In
ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
. A species habitat can be seen as the physical manifestation of its
ecological niche
In ecology, a niche is the match of a species to a specific environmental condition.
Three variants of ecological niche are described by
It describes how an organism or population responds to the distribution of resources and competitors (fo ...
. Thus "habitat" is a species-specific term, fundamentally different from concepts such as
environment
Environment most often refers to:
__NOTOC__
* Natural environment, all living and non-living things occurring naturally
* Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
or
vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic charact ...
assemblages, for which the term "habitat-type" is more appropriate.
The physical factors may include (for example):
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...
,
moisture
Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...
, range of
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied on ...
, and
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
intensity.
Biotic
Biotics describe living or once living components of a community; for example organisms, such as animals and plants.
Biotic may refer to:
*Life, the condition of living organisms
*Biology, the study of life
* Biotic material, which is derived from ...
factors will include the availability of
food
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ...
and the presence or absence of
predators. Every species has particular habitat requirements, with habitat generalist species able to thrive in a wide array of environmental conditions while habitat specialist species requiring a very limited set of factors to survive. The habitat of a species is not necessarily found in a geographical area, it can be the interior of a stem, a rotten log, a rock or a clump of
moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta ('' sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and ...
; a
parasitic organism has as its habitat the body of its
host, part of the host's body (such as the digestive tract), or a
single cell Single cell and similar can mean:
Biology
*Single-cell organism
*Single-cell protein
*Single-cell recording, a neuro-electric monitoring technique
*Single-cell sequencing
**Single cell epigenomics
*Single-cell transcriptomics
Other
* Single-cell th ...
within the host's body.
[For example:
]
Habitat types are environmental categorizations of different environments based on the characteristics of a given geographical area, particularly vegetation and climate.
Thus habitat types do not refer to a single species but to multiple species living in the same area. For example, terrestrial habitat types include
forest
A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
,
steppe
In physical geography, a steppe () is an ecoregion characterized by grassland plains without trees apart from those near rivers and lakes.
Steppe biomes may include:
* the montane grasslands and shrublands biome
* the temperate grasslan ...
,
grassland
A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...
, semi-arid or
desert.
Fresh-water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...
habitat types include
marsh
A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found a ...
es,
streams,
river
A river is a natural flowing watercourse, usually freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...
s,
lake
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much lar ...
s, and
pond
A pond is an area filled with water, either natural or Artificiality, artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% Aquatic plant, emergent vegetation helps in disting ...
s; marine habitat types include salt marshes, the coast, the
intertidal zone
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...
,
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environme ...
,
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic processes—deposition (geology), deposition of ...
s, bays, the open sea, the sea bed, deep water and
submarine vents. Habitat types may change over time. Causes of change may include a violent event (such as the eruption of a
volcano
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates ...
, an
earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
, a
tsunami
A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...
, a
wildfire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identi ...
or a change in oceanic currents); or change may occur more gradually over millennia with alterations in the
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologica ...
, as
ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at ...
s and
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...
s advance and retreat, and as different weather patterns bring changes of
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hai ...
and
solar radiation
Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre ...
. Other changes come as a direct result of human activities, such as
deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then land conversion, converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban area, urban ...
, the
plowing of ancient grasslands, the diversion and damming of rivers, the draining of marshland and the dredging of the seabed. The
introduction of alien species can have a devastating effect on native wildlife – through increased
predation
Predation is a biological interaction
In ecology, a biological interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species (intraspecific interactions), or o ...
, through competition for resources or through the introduction of pests and diseases to which the indigenous species have no immunity.
Definition and etymology
The word "habitat" has been in use since about 1755 and derives from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
''habitāre'', to inhabit, from ''habēre'', to have or to hold. Habitat can be defined as the natural environment of an
organism
In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multicellular o ...
, the type of place in which it is natural for it to live and grow.
[ ] It is similar in meaning to a
biotope; an area of uniform environmental conditions associated with a particular community of plants and animals.
Environmental factors
The chief environmental factors affecting the distribution of living organisms are temperature, humidity, climate, soil and light intensity, and the presence or absence of all the requirements that the organism needs to sustain it. Generally speaking, animal communities are reliant on specific types of plant communities.
Some plants and animals have habitat requirements which are met in a wide range of locations. The small white butterfly ''
Pieris rapae'' for example is found on all the continents of the world apart from Antarctica. Its larvae feed on a wide range of ''
Brassica
''Brassica'' () is a genus of plants in the cabbage and mustard family (Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plants. Crops from this genus are sometimes called ''cole ...
s'' and various other plant species, and it thrives in any open location with diverse plant associations.
The large blue butterfly ''
Phengaris arion
The large blue (''Phengaris arion'') is a species of butterfly in the family Lycaenidae. The species was first defined in 1758 and first recorded in Britain in 1795. In 1979 the species became mostly extinct in Britain but has been successfully ...
'' is much more specific in its requirements; it is found only in chalk grassland areas, its larvae feed on ''
Thymus
The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...
'' species and because of complex lifecycle requirements it inhabits only areas in which ''
Myrmica
''Myrmica'' is a genus of ants within the subfamily Myrmicinae. It is widespread throughout the temperate regions of the Holarctic and high mountains in Southeast Asia.
The genus consists of around 200 known species and additional subspecies, ...
'' ants live.
Disturbance is important in the creation of biodiverse habitat types. In the absence of disturbance, a climax vegetation cover develops that prevents the establishment of other species.
Wildflower meadows are sometimes created by conservationists but most of the flowering plants used are either
annuals or
biennials and disappear after a few years in the absence of patches of bare ground on which their seedlings can grow.
Lightning strikes and toppled trees in tropical forests allow species richness to be maintained as
pioneering species
Pioneer species are hardy species that are the first to colonize barren environments or previously biodiverse steady-state ecosystems that have been disrupted, such as by wildfire.
Pioneer flora
Some lichens grow on rocks without soil, so m ...
move in to fill the gaps created.
Similarly coastal habitat types can become dominated by kelp until the seabed is disturbed by a storm and the algae swept away, or shifting sediment exposes new areas for
colonisation. Another cause of disturbance is when an area may be overwhelmed by an
invasive introduced species which is not kept under control by natural enemies in its new habitat.
Types
Terrestrial
Terrestrial habitat types include forests, grasslands, wetlands and deserts. Within these broad
biome
A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...
s are more specific habitat types with varying climate types, temperature regimes, soils, altitudes and vegetation. Many of these habitat types grade into each other and each one has its own typical communities of plants and animals. A habitat-type may suit a particular species well, but its presence or absence at any particular location depends to some extent on chance, on its dispersal abilities and its efficiency as a colonizer.
Freshwater
Freshwater habitat types include rivers, streams, lakes, ponds, marshes and bogs.
Although some organisms are found across most of these habitat types, the majority have more specific requirements. The water velocity, its temperature and oxygen saturation are important factors, but in river systems, there are fast and slow sections, pools,
bayous and
backwaters which provide a range of habitat types. Similarly,
aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...
s can be floating, semi-submerged, submerged or grow in permanently or temporarily saturated soils besides bodies of water. Marginal plants provide important habitat for both invertebrates and vertebrates, and submerged plants provide oxygenation of the water, absorb nutrients and play a part in the reduction of pollution.
Marine
Marine habitats include brackish water, estuaries, bays, the open sea, the intertidal zone, the sea bed, reefs and deep / shallow water zones.
Further variations include
rock pools,
sand banks,
mudflat
Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal f ...
s,
brackish
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
lagoons, sandy and pebbly beaches, and
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families ( Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the ...
beds, all supporting their own flora and fauna. The
benthic zone or seabed provides a home for both static organisms, anchored to the
substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (locomotion), the surface over which an organism lo ...
, and for a large range of organisms crawling on or burrowing into the surface. Some creatures float among the waves on the surface of the water, or raft on floating debris, others swim at a range of depths, including organisms in the
demersal zone close to the seabed, and myriads of organisms drift with the currents and form the
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cr ...
.
Desert
A
desert is not the kind of habitat that favours the presence of amphibians, with their requirement for water to keep their skins moist and for the development of their young. Nevertheless, some frogs live in deserts, creating moist habitat types underground and hibernating while conditions are adverse.
Couch's spadefoot toad (''Scaphiopus couchii'') emerges from its burrow when a downpour occurs and lays its eggs in the transient pools that form; the tadpoles develop with great rapidity, sometimes in as little as nine days, undergo
metamorphosis, and feed voraciously before digging a burrow of their own.
Wetlands
Other organisms cope with the drying up of their aqueous habitat in other ways.
Vernal pool
Vernal pools, also called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland usually devoid of fish, and thus allow the safe ...
s are ephemeral ponds that form in the rainy season and dry up afterwards. They have their specially-adapted characteristic flora, mainly consisting of annuals, the seeds of which survive the drought, but also some uniquely adapted perennials.
Animals adapted to these extreme habitat types also exist;
fairy shrimps can lay "winter eggs" which are resistant to
desiccation
Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
, sometimes being blown about with the dust, ending up in new depressions in the ground. These can survive in a dormant state for as long as fifteen years.
Some
killifish
A killifish is any of various oviparous (egg-laying) cyprinodontiform fish (including families Aplocheilidae, Cyprinodontidae, Fundulidae, Profundulidae and Valenciidae). All together, there are 1,270 species of killifish, the biggest famil ...
behave in a similar way; their eggs hatch and the juvenile fish grow with great rapidity when the conditions are right, but the whole population of fish may end up as eggs in
diapause in the dried up mud that was once a pond.
Urban
Many animals and plants have taken up residence in urban environments. They tend to be adaptable generalists and use the town's features to make their homes.
Rat
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), ''Bandicota'' (bandicoot ...
s and
mice have followed man around the globe,
pigeon
Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...
s,
peregrines,
sparrow
Sparrow may refer to:
Birds
* Old World sparrows, family Passeridae
* New World sparrows, family Passerellidae
* two species in the Passerine family Estrildidae:
** Java sparrow
** Timor sparrow
* Hedge sparrow, also known as the dunnock or hedg ...
s,
swallows and
house martins use the buildings for nesting,
bats use roof space for roosting,
fox
Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush'').
Twelv ...
es visit the garbage bins and
squirrels,
coyotes,
raccoon
The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight o ...
s and
skunk
Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...
s roam the streets. About 2,000 coyotes are thought to live in and around
Chicago
(''City in a Garden''); I Will
, image_map =
, map_caption = Interactive Map of Chicago
, coordinates =
, coordinates_footnotes =
, subdivision_type = List of sovereign states, Count ...
.
A survey of dwelling houses in northern European cities in the twentieth century found about 175 species of invertebrate inside them, including 53 species of beetle, 21 flies, 13 butterflies and moths, 13 mites, 9 lice, 7 bees, 5 wasps, 5 cockroaches, 5 spiders, 4 ants and a number of other groups.
In warmer climates, termites are serious pests in the urban habitat; 183 species are known to affect buildings and 83 species cause serious structural damage.
Microhabitat types
A microhabitat is the small-scale physical requirements of a particular organism or population. Every habitat includes large numbers of microhabitat types with subtly different exposure to light, humidity, temperature, air movement, and other factors. The
lichens that grow on the north face of a boulder are different from those that grow on the south face, from those on the level top, and those that grow on the ground nearby; the lichens growing in the grooves and on the raised surfaces are different from those growing on the veins of quartz. Lurking among these miniature "forests" are the
microfauna, species of
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
, each with its own specific habitat requirements.
There are numerous different microhabitat types in a wood; coniferous forest, broad-leafed forest, open woodland, scattered trees, woodland verges, clearings, and glades; tree trunk, branch, twig, bud, leaf, flower, and fruit; rough bark, smooth bark, damaged bark, rotten wood, hollow, groove, and hole; canopy, shrub layer, plant layer, leaf litter, and soil; buttress root, stump, fallen log, stem base, grass tussock, fungus, fern, and moss.
The greater the structural diversity in the wood, the greater the number of microhabitat types that will be present. A range of tree species with individual specimens of varying sizes and ages, and a range of features such as streams, level areas, slopes, tracks, clearings, and felled areas will provide suitable conditions for an enormous number of biodiverse plants and animals. For example, in Britain it has been estimated that various types of rotting wood are home to over 1700 species of invertebrate.
For a parasitic organism, its habitat is the particular part of the outside or inside of its
host on or in which it is adapted to live. The
life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
* Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
* Life-cycle hypothesi ...
of some parasites involves several different host species, as well as free-living life stages, sometimes within vastly different microhabitat types.
One such organism is the trematode (flatworm) ''
Microphallus turgidus
''Microphallus turgidus'' is a widespread and locally common flatworm parasite in New Zealand lakes and streams. Multilocus allozyme genotype data show that ''Microphallus turgidus'' is a single outbred species with high levels of gene flow a ...
'', present in brackish water marshes in the southeastern United States. Its first intermediate host is a
snail
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...
and the second, a
glass shrimp. The final host is the waterfowl or mammal that consumes the shrimp.
Extreme habitat types
Although the vast majority of life on Earth lives in
mesophyllic (moderate) environments, a few organisms, most of them
microbes, have managed to colonise extreme environments that are unsuitable for more complex life forms. There are
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
, for example, living in
Lake Whillans, half a mile below the ice of Antarctica; in the absence of sunlight, they must rely on organic material from elsewhere, perhaps decaying matter from glacier melt water or minerals from the underlying rock.
Other bacteria can be found in abundance in the
Mariana Trench, the deepest place in the ocean and on Earth;
marine snow drifts down from the surface layers of the sea and accumulates in this undersea valley, providing nourishment for an extensive community of bacteria.
Other microbes live in environemts lacking in oxygen, and are dependent on chemical reactions other than
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
. Boreholes drilled into the rocky seabed have found microbial communities apparently based on the products of reactions between water and the constituents of rocks. These communities have not been studied much, but may be an important part of the global
carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major componen ...
.
Rock in mines two miles deep also harbour microbes; these live on minute traces of hydrogen produced in slow oxidizing reactions inside the rock. These metabolic reactions allow life to exist in places with no oxygen or light, an environment that had previously been thought to be devoid of life.
The
intertidal zone
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...
and the
photic zone in the oceans are relatively familiar habitat types. However the vast bulk of the ocean is inhospitable to air-breathing humans, with
scuba divers
This is a list of underwater divers whose exploits have made them notable.
Underwater divers are people who take part in underwater diving activities – Underwater diving is practiced as part of an occupation, or for recreation, where t ...
limited to the upper or so.
The lower limit for photosynthesis is and below that depth the prevailing conditions include total darkness, high pressure, little oxygen (in some places), scarce food resources and extreme cold. This habitat is very challenging to research, and as well as being little-studied, it is vast, with 79% of the Earth's
biosphere
The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also be ...
being at depths greater than .
With no plant life, the animals in this zone are either
detritivores, reliant on food drifting down from surface layers, or they are predators, feeding on each other. Some organisms are
pelagic
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...
, swimming or drifting in mid-ocean, while others are benthic, living on or near the seabed. Their growth rates and metabolisms tend to be slow, their eyes may be very large to detect what little illumination there is, or they may be blind and rely on other sensory inputs. A number of deep sea creatures are
bioluminescent; this serves a variety of functions including predation, protection and social recognition.
In general, the bodies of animals living at great depths are adapted to high pressure environments by having pressure-resistant
biomolecule
A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include larg ...
s and small organic molecules present in their cells known as
piezolytes, which give the proteins the flexibility they need. There are also unsaturated fats in their membranes which prevent them from solidifying at low temperatures.
Hydrothermal vents were first discovered in the ocean depths in 1977.
They result from seawater becoming heated after seeping through cracks to places where hot
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...
is close to the seabed. The under-water hot springs may gush forth at temperatures of over and support unique communities of organisms in their immediate vicinity.
The basis for this teeming life is
chemosynthesis
In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydrog ...
, a process by which microbes convert such substances as
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The und ...
or
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...
into organic molecules.
These bacteria and
Archaea are the primary producers in these ecosystems and support a diverse array of life. About 350 species of organism, dominated by
molluscs
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
,
polychaete worms and
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...
s, had been discovered around hydrothermal vents by the end of the twentieth century, most of them being new to science and
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...
to these habitat types.
Besides providing locomotion opportunities for winged animals and a conduit for the dispersal of
pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...
grains,
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
s and
seed
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...
s, the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. ...
can be considered to be a habitat-type in its own right. There are metabolically active microbes present that actively reproduce and spend their whole existence airborne, with hundreds of thousands of individual organisms estimated to be present in a cubic meter of air. The airborne microbial community may be as diverse as that found in soil or other terrestrial environments, however these organisms are not evenly distributed, their densities varying spatially with altitude and environmental conditions.
Aerobiology has not been studied much, but there is evidence of
nitrogen fixation
Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. At ...
in
cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
s, and less clear evidence of carbon cycling, both facilitated by microbial activity.
There are other examples of extreme habitat types where specially adapted lifeforms exist;
tar pits teeming with microbial life;
naturally occurring crude oil pools inhabited by the larvae of the
petroleum fly;
hot spring
A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by c ...
s where the temperature may be as high as and
cyanobacteria create
microbial mats;
cold seep
A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the see ...
s where the
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ear ...
and hydrogen sulfide issue from the ocean floor and support microbes and higher animals such as
mussel
Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, whic ...
s which form
symbiotic associations with these
anaerobic organisms;
salt pans Salt pans can refer to:
* Salt pan (geology), a flat expanse of ground covered with salt and other minerals, usually found in deserts
** Sabkha, a phonetic translation of the Arabic word for a salt pan (geology)
* Salt evaporation pond, a method o ...
that harbour
salt-tolerant bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
,
archaea and also fungi such as the
black yeast ''
Hortaea werneckii'' and
basidiomycete ''
Wallemia ichthyophaga'';
ice sheets in Antarctica which support fungi ''
Thelebolus
''Thelebolus'' is a genus of fungi in the Thelebolaceae family. Often considered related to Pezizales, 18S phylogenies show Thelebolales are a sister group to Pseudeurotiaceae and Leotiales. ITS is an adequate DNA barcode but there are only six ...
'' spp.,
glacial ice with a variety of bacteria and fungi;
and snowfields on which
algae
Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...
grow.
Habitat change
Whether from natural processes or the activities of man, landscapes and their associated habitat types change over time. There are the slow
geomorphological changes associated with the geologic processes that cause
tectonic uplift
Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal t ...
and
subsidence, and the more rapid changes associated with earthquakes, landslides, storms, flooding, wildfires,
coastal erosion
Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. The landwa ...
, deforestation and changes in land use.
Then there are the changes in habitat types brought on by alterations in farming practices, tourism, pollution,
fragmentation
Fragmentation or fragmented may refer to:
Computers
* Fragmentation (computing), a phenomenon of computer storage
* File system fragmentation, the tendency of a file system to lay out the contents of files non-continuously
* Fragmented distributi ...
and climate change.
Loss of habitat is the single greatest threat to any species. If an island on which an endemic organism lives becomes uninhabitable for some reason, the species will become
extinct. Any type of habitat surrounded by a different habitat is in a similar situation to an island. If a forest is divided into parts by logging, with strips of cleared land separating woodland blocks, and the distances between the remaining fragments exceeds the distance an individual animal is able to travel, that species becomes especially vulnerable. Small populations generally lack genetic diversity and may be threatened by increased predation, increased competition, disease and unexpected catastrophe.
At the edge of each forest fragment, increased light encourages secondary growth of fast-growing species and old growth trees are more vulnerable to logging as access is improved. The birds that nest in their crevices, the
epiphytes that hang from their branches and the invertebrates in the leaf litter are all adversely affected and biodiversity is reduced.
Habitat fragmentation can be ameliorated to some extent by the provision of
wildlife corridor
A wildlife corridor, habitat corridor, or green corridor is an area of habitat (ecology), habitat connecting wildlife populations separated by human activities or structures (such as roads, development, or logging). This allows an exchange of i ...
s connecting the fragments. These can be a river, ditch, strip of trees, hedgerow or even an underpass to a highway. Without the corridors, seeds cannot disperse and animals, especially small ones, cannot travel through the hostile territory, putting populations at greater risk of
local extinction
Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...
.
Habitat disturbance can have long-lasting effects on the environment. ''
Bromus tectorum'' is a vigorous grass from Europe which has been introduced to the United States where it has become invasive. It is highly adapted to fire, producing large amounts of flammable detritus and increasing the frequency and intensity of wildfires. In areas where it has become established, it has altered the local fire regimen to such an extant that native plants cannot survive the frequent fires, allowing it to become even more dominant.
A marine example is when
sea urchin
Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) ...
populations "
explode" in coastal waters and destroy all the
macroalgae present. What was previously a
kelp forest
Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on E ...
becomes an
urchin barren that may last for years and this can have a profound effect on the
food chain. Removal of the sea urchins, by disease for example, can result in the seaweed returning, with an over-abundance of fast-growing kelp.
Fragmentation
Destruction
Habitat protection
The protection of habitat types is a necessary step in the maintenance of biodiversity because if
habitat destruction
Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
occurs, the animals and plants reliant on that habitat suffer. Many countries have enacted legislation to protect their wildlife. This may take the form of the setting up of national parks, forest reserves and wildlife reserves, or it may restrict the activities of humans with the objective of benefiting wildlife. The laws may be designed to protect a particular species or group of species, or the legislation may prohibit such activities as the collecting of bird eggs, the hunting of animals or the removal of plants. A general law on the protection of habitat types may be more difficult to implement than a site specific requirement. A concept introduced in the United States in 1973 involves protecting the critical habitat of
endangered species, and a similar concept has been incorporated into some Australian legislation.
International treaties may be necessary for such objectives as the setting up of marine reserves. Another international agreement, the
Convention on the Conservation of Migratory Species of Wild Animals, protects animals that migrate across the globe and need protection in more than one country.
Even where legislation protects the environment, a lack of enforcement often prevents effective protection. However, the protection of habitat types needs to take into account the needs of the local residents for food, fuel and other resources. Faced with hunger and destitution, a farmer is likely to plough up a level patch of ground despite it being the last suitable habitat for an endangered species such as the
San Quintin kangaroo rat, and even kill the animal as a pest.
In the interests of
ecotourism
Ecotourism is a form of tourism involving responsible travel (using sustainable transport) to natural areas, conserving the environment, and improving the well-being of the local people. Its purpose may be to educate the traveler, to provide fund ...
it is desirable that local communities are educated on the uniqueness of their flora and fauna.
Monotypic habitat
A monotypic habitat-type is a concept sometimes used in
conservation biology
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an ...
, in which a single species of animal or plant is the only species of its type to be found in a specific habitat and forms a
monoculture
In agriculture, monoculture is the practice of growing one crop species in a field at a time. Monoculture is widely used in intensive farming and in organic farming: both a 1,000-hectare/acre cornfield and a 10-ha/acre field of organic kale a ...
. Even though it might seem such a habitat-type is impoverished in
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity' ...
as compared with
polytypic habitat types, this is not necessarily the case. Monocultures of the exotic plant ''
Hydrilla
''Hydrilla'' (waterthyme) is a genus of aquatic plant, usually treated as containing just one species, ''Hydrilla verticillata'', though some botanists divide it into several species. It is native to the cool and warm waters of the Old World in A ...
'' support a similarly rich fauna of invertebrates as a more varied habitat.
The monotypic habitat occurs in both botanical and zoological contexts. Some
invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...
may create monocultural stands that prevent other species from growing there. A dominant
colonization
Colonization, or colonisation, constitutes large-scale population movements wherein migrants maintain strong links with their, or their ancestors', former country – by such links, gain advantage over other inhabitants of the territory. When ...
can occur from retardant chemicals exuded, nutrient monopolization, or from lack of natural controls such as
herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...
s or climate, that keep them in balance with their native habitat types. The
yellow starthistle, ''Centaurea solstitialis'', is a botanical monotypic habitat example of this, currently dominating over in California alone.
The non-native freshwater
zebra mussel, ''Dreissena polymorpha'', that colonizes areas of the
Great Lakes
The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five la ...
and the
Mississippi River
The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it ...
watershed
Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to:
Hydrology
* Drainage divide, the line that separates neighbouring drainage basins
* Drainage basin, called a "watershe ...
, is a zoological monotypic habitat example; the predators or parasites that control it in its home-range in Russia are absent.
See also
*
*
*
*
*
*
*
* : the loss of habitat
Notes and references
External links
*
*
{{Authority control
Ecology
Landscape ecology
Systems ecology