Question

what most likely happened to the prairie ecosystem between 2004 and 2006?
a. a predator of species x was introduced to the prairie
b. the prairie species increased in number
c. the prairie ecosystem experienced a drought
d. competition decreased in the prairie ecosystem
(chart: title “populations: prairie species”, x - axis “year” (2000, 2002, 2004, 2006, 2008, 2010), y - axis “population” (0, 100, 200, 300, 400, 500, 600, 700, 800). three lines: species z (blue), species y (green), species x (orange). legend: species z (blue), species y (green), species x (orange))

Explanation:

To determine what happened to the prairie ecosystem between 2004 and 2006, we analyze the population trends of the three species (X, Y, Z) from the graph:

• Option A: If a predator of species X was introduced, we would expect species X’s population to decrease (since predators reduce prey populations). However, between 2004 and 2006, species X’s population increases (from a low in 2004 to a peak in 2006). Thus, A is incorrect.
• Option B: The “prairie species” (likely referring to one or more of X, Y, Z) shows a population increase between 2004 and 2006. For example, species X and Z (and possibly Y) have rising populations during this period. This aligns with the trend.
• Option C: A drought would typically reduce resource availability, causing populations to decline (due to limited food/water). However, populations increase between 2004–2006, so C is inconsistent.
• Option D: If competition decreased, populations would likely increase (less resource struggle). But the question asks what “most likely” happened—while competition decrease is possible, the direct observation of population increase (Option B) is a more straightforward interpretation of the trend.

Answer:

A. A predator of species X was introduced to the prairie (Incorrect, as species X population increases).
B. The prairie species increased in number (Correct, as populations of X, Y, Z rise between 2004–2006).
C. The prairie ecosystem experienced a drought (Incorrect, as drought would reduce populations, not increase them).
D. Competition decreased in the prairie ecosystem (Less direct than B, as population increase is observed, not just inferred from competition).

Final Answer: B. The prairie species increased in number