Question

1. blood concentrations of bpa in college students are compared to their recent consumption of canned food items.
2. the feeding behavior of fish in streams that receive acidic runoff from strip mines is compared to the feeding behavior of fish in unaffected streams.
3. the deformity rate in baby birds from nests in pesticide - sprayed fields is compared to the deformity rate in birds from nests in unsprayed fields.
4. tumor development is compared in mice exposed to five dosages of a known carcinogen in the laboratory.
5. foraging activity levels are compared in tadpoles exposed to four concentrations of toxic metals in the laboratory.
6. growth of corn plants is compared in field plots sprayed with three different dosages of weed killer.
7. bpa concentrations in the urine of people with diabetes are compared to bpa concentrations in the urine of people without diabetes.

Explanation:

1. In this study, researchers are observing existing conditions (BPA blood - levels and canned food consumption) without manipulating variables directly, so it's a natural study.
2. Comparing fish in streams with and without acidic runoff is observing natural conditions, a natural study.
3. Comparing bird deformity rates in sprayed and unsprayed fields is observing natural differences, a natural study.
4. Manipulating the dosage of a carcinogen in a laboratory setting is a manipulative study.
5. Manipulating the concentration of toxic metals in a laboratory for tadpoles is a manipulative study.
6. Manipulating the dosage of weed - killer in field plots for corn plants is a manipulative study.
7. Comparing BPA urine concentrations in people with and without diabetes is observing natural differences, a natural study.

Answer:

1. Natural
2. Natural
3. Natural
4. Manipulative
5. Manipulative
6. Manipulative
7. Natural