9:43 PM lSprint LTE lab015exp004.doc Experiment 4: Natural Selection Natural sel

Question

9:43 PM lSprint LTE lab015exp004.doc Experiment 4: Natural Selection Natural selection is a selection pressure that affects phenotypes in one of three ways: 1. It will create an adaptive advantage. 2. It will create an adaptive disadvantage. 3. It will remain entirely neutral. A classic example to illustrate natural selection comes from England. Prior Industrial Revolution, the native moths were normally a light color, though darker versions of the same species existed. The lighter color blended with the light bark of the local trees, while the darker moths experienced a higher predation rate they were easier for birds to spot and fewer survived to reproduce. As England entered the Industrial Revolution, the burning of fossil fuels increased pollution. The trunks of the trees became coated with soot and their color darkened. The lighter moths became more conspicuous and the darker moths were better camouflaged. The proportion of light to dark moths changed Materials (1) 100 mL Beaker Red Beads Blue Beads Access to a Printer Procedure: 1. Print the two sheets of paper marked Blue Habitat (Figure 5) and Red Habitat (Figure 6). from your manual (found at the end of this procedure). 2. Place 50 red and 50 blue beads into a 100 mL beaker. 3. Mix them well and pour them onto the sheet marked Red Habitat. 4. Keep the beads that fall onto habitat that matches their color s. For each bead that you keep (and return to the beaker), add another bead of the same color to the beaker (discard the rest) 6. Repeat this three times. 7. Record the remaining colors. Blue Red Do you observe a selective advantage for the red or blue beads? Why? 8. Repeat the process using the Blue Habitat with the remaining beads. What beads remain now? Blue Red

Explanation / Answer

Postlab question1-when you perform the experiment you will see that each time when you are picking and keeping the beads of same colour as of the printed sheet,the number of same colour beads will increase in your beaker.For example,if you are using the printed paper with red habitat then surely the number of blue beads will decrease because the area of red habitat is greater and the probability of discarding blue beads is more.

Same thing happen when you are using blue habitat paper,but this time the number of blue beads will increase.

. Hence,the phenotype changes as you change the colour of the habitat.

Postlab question2- when you choose blue habitat,their is selective disadvantage for red beads and selective advantage for blue beads and vice-versa if you choose red habitat.

postlab question3-for each case,90%population will be selected so,

1-for 1000 ,900 will be blue if blue habitat is their and 100 will be red and vice versa for red habitat.

2-for 100,it will be a 90:10 ratio

3-for 10,it will be 9:1 ratio.

question 4-population size is 85 millions,and annual growth rate is 4.2% that means each year,there will be an increase of 4.2% in net population.Hence in first one year,it wil be

( 85*4.2)/100 +85=88.57.

in next one year it will be

(88.57*4.2)/100+88.57=92.28

in third year

92.28*4.2/100 +92.28=96.16

in fourth year

96.16*4.2/100 +96.16=100.2

and at five years

100.2*4.2/100+100.2=104.4 millions answer.

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