Types of experiments: natural and manipulative

experiments in environmental toxicology can sometimes be manipulative experiments in which the researcher actively chooses and manipulates the independent variable. in hunt's study, for example, dosages of bpa were manipulated and the effects were measured. in manipulative studies, the researcher controls all the other variables in the experiment, so any health effects observed in the test subjects can be attributed to differences in the independent variable. in other cases, researchers use natural experiments in which the dependent variable (typically a measure of organism health) is measured under differing contexts that are not manipulated. say, for example, that an accidental chemical spill contaminates five ponds. to determine the possible effects of the toxic chemical on frogs, a researcher could compare the hatching rate of frog eggs laid in those five ponds to the hatching rate of eggs laid in five uncontaminated ponds nearby. this would be an example of a natural experiment because concentrations of the toxic chemical in the ponds were not controlled by the experimenter, but rather resulted from the chemical spill.1. concentrations of bpa in college students are compared to their recent consumption of canned food items 2. feeding behavior of fish in streams that receive acidic runoff from strip mines is compared to the feeding behavior of fish in unaffected streams. 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. activity levels are compared in tadpoles exposed to four concentrations of toxic metals in the laboratory. of corn plants is compared in field plots sprayed with three different dosage: s of weed killer bpa concentrations in the urine of people with diabetes are compared to bpa concentrations in the urine of people without diabetes

Answer no 1:

As in this experiment we are not changing the amounts of canned food items consumed by the college students. Hence, it would be a natural experiment. IN a natural experiment the independent variable is not changed by the researcher.

Answer no 2:

A natural experiment can be described as an experiment in which the researcher will not control the independent variable. He only checks what effect a particular substance will have on the subject of test. As in the experiment, the acidic runoff in streams is not being fluctuated by the researcher, hence it is a natural experiment.

Answer No 3:

In this experiment, the amounts of pesticide spray are not being changed. The effects of a pesticide spray on birds is being compared with those who do not receive the pesticide spray. Hence, this experiment will be a natural experiment.

Answer No 4:

Manipulative experiment can be described as an experiment in which the concentration or amounts of the independent variable are varied to check the results of varied concentration on the testing object. As in this experiment, Five different dosages of the carcinogen were given to check its effect on the mice hence, it is a manipulative experiment.

Answer no 5:

As the concentration of the toxic metals is being varied in each experiment to check the effects of each concentration on the tadpoles, hence it is a manipulative experiment.

Answer no 6:

As described above, a manipulative experiment is the one in which different dosages of an independent variable are given so that the effect of each dosage could be known on the testing object. Hence, as three different dosages of weed killers are being given in this experiment, it is a kind of manipulative experiment.

Answer no 7:

In this experiment, the amounts of BPA concentration are being compared in people with or without diabetes hence, it is a natural experiment.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.