Part I : By exploring a hypothetical world of differently colored flowers, we wi

Question

Part I: By exploring a hypothetical world of differently colored flowers, we will understand how several conditions are necessary in order for evolution by natural selection to occur.

A. Your greenhouse contains diploid flowers. Some are blue, some are red, and some are yellow. Each flower has two of the same allele for gene color: blue flowers are bb at the color locus, red flowers are rr, and yellow flowers are yy. They exclusively self-pollinate to reproduce.

What color are offspring of the blue plant?              The red?         The yellow?

If your little sister’s favorite color was blue, and she had a tendency to grab these flowers out of the greenhouse and bring them inside, how would you expect your flower population to change?    What process would be occurring?

B. Imagine now that your flowers are not colored differently because of any difference in genes; they are all naturally white (ww) at the color locus, and still only self-pollinate. This time, their color derives from the food coloring you’ve added to their water.

Your sister returns to terrorize the blue flowers. What effect does her preference have now on the frequency various alleles in the population?

Which condition is not met for evolution by selection?

What kind of characteristic is flower color due to food coloring?

C. In your group of four, brainstorm a way you can alter the greenhouse scenario slightly. Make it where a different condition not involving natural selection occurs. Describe.   How does your situation affect allele frequencies?

Part IIA: To understand why genetic variation must exist in a population before evolution by natural selection can occur, let’s consider how man’s best friend got his title.

Genetic markers tell us that all dog breeds share a common ancestor with modern wolves. Consider the IGF1 (insulin-like growth factor 1) gene. Miniature breeds have an adenine at position 44228468 in the dog genome; wolves have a guanine. Assuming you start with a population of the common ancestor of modern wolves, answer the following questions as a group:

How would you produce Chihuahuas?

Would you be able to produce Chihuahuas if the entire population was genetically homogenous?

Do you think Chihuahuas could have evolved with no human influence? Why or why not?

Part IIB: Mice help us understand a little more about evolution by natural selection. Oldfield deer mice (beach mice) in the southeastern United States are protected from would-be predators by their fur blending into their surroundings. There is a subspecies that lives on Santa Rosa Island in Florida which is covered in light sand dunes. What fur color would you expect on Peromyscus polionotus? There is a single nucleotide difference in the melanocortin-1 receptor that seems to be responsible for this difference in color.

1. Assume beach mice colonized the island when sea levels were lower (before it was an island!), and that all of the mice colonizing the island had brown fur.

How did the population of brown mice on Santa Rosa Island become white?

2. Gerald, the smallest mouse on the island, loves the color red. One day, a nearby volcano spews red ash into onto all the mice and turns the sand red. Gerald is ecstatic! Most mice go for a swim to wash off the red dust, but Gerald wears it proudly. There is very little rain on the island, so we can assume the ash permanently turns the sand red. Are Gerald’s offspring more likely to survive than his sister’s?   Explain.

3. Geraldina, Gerald’s sister, wants her children to be red so they can better survive on the now-red island. What can she do to increase her children and grandchildren’s survival?

4. If Geraldina’s favorite color were purple, would her children be more, equally, or less likely to come out purple as they are to come out red?

Explanation / Answer

1. A The exclusive self pollination will result in blue color to produce blue and red to produce red and yellow to produce yellow.

If the flower population changes it will be due to cross pollination which might have occurred between two different colors.

B. Since the color is artificially added her preference will be only white even though if she pick blue color.

Change in the gene is not met for natural selection and evolution to occur.

The flower color is still white it has just adsorbed the food color on its surface.

Cross pollinating the flowers will alter the frequency of flower color in the green house. Which ever color is dominant will be in higher numbers in the F1 generation.

Part II

Chihuahuas cannot be produced because the gene for Insulin will be either with A or with G, it cannot be both.

If the entire population is homozygous Chihuahuas cannot be produced, since there is no chance of recombination to happen.

Chihuahuas could have happened without human influence in case of cross breeding between dogs and wolfs.

Part II B

The fur color could be the color of the sand in which they live because out of evolution they might have acquired the gene to change the fur color according to environment.

The brown color mice in the population would have had heterozygous gene for brown color hence in next generation due to cross between two heterozygous brown mice they had homozygous gene for white and hence the Island has the white mice.

If Geraldina had undergone mutation in its gene for survival due to its action then it its offspring will survive more than its sister or else they will not survive.

To increase the children and grandchildren survival they can think of cross breeding with better survivors of the island.

No they cannot change the color according to their wish. It can be possible only through genetic inheritance.

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