Question

The zebra mussel is a non-native species of freshwater mussel that has firmly established populations throughout the Great Lakes. It is originally from southern Russia. Zebra mussels breed quickly and can attach to any hard surface. Their shells can attach to each other in layers that clog pipes and waterways. They can also kill native mussels by attaching to their shells. However, zebra mussels are also very good at filtering the water. Many lakes infested with zebra mussels are cleaner. Which statement about non-native species is supported by the story about zebra mussels?
A.
Non-native species can have both positive and negative effects.
B.
The positive impact of non-native species always outweighs the negative.
C.
Non-native species can only come from nearby ecosystems.
D.
The impact that non-native species have on other ecosystems is small.

Answer 1

A- non-native species can have positive and negative affects

Answer 2

Answer:

A.  Non-native species can have both positive and negative effects.

Explanation:

Zebra mussels have invaded new ecosystems located far from its native place. By killing the native mussels of the system, they exert huge adverse impact on the new ecosystem. Also, they have the positive impact of filtering the water. However, even non-native species can have both positive and negative effects, the positive effects do not outweigh the numerous negative effects of the invading species.