Amphibians (frogs, toads, salamanders, and newts) are declining worldwide. Two h
ID: 47466 • Letter: A
Question
Amphibians (frogs, toads, salamanders, and newts) are declining worldwide. Two hypotheses for why this is happening are pesticides and predators. To test these hypotheses, scientists raised several frog species as tadpoles in small ponds. Ponds had no predators, predatory newts, or predatory beetle larvae; in addition, ponds were exposed to either the insecticide malathion or the herbicide Roundup, two globally common pesticides. The scientists then monitored subsequent survival of the tadpoles in each pond. Consider the following figure:
What is/are the independent variable(s) in this study?
Predators
Pesticides
Predators and pesticides
Tadpole survival
What is/are the dependent variable(s) in this study?
Predators
Pesticides
Predators and pesticides
Tadpole survival
How many different treatment combinations are there in this experimental design?
Two
Three
Six
Nine
Which treatment would you consider to be the ?control??
No pesticide
No predator
No pesticide, no predator
No tadpole
Which treatment appears to have had the greatest impact on tadpole survival?
No pesticide, no predator
Newts, roundup
Beetles, Malathion
Cannot be determined
Not considering pesticides, what effect did predators have on tadpole survival?
Positive
Negative
None
Depends on the predator
Not considering predators, what effect did pesticides have on tadpole survival?
Positive
Negative
None
Depends on the pesticide
Based on these results, what decision would you make regarding pesticides if you were a resource manager?
Ban both
Ban only roundup
Ban only malathion
Ban neither
Explanation / Answer
Pesticides
Tadpole survival
Nine
No pesticide, no predator
Newts, roundup
Depends on the predator
Negative
Ban only roundup
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