1. THE CARBON-
OXYGEN CYCLE

2. Respiration and photosynthesis are
the two importatnt processes involved in the
carbon-oxygen cycle.In this cycle,plants
and other chlorophyll-bearing organisms
take in carbon dioxide from the environment
and use this gas during photosynthetic
organisms such as algae and certain
protists release oxygen,a by-product of
photosynthesis,into the atmosphere and
this is taken in by animals and other aerobic
organisms (including microorganisms and
decomposers).Terrestrial organisms obtain
oxygen directly from the atmosphere,while
aquatic organisms obtain oxygen dissolved
in water.

3. The element carbon is stored in
various forms of organis compounds
such as carbohydrates,fats,proteins,and
nucleic acids.It is also retained in the
bodies of consumers until they
die.Carbon and waste products of dead
organisms accumulate in the soil.After
hundreds to thousands of years,the
organic compounds form part of fossls
and fossil fuels.Ocean uptake may also
bring about release of carbon dioxide.

4. Organic carbon found in
carbohydrates produced in photosynthesis
is utilized during cellular respiration.It is
passed from producers to consumers,for
example,from trees to sheep.Carbon
stored in the form of compounds of
carbohydrates,fats,and the like is retained
in the bodies of the consumers until they
die.It is finally released as carbon dioxide
when the remains of the consumers
decompose.The remains of plants and
animals accumulate in the ground for over
millions of years,and are subjected to
physical prosses that transform them into
fossil fuels,such as coal and petroleum.