Nutrient Cycles and Energy Flow Lesson 3 August 26th, 2010

Review of what you covered Biomes Temperate Decidious forest Tundra Grassland Boreal forest

Nutrient Cycles and Energy Flow Nutrient – Substances that an organism uses to build and repair cells in the body.

Nutrient Cycles In a cycle there is no beginning or end. Nutrients cycle back and forth between the biotic and abiotic parts of ecosystems. Water, carbon and nitrogen are nutrients that all have reservoirs.

The Water Cycle The sun warms the surface water, and the water evaporates into the atmosphere. The water vapour cools and condenses to form clouds. Water falling from the clouds to the ground is called precipitation Water that runs from the ground into streams or rivers is called run-off.

The Water Cycle Some water seeps through the soil and into ground water. Large underground lakes are known as aquifers. Plants absorb some of the water in the ground and release it through their leaves in a process known as transpiration The water vapour rises and the cycle continues.

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The Nitrogen Cycle All organisms need nitrogen to make proteins 78 % of the atmosphere is nitrogen but it cannot be directly used by organisms. Organisms get nitrogen from substances that contain nitrogen.

The Nitrogen Cycle The act of converting nitrogen gas (N2) to ammonia is called Nitrogen fixation   Nitrogen fixing bacteria perform this critical step Without the bacteria the cycle would stop Lighting only fixates 1% of the worlds nitrogen Most plants cannot use the ammonia created

The Nitrogen Cycle Nitrifying bacteria convert the ammonia into nitrates Nitrates are absorbed and used by the plants Animals eat plants to obtain nitrogen. The animals then produce ammonia which is removed as waste. Nitrifying bacteria then convert the ammonia to nitrates. Denitrifying bacteria in the soil convert nitrates back into nitrogen gas.

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Read 62-65 Answer page 65 # 1, 3-6