Evolution of Goldfish Lab

Evolution of Goldfish Experimental Question: If individuals of a population vary in their ability to avoid consumption, how would the population evolve under the pressure of a predator? Hypothesis: In order to consider the mechanisms that cause a population to evolve, it is helpful to examine, for comparison, the genetic structure of a non-living population. Such a gene pool is described by the Hardy- Weinberg principle. It states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change. The sexual shuffling of alleles due to meiosis and random fertilization has no effect on the overall genetic structure of a population. The situation when allele frequencies remain constant is called genetic equilibrium, and the population will not evolve. You can quantify this principle using the Hardy-Weinberg equation, which shows that the genetic structure of a non-evolving population will remain constant over generations. Genotype proportions can be calculated from allele frequency and should remain constant. If p is the frequency of dominant allele for a trait and q is the frequency of recessive allele for the same trait, then genotype proportions are given by p2pqq² 1. Genotype proportions must add up to 1. The Hardy-Weinberg principle requires five conditions for genetic equilibrium to be maintained in a population: 1. Very large population size (in small populations, genetic drift, which is chance fluctuation in the gene pool, can change the allele frequencies) 2. Isolation from other populations (there can be no movement into or out of the population) 3. No net mutations (by changing one allele into another, mutations alter the gene pool) 4. Random mating (if individuals select mates having certain heritable traits, then random mixing of gametes does not occur) 5. No natural selection (differential survival and differential reproductive success alters the gene pool by favaring some alleles at the expense of others) These five conditions required to maintain Hardy-Weinberg provide a framework for understanding the process of evolution. There are five potential agents for evolution: genetic drift, gene flow, mutation, nonrandom mating and natural selection, In this activity, students will represent predators, a shark that eats goldfish, which selectively preys upon (eats) goldfish in a small population. There are two kinds of fish that you like to eat: gold fish (cheese flavored) and brown fish (pretzel flavored). The goldfish are easy for you to see, so they are easy for you to catch and eat. Brown fish travel more quickly and can evade capture more easily. Because of this, you eat only goldfish, unless there are no goldfish around, in which case you eat brown fish. Fish are replaced with individuals randomly selected from an ocean (mixing bowl full of crackers). Brown fish are determined by the presence of a dominant allele (B), and gold fish by a recessive allele (b). Materials Several large bowls paper plates graph paper calculator Several packages of cheese flavored goldfish crackers Several packages of pretzel flavored goldfish crackers Procedures 1. Empty one bag of each type of crackers (cheese and pretzel) into a large bowl and mix. 2. Send one student from your group to collect a random population of 20 fish (crackers) from the large bowls "ocean", place them on a paper plate and take them back to your lab group. It is important that the population be random, so don't look while you are grabbing the fish. 3. In data table 1, for generation 1, record the number of gold and brown fish in the random population. You can calculate your frequencies later. 4. Brown fish (pretzel flavored) express the dominant allele (B) and gold fish (cheese flavored) express the recessive allele (b). 5. Choose three gold fish from the first generation and eat them. If you do not have three gold fish. fill in the missing number by eating brown fish, for a total of three fish eaten. 6. Send one student choose, at random, three fish from the ocean" and add them to your population. Again, be careful to choose your fish randomly, DON'T LOOK! 7. In data table 1, for generation 2, record the number of gold and brown fish.. 8. Repeat steps 5 to 7 until you have data for all five generations 9. In table 2, calculate the allele and genotype frequencies for each generation using the data in data table 1. DATA TABLE 1 Generation Number of Gold fish Number of Brown fish Percent Gold fish: # of Gold fish divided by total number of fish Percent Brown fish: # of Brown fish divided by total number of fish 1 2 3 4 5 Using the information from the data table above, plot your data on a graph below to show how your population changed over time. For each generation, plot two separate points: use one color to represent the percent population of gold fish, use another color to plot the percent population of brown fish. Percentage of fish per generation Graph 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Gen. 1 Gen. 2 Gen. 3 Gen. 4 Gen, 5