Problem
Let's go back to the frogs. A scientist find that frogs from streams in a protected National Forest have lower rates of limb deformities than frogs from streams near agricultural fields. Which would be an appropriate next step before this scientist concludes that pesticides directly cause limb deformities? Select all that apply. Experimentally treat tadpoles with varying levels of pesticides while keeping all other factors constant, and measure the rates of limb deformities. Determine whether the forest and agricultural streams differ in any other factor that might affect limb development. Look for limb deformities in frogs that live in suburban backyard ponds. None of these steps are needed; the scientist has already demonstrated causation.