BIOCHEMICAL CYCLES REVIEW Energy and matter move through the biosphere very differently. Unlike the one-way flow of energy, matter is recycled within and between ecosystems All the chemical substances that an organism needs to live are called nutrients.

NITROGEN CYCLE All organisms require nitrogen to make amino acids, which are the building blocks to making proteins. Nitrates (NO3 and NO2) are found in the wastes produced by organisms and in dead and decaying matter. Bacteria that live in the soil on the roots of plants convert nitrogen gas into ammonia, this process is called nitrogen fixation. Bacteria that convert nitrates into nitrogen gas that is released into the atmosphere, this process is called denitrification.

WATER CYCLE ALL LIVING THINGS NEED WATER TO SURVIVE. The process by which water changes from liquid form to an gas is called evaporation. Water entering the atmosphere by evaporating from leaves of plants is called transpiration.

CARBON DIOXIDE CYCLE Carbon is the key ingredient in all living organisms. Biological processes, geochemical processes, mixed biogeochemical processes and human activity are the four different kinds of processes involved in the carbon cycle.

PHOSPHORUS CYCLE Essential to living organisms because it forms part of the DNA and RNA Not very common in the biosphere Phosphorus does not enter the atmosphere like the other cycles. Phosphorus remains mostly on land in rock and soil minerals, and in ocean sediments. Phosphorus is released when the rocks and sediments wear down.

NUTRIENT LIMITATION When an ecosystem is limited by a single nutrient that is scarce or cycles very slowly, this limitation is called nutrient limitation. Open oceans are nutrient-poor (nitrogen) compared to land and in streams.In lakes and freshwater environments, Phosphorus is the limiting nutrient.