Question

the graph below shows the number of a certain species of deer in a population from 1978 through 2001.

from 1984 through 1986, the area where the deer lived received more rain than normal, causing more vegetation to grow. between 1993 and 2000, the area where the deer lived experienced a drought, which caused less vegetation to grow.

based on the information given, which statement best describes the deer population in this area?

a. it increases during times of drought.
b. it depends on the amount of available vegetation.
c. it decreases during years with excess rain.
d. it remains stable when the amount of vegetation changes.

Explanation:

Analyze the given environmental conditions

The prompt describes two distinct periods:

1. From 1984 through 1986, increased rainfall led to more vegetation growth.
2. Between 1993 and 2000, a drought led to less vegetation growth.

Correlate conditions with population data

Using the Human Impact on Ecosystems knowledge point

• From 1984 to 1986, the graph shows the deer population increasing from around 150,000 to over 200,000 as vegetation increased.
• From 1993 to 2000, the graph shows the deer population declining and remaining lower (around 110,000 to 130,000) during the drought period when vegetation was scarce.

Evaluate the given options

• A: Incorrect. The population decreased during the 1993–2000 drought.
• B: Correct. The population rises when vegetation increases and falls when vegetation decreases, showing a direct dependence.
• C: Incorrect. The population increased during the wet years of 1984–1986.
• D: Incorrect. The population fluctuates significantly as vegetation levels change.

Answer:

• (A) It increases during times of drought.
• (B) It depends on the amount of available vegetation. (Correct answer)
• (C) It decreases during years with excess rain.
• (D) It remains stable when the amount of vegetation changes.