I. Toxicity Threshold II. Bioaccumulation III. Biomagnification IV. Carcinogens V. Teratogens A. Chemicals that cause or support cancer B. Substances that cause mutations and birth defects C. The dose of a chemical above which there is a measurable decline in the health measure D. The process by which chemicals are stored in the tissues of living organisms E. Concentrations of a chemical increase at each higher level of the food web

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.