. Which of these choices would help explain why the Zebra mussel population was 0 in 1991, while the population of native Unionid mussels was over 3000 organisms per square meter? a
The scientists had a hard time spotting the mussels that year.
b
The climate was too cold for the Zebra mussels to reproduce that year.
c
The Zebra mussels had not yet been introduced to the area.
d
The water was moving too fast for the Zebra mussels to survive that year.
2. Over the 18 years of data depicted here, which mussel species was generally more successful?
Unionid Mussels
Zebra Mussels

How does the digestive system interact with the circulatory system? a. messages sent as electrical impulses from the digestive system are transported throughout the body by the circulatory system. b. nutrients taken in and broken down by the digestive system are carried to various parts of the body by the circulatory system. c. nutrients and gases are absorbed by organs in the circulatory system. then, they are transported to all parts of the body by organs in the digestive system. d. oxygen and carbon dioxide are exchanged by organs in the digestive system, and the gases are carried to the rest of the body by the circulatory system.