Energy Flow and Biogeochemical Cycles

Food Chain

linear sequence of organisms through which nutrients and energy pass

Primary producers

the bottom of the food chain, usually photosynthetic organisms (plants and/or phytoplankton)

Primary consumer

consumes the primary producer

Secondary consumers

usually carnivores that eat the primary consumers

apex consumer

the highest-level consumer in the ecosystem

Decomposers

feed on dead'/decaying organisms

decreases

Energy _——— as you move up the food chain

Holistic ecosystem models

attempt to quantify the composition, interaction, and dynamics of entire ecosystems

• most representative of the ecosystem in its natural state

Experimental systems

usually involve either partitioning an ecosystem

Mesocosm

part of a natural ecosystem that can be used for experiments

Microcosm

recreating an ecosystem entirely in an indoor or outdoor laboratory environment

Conceptual model

consists of flow charts to show interactions of different compartments of the living and nonliving components of the ecosystem (maps)

Analytical model

uses simple mathematical formulas to predict the effects of changes on ecosystem structure and dynamics (math)

Simulation model

uses complex computer algorithms to model ecosystems and to predict the ffect of changes (computers)

Biomass

total mass, in a unit area at the time of measurement, of living or previously living organisms within a trophic level

Gross primary productivity

Rate at which photosynthetic primary producers incorporate energy from the sun

Net primary productivity

energy that remains in the primary producers after accounting for the organisms’ respiration and heat loss

• net productivity is then available to the primary consumers at the next trophic level

Trophic level transfer efficiency (TLTE)

measurement of energy transfer efficiency between two successive trophic levels

• average around 10%, only 10% of energy form one level is passed on to the next

• production at present trophic level/production at previous trophic level x 100

Energy pyramids

• Always upright (skinny at top, widest at bottom)

Biomagnification

the increasing concentration of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers

Biogeochemical cycles

depict the recycling of inorganic matter between living organisms and either environment

• Carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus