Nutrient Cycles Pre AP Biology

Nutrients are recycles into the ecosystem unlike energy The major nutrient cycles are water, carbon, nitrogen, and phosphorus

In the carbon cycle, carbon is recycled mainly through the process of photosynthesis, cellular respiration and burning of fossil fuels.

Producers fix or make carbohydrates taking CO2 out of the ecosystem through the process of photosynthesis. While the process of cellular respiration and burning of fossil fuels put the CO2 into ecosystems.

Nitrogen is needed for proteins and nucleic acids Nitrogen is needed for proteins and nucleic acids. The air is over 75% N2, but this nitrogen we can not use because of its triple bond. N2 is broken down by bacteria into NH4 (ammonia), then NO2 (nitrite) and finally NO3 (nitrate).

Plant roots absorb this NH4, NO2 or NO3 and then make amino acids and then proteins. Animals get their nitrogen from eating plants or other animals. Nitrogen also gets into the soil when man uses fertilizers made from factories. Nitrification is the process of putting N2 into the ecosystem. Another way to get nitrogen into the ecosystem is through decaying organisms and wastes.

Nitrogen is returned to the atmosphere through bacteria that can decompose nitrogen sources turning them into N2. This is denitrifying bacteria.

Plants absorb water through their roots Plants absorb water through their roots. Land animals absorb water from their food or drink it. Aquatic animals are bathed in it. Aquatic animals are bathed in it. Water gets into the atmosphere from cellular respiration, transpiration and evaporation from the oceans.

Water vapor condensing will result in precipitation (rain or snow) Water vapor condensing will result in precipitation (rain or snow). The excess nitrogen and sulfur in the air (pollution) combines with the water. This results in acid rain. This leeches minerals from the soil killing plants.

The phosphate cycle is the one nutrient that does not have an atmospheric component. It cycles through the soil and water. The main source of phosphorus is the weathering of rocks.

Biological Magnification There are times when unwanted chemicals accumulate in organisms through the food chains. In the 1960’s, cities sprayed with DDT, a chemical to get rid of mosquitoes. This chemical accumulated in the lakes. It found its bay into the aquatic plants. Fish ate the plants and DDT accumulated in the fish. Eagles ate the fish. DDT accumulated in the eagles. It affected their eggs as the shells were not hard. The chicks would not hatch. As a result, eagles became endangered. This process is called biological magnification.