Unionid mussels are native to the Hudson River in New York State. In the early 1990s, zebra mussels were introduced into the Hudson River. The table shows the number of unionid mussels and zebra mussels over the course of six years.

How did the population of unionid mussels change after zebra mussels were introduced? Why did this change occur?

sample:

Explanation:

The population of unionid mussels in the Hudson River decreased after zebra mussels were introduced. Zebra mussels, a nonnative species, competed with the unionid mussels for food. The zebra mussels were able to outcompete the unionid mussels, allowing the zebra mussel population to increase dramatically over six years. The unionid mussel population decreased due to a lack of food.

yes

no

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