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. The impact that non-native species have on other ecosystems is small. B. The positive impact of non-native species always outweighs the negative. C. Non-native species can have both positive and negative effects. D. Non-native species can only come from nearby ecosystems.
Answers
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. The impact that non-native species have on other ecosystems is small. B. The positive impact of non-native species always outweighs the negative. C. Non-native species can have both positive and negative effects. D. Non-native species can only come from nearby ecosystems.
Answer: B. The positive impact of non-native species always outweighs the negative.
Reason for the answer: Mostly there are positive impact on the nature and very less negative impact so option B is correct.
Only Option C. holds true.
This is supported by the fact that the zebra mussels can filter water, but at the same time kill native species.
The sentences which support this are:
“zebra mussels are also very good at filtering the water. Many lakes infested with zebra mussels are cleaner”, which shows the positive effects and “They can also kill native mussels by attaching to their shells” being the negative effect.