V.C.E. Biology Unit 2 Movement of energy and matter in ecosystems

Energy Transfer Energy enters natural ecosystems from the sun, or in rarer cases from geothermal and chemical sources, as plants use the light energy to combine carbon dioxide and water to make glucose – Photosynthesis. The rate at which an ecosystem is able to convert light energy to chemical energy is referred to as the primary productivity of the ecosystem. The amount of chemical energy stored in the ecosystem is referred to as its Biomass.

An inefficient System The system is inherently inefficient. Only 1% of the incoming solar radiation is converted to glucose. At each level of the ecological pyramid energy is lost from the ecosystem. Each subsequent trophic level has less energy available to it and therefore there are far fewer highest order consumers than producers.

Bioaccumulation Energy and nutrients flow through food webs, but so do toxins. If a toxin is released into an ecosystem, then at each step of the trophic level the toxin becomes more concentrated. This causes all sorts of nasty consequences for the highest order consumers.

Nutrient Cycles The Carbon Cycle Carbon enters the food web when carbon dioxide is converted to glucose and accumulates in organic matter.

Nutrient Cycles Nitrogen exists mostly in its gaseous form. Plants can’t use it in this form, but all organisms require it to make proteins. A range of bacteria exist in the soil and in association with plant roots that are able to fix atmospheric nitrogen making it into a form that plants can use.

Nutrient Cycle All organisms are made of water and need it to survive. The global water cycle keeps water flowing through natural ecosystems.