Science Assessment ~ Topics ~ Interdependence in Ecosystems ~ Item IE028005 ~ Student Performance

The diagram below shows the feeding relationships between populations of organisms L, M, N, O, and P. The arrows point from the organisms being eaten to the organisms that eat them.

Using only the relationships between the organisms shown in the diagram, what will happen to the number of Ns if most of the Os are killed and why?

The number of Ns will decrease because the number of individuals in all of the populations of organisms in this diagram will decrease when the number of Os decreases.
The number of Ns will decrease because there will be more Ms to eat the Ls, so fewer Ls will be available for the Ns to eat.
The number of Ns will stay the same because there will be no effect on the number of individuals in the populations of organisms below the Os in the diagram.
The number of Ns will stay the same because Os and Ns are not connected by an arrow in the diagram.

Distribution of responses
Answer Choice		Overall	Grades		Gender		Primary Language
		n = 2774	6–8 n = 1517	9–12 n = 1248	Male n = 1353	Female n = 1362	English n = 2475	Other n = 236
A.	The number of Ns will decrease because the number of individuals in all of the populations of organisms in this diagram will decrease when the number of Os decreases.	10%	11%	9%	10%	10%	10%	13%
B.	The number of Ns will decrease because there will be more Ms to eat the Ls, so fewer Ls will be available for the Ns to eat.	38%	35%	42%	39%	37%	38%	37%
C.	The number of Ns will stay the same because there will be no effect on the number of individuals in the populations of organisms below the Os in the diagram.	24%	25%	22%	23%	24%	24%	23%
D.	The number of Ns will stay the same because Os and Ns are not connected by an arrow in the diagram.	28%	29%	27%	27%	28%	28%	27%

Science Assessment

Item IE028005: Changes in a population may affect populations that are not directly connected by a feeding relationship even if they are several steps away and not within the same chain in a food web (no specific organisms identified).