Cycles within Ecosystems

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.

The Water Cycle

  • 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.

The Nitrogen 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.

Role of Decomposers

  • 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.