Deployment cost-benefit selection in physiology
Encyclopedia
Deployment cost–benefit selection in physiology concerns the costs and benefits of physiological process
that can be deployed and selected in regard to whether they will increase or not an animal’s survival and biological fitness. Variably deployable physiological processes relate mostly to processes that defend or clear infections as these are optional while also having high costs and circumstance linked benefits. They include immune system
responses, fever
, antioxidants and the plasma level of iron
. Notable determining factors are life history
stage, and resource availability.
-like evaluations of future benefits and costs as to its biological fitness. In many circumstances, such trade-off calculations explain why immune responses are suppressed
and infections are tolerated. Circumstances where immunity are not activated due to lack of an actuarial benefit include:
) cost, and the risk of hyperpyrexia. Where it is achieved internally
, each degree raise in blood temperature, raises BMR by 10–15%. 90% of the total cost of fighting pneumonia
, goes, for example, on energy devoted to raising body temperature. During sepsis
, the resulting fever can raise BMR by 55%—and cause a 15% to 30% loss of body mass. Circumstances in which fever deployment is not selected or is reduced include:
, Vitamin E
, and enzymes such as superoxide dismutase
(SOD) and glutathione peroxidase
(GPx) can protect against reactive oxygen species
that damage DNA
, proteins and lipids, and result in cell senescence
and death. A cost exists in creating or obtaining these antioxidants. This creates a conflict between the biological fitness benefits of future survival compared with the use of these antioxidants to advantage present reproductive success. In some birds, antioxidants are diverted from maintaining the body to reproduction for this reason with the result that they have accelerated senescence Related to this, birds can show their biological capacity to afford the cost of diverting antioxidants (such as carotenoids) in the form of pigments into plumage
as a costly signal.
, but also to bacteria
infecting the host. A biological fitness advantage can exist for hosts to reduce the availability of iron within itself to such bacteria (hypoferremia), even though this happens at a cost of the host impairing itself with anemia
. The potential benefits of such self impairment is illustrated by the paradoxical effect that providing iron supplements
to those with iron deficiency (which interferes with its antibacterial action) can result in an individual being cured of anemia but having increased bacterial illness.
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
that can be deployed and selected in regard to whether they will increase or not an animal’s survival and biological fitness. Variably deployable physiological processes relate mostly to processes that defend or clear infections as these are optional while also having high costs and circumstance linked benefits. They include immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
responses, fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, antioxidants and the plasma level of iron
Iron deficiency (medicine)
Iron deficiency is one of the most common of the nutritional deficiencies. Iron is present in all cells in the human body, and has several vital functions...
. Notable determining factors are life history
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
stage, and resource availability.
Immunity
Activating the immune system has the present and future benefit of clearing infections, but it is also both expensive in regard to present high metabolic energy consumption, and in the risk of resulting in a future immune related disorder. Therefore, an adaptive advantage exists if an animal can control its deployment in regard to actuaryActuary
An actuary is a business professional who deals with the financial impact of risk and uncertainty. Actuaries provide expert assessments of financial security systems, with a focus on their complexity, their mathematics, and their mechanisms ....
-like evaluations of future benefits and costs as to its biological fitness. In many circumstances, such trade-off calculations explain why immune responses are suppressed
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
and infections are tolerated. Circumstances where immunity are not activated due to lack of an actuarial benefit include:
- MalnutritionMalnutritionMalnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....
- Old ageOld ageOld age consists of ages nearing or surpassing the average life span of human beings, and thus the end of the human life cycle...
- HibernationHibernationHibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
- ParasitismParasitismParasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
(low or high risk) - Sexually transmitted diseases (low or high risk)
- Light patterns associated with winter (probable resource shortage)
Fever
Cost benefit trade-off actuary issues apply to the antibacterial and antiviral effects of fever (increased body temperature). Fever has the future benefit of clearing infections since it reduces the replication of bacteria and viruses. But it also has great present metabolic (BMRBMR
BMR may refer to:*UK Music subsidiary British Music Rights*Basal metabolic rate*Pegaso BMR, a 6x6 wheeled armoured personnel carrier produced in Spain*BMR Advisors, Indian tax advisory firm...
) cost, and the risk of hyperpyrexia. Where it is achieved internally
Warm-blooded
The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...
, each degree raise in blood temperature, raises BMR by 10–15%. 90% of the total cost of fighting pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
, goes, for example, on energy devoted to raising body temperature. During sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
, the resulting fever can raise BMR by 55%—and cause a 15% to 30% loss of body mass. Circumstances in which fever deployment is not selected or is reduced include:
- Aged individuals—the burden of tolerating infection will exist for a short time which reduces the actuarial future benefits of clearing an infection compared to the costs of its removal. This change favors reduced or no deployment of fever.
- When internal resources are limited (such as in winter), and the ability to afford high expenditure on increased metabolism is reduced. This increases the risks of activating fever relative to its potential benefit, and animals are less likely to use fever to fight infections.
- Late PregnancyPregnancyPregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
Antioxidants
Antioxidants such as carotenoids, vitamin CVitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
, Vitamin E
Vitamin E
Vitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...
, and enzymes such as superoxide dismutase
Superoxide dismutase
Superoxide dismutases are a class of enzymes that catalyze the dismutation of superoxide into oxygen and hydrogen peroxide. As such, they are an important antioxidant defense in nearly all cells exposed to oxygen...
(SOD) and glutathione peroxidase
Glutathione peroxidase
Glutathione peroxidase is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage...
(GPx) can protect against reactive oxygen species
Reactive oxygen species
Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....
that damage DNA
DNA damage theory of aging
The DNA damage theory of aging proposes that aging is a consequence of unrepaired DNA damage accumulation. Damage in this context includes chemical reactions that mutate DNA and/or interfere with DNA replication. Although both mitochondrial and nuclear DNA damage can contribute to aging, nuclear...
, proteins and lipids, and result in cell senescence
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
and death. A cost exists in creating or obtaining these antioxidants. This creates a conflict between the biological fitness benefits of future survival compared with the use of these antioxidants to advantage present reproductive success. In some birds, antioxidants are diverted from maintaining the body to reproduction for this reason with the result that they have accelerated senescence Related to this, birds can show their biological capacity to afford the cost of diverting antioxidants (such as carotenoids) in the form of pigments into plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
as a costly signal.
Hypoferremia
Iron is vital to biological processes, not only of a hostHost (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
, but also to bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
infecting the host. A biological fitness advantage can exist for hosts to reduce the availability of iron within itself to such bacteria (hypoferremia), even though this happens at a cost of the host impairing itself with anemia
Iron deficiency anemia
Iron-deficiency anemia is a common anemia that occurs when iron loss occurs, and/or the dietary intake or absorption of iron is insufficient...
. The potential benefits of such self impairment is illustrated by the paradoxical effect that providing iron supplements
Iron supplements
Iron supplements are supplements that can be prescribed by a doctor for a medical reason. Iron can also be a dietary supplement, which can be purchased in supermarkets etc. These two categories should not be confused....
to those with iron deficiency (which interferes with its antibacterial action) can result in an individual being cured of anemia but having increased bacterial illness.