Everything Life Sciences Grade 10

FACT

WATCH:a video

about he oxygen

cycle. Focus on the

first part of the

video clip and the

summary at the end.

See video:

SHORTCODEat

http://www.everythingscience.co.za

Figure 9.20: Oxygen cycle

Carboncycle DUMMY

Carbonis the basic building block of allorganicmaterials, and therefore, of living organisms.
Most of the carbon on earth can be found in the crust. Other reservoirs of carbon include
the oceans and atmosphere.

Carbon moves from one reservoir to another by these processes:

• Combustion: burning of wood and fossil fuels by factory and auto emissions transfers
  carbon to the atmosphere as carbon dioxide.


• Photosynthesis: carbon dioxide is taken up by plants during photosynthesis and is
  converted into energy rich sources, such as glucose, which contains carbon.


• Cellular respiration: animals eat plants for food, taking up the carbon. Plants and ani-
  mals release carbon into the atmosphere as carbon dioxide during gaseous exchange


• Metabolism: organisms convert carbon intoorganicmolecules like fats, carbohydrates
  and proteins when they eat plants or animals.


• Precipitate: carbon dioxide in the atmosphere can alsoprecipitateas carbonate in
  ocean sediments.


• Decay: carbon dioxide gas is also released into the atmosphere during the decay of all
  organisms.

Photosynthesisandgaseous exchangeare the main carbon cycling processes involving living
organisms. Figure 9.21 depicts the carbon cycle.

Chapter 9. Biospheres to ecosystems 283