Chapter 4: Ecosystems - Energy Flow and Cycles of Matter

Vocabulary practice flashcards covering primary producers, consumers, ecological pyramids, biogeochemical cycles, and nutrient limitations from Chapter 4: Ecosystems.

Algal Bloom

An out-of-control growth of algae caused by an oversupply of limiting nutrients such as nitrogen or phosphorus combined with favorable environmental factors, which can produce toxic sludge and kill aquatic life.

Autotroph

An organism that captures energy from nonliving sources and converts it into forms living cells can use; also referred to as a primary producer.

Primary Producer

The first producer of energy-rich compounds that can be used later by other organisms; includes plants, algae, and certain bacteria.

Photosynthesis

A biological process in which solar energy is harnessed by algae, plants, and certain bacteria to convert carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$) into oxygen ($\text{O}_2$) and energy-rich carbohydrates like sugars and starches.

Chemosynthesis

A process in which autotrophic bacteria use chemical energy stored in inorganic molecules, such as hydrogen sulfide, to produce carbohydrates in the absence of light.

Heterotroph

An organism that cannot harness energy directly from the environment and must acquire energy and nutrients by consuming other organisms; also known as a consumer.

Carnivore

A consumer that obtains energy and nutrients by killing and eating other animals.

Scavenger

An animal that consumes the carcasses of other animals that have been killed by predators or have died of other causes.

Herbivore

A consumer that obtains energy and nutrients by eating plant leaves, roots, seeds, or fruits.

Omnivore

An animal whose diet naturally includes both plants and other animals.

Decomposer

An organism, such as a fungus or bacterium, that feeds by chemically breaking down organic matter, producing detritus and releasing nutrients.

Detritus

Small pieces of dead and decaying plant and animal remains produced by the chemical breakdown of organic matter by decomposers.

Detritivore

An organism that chews or grinds detritus particles into smaller pieces, commonly digesting decomposers that live on and in the detritus.

Cud

A regurgitated mixture of pulped food and cellulose-digesting bacteria that grazing animals re-chew and reswallow to extract energy from tough plant matter.

Food Chain

A series of organisms in which energy is transferred in a one-way stream from one organism to another through feeding relationships.

Phytoplankton

Tiny floating aquatic algae that carry out photosynthesis and act as primary producers in open-ocean and freshwater food chains.

Food Web

A complex network of interconnected feeding interactions in an ecosystem through which both energy and matter move.

Trophic Level

Each step or level in a food chain or food web, starting with primary producers at the first level.

Ecological Pyramid

A graphical model that illustrates the relative amount of energy or matter contained within each trophic level in a food chain or food web.

Pyramid of Energy

A model showing the relative amount of energy available at each trophic level, demonstrating that on average only about $10\%$ of available energy transfers from one level to the next.

Biomass

The total amount of living tissue within a given trophic level, usually measured in grams of organic matter per unit area.

Pyramid of Biomass

A model that illustrates the relative amount of living organic matter present in each trophic level of an ecosystem.

Pyramid of Numbers

A model showing the relative number of individual organisms found at each trophic level in an ecosystem.

Biogeochemical Cycle

A cycle powered by the flow of energy that moves matter from one trophic level to another and recycles chemical elements within and among global systems.

Biological Processes

Activities performed by living organisms—including photosynthesis, cellular respiration, eating, and waste elimination—that mainly occur in the biosphere.

Geological Processes

Earth processes occurring mainly in the geosphere, including volcanic eruptions, the formation and breakdown of rock, and major movements of matter within and below Earth's surface.

Physical and Chemical Processes

Processes including cloud formation, precipitation, surface runoff, river flows, and lightning strikes that occur primarily across the hydrosphere, atmosphere, and geosphere.

Transpiration

The process by which groundwater absorbed by plant roots evaporates into the atmosphere from the leaves of plants.

Runoff

Precipitation that flows along the surface of land until it enters a river, stream, lake, or ocean.

Groundwater

Precipitation that seeps into soil, where it can be taken up by plant roots, enter streams or lakes, or collect in deep underground reservoirs.

Fossil Fuels

Deposits of coal, oil, and natural gas formed over millions of years from organic carbon of buried, undecomposed plant and marine remains exposed to heat and pressure.

Nitrogen Fixation

The biological or chemical process of converting abundant atmospheric nitrogen gas ($\text{N}_2$) into ammonia ($\text{NH}_3$), performed naturally by specific bacteria.

Denitrification

The process by which specific bacteria obtain energy by converting nitrates ($\text{NO}_3^-$) back into nitrogen gas ($\text{N}_2$), which is released into the atmosphere.

Phosphorus Cycle

A biogeochemical cycle that does not cycle through the atmosphere, circulating phosphorus strictly between land, rocks, soil minerals, ocean sediments, and living organisms.

Primary Productivity

The rate at which primary producers create new organic material within an ecosystem.

Limiting Nutrient

Any essential nutrient whose scarce supply restricts or limits the primary productivity of an ecosystem.

Sustainable Agriculture

A method of growing and raising food by taking advantage of natural biogeochemical cycles without disrupting them.