Natural Selection With Goldfish PDF

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NATURAL SELECTION WITH GOLDFISH Introduction: Evolution is a change over time, of the allele frequency of a population of organisms. In this lab, we will be using goldfish crackers to aid us in understanding natural selection and evolution. The population of fish has two traits from the characteristic of color. One trait will be designated as adaptive to the environment, and the other will be considered nonadaptive. Background story: You are a piscivore, a fish that eats other fish. The species you like to eat comes in two forms: light-colored and dark-colored. You eat the fish that are easiest to find in their surroundings. Since the fish you eat swim near the top of the pond and you hunt from below, the dark-colored fish are easier to see from below and eaten more often. Since the dark colored-trait is recessive, the dark-colored fish are homozygous recessive. Because the light-colored trait is dominant, the light-colored fish are either homozygous or heterozygous dominant.

Materials: On campus, we use original, cheddar, and pretzel goldfish crackers to represent the different types of fish. You may use any edible snack that comes in two light colors and one dark color. (You could also make paper fish.) A video demonstrating how to complete this lab, including how to do the calculations is available. It is the other file in the assignment. Procedure: 1. You will observe natural selection according to the above story. You will follow the change in the population of fish over five generations. On the Data and Observation page, predict the outcome of predation on the population over the five generations. 2. Create a source population of approximately equal numbers of original (homozygous dominant), cheddar (heterozygous), and pretzel (homozygous recessive) fish. Obtain a population of 32 fish randomly selected from your source population to be the first generation. Record the number of homozygous dominant fish (original), heterozygous fish (cheddar), and homozygous recessive (pretzel) fish in Table 1 on the Data and Observation sheet. 3. Calculate the allele frequency as if the population was in Hardy-Weinberg Equilibrium and enter the data in 3 on the Data and Observation sheet. The general formulas for calculating Hardy-Weinberg Equilibrium are p + q = 1 and p2 + 2pq + q2 = 1 Where p = the frequency of the dominant (light) allele. q = the frequency of the recessive (dark) allele. p2 = the frequency of homozygous dominant individuals 2pq = the frequency of heterozygous individuals.

q2 = the frequency of homozygous recessive individuals. To find the frequency of p you need to add up all the p alleles (2 from each AA fish and 1 from each Aa fish) and divide by the total number of alleles (64, two in each of the 32 fish). Say your original population is 14 AA (original), 9 Aa (cheddar), 9 aa (pretzel). This population has 14 + 14 + 9 A alleles. Divided by 64 total alleles. This gives p = 0.578. This population has 9 + 9 + 9 a alleles. Divided by 64 total alleles. This gives q = 0.482 3. Eat four dark-colored fish. (If you do not have enough dark-colored fish, then randomly pick some light-colored fish to eat.) Enter the number of fish of each color after predation in Table 2 on the Data and Observation page. 4. Obtain a new generation. The new generation will also have 32 fish. The first step to finding the new generation is to calculate p and q after predation and enter these numbers in Table 2. To find the frequency of p you need to add up all the p alleles (2 from each AA fish and 1 from each Aa fish) and divide by the total number of alleles which is now 56. Continuing the example from above, you now have 14 AA fish, 9 Aa fish, and 5 aa fish. p = (14 + 14 + 9)/56 = 0.661 q = (9 + 5 + 5)/56 = 0.339 New generation numbers will be: AA = p2 x 32 = 0.661 x 0.661 x 32 = 14 Aa = 2pq x 32 = 2 x 0.661 x 0.339 x 32 = 14 aa = q2 x 16 = 0.339 x 0.339 x 32 = 4 Enter the number of each type of fish that will be in the next generation in Table 1. 5.

Repeat steps 3 and 4 three more times.

6. Calculate the allele frequencies of generation 5 and enter them in 5 on the Data and Observation Sheet. 7. On the Data and Observation page, write a paragraph describing what happened to each type of fish and explain why. Contrast the conclusions derived with your original predictions. 8.

Answer the remaining questions.

9.

Add a picture of your fish in their pond and a selfie of you being a predator.

Data and Observation - Natural Selection & Evolution Name Frankline Olum 1. Predict the outcome for the population of orange fish and for the population of brown fish over three generations.

2.

Table 1: Number of fish of each color in each generation before predation. Homozygous Heterozygous Homozygous Generation dominant (cheddar) Aa recessive (original) AA (pretzel) aa 14 7 1 11 9 12 11 2 7

3 4

5 13

5 3.

32 32

11

14

32

17

10

32

9

10

32

Starting allele frequencies. p=_0.625_

4.

Total Fish

q=_0.281

Table 2. Allele frequencies after predation. Generation Homozygous Heterozygous dominant (cheddar) Aa (original) AA 14 1 11 9 12 2 3 4

7 5

Homozygous recessive (pretzel) aa 13

0.4375

0.141

7

0.484

0.323

11

10

0.516

0.467

17

6

0.625

0.281

p

q

5. Ending allele frequencies. p=_0.625__

q=0.281____

6. What happened to each color of fish and why? Did your original predictions agree with the outcome? If not, how did they differ? Cheddar and original maintain their population, however it is important to note that the red fish decreased due to predation.

4. Which trait is not favorable? Why? Aa seems to be recessive and its population was significantly reduced by predators, its trait worked in favor of the predator and against it. 5. Which phenotype is reduced in the population? aa- homozygous recessive. 6.

Did this phenotype disappear from the population? Why or why not?

It did not disappear completely at the end of experiment, but I believe with more time and space, or extended period, it will disappear completely. 7. Explain why the recessive allele (a) does not disappear from the population. Every generation will carry that a allele even if it seems not to be dominant, there will always be an offspring as the genes continues to evolve. And even after there are no more recessive genes, AA and Aa ill still produce an offspring of a in their lifetime. 8.

Did evolution occur? Explain. Yes, it did occur, it was however quick and led to evolving.

9. Explain what would happen if the selection pressure changed and the dark-colored fish were less likely to be eaten. This would lead the recessive gene to be more prominent. 10. What would happen if it were better to be heterozygous (Aa)? Will there be homozygous fish? Explain. Yes, there would have been an homozygous fish in such a scenario if the variables is manipulated as suggested, there will be 0.5 probability of recessive gene.

11. Paste a picture of your fish in the pond. My discussion here is based on the lab video posted on canvas for the purpose of this lab experiment. This is a respond to question 11 and 12. 12. Paste a selfie of you being a predator....