NATURAL SELECTION AND GENE FREQUENCY WHAT IS THAT? • Natural selection is a key mechanism of • Gene frequency demonstrates the evolution. occurrence of an allele compared to other • It is the process in which individuals with alleles of the same gene in a population. certain heritable traits survive and reproduce • The Hardy-Weinberg Principle states allele at higher rates than other individuals without frequencies will remain the same through those traits. generations in a population: with • These traits allow them to adapt to various extremely large in size, that randomly environmental pressures, favoring their mates, and with the absence of mutations, survival and passing on of those suitable traits gene flow, and natural selection. to succeeding generations, thereby altering allele frequencies. The Natural Selection Experiment The Hardy Weinberg Experiment Purpose: Purpose: The natural selection lab aims to simulate the process To create a population and demonstrate how by which biological traits become more or less consistent Hardy-Weinberg's principle really is. prevalent in a population that has a changing To observe the survival rates in genotypes and environment. The natural selection lab will also attempt phenotypes of a population over a span of 6 to show the relationship between predators and prey. generations. Hypothesis: Hypothesis: We predict that the predator will naturally pick out the Since there are mutations, certain allele frequencies prey that is most contrasting in color to its will decrease dramatically due to the circumstances of environment. The species that blends in the most to its the mutation standards. For other cases of mutation, environment in color will thrive and reproduce to make new species will emerge. more generations of offspring. SPECIMENS & MATERIALS The Natural Selection Experiment The Hardy Weinberg Experiment Specimens: Specimens: • 40 small colored paper dots which • Red, white, and black beads which represented represent the prey alleles. • One clawed and double clawed Materials: predators that kill the species. • Red beads were used to represent red alleles. Materials: • Black beads were used to represent black alleles. • 1 plastic cup for the “dead” dots • White beads were used to represent white alleles. • 2 distinct fabric mats which • 6 cups to place different allele combination in. represented different environments for • 1 petri dish lid used to place allele combinations your dots in. • A computer to record results on excel 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 NATURAL SELECTION ANALYSIS
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. HARDY WEINBERG METHODS
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. GENE FREQUENCY RESULTS: Mutation Effects GENE FREQUENCY RESULTS: Population Percent 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. • 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. HOW ARE THEY RELATED?
• 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. WORKS CITED
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. Photo Credits 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