Acommunity includes a. all of the living organisms in a specific place at a specific time. b. only the plants in a specific place at a specific time. c. only the animals in a specific place at a specific time.

Explain why in any given geographical region, women tend to have lighter skins( by 3-4% on average) than men?

1. the passing of is the basis of heredity. 2. our encode the instructions that define our traits. 3. each of us has thousands of genes, which are made of and reside in our chromosomes. 4. in addition to our genes, the we live in also define our traits. 5. humans have two complete sets of chromosomes. 6. when parents conceive a child, each parent contributes set of chromosomes. 7. every child receives of its chromosomes from the mother and half from the father. 8. this transfer takes place at when the father’s sperm joins the mother’s egg. 9. while most cells in our bodies have two sets of chromosomes, or a total of egg and sperm each have chromosomes. 10. when egg and sperm unite they create a single cell called a 11. each parent contributes complete set of chromosomes to their child. 12. since the parents contribute the chromosomes to each new child, every child inherits a unique set of chromosomes. 13. as a result, every baby will have a combination of traits.

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. drag type of experiment on the left to the example of experiment on the right. blood concentrations of bpa in college students are compared to their recent manipulative 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. 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 foraging activity levels are compared in tadpoles exposed to four concentrations of toxic metals in the laboratory. growth of corn plants is compared in field plots sprayed with three different dosage: s 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 - natural; manipulative