Lab 4-Natural Selection

Lab 4: Natural Selection: Worksheet Imagine your anthropology professor studies a primate that eats insects. The primate’s favorite food is a type of ant. She asks if you are interested in helping her analyze the data. You, of course, say yes! Your professor tells you more about the ants, the primates, and the habitat. Ant color is determined by one gene. There are two alleles for this color gene: the brown allele and the green allele. The primates eat the ants year-round, but your professor knows that the way they eat the ants differs between the rainy season and the dry season. During the rainy season, when there are green leaves on the trees, the primates eat the ants off the green leaves. During the dry season, when the trees lose their leaves, the primates eat the ants off the brown tree branches. Your professor has collected data to investigate if the primate acts as a selective pressure on the ant population, possibly changing the allele frequencies over time. Step One: Hypothesis You need to start with a hypothesis. The following questions will help you to frame your hypothesis. 1. How do the ants vary? they vary because they are determined by one gene they also very because of the food different ants eat 0. What is the selective pressure? the selective pressures in this situation would be the seasons as the change of seasons impacts what food and what is more accessible for the primates to eat 0. What is the dependent variable? the color of the ant( green or brown) based in what food they will eat 0. What is the independent variable? the type of ants the primate will eat? 0. Now, write a hypothesis for the following question: During the rainy season, which allele frequency (brown or green) will increase over time? ha during the raining seasons, the green allele frequency will increase because the food source the primate will be the green ants that at this time will be found on leaves. Step Two: The Rainy Season Data Your professor is happy with the hypothesis that you have written. She gives you the data that she collected on the ant population. Because of the fast rate of reproduction among ants, she

was able to collect a number of ants of each color over four generations. The data are in the table below. Table 1: Number of ants collected during the rainy season Generation of ants Brown ants Green ants Total ants Generation 1 100 100 200 Generation 2 90 120 210 Generation 3 75 150 225 Generation 4 65 170 235 Calculate the frequency of the brown allele and of the green allele in each of the generations. We assume that each ant is a homozygote. Round to the nearest thousandths. To calculate allele frequencies within each generation: 1. Calculate the number of brown alleles by multiplying the number of brown ants (from Table 1) by 2. Calculate the number of green alleles by multiplying the number of green ants (from Table 1) by 2. Write in Table 2. 2. Calculate the total number of alleles by adding the number of brown alleles and the number of green alleles. Write in Table 2. 3. Calculate the brown allele frequency by dividing the number of brown alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 2. 4. Calculate the green allele frequency by dividing the number of green alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 2. 5. Check your math by calculating the total allele frequency. Write in Table 2. Table 2: Allele frequencies in the rainy season Generation 1 Generation 2 Generation 3 Generation 4 brown green brown green brown green brown green Number of alleles 200 200 180 240 150 300 130 340 Total # alleles in generation (brown + green) 400 420 450 470 Allele frequency .5 .5 .429 .r521 .333 .667 .277 .723 Total allele frequency in 1 1 1 1

Calculate the frequency of the brown allele and of the green allele in each of the generations. We assume that each ant is a homozygote. Round to the nearest thousandths. To calculate allele frequencies: Within each generation, 1. Calculate the number of brown alleles by multiplying the number of brown ants (from Table 3) by 2. Calculate the number of green alleles by multiplying the number of green ants (from Table 3) by 2. Write in Table 4. 2. Calculate the total number of alleles by adding the number of brown alleles and the number of green alleles. Write in Table 4. 3. Calculate the brown allele frequency by dividing the number of brown alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 4. 4. Calculate the green allele frequency by dividing the number of green alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 4. 5. Check your math by calculating the total allele frequency. Write in Table 4. Table 4: Allele frequencies in the dry season Generation 1 Generation 2 Generation 3 Generation 4 brown green brown green brown green brown green Number of alleles 130 340 180 300 250 240 300 200 Total # alleles in generation (brown + green) 470 480 490 500 Allele frequency .277 .723 .375 .625 .510 .490 .600 .400 Total allele frequency in generation (brown + green) 1 1 1 1 Answer the following questions based on the above (dry season) data. 1. What was the general trend (comparing Generation 1 to Generation 4) in allele frequency that you observed for the brown allele over the four generations? Did the brown allele increase or decrease in allele frequency? Write the actual numbers for each generation here in support of your answer. (G1=130, G2=180,G3=250,G4=300) The brown alleles frequency from the first generation increased during the dry season 0. What was the general trend (comparing Generation 1 to Generation 4) in allele frequency you observed for the green allele over the four generations? Did the green allele increase or decrease in allele frequency? Write the actual numbers for each generation here in support of your answer.

The green alleles decreased starting from Generation 1 with 340, generation 2 with 300 generation 3 with 240 and finally Generation 4 with 200 0. Was your hypothesis at the beginning of Step Three supported? Explain why or why not. yes I do think the Hypothesis was correct as the primates of the brown allele frequency did increase during the dry season Step Four: Wrap Up The following questions refer to the whole lab. 1. How did the ants in this population vary? In other words, what is the main difference between them? 0. Why is variation necessary for natural selection to work? Variation is necessary for natural selection to work because it is an integral factor in increasing or decreasing an allele's frequency. If there is no variation, then there would be a decline of either one of the ants' populations, with one type of ant having an increase in population because they are not the primate's main food source and the other type's population going on a steep decline because it is the primate's only source of food, making natural selection not possible 0. Explain selective pressure. What was the selective pressure in this simulation? In this simulation, The Selective pressures were the seasonal changes that forced the primates to change their diet and adapt to the new season to find it like new food and different nutrients consumed with the different types of ants 0. What is the definition of allele frequency? How are allele frequencies related to the idea of evolution? Well because Generations can extinct or thrive pending on where they live and how they adapt the frequencies of the ants is what is related to evolution. 0. Because some individuals in a population are more fit than others, the ultimate result of natural selection is a population that is better adapted to its environment. 0. What trait was adaptive in the rainy season? of ants Being able to live off the leaves and being the leaves b. What trait was adaptive in the dry season?