Cycles within Ecosystems

The Carbon Cycle

Carbon is essential to life; it’s a key component of carbohydrates, proteins, fats, and nucleic acids.
The carbon cycle describes how carbon atoms are recycled in the ecosystem.
Plants absorb carbon dioxide from the environment and incorporate it into living tissue through photosynthesis.
Animals get carbon by feeding on plants or other animals.
Carbon is returned to atmosphere through respiration (in plants and animals) and decomposition of dead organisms and waste products.
Combustion, such as burning fossil fuels or wood, also releases carbon dioxide back into the atmosphere.

Water cycle describes the continuous movement of water on, above and below the surface of the Earth.
Water evaporates from oceans, rivers, and lakes into the atmosphere—this process is called evaporation.
The same happens in plants through transpiration.
The water vapour cools and condenses forming clouds, which is known as condensation.
Water falls back to the Earth’s surface as precipitation (like rain or snow).
Water can then infiltrate the soil (known as infiltration) or run off to rivers and eventually make it back to the sea, completing the cycle.

Nitrogen is crucial for life as it’s a key part of amino acids and nucleic acids.
The nitrogen cycle outlines how nitrogen gets converted into various chemical forms.
The atmosphere is approximately 78% nitrogen gas (N2), but most organisms can’t use nitrogen in this form.
Nitrogen gas is converted or ‘fixed’ into a usable form (like ammonia) through nitrogen fixation by bacteria or by lightning.
Nitrogen-fixing bacteria can live freely in soil, or in a symbiotic relationship with legumes in root nodules.
Decomposers break down organic waste and dead organisms, converting the complex nitrogen compounds into simpler forms.
Through a process called denitrification, some bacteria convert nitrates back into nitrogen gas, which is released back into the atmosphere, completing the cycle.

Decomposers are organisms like bacteria and fungi that break down dead organisms and waste products.
They play a crucial role in both the carbon and nitrogen cycles by breaking down organic material and releasing carbon and nitrogen into the environment.
Decomposition recycles nutrients, making them available for other organisms to re-use.