Chapter 4: Ecosystems & Communities

Biology & LS Biology

autotroph

organism that is able to capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer

primary producer

first producer of energy-rich compounds that are later used by other organisms

photosynthesis

process used by plants and other autotrophs to capture light energy and use it to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates such as sugars and starches

chemosynthesis

process in which chemical energy is used to produce carbohydrates

heterotroph

organism that obtains food by consuming other living things; also called a consumer

consumer

organism that relies on other organisms for its energy and food supply; also called a heterotroph

detritus

small pieces of dead or decaying plant or animal remains

food chain

a series of in an ecosystem steps in which organisms transfer energy by eating or being eaten

phytoplankton

photosynthetic algae found near the surface of the ocean

food web

network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem

trophic level

each step in a food chain or food web

ecological pyramid

illustration of relative amounts of energy or matter contained within each trophic level in a food chain or food web

biomass

the total mass of living tissue within a trophic level

biogeochemical cycle

process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another

nutrient

chemical substance that an organism needs to sustain life

nitrogen fixation

process of converting nitrogen gas into nitrogen compounds that plants can absorb and use

denitrification

process by which soil bacteria convert nitrates into nitrogen gas

limiting nutrient

single essential nutrient that limits productivity in an ecosystem