Nutrient Cycles

Nutrient Cycles:

• In all ecosystems, Nutrients are used by organisms and eventually returned to it again.
• These are known as the nutrient cycles.
• There are 3 well known of these cycles.

1. The Water Cycle.
2. The Nitrogen Cycle.
3. The Carbon Cycle.
4. The Phosphorous Cycle

The Water Cycle

• Water is the most important non-organic component of an ecosystem.
• Plants play an important role in retaining water in an ecosystem.

• In this cycle the following occurs.
• Rain falls to earth either runs off to the ocean, evaporates into air, or is held by plants and is transpired back into the atmosphere. (90% of the water which passes into an ecosystem passes through plants).
• Evaporated moisture (from land, plants & ocean) condenses in the form of clouds and returns to land in the form of precipitation.

The Nitrogen Cycle

• Nitrogen is an important component in the production of proteins.
• Most nitrogen is inert and unusable by plants & animals.
• Certain bacteria known as Nitrogen fixing bacteria, have the ability to convert N₂ gas, into NH₃ (ammonia) which is a usable form of Nitrogen.
• These bacteria are often decomposers, and release ammonia when an animal is decomposing.
• Others live in the roots of certain plants in a symbiotic relationship.(eg peanuts). The bacteria provides Nitrogen compounds for the plant. The plant proivides food for the bacteria.

The Carbon Cycle:

• Carbon is the building block of all organic molecules.
• Carbon cycle is based on the creation and absorption of CO₂ (carbon dioxide).
• CO₂ is produced by plant & animal respiration & by combustion (fires, industry, cars, etc…)
• CO₂ is absorbed by plants and converted to food (sugars) by plants through photosynthesis.
• This food is, in turn, converted back to CO2 through respiration by plants & animals.

The Phosphorous Cycle:

• Phosphorous is a critical mineral in plant growth. Due to its scarcity it often is a significant limiting factor in plant growth.
• Often Phosphate-Rich detergents can disrupt an aquatic ecosystem by stimulating algeal blooms, choking off light to lower levels of water.