Cycles in Nature Standard 1 Objective 2: Explain relationships between matter cycles and Energy a) use diagrams to trace the movement of matter through a cycle b) Explain how water is a limiting factor in various Ecosystems HS Biology
Energy Flow Through an Ecosystem Introduction to Cycles of Matter & Energy Transfer Food Webs & Food Pyramids
Earth Cycles Video Mr. Anderson Earth s biosphere contains a fixed amount of water, carbon, nitrogen, oxygen, and other materials that cycle through the environment and are reused by different organisms.
Water Cycle How water moves from the Earth s surface to the atmosphere and back to the surface again
2. condensation 3. Precipitation 2. condensation 3. Precipitation 5. snow Runoff 1. Evaporation e 4. Transpiration 1. Evaporation 6. Groundwater flow
Components of the Water Cycle Evaporation: when liquid water changes into water vapor and enters the atmosphere Condensation: the process of changing water from a gas to a liquid Precipitation: when water drops become large enough and fall to the ground as rain, snow, sleet, etc. Transpiration: Transpiration is the process by which plants lose water out of their leaves. Transpiration gives evaporation a bit of a hand in getting the water vapor back up into the air.
Nitrogen cycle The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere The growth of all organisms depends on the availability of mineral nutrients, and none is more important than nitrogen, which is required in large amounts as an essential component of proteins, nucleic acids and other cellular constituents.
Nitrogen Cycle (cont.) There is an abundant supply of nitrogen in the earth's atmosphere - nearly 79% in the form of N2 gas. However, N2 is unavailable for use by most organisms because there is a triple bond between the two nitrogen atoms, making the molecule almost inert.
Nitrogen Fixation In order for nitrogen to be used for growth it must be "fixed" (combined) in the form of ammonium (NH3) or nitrate (NO3) ions. some bacteria can convert N2 into ammonia by the process termed nitrogen fixation; these bacteria are either free-living or form symbiotic associations with plants or other organisms (e.g. termites, protozoa) Nitrogen-fixing bacteria can be found in the soil as well as on submerged objects in lakes and ponds. These are called cyanophytes (blue-green algae).
Legume symbioses The most familiar examples of nitrogenfixing symbioses are the root nodules of legumes (peas, beans, clover, etc.).
More ammonia A small amount of nitrogen fixation also results from the passage of ultraviolet light and lightning through the air, causing nitrogen to react with oxygen to form nitrate ions. Additional amounts of nitrate and ammonia are put into the atmosphere by volcanoes, by combustion of fossil fuels, and by forest fires.
Other nitrogen Farmers replace nitrogen in the soil by growing nitrogen-fixing crops or using fertilizers that contain nitrogen compounds that plants need for growth.
Ammonification At any one time a large proportion of the total fixed nitrogen will be locked up in the biomass or in the dead remains of organisms. The excretions of animals and dead bodies are broken down in the soil by decomposers This produces ammonia.
Nitrification Some bacteria called nitrifying bacteria take the ammonia and change it to a nitrite ion, and then a different group of nitrifying bacteria change that nitrite ion to a nitrate ion. This then can be taken up into the roots of the plant and be used.
Problems of nitrification The ammonium ion is readily adsorbed onto the clay soil and soil organic matter, preventing it from being washed out of the soil by rainfall. In contrast, the nitrate ion is not held on soil particles and so can be washed down the soil - the process termed leaching In this way, valuable nitrogen can be lost from the soil, reducing the soil fertility.
The problems with too many nitrates The nitrates can then accumulate in groundwater, and ultimately in drinking water. There are strict regulations governing the amount of nitrate that can be present in drinking water, because nitrates can be changed to nitrites by microorganisms in the gut. Nitrites are absorbed from the gut and bind to haemoglobin in your blood, reducing its oxygen-carrying capacity.
Denitrification If the soil becomes too compacted or gets too wet, air cannot penetrate. This allows bacteria called denitrifying bacteria to convert nitrate to nitrous oxide or nitrogen gas which is then lost to the atmosphere. That is why it is important for farmland to be kept well drained and plowed. video
Carbon Cycle How carbon molecules move between the living and nonliving world The same carbon atoms in your body today have been used in countless other molecules since time began. Plants absorb carbon dioxide from the atmosphere and use it, combined with water they get from the soil, to make the substances they need for growth.
Carbon Cycle (cont.) Animals, like a rabbit, eat the plants and use the carbon to build their own tissues. Other animals, such as the fox, eat the rabbit and then use the carbon for their own needs. These animals return carbon dioxide into the air when they breathe, and when they die, since the carbon is returned to the soil during decomposition.
Carbon cycle (cont.) The carbon atoms in soil may then be used in a new plant or small microorganisms. Ultimately, the same carbon atom can move through many organisms and even end in the same place where it began.
video Video II