Ecology 4.docx

The Carbon Cycle starts with CO2 in the atmosphere where the concentration is about 0.03% and rising. - Plants remove carbon from the environment in photosynthesis and return it in respiration. - Animals obtain their carbon by eating plants; they release carbon in respiration. - Microorganisms (such...

The Carbon Cycle starts with CO2 in the atmosphere where the concentration is about 0.03% and rising. - Plants remove carbon from the environment in photosynthesis and return it in respiration. - Animals obtain their carbon by eating plants; they release carbon in respiration. - Microorganisms (such as fungi and bacteria) return carbon to the environment when they decompose dead plants and animals. - Burning fossil fuels increases carbon dioxide in air and deforestation decrease uptake of carbon dioxide by plants. Nitrogen Cycle (8) Nitrogen Fixation - Nitrogen is needed by plants to make proteins, DNA, RNA, ATP, NAD+, NADP+, Chlorophyll etc. Nitrogen fixation is the conversion of nitrogen into nitrate, a form that can be used by plants. This is carried out by volcanic action, lightning, industrial processes and by some bacteria. Nitrogen-fixing bacteria can be found free in the soil or live in the root nodules of legumes (peas. beans, clover)The bacteria use the plant as a carbohydrate source of energy, protection & shelter (anaerobic conditions too) and the plant uses the nitrate produced by the bacterium (e.g., of mutualism). Assimilation- Nitrates are converted into plant and animal protein, DNA and RNA. Decomposition - Bacteria and fungi of decay convert the dead remains of plants or animals or their waste products to ammonia (NH3). Nitrification - The ammonia is converted to nitrites and then to nitrates by nitrifying bacteria. Some of the nitrate formed in the soil is absorbed and assimilated by the plants. Denitrification - The conversion of nitrates to nitrogen gas. It is carried out by denitrifying bacteria in the soil. These bacteria are anaerobic and live in swampy soil or deep down in the soil (where water collects). Role of Organisms in The Nitrogen Cycle - Bacteria play a central role: a. Nitrogen-fixing bacteria, which convert atmospheric nitrogen to nitrates. b. Bacteria of decay, which convert decaying nitrogen waste to ammonia. c. Nitrifying bacteria, which convert ammonia to nitrates/nitrites. d. Denitrifying bacteria, which convert nitrates to nitrogen gas. - Fungi, like bacteria, help to convert dead plants and animals and their wastes into ammonia in the soil. - Plants absorb nitrates from the soil to make proteins. - Animals consume plants and use it to form animal protein.