Support Ecosystem Cycling With Evidence Practice Test

Claim: Matter (atoms) cycles through living and nonliving parts of an ecosystem.

Evidence:

1. A student feeds a rabbit lettuce grown in air containing a harmless carbon “label,” and later detects that labeled carbon in the rabbit’s body tissues.

2. Later, a hawk eats the rabbit, and labeled carbon is detected in the hawk’s tissues.

3. A sensor shows CO$_2$ increases in a jar containing only a snail over time.

4. Predators usually have sharper teeth than herbivores.

Which evidence best demonstrates carbon transfer through a food web (matter cycling between organisms)?

Claim: Energy flows one-way through ecosystems and does not cycle.

Evidence collected by a class:

1. When the Sun is blocked from a patch of grass for 2 weeks, the grass stops growing and many plants die.

2. Biomass measurements in a field show about 9,000 kg of plants, 900 kg of herbivores, and 90 kg of carnivores.

3. A temperature probe shows a compost pile warms up as decomposers break down leaves.

4. Earthworms are more common in moist soil than dry soil.

Which evidence is most relevant to supporting the claim about energy flow (not cycling)?