by SCC Biology 3 Students

WORKS CITED

Photo Credits