An organism that converts energy from sunlight or from inorganic chemical compounds in the environment into chemical energy stored in the carbon–carbon bonds of organic compounds. Compare heterotroph.
C3 photosynthetic pathway
A biochemical pathway involving the uptake of CO2 by the enzyme ribulose 1,5 bisphosphate carboxylase/oxygenase (rubisco) and synthesis of sugars by the Calvin cycle. Compare C4 photosynthetic pathway, crassulacean acid metabolism.
C4 photosynthetic pathway
A biochemical pathway involving the daytime uptake of CO2 by the enzyme phosphoenol pyruvate carboxylase (PEPcase) in mesophyll cells; the carbon is then transferred as a four carbon acid to the bundle sheath cells, where CO2 is released to the Calvin cycle for sugar synthesis. Compare C3 photosynthetic pathway, crassulacean acid metabolism.
Calvin cycle
The biochemical pathway used by photosynthetic and chemosynthetic organisms to fix CO2 and synthesize sugars.
chemosynthesis
The use of energy from inorganic chemical compounds to produce carbohydrates; also known as chemolithotrophy.
crassulacean acid metabolism (CAM)
A photosynthetic pathway in which CO2 is fixed and stored as an organic acid at night, and then released to the Calvin cycle during the day. Compare C3 photosynthetic pathway, C4 photosynthetic pathway.
facultative CAM
The ability to switch from C3 to CAM photosynthesis when water availability decreases.
fixation
The uptake of the gaseous form of a compound, including CO2 in photosynthesis and N2 in nitrogen fixation, by organisms for use in metabolic functions.
heterotroph
An organism that obtains energy by consuming energy-rich organic compounds from other organisms. Compare autotroph.
marginal value theorem
A conceptual optimal foraging model proposing that an animal should stay in a food patch until the rate of energy gain in that patch has declined to the average rate for the habitat, then depart for another patch.
optimal foraging
A theory proposing that animals will maximize the amount of energy acquired per unit of time, energy, and risk involved in finding food.
photorespiration
A chemical reaction in photosynthetic organisms in which the enzyme rubisco takes up O2, leading to the breakdown of sugars, the release of CO2, and a net loss of energy.
photosynthesis
A process that uses sunlight to provide the energy needed to take up CO2 and synthesize sugars.
