The Nitrogen Cycle

The Nitrogen Cycle — page 1 — EVERY LIVING THING NEEDS NITROGEN From tiny insects to plants and people all living things need nitrogen to survive Nitrogen is a chemical element that has no color taste or smell Scientists use symbols to stand for the names of chemical elements VOCABULARY A chemical element is a basic substance that cannot be broken down into simpler substances The gases that make up air nitrogen 78 oxygen 21 argon carbon dioxide and others 1 2011 Encyclopædia Britannica Inc Air is a mixture of several gases mostly nitrogen and

The Nitrogen Cycle — page 2 — Nitrogen is found in all living things including people and animals The symbol for nitrogen is N Nitrogen is a gas that makes up about 78 percent of Earth’s atmosphere This gas form is sometimes called free nitrogen In addition free nitrogen is found in many meteorites and in some stars It is also in the gases of volcanoes mines and some mineral springs Nitrogen is one of the main chemical elements found in all living things But living things cannot use nitrogen in its gas form The nitrogen that is found in living things must first be combined with other elements Such combinations are called compounds 5

The Nitrogen Cycle — page 3 — Plants such as these bluebell flowers need nitrogen in order to make chlorophyll Most plants get the nitrogen they need from compounds in the soil or water Nitrogen is what helps green plants make chlorophyll a substance that plants use to make their own food The process that plants use to do this is called photosynthesis Animals including people get the nitrogen they need by eating plants that have nitrogen or by eating other animals that eat plants Animals need nitrogen to make the proteins that help them have strong healthy bodies When plants and animals die they decompose 6

The Nitrogen Cycle — page 4 — Compare and Contrast Plants and animals need nitrogen Compare the ways that living things use nitrogen How do plants and people get nitrogen differently or break up This process returns nitrogen to the soil Nitrogen in various forms constantly circulates through nature This process is called the nitrogen cycle Children need nitrogen in their diet to be healthy and active 7

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