- Photosynthesis is the production of organic substances, cheifly sugars, from
and water, in green plant cells
that are supplied with enough light. This light allows chlorophyll (the
green-colored substance present in plant cells) to aid in the transformation
of the radiant energy (like sunlight) into a chemical form.
- Oxygen is released to solution during photosynthesis and consumed during respiration.
- Some types of bacteria can convert
and water to organic matter by using energy from chemical reactions
rather than light. This process is called chemosynthesis.
- Chemosynthesis is mostly used by life near hydrothermal
vents on oceanic ridges, but also occurs in ocean water that is vented
or seep from ocean sediment near subduction zones.
- Photosynthetic and chemosynthetic organisms can be
called either primary producers or autotrophs because they make their
Length of Food Chain
- Organisms can be labeled by their position in a who-eats-whom
(or what) feeding heiarchy called a trophic pyramid.
- The primary producers at the base of the pyramid
are mostly chlorophyll-containing photosyntheizers.
- The heterotrophs that eat them are called primary consumers (or herbivores).
- The animals that eat primary consumers are called secondary consumers.
- At the top of the trophic pyramid we find the top consumer (top carnivore).
- Some consumers are referred to as omnivores (eat plants and animals).
- As organisms at one trophic level are consumed by
those at the next higher trophic level, food biomass ingested is not
used entirely to create biomass (flesh) of the consumer species at the
higher trophic level. An average of ony about ten percent (varies from
1 to 40%) of food consumed is used for growth. The remaining 90% is
used during respiration to provide the consumer with energy or excreted
- Transfer of food in food chains is clearly inefficient.
- Long marine food chains that lead to higher trophic
level consumers, such as tuna, utilize primary production hundreds of
times less efficiently than short marine food chains, such as those
that support anchovy or sardine.