Plants, algae, cyanobacteria

2. CONSUMERS or HETEROTROPHS

a. Herbivores feed on plants
b. Carnivores feed on other animals
c. Omnivores feed on both plants and animals

3. DECOMPOSERS and DETRITOVORES

Break down the organic compounds found in waste organic matter and dead organisms (detritus). Decomposers are primarily microscopic bacteria and fungi whereas detritovores are typically larger animals such as worms, snails, slugs, insects, and in some cases, larger animals.

KEY STEPS IN CARBON CYCLE

1. CO₂ from atmosphere or ocean is used by terrestrial or land plants during photosynthesis.
Carbon Dioxide + Water + Sunlight ---> Glucose + Oxygen


Energy + 6 CO₂+6H₂O ---> C₆H₁₂O₆+ 6O₂


2. Glucose made by plants is used by consumers in oceans or on land through process of cellular respiration (opposite of photosynthesis). CO₂ that is generated is returned to atmosphere. Plants also release CO₂ during cellular respiration.

3. Decomposers which eat wastes and remains from plants and animals also return CO₂to oceans or atmosphere.

4. Large amounts of CO₂ released into atmosphere by burning fossil fuels and wood which has accumulated carbon for hundreds or millions of years.

5. Shells of marine organisms have been covered by sediments and cemented together to form limestone. Over millions of years, limestone has been lifted to form land surfaces. This returns carbon to water and atmosphere.

STEPS IN NITROGEN CYCLE

1. Nitrogen fixation
Conversion of gaseous nitrogen to ammonia by nitrogen - fixing bacteria in soil and water. Examples of organisms include Rhizobium which live in special swellings or nodules on roots of legumes.

2. Nitrification
Conversion of ammonia to nitrate by soil bacteria known as nitrifying bacteria.

3. Assimilation
Incorporation of nitrate (and ammonia) into plant proteins and nucleic acids. Animals assimilate nitrogen by taking in plant nitrogen compounds.

4. Ammonification
Conversion of biological nitrogen compounds (waste products of living organisms and dead organisms) into ammonia by ammonifying bacteria. Ammonia then available for nitrification and assimilation.

5. Denitrification
Reduction of nitrate to gaseous nitrogen by denitrifying bacteria. Nitrogen returned to atmosphere.

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