Answer Key

The picture below shows the process of ecological succession after a big fire, which occurs after an ecosystem experiences a disturbance (for example, a big fire).

Target level: Ecosystems 1a

1. Which is the best summary of succession, as shown in the figure above?

A. In an ecosystem, there are lots of different types of plants

B. As time goes on, the ecosystem changes and develops

C. Trees can live in the same ecosystem as grasses

D. The hardwood forest stage is the first stage of succession

Target level: Ecosystems 1a

2. Which of the following stages includes NO living organisms in the ecosystem?

A. Fire stage

B. Bare field stage

C. Hardwood forest stage

D. None of the stages include living organisms

E. All of the stages include living organisms

Target level: Ecosystems 1c

3. Which of the following descriptions best defines the relationship between grasses and pine trees in the Pine Forest stage?

A. One benefits while the other is harmed.

B. They both benefit from each other.

C. They compete for resources.

D. One benefits while the other is unaffected.

Scientists were interested in studying what happens to an area after a fire. The scientists conduct experiments. Here are some results from experiments.

Experiment 1: Scientists added nutrients to bare fields early in succession. Then, scientists observed that big trees started to grow in those ecosystems.

Experiment 2: Scientists planted grass seeds in a very shady hardwood forest. Then, scientists observed that grass did not grow at all below the big tall trees.

Target level: Argumentation 2b

4. Choose the best reason why grasses are the first things to grow on a bare field after a fire. Use the scientists’ evidence above.

A. Grasses grow first because light is not blocked by larger trees.

B. Grasses grow first because they require more nutrients to grow than big trees.

C. Grasses grow first because the old grasses weren’t completely destroyed by the fire.

D. Grasses grow first because grass grows more quickly than other plants in the ecosystem.

Justin says:

I think grasses are the first thing to grow because there is plenty of light available early in succession.

The experiment showed that grass couldn’t grow beneath big tall trees.

Since grass cannot grow under big trees, they are more likely to grow early in succession when there aren’t any big trees yet.

Target level: Argumentation 1d

5. What evidence would add support to Justin’s argument?

Scientists plant grass [[A1]in a bare field that is shaded by nearby buildings | [A2]in a very shady hardwood forest and add lots of nutrients], and [[B1]grows | [B2]does not grow].

Kai says:

I think grasses are the first things to grow because bigger plants need more nutrients than are available early in succession.

The experiment showed that adding nutrients to an early succession ecosystem made big trees grow.

This shows that nutrients control what can grow in an ecosystem. Since grasses don’t need as many nutrients, they can grow early in succession.

Target level: Argumentation 1d

9. Nestor says, “If the trees were cut down, the caterpillar population would stay the same because the caterpillars would eat something else instead of trees.” What is the best piece of evidence to support Nestor’s claim?

A. Caterpillars do not eat grass.

B. Caterpillars would be harder for robins to see in the grass.

C. Caterpillars eat grass when trees are not available.

D. Caterpillars are not eaten by mice.

Target level: Argumentation 1d

6. What evidence would add support to Kai’s argument?

Scientists plant grass [[A1]in a bare field that is shaded by nearby buildings | [A2]in a very shady hardwood forest and add lots of nutrients], and [[B1]grows | [B2]does not grow].

Target level: Argumentation 1d

7. Mice use plants as shelter to protect themselves from predators like owls. Mice can protect themselves from the high temperatures of fires by hiding in holes underground.

Given this information about how mice protect themselves, what evidence would explain why the mouse population would increase from the grass stage to the shrub stage?

A. Mice store their food underground and it is not destroyed during the fire.

B. Owls are not killed during the fire because they can escape by flying away from the area.

C. Owls live in hardwood trees, not holes in the ground.

D. Mice can hide in shrubs but not grass.