LAB: GOLDFISH EVOLUTION

BACKGROUND INFORMATION:

In this activity, students will represent predators, a fish eating shark, which selectively eats fish in a small population. There are two kinds of fish that you like to eat: gold fish (cheddar flavored) and yellow fish (original flavored). The gold fish are easy for you to see, so they are easy for you to catch and eat. Yellow fish travel more quickly and can evade capture more easily. Because of this, you eat only gold fish, unless there are no gold fish around, in which case you eat yellow fish. Fish are replaced with individuals randomly selected from an ocean (mixing bowl full of gold and yellow fish). Yellow fish are determined by the presence of a dominant allele (YY or Yy), and gold fish by a recessive allele (yy).

MATERIALS:

§  paper bowls

§  gold fish

§  yellow fish

DIRECTIONS:

1)  You will have plenty of time to eat the fish, so only do so when directed.

2)  When told, go to the “ocean” to collect a random population of 10 fish. DON’T LOOK WHEN YOU GRAB THE FISH!

3)  In DATA TABLE 1, for generation 1, record the number of gold and yellow fish in your population.

4)  Choose three gold fish from this generation and eat them. If you do not have three gold fish, fill the missing number by eating yellow fish, for a total of three fish eaten.

5)  Go back to the “ocean” to choose three more fish at random. Add the fish to your population.

6)  In DATA TABLE 1, for generation 2, record the number of gold and yellow fish.

7)  Repeat steps 4-6 until you have data for all five generations.

8)  Use DATA TABLE 1 to fill in the graph in DATA TABLE 2.

9)  Eat any remaining fish and clean up.

DATA:

DATA TABLE 1

Generation / Number of
Gold fish / Number of Yellow fish / Percent Gold fish: # of Gold fish divided by total number of fish (10) / Percent Yellow fish: # of Yellow fish divided by total number of fish (10)
1
2
3
4
5

Using the information from the DATA TABLE 1, 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 Yellow fish.

Percentage of fish per generation Graph

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0% / Y / G / Y / G / Y / G / Y / G / Y / G
Gen. 1 Gen. 2 Gen. 3 Gen. 4 Gen. 5

FILL IN THE GRAPH USING THE DATA FOR YELLOW FISH IN “Y”. PUT THE GOLD FISH IN “G”. BE SURE TO USE A DIFFERENT COLOR FOR EACH TYPE OF FISH. MAKE A LEGEND SO ANYONE CAN READ YOUR GRAPH, SHOWING WHICH COLOR MEANS WHAT FISH.

ANALYSIS QUESTIONS:

1)  How did the frequency of yellow fish change from generation 1 to generation 5?

2)  How did the frequency of gold fish change from generation 1 to generation 5?

3)  Which phenotype was reduced in this population over time? Explain why.

4)  What event is occurring if there is a change in frequencies? (this should be one of the conditions of the Hardy-Weinberg Principle)

5)  Explain what would happen if the yellow fish were easier to catch.

6)  What would happen if both fish were equally easy to catch?