Short Essay Practice ap exam Review Fall 2014 short essay #1

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Short Essay Practice AP Exam Review Fall 2014


Evolution is the change in allele frequencies in a population over time. This can occur through a variety of mechanisms, three of which are listed below:

Natural Selection

Genetic Drift

Define two of the three forces of evolution listed above, and provide a biological example.
You are studying a population of field mice that includes individuals with light and dark brown coats. Every six months you perform capture/recapture experiments to census the proportion of light and dark individuals. The following numbers indicate the percentage of dark-coat individuals caught in each successive census over the course of five years:

96, 94, 95, 91, 93, 95, 74, 73, 77, 76
Explain which of the three processes of evolution is most consistent with this data, and give a hypothetical explanation for the observed changes in phenotype frequencies in this mouse population.

Definition & Examples (2 Points Max)

  • (+ ½ ) Natural Selection is process by which certain alleles increase in frequency in a population because of the survival or reproduction benefit they give to those individuals who possess them.

  • (+ ½ ) Possible examples include sickle cell allele persists in populations where malaria is present. Other relevant biological examples are acceptable.

  • (+ ½ ) Genetic drift is the random change in allele frequency in a population over time.

  • (+ ½ ) Possible examples include brief discussion of either founder effect or bottleneck effect.

  • (+ ½ ) Mutation is a change in a DNA sequence.

  • (+ ½ ) Mentioning that mutation can create new alleles.

  • (+ ½ ) Mentioning that evolution by mutation can occur even if the new alleles are not acted on by natural selection.

  • (+ ½ ) Possible examples include: eye color gene mutates to a different color without any change in vision or behavior. Other relevant biological examples are acceptable.

Explanation of Data (2 Points Max)

  • (+ 1 ) Mentioning changes could not be the gradual process of natural selection because they occurred rapidly between the two censuses.

  • (+ 1 ) Indicating that the changes could be caused by genetic drift.

  • (+ 1 ) Indicating that the changes could be caused by some environmental event (flood, fire, etc.) that randomly killed many dark-coated mice.


Homeostasis, or the maintenance of a steady-state environment, is a characteristic of all living organisms.
For two of the following physiological parameters, describe how homeostasis is maintained.

Blood Glucose Levels

Body Temperature

Blood Calcium Levels
Discuss how disruptions to the mechanisms that control blood glucose levels can have deleterious effects on the homeostasis of a particular organism of your choice.

Blood Glucose Levels (1.5 Points Max)

  • (+ ½ ) Mentioning insulin/glucagon is released from pancreas.

  • (+ ½ ) Mentioning insulin stimulates uptake of glucose from the blood to the liver.

  • (+ ½ ) Mentioning insulin causes glucose to be stored as glycogen in the liver.

  • (+ ½ ) Mentioning insulin signals body cells to take up glucose for energy use.

  • (+ ½ ) Mentioning glucagon stimulates the liver to release glucose into the bloodstream.

Body Temperature (1.5 Points Max)

  • (+ ½ ) Describing how body insulation (hair, fat, feathers) reduces heat loss.

  • (+ ½ ) Mentioning that vasodilation results in increased blood flow and increased heat loss.

  • (+ ½ ) Mentioning that vasoconstriction results in decreased blood flow and decreased heat loss.

  • (+ ½ ) Mentioning that sweating results in evaporative cooling.

  • (+ ½ ) Mentioning that shivering generates energy.

Blood Calcium Levels (1.5 Points Max)

  • (+ ½ ) Mentioning that parathyroid hormone (PTH) is released by the parathyroid gland.

  • (+ ½ ) Mentioning that PTH increases the amount of calcium in circulation.

  • (+ ½ ) Mentioning that PTH causes release of calcium from bones.

  • (+ ½ ) Mentioning that PTH leads to increased absorption of calcium by the intestines and kidneys.

  • (+ ½ ) Mentioning that calcitonin is released by the thyroid gland.

  • (+ ½ ) Mentioning that calcitonin decreases the amount of calcium in circulation.

  • (+ ½ ) Mentioning that calcitonin promotes reabsorption of calcium by the bones.

  • (+ ½ ) Mentioning that calcitonin leads to decreased absorption of calcium by the kidneys and intestines.

Disruption to Homeostasis (1 Point Max)

  • (+ 1) Appropriate discussion of diabetes mellitus.


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