Science Assessment ~ Topics ~ Interdependence in Ecosystems ~ Item IE016008 ~ Student Performance

The diagram below shows the feeding relationships between populations of plants and animals in an area. The arrows point from the organisms being eaten to the organisms that eat them.

A new species that eats only mice becomes part of this food web, greatly reducing the number of mice in this area. Using only the relationships between the plants and animals shown in the diagram, what effect would the new species have on the caterpillar population if the number of foxes stays the same?

The number of caterpillars would increase.
The number of caterpillars would decrease.
The number of caterpillars would stay the same.
There is not enough information to tell what would happen to the number of caterpillars.

Distribution of responses
Answer Choice		Overall	Grades		Gender		Primary Language
		n = 1371	6–8 n = 760	9–12 n = 608	Male n = 685	Female n = 661	English n = 1278	Other n = 68
A.	The number of caterpillars would increase.	23%	20%	27%	24%	22%	24%	15%
B.	The number of caterpillars would decrease.	20%	21%	19%	19%	21%	19%	34%
C.	The number of caterpillars would stay the same.	37%	38%	37%	38%	37%	38%	35%
D.	There is not enough information to tell what would happen to the number of caterpillars.	19%	21%	16%	19%	19%	19%	16%

Science Assessment

Item IE016008: Changes in a population (introduction of a new species) may affect populations that are not directly connected by a feeding relationship (caterpillars) even if they are several steps away in a food web.