The cycling of matter and minerals through the living and non-living parts of the Earth are described by nutrient cycles.
z Organism
Organisms die
Plants take up nutrients
Litter release nutrients
Decomposing organisms
Soil
Fig. 22.2.2 A nutrient cycle
22.2
Rock
Nutrients added by weathered rock
Nutrients lost by leaching
1. The nutrients released into the soil when rocks are broken down are taken up by organisms.
2. When an organism dies it becomes known as ‘litter’ and it returns nutrients to the soil as it decomposes (breaks down).
3. Some nutrients are lost from the soil due to high rainfall or irrigation. This is known as leaching.
The Carbon Cycle
Carbon is present in all living things. When the organisms die, carbon is recycled by decomposers as part of the carbon cycle.
The carbon cycle explains how carbon is recycled through the Earth. z z
Anything that takes carbon out of the atmosphere is known as a carbon sink. For example, plants take carbon out of the atmosphere as carbon dioxide during photosynthesis.
Learn more about photosynthesis in Biological World 3.2 zz
Anything that releases carbon into the atmosphere is known as a carbon source. For example, all living things release carbon into the atmosphere as carbon dioxide during respiration.
Learn more about respiration in Biological World 3.3 385
