Primary production

Global oceanic and terrestrial photoautotroph abundance, from September 1997 to August 2000. As an estimate of autotroph biomass, it is only a rough indicator of primary-production potential, and not an actual estimate of it. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE.
The Calvin cycle of photosynthesis
Marine diatoms; an example of planktonic microalgae
Differences in relative photosynthesis between plankton species under different irradiance
A kelp forest; an example of attached macroalgae
Annual mean sea surface nitrate for the World Ocean. Data from the World Ocean Atlas 2009.
An oak tree; a typical modern, terrestrial autotroph
The Konza tallgrass prairie in the Flint Hills of northeastern Kansas

Synthesis of organic compounds from atmospheric or aqueous carbon dioxide.

- Primary production

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Study of the relationships between living organisms, including humans, and their physical environment.

Biodiversity of a coral reef. Corals adapt to and modify their environment by forming calcium carbonate skeletons. This provides growing conditions for future generations and forms a habitat for many other species.
Long-tailed broadbill building its nest
Termite mounds with varied heights of chimneys regulate gas exchange, temperature and other environmental parameters that are needed to sustain the internal physiology of the entire colony.
Interspecific interactions such as predation are a key aspect of community ecology.
A riparian forest in the White Mountains, New Hampshire (USA) is an example of ecosystem ecology
Generalized food web of waterbirds from Chesapeake Bay
A trophic pyramid (a) and a food-web (b) illustrating ecological relationships among creatures that are typical of a northern boreal terrestrial ecosystem. The trophic pyramid roughly represents the biomass (usually measured as total dry-weight) at each level. Plants generally have the greatest biomass. Names of trophic categories are shown to the right of the pyramid. Some ecosystems, such as many wetlands, do not organize as a strict pyramid, because aquatic plants are not as productive as long-lived terrestrial plants such as trees. Ecological trophic pyramids are typically one of three kinds: 1) pyramid of numbers, 2) pyramid of biomass, or 3) pyramid of energy.
Sea otters, an example of a keystone species
Social display and colour variation in differently adapted species of chameleons (Bradypodion spp.). Chameleons change their skin colour to match their background as a behavioural defence mechanism and also use colour to communicate with other members of their species, such as dominant (left) versus submissive (right) patterns shown in the three species (A-C) above.
Mutualism: Leafhoppers (Eurymela fenestrata) are protected by ants (Iridomyrmex purpureus) in a mutualistic relationship. The ants protect the leafhoppers from predators and stimulate feeding in the leafhoppers, and in return, the leafhoppers feeding on plants exude honeydew from their anus that provides energy and nutrients to tending ants.
Bumblebees and the flowers they pollinate have coevolved so that both have become dependent on each other for survival.
Parasitism: A harvestman arachnid being parasitized by mites. The harvestman is being consumed, while the mites benefit from traveling on and feeding off of their host.
The leaf is the primary site of photosynthesis in most plants.
The architecture of the inflorescence in grasses is subject to the physical pressures of wind and shaped by the forces of natural selection facilitating wind-pollination (anemophily).
The layout of the first ecological experiment, carried out in a grass garden at Woburn Abbey in 1816, was noted by Charles Darwin in The Origin of Species. The experiment studied the performance of different mixtures of species planted in different kinds of soils.

Ecosystem processes, such as primary production, nutrient cycling, and niche construction, regulate the flux of energy and matter through an environment.

Biomass (ecology)

Mass of living biological organisms in a given area or ecosystem at a given time.

An energy pyramid illustrates how much energy is needed as it flows upward to support the next trophic level. Only about 10% of the energy transferred between each trophic level is converted to biomass.
Humans and their livestock represent 96% of all mammals on earth in terms of biomass, whereas all wild mammals represent only 4%.
Globally, terrestrial and oceanic habitats produce a similar amount of new biomass each year (56.4 billion tonnes C terrestrial and 48.5 billion tonnes C oceanic).
Grasses, trees and shrubs have a much higher biomass than the animals that consume them
Antarctic krill form one of the largest biomasses of any individual animal species.<ref name="NE97">{{cite book | vauthors = Nicol S, Endo Y |url= |title=Fisheries Technical Paper 367: Krill Fisheries of the World |publisher=FAO |year=1997}}</ref>

The total live biomass on Earth is about 550–560 billion tonnes C, and the total annual primary production of biomass is just over 100 billion tonnes C/yr.

Food web

Natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community.

A freshwater aquatic food web. The blue arrows show a complete food chain (algae &rarr; daphnia &rarr; gizzard shad &rarr; largemouth bass &rarr; great blue heron)
A simplified food web illustrating a three trophic food chain (producers-herbivores-carnivores) linked to decomposers. The movement of mineral nutrients is cyclic, whereas the movement of energy is unidirectional and noncyclic. Trophic species are encircled as nodes and arrows depict the links.
A trophic pyramid (a) and a simplified community food web (b) illustrating ecological relations among creatures that are typical of a northern Boreal terrestrial ecosystem. The trophic pyramid roughly represents the biomass (usually measured as total dry-weight) at each level. Plants generally have the greatest biomass. Names of trophic categories are shown to the right of the pyramid. Some ecosystems, such as many wetlands, do not organize as a strict pyramid, because aquatic plants are not as productive as long-lived terrestrial plants such as trees. Ecological trophic pyramids are typically one of three kinds: 1) pyramid of numbers, 2) pyramid of biomass, or 3) pyramid of energy.
Multitrophic interaction: Euphydryas editha taylori larvae sequester defensive compounds from specific types of plants they consume to protect themselves from bird predators
Energy flow diagram of a frog. The frog represents a node in an extended food web. The energy ingested is utilized for metabolic processes and transformed into biomass. The energy flow continues on its path if the frog is ingested by predators, parasites, or as a decaying carcass in soil. This energy flow diagram illustrates how energy is lost as it fuels the metabolic process that transform the energy and nutrients into biomass.
An expanded three link energy food chain (1. plants, 2. herbivores, 3. carnivores) illustrating the relationship between food flow diagrams and energy transformity. The transformity of energy becomes degraded, dispersed, and diminished from higher quality to lesser quantity as the energy within a food chain flows from one trophic species into another. Abbreviations: I=input, A=assimilation, R=respiration, NU=not utilized, P=production, B=biomass.
Illustration of a range of ecological pyramids, including top pyramid of numbers, middle pyramid of biomass, and bottom pyramid of energy. The terrestrial forest (summer) and the English Channel ecosystems exhibit inverted pyramids.Note: trophic levels are not drawn to scale and the pyramid of numbers excludes microorganisms and soil animals. Abbreviations: P=Producers, C1=Primary consumers, C2=Secondary consumers, C3=Tertiary consumers, S=Saprotrophs.
A four level trophic pyramid sitting on a layer of soil and its community of decomposers.
A three layer trophic pyramid linked to the biomass and energy flow concepts.
Paleoecological studies can reconstruct fossil food-webs and trophic levels. Primary producers form the base (red spheres), predators at top (yellow spheres), the lines represent feeding links. Original food-webs (left) are simplified (right) by aggregating groups feeding on common prey into coarser grained trophic species.
An illustration of a soil food web.
A simplified version of a food web in the Gulf of Naples in eutrophic (Green) and oligotrophic (Blue) summer conditions. In the Green system state, both copepods and microzooplankton exert a strong grazing pressure on phytoplankton, while in the Blue state, copepods increase their predation over microzooplankton, which in turn shifts its predation from phytoplankton to bacterial plankton or picoplankton. These trophic mechanisms stabilize the delivery of organic matter from copepods to fish.
Victor Summerhayes and Charles Elton's 1923 food web of Bear Island (Arrows point to an organism being consumed by another organism).

Autotrophs produce more biomass energy, either chemically without the sun's energy or by capturing the sun's energy in photosynthesis, than they use during metabolic respiration.


Organism that produces complex organic compounds using carbon from simple substances such as carbon dioxide, generally using energy from light (photosynthesis) or inorganic chemical reactions (chemosynthesis).

Overview of cycle between autotrophs and heterotrophs. Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water ( green arrow ).
Flowchart to determine if a species is autotroph, heterotroph, or a subtype
Green fronds of a maidenhair fern, a photoautotroph

Autotrophs do not need a living source of carbon or energy and are the producers in a food chain, such as plants on land or algae in water (in contrast to heterotrophs as consumers of autotrophs or other heterotrophs).

Photic zone

Uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis.

Zones of the water column as defined by the amount of light penetration. The mesopelagic is sometimes referred to as the dysphotic zone.
Layers of the pelagic zone
Comparison of the depths which different colors of light penetrate open ocean waters and the murkier coastal waters. Water absorbs the warmer long wavelengths colours, like reds and oranges, and scatter the cooler short wavelength colours.

It also varies with seasonal changes in turbidity, which can be strongly driven by phytoplankton concentrations, such that the depth of the photic zone often decreases as primary production increases.


An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact.

Rainforest ecosystems are rich in biodiversity. This is the Gambia River in Senegal's Niokolo-Koba National Park.
Flora of Baja California Desert, Cataviña region, Mexico
Global oceanic and terrestrial phototroph abundance, from September 1997 to August 2000. As an estimate of autotroph biomass, it is only a rough indicator of primary production potential and not an actual estimate of it.
Sequence of a decomposing pig carcass over time
Biological nitrogen cycling
Loch Lomond in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained stable over a long period until a number of introductions in the 1970s restructured its food web.
Spiny forest at Ifaty, Madagascar, featuring various Adansonia (baobab) species, Alluaudia procera (Madagascar ocotillo) and other vegetation
A hydrothermal vent is an ecosystem on the ocean floor. (The scale bar is 1 m.)
The High Peaks Wilderness Area in the 6000000 acre Adirondack Park is an example of a diverse ecosystem.
The Forest Landscape Integrity Index measures global anthropogenic modification on remaining forests annually. 0 = Most modification; 10= Least.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).

Littoral zone

Part of a sea, lake, or river that is close to the shore.

The littoral zone of an ocean is the area close to the shore and extending out to the edge of the continental shelf.
The intertidal zone of a beach is also part of the littoral zone.
Estuaries are also in the littoral zone.
The three primary zones of a lake are the littoral zone, the open-water (also called the photic or limnetic) zone, and the deep-water (also called the aphotic or profundal) zone.
Shoreline of a lake with nearly unvegetated littoral zone

This results in high primary production and makes the sublittoral zone the location of the majority of sea life.


Phytoplankton are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems.

Photosynthesis requires light, so phytoplankton must operate in surface layers of the ocean where light penetrates. The depth phytoplankton operate at varies, sometimes confined just to the surface, and at other times drifting to 100 metres deep.
World concentrations of surface ocean chlorophyll as viewed by satellite during the northern spring, averaged from 1998 to 2004. Chlorophyll is a marker for the distribution and abundance of phytoplankton.
This map by NOAA shows coastal areas where upwelling occurs. Nutrients that accompany upwelling can enhance phytoplankton abundance
(A) The natural logarithm of the annual mean of monthly phytoplankton richness is shown as a function of sea temperature (k, Boltzmann's constant; T, temperature in kelvin). Filled and open circles indicate areas where the model results cover 12 or less than 12 months, respectively. Trend lines are shown separately for each hemisphere (regressions with local polynomial fitting). The solid black line represents the linear fit to richness, and the dashed black line indicates the slope expected from metabolic theory (−0.32). The map inset visualizes richness deviations from the linear fit. The relative area of three different thermal regimes (separated by thin vertical lines) is given at the bottom of the figure. Observed thermal (B) and latitudinal (C) ranges of individual species are displayed by gray horizontal bars (minimum to maximum, dots for median) and ordered from wide-ranging (bottom) to narrow-ranging (top). The x axis in (C) is reversed for comparison with (B). Red lines show the expected richness based on the overlapping ranges, and blue lines depict the species' average range size (±1 SD, blue shading) at any particular x value. Lines are shown for areas with higher confidence.
(A) Annual mean of monthly species richness and (B) month-to-month species turnover projected by SDMs. Latitudinal gradients of (C) richness and (D) turnover. Colored lines (regressions with local polynomial fitting) indicate the means per degree latitude from three different SDM algorithms used (red shading denotes ±1 SD from 1000 Monte Carlo runs that used varying predictors for GAM). Poleward of the thin horizontal lines shown in (C) and (D), the model results cover only <12 or <9 months, respectively.
As for any other species or ecological community, the oxygen-plankton system is affected by environmental noise of various origins, such as the inherent stochasticity (randomness) of weather conditions.
Cyanobacteria, diatom, dinoflagellate, green algae and coccolithophore (L&ndash;R).

Their cumulative energy fixation in carbon compounds (primary production) is the basis for the vast majority of oceanic and also many freshwater food webs (chemosynthesis is a notable exception).


Oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface.

During an El Niño, wind indirectly drives warm water to the South American coast, reducing the effects of cold upwelling

The increased availability of nutrients in upwelling regions results in high levels of primary production and thus fishery production.

Plant litter

Dead plant material that have fallen to the ground.

Leaf litter, mainly White Beech, Gmelina leichhardtii, from Black Bulga State Conservation Area, NSW, Australia
Plant litter, mainly western hemlock, Tsuga heterophylla, in Mount Baker-Snoqualmie National Forest, Washington, United States
Litter fall in the North American Baldcypress Swamp Network, Illinois to Louisiana, 2003
Common wood sorrel (Oxalis acetosella) in Ivanovo Oblast, Russia
Fungi in the forest floor (Marselisborg Forests in Denmark)
A skink, Eutropis multifasciata, in leaf litter in Sabah, Malaysia
A budget for organic matter in a mature (120-year-old) Scots pine monoculture (SWECON site). Based on data from Andersson et al.(1980). Units are in kg of organic matter per ha. Att. -attached; Surf. -surface; min. -mineral; and veg. -vegetation
Litterfall and throughfall collectors at beech stand in Thetford, East Anglia

Net primary production and litterfall are intimately connected.