# Name Date Natural Selection Goldfish Crackers lab Introduction: Evolution is the change over time in the genetic makeup of a population. Natural selection is important in understanding this process, which is the basic idea that a population can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals. Natural selection consists of four main steps: 1) Every species contains genetic variation, 2) Because organisms produce more offspring than can survive, living things face a constant struggle for existence, 3) Only some individuals survive and reproduce, and 4) Because each generation consists of the offspring of individuals that successfully reproduced, natural selection results in genetic change. These four steps of natural selection drive evolution. Understanding natural selection can be confusing and difficult. Although you have just learned that evolution works on populations over time and NOT on individuals, people often think that animals consciously adapt to their environments that the peppered moth can change its color, the giraffe can permanently stretch its neck, the polar bear can turn itself white all so that they can better survive in their environments. In this lab you will use goldfish crackers to help further your understanding of natural selection and evolution. Background: Facts about the fish 1. Although they look different, these fish all belong to the SAME species. 2. These little fish are the natural prey of the terrible carnivorous predators YOU! 3. Fish come in two phenotypes brown and gold. These two phenotypes are controlled by a gene with two different alleles: a. Brown: these fish taste bitter and are sneaky and hard to catch b. Gold: these fish taste yummy and are easy to catch 4. You, the terrible carnivorous predators, much prefer to eat the yummy gold fish; you eat ONLY gold fish unless none are available, in which case you resort to eating brown ones in order to stay alive. 5. New fish are born every year; the birth rate equals the death rate.
Your Data Table Gold Brown Total 1 2 3 4 5 Lab Group Data Table Gold Brown Total 1 2 3 4 5
Analysis: Complete a bar graph of the results of your lab. Each generation should have TWO different colored bars one for the number of brown fish and one for the number of gold fish. 9 8 Key Brown Fish Gold Fish Number of Fish # of animals 7 6 5 4 3 2 1 1 2 3 44 55 Complete a bar graph of the results of your lab group. Each generation should have TWO different colored bars one for the number of brown fish and one for the number of gold fish. Number of Fish # of of animals # of animals 4 3 4 2 3 2 Key Brown Fish Gold Fish 1 2 3 4 5 2 3 4 5 1 2 3 4 5
Copy the results of the class into the table below. Class Data Table Gold Brown Total 1 2 3 4 5 Complete a bar graph of the results of the class. Each generation should have TWO different colored bars one for the number of brown fish and one for the number of gold fish. Key Brown Fish Gold Fish # of of animals Number of Fish 4 3 2 1 2 3 4 5 2 3 4 5
Analyze: 1. According to the bar graphs, what happens to the allele frequencies (number of the brown and gold alleles) from generation 1 to generation 5? 2. Explain which phenotype (color) is NOT favorable to the animals and why. 3. What process is occurring when there is a change in the genetic makeup of a population over a long period of time? 4. If you were to repeat this same experiment but with a blindfold so that you could not see which color fish cracker you were eating, would you expect a certain color to become more common over generations? HINT: If the predators of the fish crackers could only find fish by touch, would it be better for the fish cracker (prey) to be one color or the other? 5. What do you think would have happened in this experiment if you continued for more generations? 6. What did you learn from this experiment?
Natural Selection Goldfish Crackers lab Teacher s Notes 1.) Need two types of goldfish crackers. Brown and Gold. 2.) Split the class into groups. 3.) R ead first page together as a whole class. Discuss. 4.) For 1 Pass out goldfish crackers randomly to each student. They then log in their data table number of each color. Then the group fills in the number of each color in the group data table. Students eat 4 goldfish; unless there are none then they eat brown. (no more than 4) 5.) For 2 Pass out 4 goldfish crackers randomly to each student. They then log in their data table number of each color. Then the group fills in the number of each color in the group data table. Students eat 4 goldfish; unless there are none then they eat brown. (no more than 4) 6.) For 3 Pass out 4 goldfish crackers randomly to each student. They then log in their data table number of each color. Then the group fills in the number of each color in the group data table. Students eat 4 goldfish; unless there are none then they eat brown. (no more than 4) 7.) For 4 Pass out 4 goldfish crackers randomly to each student. They then log in their data table number of each color. Then the group fills in the number of each color in the group data table. Students eat 4 goldfish; unless there are none then they eat brown. (no more than 4) 8.) For 5 Pass out 4 goldfish crackers randomly to each student. They then log in their data table number of each color. 9.) Students now work with their group or individually to graph the results and analyze the results.