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Ecosystem Recycling

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The Water Cycle Water, carbon, nitrogen, calcium and phosphorus flow through ecosystems and are recycled and reused. These minerals may move from the abiotic portion of the environment into living things and back again. These are called biogeochemical cycles

Water Cycle Water is crucial to life. Cells contain between 70 and 90% water. The availability of water is a key factor in the productivity of an ecosystem. Most water is in bodies of water such as lakes, rivers, ocean etc. Water exists in living things. Water exists in the atmosphere as well.

The Water Cycle Three important processes in the water cycle. –Evaporation – Water enters the atmosphere as vapor. –Transpiration – The process by which plants release droplets of water through their stomata. At least 90% of water that evaporates passes through plants in this process.

The Water Cycle –Precipitation - Water leaves the atmosphere in the form of rain, sleet, hail, snow, or fog. Vocabulary –Ground water – water in the ground stored in porous rocks. –Water cycle – The movement of water through various reservoirs (life, lakes, oceans, etc.)

Water Cycle

The Carbon Cycle Together, photosynthesis and cellular respiration form the basis of the carbon cycle. During photosynthesis, autotrophic organisms take carbon dioxide in (along with water and sunlight) to make carbohydrates.

The Carbon Cycle Both autotrophs and heterotrophs use oxygen to break down the carbohydrates during cellular respiration. Cellular respiration releases water and CO 2 into the atmosphere. Decomposers also release CO 2 into the atmosphere when they break down organic compounds.

Carbon Cycle How do humans affect the carbon cycle? Burning of fossil fuels and in the destruction of plants which produce oxygen.

Carbon Cycle

The Nitrogen Cycle Nitrogen is essential to life All organisms need nitrogen to make nucleic acids and proteins. Nitrogen gases makes up approximately 78% of the atmosphere. Shortages of nitrogen can limit the productivity of plants.

The Nitrogen Cycle Question With so much nitrogen in the atmosphere, how can there be a nitrogen shortage? Answer Most plants can only use nitrogen in the form of nitrate.

Nitrogen Fixation Nitrogen gas becomes useable to plants after it has undergone a transformation called nitrogen fixation. Nitrogen fixing bacteria convert gas into ammonia, nitrite, and then nitrate (the useable form to plants).

The Nitrogen Cycle Nitrogen fixing bacteria have formed mutualistic relationships in which the plants provide the bacteria with a home and the bacteria provide the plants with nitrate. Excess nitrate is deposited in the soil.

Recycling Nitrogen Ammonification is the process in which decomposers break down waste such as urine and excrement and dead organic matter and release the nitrogen they contain as ammonia. Nitrification takes place when bacteria in the soil take up ammonia and oxidize it into nitrites and nitrates.

The Nitrogen Cycle Nitrogen is returned to the atmosphere through denitrification. Anaerobic bacteria break down nitrates and release the nitrogen back into the atmosphere. Plants may absorb nitrates but animals may not, they must ingest them by eating plants and other organisms.

Nitrogen Cycle