Biotic community of organisms in an area plus the abiotic environment. Concerned with movement of energy and materials within an ecosystem. Primary producer (autotroph). primary consumer (herbivore), secondary consumer (carnivore), etc. (heterotrophs) Harvest light or chemical energy, store it in carbon bonds. Photosynthetic autotrophs use photosynthesis to make food (organic compounds). Chemoautotrophs make food using inorganic compounds (hydrothermal vent bacteria). In ecosystems, feeding relationships are more than linear. Chain lengths are short (number of links between trophic levels). Percentage of energy assimilated by an organism that becomes incorporated into new biomass. x100. Amount of energy at one trophic level that is acquired by the trophic level above and incorporated into biomass. x100. Low, most organisms cannot digest whole prey, much lost as heat. Pyramid of numbers (number of individuals decreases at higher trophic levels). Inverted pyramid, single producer supports lots of primary consumers. Standing crop of small phytoplankton supports higher biomass of zooplankton by processing large amounts of energy.