E. Nutrient Cycle

NUTRIENT CYCLING IN AN ECOSYSTEM

• • Essential nutrients for life include carbon, oxygen, nitrogen and water.

  • In natural ecosystems, the nutrients are released back into the soil when organisms die.

  • Decomposers (eg fungi and bacteria) break down dead organisms to return materials in the dead organisms to the physical environment, to be used by green plants.

  • In a balanced ecosystem, nutrients are not lost but are continually recycled.

  • The cycling of nutrients results from physical, chemical and biological processes that include abiotic and biotic environments.

Carbon Cycle

• • • 1. Photosynthesis: During photosynthesis, plants absorb carbon dioxide and use it to synthesise carbohydrates. Some of the carbohydrates are converted into proteins and fats.

      2. Feeding: Animals obtain carbon compounds by feeding on plants or other animals.

      3. Respiration: Plants and animals respire, releasing carbon dioxide into the atmosphere.

      4. Decomposition: Decomposers such as bacteria, microbes and fungi break down dead organic matter and release carbon dioxide.

      5. Combustion: Dead bodies of organisms buried in the Earth for millions of years produce fossil fuels such as coal, natural gas and oil. Combustion of fossil fuels releases carbon dioxide into the environment.

Importance of the carbon cycle

1. The carbon cycle ensures that there is a continuous supply of carbon dioxide for plants to carry out photosynthesis. Photosynthesis converts light energy from the Sun into chemical energy in carbohydrates. This energy is then transferred to different trophic levels of food chains and food webs.

2. Carbon-containing compounds, eg carbohydrates, proteins and fats carry the stored energy from organism to organism in the food chains of an ecosystem. This enables energy to be transferred through the trophic levels in food chains and food webs.

3. Carbon cycle maintains the appropriate concentration of carbon dioxide in the atmosphere. Disturbances to the carbon cycle can lead to increased global warming.