Identifying and Describing Population Change
Number
per
Organism
Number Number
per per
square square
meter meter
(1991) (1994)
square
meter
(1997)
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?
Unionid
mussels
Zebra
mussels
1.329
3,181