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Test: Common Core: 5th Grade English Language Arts
Passage 2: Unwanted Guests: The Dangers of Invasive Species (2016)
Groups of different animals affect one another in the natural world. For example, imagine that wolves and deer live in an area. A certain number of wolves need to eat a certain number of deer to survive. This keeps the population of the deer from getting too big. Similarly, the deer eat grass and vegetation. If there were more deer, they’d need to eat more grass.
The natural world is full of balances like these. Unfortunately, sometimes these balances are upset by invasive species. An invasive species is an animal or plant that has moved or been moved from its original environment to a new one. It has established a stable population there that is causing problems. Invasive species don’t cause problems in their original environments because they are kept in check by other plants and animals. In new environments, though, they have nothing stopping them from taking over.
One example of an invasive species is the zebra mussel. This animal originally only lived near Russia. Zebra mussels got into the Great Lakes by attaching themselves to the bottoms of ships. They now live in the Great Lakes too, where they upset the ecosystem. Zebra mussels eat algae, but so do fish. Many fish die as a result of there not being enough algae for all the animals to eat.
Plants can be invasive species too. Another example of an invasive species is the kudzu vine. Humans introduced the plant to the United States on purpose. Farmers were encouraged to grow it to protect their soil. Since then, it has gotten out of control. It now covers large parts of the South, outcompeting native plants for resources like water and sunlight.
Invasive species can cause environmental problems that are very difficult to fix. Because of this, it’s important to rethink introducing any species to a new environment. It’s also important to check to make sure when traveling that you are not bringing any plants or animals with you!
| 1. | Which of the following excerpts from the passage best states its main idea? |
"Plants can be invasive species too."
"Groups of different animals affect one another in the natural world."
"One example of an invasive species is the zebra mussel."
"Invasive species don’t cause problems in their original environments because they are kept in check by other plants and animals."
"Invasive species can cause environmental problems that are very difficult to fix."
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