Ecophysiology (from
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
, ''oikos'', "house(hold)"; , ''physis'', "nature, origin"; and , ''
-logia
''-logy'' is a suffix in the English language, used with words originally adapted from Ancient Greek ending in ('). The earliest English examples were anglicizations of the French '' -logie'', which was in turn inherited from the Latin '' -logi ...
''), environmental physiology or physiological ecology is a
biological
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...
discipline
Discipline refers to rule following behavior, to regulate, order, control and authority. It may also refer to punishment. Discipline is used to create habits, routines, and automatic mechanisms such as blind obedience. It may be inflicted on ot ...
that studies the response of an
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
's
physiology
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
to environmental conditions. It is closely related to
comparative physiology
Comparative physiology is a List of academic disciplines, subdiscipline of physiology that studies and exploits the diversity of functional characteristics of various kinds of organisms. It is closely related to evolutionary physiology and environ ...
and
evolutionary physiology
Evolutionary physiology is the study of the biological evolution of physiological structures and processes; that is, the manner in which the functional characteristics of individuals in a population of organisms have responded to natural selectio ...
.
Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (; 16 February 1834 – 9 August 1919) was a German zoologist, naturalist, eugenicist, philosopher, physician, professor, marine biologist and artist. He discovered, described and named thousands of new sp ...
's coinage bionomy is sometimes employed as a synonym.
Plants
Plant ecophysiology is concerned largely with two topics: mechanisms (how plants sense and respond to environmental change) and scaling or integration (how the responses to highly variable conditions—for example, gradients from full sunlight to 95% shade within tree canopies—are coordinated with one another), and how their collective effect on plant growth and gas exchange can be understood on this basis.
In many cases,
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s are able to escape unfavourable and changing environmental factors such as heat, cold, drought or floods, while
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s are unable to move away and therefore must endure the adverse conditions or perish (animals go places, plants grow places). Plants are therefore
phenotypically plastic and have an impressive array of
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s that aid in acclimating to changing conditions. It is hypothesized that this large number of genes can be partly explained by plant species' need to live in a wider range of conditions.
Light
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 tera ...
is the food of plants, i.e. the form of energy that plants use to build themselves and reproduce. The organs harvesting light in plants are
leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
and the process through which light is converted into biomass is
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 ...
. The response of photosynthesis to light is called light response curve of net photosynthesis (
PI curve
The PI (or photosynthesis-irradiance) curve is a graphical representation of the empirical relationship between solar irradiance and photosynthesis. A derivation of the Michaelis–Menten curve, it shows the generally positive correlation between ...
). The shape is typically described by a non-rectangular hyperbola. Three quantities of the light response curve are particularly useful in characterising a plant's response to light intensities. The inclined
asymptote
In analytic geometry, an asymptote () of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the ''x'' or ''y'' coordinates tends to infinity. In projective geometry and related contexts, ...
has a positive slope representing the efficiency of light use, and is called quantum efficiency; the x-intercept is the light intensity at which biochemical assimilation (gross assimilation) balances leaf respiration so that the net CO
2 exchange of the leaf is zero, called light compensation point; and a horizontal asymptote representing the maximum assimilation rate. Sometimes after reaching the maximum assimilation declines for processes collectively known as
photoinhibition
Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term ...
.
As with most abiotic factors, light intensity (irradiance) can be both suboptimal and excessive. Suboptimal light (shade) typically occurs at the base of a plant canopy or in an understory environment.
Shade tolerant
In ecology, shade tolerance is a plant's ability to tolerate low light levels. The term is also used in horticulture and landscaping, although in this context its use is sometimes imprecise, especially in labeling of plants for sale in commercial ...
plants have a range of adaptations to help them survive the altered quantity and quality of light typical of shade environments.
Excess light occurs at the top of canopies and on open ground when cloud cover is low and the sun's zenith angle is low, typically this occurs in the tropics and at high altitudes. Excess light incident on a leaf can result in
photoinhibition
Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term ...
and
photodestruction
In optics, photobleaching (sometimes termed fading) is the photochemical alteration of a dye or a fluorophore molecule such that it is permanently unable to fluoresce. This is caused by cleaving of covalent bonds or non-specific reactions between ...
. Plants adapted to high light environments have a range of adaptations to avoid or dissipate the excess light energy, as well as mechanisms that reduce the amount of injury caused.
Light intensity is also an important component in determining the temperature of plant organs (energy budget).
Temperature
In response to extremes of temperature, plants can produce various
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s. These protect them from the damaging effects of ice formation and falling rates of
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
catalysis at low temperatures, and from enzyme
denaturation and increased
photorespiration
Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The desired reaction i ...
at high temperatures. As temperatures fall, production of
antifreeze protein
Antifreeze proteins (AFPs) or ice structuring proteins refer to a class of polypeptides produced by certain animals, plants, fungi and bacteria that permit their survival in temperatures below the freezing point of water. AFPs bind to small i ...
s and
dehydrin
Dehydrin (DHN) is a multi-family of proteins present in plants that is produced in response to cold and drought stress. DHNs are hydrophilic, reliably thermostable, and disordered. They are stress proteins with a high number of charged amino aci ...
s increases. As temperatures rise, production of
heat shock protein
Heat shock proteins (HSP) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock, but are now known to also be expressed during other stresses including expo ...
s increases. Metabolic imbalances associated with temperature extremes result in the build-up of
reactive oxygen species
In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen.
The reduction of molecular oxygen () p ...
, which can be countered by
antioxidant
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...
systems.
Cell membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...
s are also affected by changes in temperature and can cause the membrane to lose its
fluid properties and become a gel in cold conditions or to become leaky in hot conditions. This can affect the movement of compounds across the membrane. To prevent these changes, plants can change the composition of their membranes. In cold conditions, more
unsaturated fatty acids
In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food.
The term often refers spec ...
are placed in the membrane and in hot conditions, more
saturated fatty acid
A saturated fat is a type of fat in which the fatty acid chains have all single bonds. A fat known as a glyceride is made of two kinds of smaller molecules: a short glycerol backbone and fatty acids that each contain a long linear or branched c ...
s are inserted.
Plants can avoid overheating by minimising the amount of sunlight absorbed and by enhancing the cooling effects of wind and
transpiration
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...
. Plants can reduce light absorption using reflective leaf hairs, scales, and waxes. These features are so common in warm dry regions that these habitats can be seen to form a 'silvery landscape' as the light scatters off the canopies.
Some species, such as ''Macroptilium purpureum'', can move their leaves throughout the day so that they are always orientated to avoid the sun (''
paraheliotropism Paraheliotropism refers to the phenomenon in which plants orient their leaves parallel to incoming rays of light, usually as a means of minimizing excess light absorption. Excess light absorption can cause a variety of physiological problems for pla ...
'').
Knowledge of these mechanisms has been key to
breeding for heat stress tolerance
Plant breeding is process of development of new cultivars. Plant breeding involves development of varieties for different environmental conditions – some of them are not favorable. Among them, heat stress is one of such factor that reduces the pr ...
in agricultural plants.
Plants can avoid the full impact of low temperature by altering their
microclimate
A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...
. For example, ''
Raoulia
''Raoulia'' is a genus of New Zealand plants in the tribe Gnaphalieae within the family Asteraceae.
Many ''Raoulia'' species grow in alpine areas, forming very fine and dense growths. These compact growths form large amorphous cushion-like masse ...
'' plants found in the uplands of New Zealand are said to resemble 'vegetable sheep' as they form tight cushion-like clumps to insulate the most vulnerable plant parts and shield them from cooling winds. The same principle has been applied in agriculture by using
plastic mulch
Plastic mulch is a product used in plasticulture in a similar fashion to mulch, to suppress weeds and conserve water in crop production and landscaping. Certain plastic mulches also act as a barrier to keep methyl bromide, both a powerful fumigant ...
to insulate the growing points of crops in cool climates in order to boost plant growth.
Water
Too much or too little water can damage plants. If there is too little water then tissues will dehydrate and the plant may die. If the soil becomes waterlogged then the soil will become anoxic (low in oxygen), which can kill the roots of the plant.
The ability of plants to access water depends on the structure of their roots and on the
water potential
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure and mat ...
of the root cells. When soil water content is low, plants can alter their water potential to maintain a flow of water into the roots and up to the leaves (
Soil plant atmosphere continuum
The soil-plant-atmosphere continuum (SPAC) is the pathway for water moving from soil through plants to the atmosphere. Continuum in the description highlights the continuous nature of water connection through the pathway. The low water potential of ...
). This remarkable mechanism allows plants to lift water as high as 120 m by harnessing the gradient created by
transpiration
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...
from the leaves.
In very dry soil, plants close their stomata to reduce transpiration and prevent water loss. The closing of the stomata is often mediated by chemical signals from the root (i.e.,
abscisic acid
Abscisic acid (ABA) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure. It is especially important for plants in the response to environmental s ...
). In irrigated fields, the fact that plants close their stomata in response to drying of the roots can be exploited to 'trick' plants into using less water without reducing yields (see
partial rootzone drying
Irrigation in viticulture is the process of applying extra water in the cultivation of grapevines. It is considered both controversial and essential to wine production. In the physiology of the grapevine, the amount of available water affects phot ...
). The use of this technique was largely developed by Dr Peter Dry and colleagues in Australia (see
nominative determinism
Nominative determinism is the hypothesis that people tend to gravitate towards areas of work that fit their names. The term was first used in the magazine ''New Scientist'' in 1994, after the magazine's humorous "Feedback" column noted several ...
).
If drought continues, the plant tissues will dehydrate, resulting in a loss of
turgor pressure
Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall.
It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibri ...
that is visible as
wilting
Wilting is the loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells. Wilting also serves to reduce water loss, as it m ...
. As well as closing their stomata, most plants can also respond to drought by altering their water potential (osmotic adjustment) and increasing root growth. Plants that are adapted to dry environments (
Xerophytes
A xerophyte (from Greek ξηρός ''xeros'' 'dry' + φυτόν ''phuton'' 'plant') is a species of plant that has adaptations to survive in an environment with little liquid water, such as a desert such as the Sahara or places in the Alps or the ...
) have a range of more specialized mechanisms to maintain water and/or protect tissues when desiccation occurs.
Waterlogging reduces the supply of oxygen to the roots and can kill a plant within days. Plants cannot avoid waterlogging, but many species overcome the lack of oxygen in the soil by transporting oxygen to the root from tissues that are not submerged. Species that are tolerant of waterlogging develop specialised roots near the soil surface and
aerenchyma
Aerenchyma or aeriferous parenchyma or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and t ...
to allow the diffusion of oxygen from the shoot to the root. Roots that are not killed outright may also switch to less oxygen-hungry forms of cellular respiration. Species that are frequently submerged have evolved more elaborate mechanisms that maintain root oxygen levels, such as the aerial roots seen in
mangrove
A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
forests.
However, for many terminally overwatered houseplants, the initial symptoms of waterlogging can resemble those due to drought. This is particularly true for flood-sensitive plants that show drooping of their leaves due to
epinasty
Nastic movements are non-directional responses to stimuli (e.g. temperature, humidity, light irradiance), and are usually associated with plants. The movement can be due to changes in turgor. Decrease in turgor pressure causes shrinkage while ...
(rather than wilting).
concentration
is vital for plant growth, as it is the substrate for photosynthesis. Plants take in through
stomatal pores on their leaves. At the same time as enters the stomata, moisture escapes. This trade-off between gain and water loss is central to plant productivity. The trade-off is all the more critical as
Rubisco
Ribulose-1,5-bisphosphate carboxylase-oxygenase, commonly known by the abbreviations RuBisCo, rubisco, RuBPCase, or RuBPco, is an enzyme () involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is con ...
, the enzyme used to capture , is efficient only when there is a high concentration of in the leaf. Some plants overcome this difficulty by concentrating within their leaves using
carbon fixation or
Crassulacean acid metabolism
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night. ...
. However, most species used
carbon fixation and must open their stomata to take in whenever photosynthesis is taking place.
The concentration of
in the atmosphere is rising due to
deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...
and the combustion of
fossil fuels
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ...
. This would be expected to increase the efficiency of photosynthesis and possibly increase the overall rate of plant growth. This possibility has attracted considerable interest in recent years, as an increased rate of plant growth could absorb some of the excess and reduce the rate of
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Extensive experiments growing plants under elevated using
Free-Air Concentration Enrichment
Free-Air Carbon dioxide Enrichment (FACE) is a method used by ecologists and plant biologists that raises the concentration of in a specified area and allows the response of plant growth to be measured. Experiments using FACE are required bec ...
have shown that photosynthetic efficiency does indeed increase. Plant growth rates also increase, by an average of 17% for above-ground tissue and 30% for below-ground tissue. However, detrimental impacts of global warming, such as increased instances of heat and drought stress, mean that the overall effect is likely to be a reduction in plant productivity.
Reduced plant productivity would be expected to accelerate the rate of global warming. Overall, these observations point to the importance of avoiding further increases in atmospheric rather than risking
runaway climate change
In climate science, a tipping point is a critical threshold that, when crossed, leads to large and often irreversible changes in the climate system. If tipping points are crossed, they are likely to have severe impacts on human society. Tippin ...
.
Wind
Wind has three very different effects on plants.
* It affects the exchanges of mass (water evaporation, ) and of energy (heat) between the plant and the atmosphere by renewing the air at the contact with the leaves (
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
).
* It is sensed as a signal driving a wind-acclimation syndrome by the plant known as
thigmomorphogenesis
Thigmomorphogenesis (from Ancient Greek θιγγάνω (thingánō) to touch, μορφή (''morphê'') shape, and γένεσις (génesis) creation) is the response by plants to mechanical sensation (touch) by altering their growth patterns. In ...
, leading to modified growth and development and eventually to wind hardening.
* Its
drag force can damage the plant (leaf abrasion, wind ruptures in branches and stems and
windthrow
In forestry, windthrow refers to trees uprooted by wind. Breakage of the tree bole (trunk) instead of uprooting is called windsnap. Blowdown refers to both windthrow and windsnap.
Causes
Windthrow is common in all forested parts of the w ...
s and toppling in trees and
lodging
Lodging refers to the use of a short-term dwelling, usually by renting the living space or sometimes through some other arrangement. People who travel and stay away from home for more than a day need lodging for sleep, rest, food, safety, shel ...
in crops).
Exchange of mass and energy
Wind influences the way leaves regulate moisture, heat, and carbon dioxide. When no wind is present, a layer of still air builds up around each leaf. This is known as the
boundary layer
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condi ...
and in effect insulates the leaf from the environment, providing an atmosphere rich in moisture and less prone to convective heating or cooling. As wind speed increases, the leaf environment becomes more closely linked to the surrounding environment. It may become difficult for the plant to retain moisture as it is exposed to dry air. On the other hand, a moderately high wind allows the plant to cool its leaves more easily when exposed to full sunlight. Plants are not entirely passive in their interaction with wind. Plants can make their leaves less vulnerable to changes in wind speed, by coating their leaves in fine hairs (
trichomes
Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...
) to break up the airflow and increase the boundary layer. In fact, leaf and canopy dimensions are often finely controlled to manipulate the boundary layer depending on the prevailing environmental conditions.
Acclimation
Plants can sense the wind through the deformation of its tissues. This signal leads to inhibits the elongation and stimulates the radial expansion of their shoots, while increasing the development of their root system. This syndrome of responses known as
thigmomorphogenesis
Thigmomorphogenesis (from Ancient Greek θιγγάνω (thingánō) to touch, μορφή (''morphê'') shape, and γένεσις (génesis) creation) is the response by plants to mechanical sensation (touch) by altering their growth patterns. In ...
results in shorter, stockier plants with strengthened stems, as well as to an improved anchorage. It was once believed that this occurs mostly in very windy areas. But it has been found that it happens even in areas with moderate winds, so that wind-induced signal were found to be a major ecological factor.
Trees have a particularly well-developed capacity to reinforce their trunks when exposed to wind. From the practical side, this realisation prompted arboriculturalists in the UK in the 1960s to move away from the practice of staking young
amenity trees to offer artificial support.
Wind damage
Wind can damage most of the organs of the plants. Leaf abrasion (due to the rubbing of leaves and branches or to the effect of airborne particles such as sand) and leaf of branch breakage are rather common phenomena, that plants have to accommodate. In the more extreme cases, plants can be mortally damaged or uprooted by wind. This has been a major selective pressure acting over terrestrial plants. Nowadays, it is one of the major threatening for agriculture and forestry even in temperate zones.
It is worse for agriculture in hurricane-prone regions, such as the banana-growing Windward Islands in the Caribbean.
When this type of
disturbance
Disturbance and its variants may refer to:
Math and science
* Disturbance (ecology), a temporary change in average environmental conditions that causes a pronounced change in an ecosystem
* Disturbance (geology), linear zone of faults and folds ...
occurs in natural systems, the only solution is to ensure that there is an adequate stock of seeds or seedlings to quickly take the place of the mature plants that have been lost- although, in many cases, a
successional stage will be needed before the ecosystem can be restored to its former state.
Animals
Humans
The environment
The natural environment or natural world encompasses all living and non-living things occurring naturally, meaning in this case not artificial. The term is most often applied to the Earth or some parts of Earth. This environment encompasses t ...
can have major influences on human
physiology
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
. Environmental effects on human physiology are numerous; one of the most carefully studied effects is the alterations in
thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
in the body due to outside
stresses. This is necessary because in order for
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s to function,
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
to flow, and for various body
organ
Organ may refer to:
Biology
* Organ (biology), a part of an organism
Musical instruments
* Organ (music), a family of keyboard musical instruments characterized by sustained tone
** Electronic organ, an electronic keyboard instrument
** Hammond ...
s to operate,
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 o ...
must remain at consistent, balanced levels.
Thermoregulation
To achieve this, the body alters three main things to achieve a constant, normal body temperature:
* Heat transfer to the
epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
* The rate of
evaporation
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
* The rate of heat production
The hypothalamus plays an important role in thermoregulation. It connects to thermal receptors in the
dermis
The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...
, and detects changes in surrounding blood to make decisions of whether to stimulate internal heat production or to stimulate evaporation.
There are two main types of stresses that can be experienced due to extreme environmental temperatures:
heat stress
Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...
and
cold stress
Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe h ...
.
Heat stress is physiologically combated in four ways:
radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
,
conduction
Conductor or conduction may refer to:
Music
* Conductor (music), a person who leads a musical ensemble, such as an orchestra.
* Conductor (album), ''Conductor'' (album), an album by indie rock band The Comas
* Conduction, a type of structured f ...
,
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
, and
evaporation
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
. Cold stress is physiologically combated by shivering, accumulation of
body fat
Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular en ...
, circulatory adaptations (that provide an efficient transfer of heat to the epidermis), and increased blood flow to the extremities.
There is one part of the body fully equipped to deal with cold stress. The
respiratory system
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
protects itself against damage by warming the incoming air to 80-90 degrees Fahrenheit before it reaches the
bronchi
A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...
. This means that not even the most frigid of temperatures can damage the respiratory tract.
In both types of temperature-related stress, it is important to remain well-hydrated. Hydration reduces cardiovascular strain, enhances the ability of energy processes to occur, and reduces feelings of exhaustion.
Altitude
Extreme temperatures are not the only obstacles that humans face.
High altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
s also pose serious physiological challenges on the body. Some of these effects are reduced
arterial , the rebalancing of the
acid-base content in body fluids, increased
hemoglobin
Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
, increased
RBC synthesis, enhanced circulation, and increased levels of the
glycolysis
Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
byproduct
2,3 diphosphoglycerate, which promotes off-loading of O
2 by
hemoglobin
Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
in the
hypoxic tissues
Hypoxia is a condition in which the body or a region of the body is deprived of adequate oxygen supply at the tissue (biology), tissue level. Hypoxia may be classified as either ''Generalized hypoxia, generalized'', affecting the whole body, or '' ...
.
Environmental factors can play a huge role in the human body's fight for
homeostasis
In biology, homeostasis (British English, British also homoeostasis) Help:IPA/English, (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physics, physical, and chemistry, chemical conditions maintained by organism, living systems. Thi ...
. However, humans have found ways to adapt, both
physiologically
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
and tangibly.
Scientists
George A. Bartholomew (1919–2006) was a founder of animal physiological ecology. He served on the faculty at
UCLA
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...
from 1947 to 1989, and almost 1,200 individuals can trace their academic lineages to him.
[2-CO2 diagram, which formed the basis for much of Rahn's future work. Rahn's research into applications of this diagram led to the development of aerospace medicine and advancements in hyperbaric breathing and high-altitude respiration. Rahn later joined the ]University at Buffalo
The State University of New York at Buffalo, commonly called the University at Buffalo (UB) and sometimes called SUNY Buffalo, is a public research university with campuses in Buffalo and Amherst, New York. The university was founded in 1846 ...
in 1956 as the Lawrence D. Bell Professor and Chairman of the Department of Physiology. As Chairman, Rahn surrounded himself with outstanding faculty and made the University an international research center in environmental physiology.
See also
* Comparative physiology
Comparative physiology is a List of academic disciplines, subdiscipline of physiology that studies and exploits the diversity of functional characteristics of various kinds of organisms. It is closely related to evolutionary physiology and environ ...
* Evolutionary physiology
Evolutionary physiology is the study of the biological evolution of physiological structures and processes; that is, the manner in which the functional characteristics of individuals in a population of organisms have responded to natural selectio ...
* 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 overlaps wi ...
* Phylogenetic comparative methods
Phylogenetic comparative methods (PCMs) use information on the historical relationships of lineages (phylogenies) to test evolutionary hypotheses. The comparative method has a long history in evolutionary biology; indeed, Charles Darwin used diffe ...
* Plant physiology
Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (bi ...
* Raymond B. Huey Raymond Brunson Huey (born 14 September 1944) is a biologist specializing in evolutionary physiology. He has taught at the University of Washington (UW), and he earned his Ph.D. in biology at Harvard University under E. E. Williams. He has recent ...
* Theodore Garland, Jr.
* Tyrone Hayes
Tyrone B. Hayes (born July 29, 1967) is an American biologist and professor of integrative biology at the University of California, Berkeley. He is known for his research in frogs, concluding that the herbicide atrazine is an endocrine disruptor ...
References
Further reading
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* Spicer, J. I., and K. J. Gaston. 1999. Physiological diversity and its ecological implications. Blackwell Science, Oxford, U.K. x + 241 pp.
* . Definitions and Opinions by: G. A. Bartholomew, A. F. Bennett, W. D. Billings, B. F. Chabot, D. M. Gates, B. Heinrich, R. B. Huey, D. H. Janzen, J. R. King, P. A. McClure, B. K. McNab, P. C. Miller, P. S. Nobel, B. R. Strain.
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Subfields of ecology
Physiology
Animal physiology
Plant physiology
Ecology terminology
Animal ecology
Plant ecology
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