changes to an ecosystem

Which one is NOT an example of a decomposer?

• mushroom
• leaves
• mold
• worm

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Which of the following is true about an ecosystem?

• Ecosystems can never change.

• Natural disasters cannot harm an ecosystem.

• Humans are the only threat to an ecosystem.

• Ecosystems can change over time.

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Which of the following would be the normal habitat for an alligator?

• A swampy wetland

• A dry, sandy desert

• An open grassland

• A thick evergreen forest

A manatee is a water-dwelling herbivore on the list of endangered species. If manatees were to become extinct, what would be the most likely result in areas where they had lived?

• Certain producer organisms would increase in the area.

• Other manatees would move into the area and restore balance.
• Predators in the area would have more food to eat.
• The area would not be affected.

How would beavers building a dam cause an increase in the fish population? The dam

• blocks a river and creates a lake.
• causes predators to hunt more fish.
• forces many birds to leave the ecosystem.
• removes trees from around the river.

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Scientists are concerned about overfishing of shark populations. Sharks feed on rays and rays feed on scallops. Without sharks, rays consume all the scallop beds. This situation demonstrates that: 

• humans can improve an ecosystem by removing predators.
• humans can upset an ecosystem by removing species.
• reducing the shark population increases the quantity of scallops that can be taken.
• sharks are not important for the stability of the ecosystem.

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The Coqui frog is native to Puerto Rico. These frogs were accidentally introduced in Hawaii. Coqui frogs are extremely noisy; since they are nocturnal they make loud noises at night. Although these frogs are small, they eat a lot! They eat insects and spiders that are also eaten by birds in Hawaii. Besides being noisy, how do these frogs most likely harm other animals? 

• By causing other animals to reproduce more.
• By competing with other animals for food.
• By eating foods that no other animals eat.
• By moving slower than most other animals.

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A foreign insect is introduced in Texas. It eats a lot of leaves, and trees start to become leafless. Many different animals feed on the new insect, but even they cannot control its numbers. Eventually, trees begin to die. Why would a rapid increase of the new insect population cause certain species of herbivores to vanish or be fewer in number?

• They would not have enough to eat.

• They would not have enough space to live.

• They would not have tree bark to eat.

Raccoons eat aquatic animals. If chemicals entered the lake with rain water and destroyed the plants, how would this impact the raccoon population?

• Raccoons would have more aquatic animals to eat.
• Raccoons would begin eating land plants.
• Raccoons would have less aquatic animals to eat.
• Raccoons would only drink water.

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A park is home to a large number of robins, squirrels and rabbits. The robins and squirrels live in the park’s trees. The robins feed on earthworms and insects that live on the ground. The squirrels eat the acorns produced by the park’s oak trees. The rabbits hide in the bushes and feed on the grass. Which factor would negatively impact the number of rabbits living in the park?

• Collecting acorns off the ground.
• Planting more trees.
• Removing park bushes.
• Removing the squirrels.

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