Nutrient Cycling (DP IB Biology)

Interaction Between Autotrophs & Heterotrophs

• The process of photosynthesis, carried out by most autotrophs, takes in carbon dioxide from the atmosphere and converts it into carbon compounds and oxygen

  • This process is the source of atmospheric oxygen on Earth

• Aerobic respiration depends on oxygen, so organisms that respire aerobically can make use of the oxygen produced during photosynthesis when they respire, in turn producing carbon dioxide as a waste product, which can be used in photosynthesis

  • Note that both autotrophs and heterotrophs make use of oxygen in respiration

• The combined photosynthesis of all photosynthetic organisms on earth removes a huge volume of carbon dioxide and releases a huge volume of oxygen into the atmosphere, while the combined respiration of all aerobically respiring organisms removes a huge volume of oxygen and releases a huge volume of carbon dioxide

  • This is a major interaction between autotrophs and heterotrophs

• The process that transfer carbon are known as fluxes; huge carbon fluxes take place on Earth every year due to photosynthesis and respiration

Recycling of Chemical Elements in Ecosystems

• In a functioning ecosystem the elements that living organisms need are constantly recycled

  • Producers access inorganic nutrients from the abiotic environment and convert them into carbon compounds

  • Consumers gain organic nutrients from ingesting the tissues of producers and other consumers

  • Decomposers break down the organic molecules in dead tissues and waste matter, making them available again to producers

• This cycling of nutrients applies to carbon, which is taken in from the atmosphere by producers and then returned to the atmosphere by decomposers

• Many other mineral elements are also cycled through ecosystems, e.g.

  • Nitrogen

  • Calcium

  • Phosphorus

  • Sulfur

  • Potassium

• These elements are incorporated into biological molecules within the tissues of living organisms, and then released back into the environment when decomposers break down tissues after death

Public domain, via Flickr

Carbon is returned to the atmosphere and other mineral elements are returned to the soil by the action of decomposers, such as fungi and bacteria, on dead matter