Answer Key

The purple loosestrife, a wetland plant, was imported to North America from Europe. The purple loosestrife has spread to many wetland ecosystems in the United States

Observations by scientists:

Observation #1: The purple loosestrife is a plant that grows twice as fast as the winged loosestrife (a native plant in these wetlands)

Observation #2: The winged loosestrife is a plant that has 10 different species of insect that eats its leaves. The purple loosestrife has 3 different species of insects and 2 species of birds that eats its leaves.

Observation #3: Snakes have been observed underneath both the winged loosestrife and purple loosestrife. The snakes eat bird eggs.

Target level: Ecosystems 1a

1. Which is an example of an herbivore in this ecosystem?

A. winged loosestrife

B. purple loosestrife

C. insect

D. snake

Target level: Ecosystems 2b

2. Which of the following can limit the growth of a population of organisms?

A. Both the number of predators and the availability of resources can limit the growth of a population of organisms.

B. The number of predators can limit the growth of a population of organisms, but the availability of resources cannot.

C. The availability of resources can limit the growth of a population of organisms, but the number of predators cannot.

D. Neither the number or predators nor the availability of resources can limit the growth of a population of organisms.

Target level: Ecosystems 1c

3. Which of the following statements is TRUE about competition between organisms with the same needs when resources are limited?

A. Plants and animals compete for resources.

B. Only animals compete for resources.

C. Only plants compete for resources.

D. Neither plants nor animals compete for resources.

Students wonder why the purple loosestrife is such a successful invader in the ecosystem.

Sophie says: I think the purple loosestrife is a successful invader because there are very few herbivores that eat it.

Target level: Argumentation 1d

4. What evidence listed below supports Sophie’s claim?

A. There are only 5 species that eat the purple loosestrife compared to 10 species that eat the winged loosestrife.

B. The purple loosestrife grows twice as fast as the native winged loosestrife.

C. Snakes eat the eggs of birds under the loosestrife.

Target level: Argumentation 2b

5. Why does the evidence you picked support Sophie’s claim?

A. If the purple loosestrife grows faster than other species, then it can compete better for light, nutrients, and space.

B. Since few herbivores eat the purple loosestrife, it can just keep growing and take over the ecosystem.

C. There are fewer herbivores to eat the purple loosestrife.

D. Birds are larger and need to eat much more of the loosestrife than insects.

Target level: Argumentation 3a

6. Scientists gather additional evidence about the ecosystem. What evidence would weaken Sophie’s claim?

Sophie’s claim: I think the purple loosestrife is a successful invader because there are very few herbivores that eat it.

A. The herbivores that eat the purple loosestrife also eat the winged loosestrife.

B. The 10 species that eat the winged loosestrife eat more than the 5 species that eat the purple loosestrife.

C. Overall, the 10 species that eat the winged loosestrife eat fewer plants that the 5 species that eat the purple loosestrife.

D. Some of the species that eat the purple loosestrife are omnivores.

Students continue to wonder why the purple loosestrife is such a successful invader in this ecosystem?

Tina says: I think the purple loosestrife is a successful invader because it grows much faster than other plants. According to the scientists’ observations, the purple loosestrife grows twice as fast as the native winged loosestrife.

Target level: Argumentation 2b

7. Which statement below explains why the evidence provided supports Tina’s claim?

A. The purple loosestrife can compete better for light, nutrients, and space because it is fast-growing.

B. Since so few herbivores eat the purple loosestrife, it keeps growing.

C. Snakes eating bird eggs means that there are fewer birds to eat the purple loosestrife.

D. Birds will eat much more than insects.