E&S 5

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The Cycling of Matter

Over time, matter—such as water, carbon, oxygen and nitrogen—is transferred between organisms and the physical environment.

Processes in the Water Cycle

Evaporation: Water turns from a liquid to a gas when it evaporates. Energy from the Sun can evaporate water from all places on the Earth's surface such as puddles, ponds, lakes and oceans.
Condensation: After evaporation, water can cool and convert from gas to liquid, often forming clouds.
Transport: Water within clouds can be blown many miles by strong winds and so is transported to other areas.
Precipitation: Precipitation occurs when rain, snow, hail and sleet fall from the sky.
Surface runoff: Much water will be absorbed into the ground after precipitation but if a large volume falls or the ground is already wet then some water can run along the surface of the ground.
Infiltration: This occurs when water that has fallen as precipitation is absorbed into the ground. This can then be stored within underground rocks called aquifers.
Transpiration: Plants need to maintain a constant stream of water to their leaves for photosynthesis, support and transport of minerals. They allow some water to evaporate as water vapour from their leaves so that more water is continuously 'pulled' to their leaves from the soil.

Processes in the Carbon Cycle

Removing carbon dioxide from the atmosphere: Plants use carbon dioxide from the atmosphere for photosynthesis. The carbon becomes part of complex molecules in the plants, such as proteins, fats and carbohydrates.
Passing carbon from one organism to the next: When an animal eats a plant, carbon from the plant becomes part of the fats and proteins in the animal. Microorganisms and some animals feed on waste material from animals, and the remains of dead animals and plants. The carbon then becomes part of these organisms.
Returning carbon dioxide to the atmosphere: Carbon dioxide is released to the atmosphere through respiration by animals, plants and microorganisms. It is also released by the combustion of wood and fossil fuels (such as coal, oil and natural gas). The use of fossil fuels is gradually increasing the carbon dioxide levels in the atmosphere.
Decomposition or decay also releases carbon dioxide. This process happens faster in warm, moist conditions with plenty of oxygen because it involves microorganisms. Decay can be very slow in cold, dry conditions, and when there is a shortage of oxygen.