Cycling of Materials

All the elements that make up living organisms are recycled through ecosystems. Materials pass between the living and non-living parts of the environment in continuous cycles. This lesson covers the carbon cycle, water cycle, decomposition and the nitrogen cycle.

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Why Do Materials Cycle?

The Earth is essentially a closed system — very little new matter enters or leaves the planet. This means that the elements needed for life (carbon, nitrogen, oxygen, hydrogen, etc.) are finite and must be recycled.

• Materials are taken from the environment by living organisms
• They are passed along food chains through feeding
• They are returned to the environment through respiration, excretion, death and decomposition
• These materials are then available for new organisms to use

Without recycling, elements would become locked up in dead organisms and waste, and life would eventually run out of raw materials.

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The Carbon Cycle

The carbon cycle describes how carbon moves between the atmosphere, living organisms, the oceans and the Earth's crust.

Carbon Enters the Atmosphere (as CO₂)