Glossary of Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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- A -

acclimatization   click this icon to hear the preceding term pronounced
changes in the body in response to environmental stresses such as high or low temperatures, intense ultraviolet radiation from sun light, or high altitude.  The anatomical and physiological changes made in acclimatization are usually reversible.
adaptation  click this icon to hear the preceding term pronounced
the process by which populations of organisms respond to long term environmental stresses by permanent genetic change--i.e., by evolving.  See adjustment.
adjustment
the process by which individual organisms respond to environmental stresses during their lifetime without changing genetically.  Adjustments are generally not inheritableAcclimatization and developmental adjustment are examples of adjustment.  See adaptation.
albinism  click this icon to hear the preceding term pronounced
the genetically inherited condition in which there is a marked deficiency of pigmentation in skin, hair, and eyes.  An individual with these traits is an "albino."  The gene for albinism is recessive.
alleles  click this icon to hear the preceding term pronounced
alternate forms or varieties of a gene.
Allen's Rule  click this icon to hear the preceding term pronounced
within the same species of warm-blooded animals, individuals from populations living in colder environments usually have shorter appendages than do those from populations in warmer areas.  This is because of the selective advantage it provides.  Short arms, legs, and other appendages have relatively less skin surface area that can radiate heat into the surrounding environment.  Subsequently, the body retains more of it.   Allen's Rule is a corollary of Bergmann's Rule.   Allen's  Rule was named after Joel Allen, a 19th century naturalist. 
anatomy   click this icon to hear the preceding term pronounced
referring to the structural makeup or parts of organisms.  See physiology.
anemia   click this icon to hear the preceding term pronounced
a medical condition in which the blood contains too few functioning red cells or there isn't enough blood.  The result in both cases is a significantly reduced ability to get oxygen to the cells of the body.  Symptoms include fatigue, weakness, poor appetite, weight loss, and a yellowish tinge to the skin and eyes.  There are many different genetic and environmental causes of anemia.
anencephaly   click this icon to hear the preceding term pronounced
the failure to develop a brain at the end of the spinal chord.  This type of neural tube defect always causes the death of a fetus or newborn child.
apparent temperature
what the air temperature actually feels like to people.  This varies with the relative humidity of the air.  The higher the relative humidity, the higher the apparent temperature is even if the air temperature does not change because evaporation of sweat is progressively less efficient in cooling the body.
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- B -

basal metabolic rate  click this icon to hear the preceding term pronounced    (BMR)
the measure of the total energy utilized by the body to maintain its necessary processes while at rest.  Those processes include  keeping the heart, brain, and other organs functioning normally and the necessary replacement of old or damaged cells.  About 75% of the food energy that we burn every day is used for these functions.  The remaining energy is used to fuel physical work or is stored in fat reserves for when it is needed.  Basal metabolic rate also refers to the minimum level of heat produced by the body at rest.
Bergmann's Rule  click this icon to hear the preceding term pronounced
within the same species of warm-blooded animals, individuals from populations living in colder environments usually have greater body mass than do those from populations in warmer areas.  This is because of the selective advantage it provides.  A massive body produces more internal heat and radiates relatively less of it into the surrounding environment because the skin surface area is relatively smaller.  Subsequently, a massive body produces and retains more heat.    Bergmann's Rule was named after Carl Bergmann, a 19th century naturalist.  See Allen's Rule.
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- C -

capillaries  click this icon to hear the preceding term pronounced
the hair thin blood vessels connecting small branches of arteries and veins that form a vascular network throughout the body of animals.
carotene  click this icon to hear the preceding term pronounced
any of several reddish-orange organic pigments.  While carotene is present in human skin, it is also found in higher concentrations in butter, carrots, and some other vegetables.  Carotene is involved in the synthesis of vitamin A in people and other animals.
cerebral edema  click this icon to hear the preceding term pronounced
an abnormal accumulation of fluid around the brain causing it to swell.  This potentially life threatening condition can be caused by hypoxia at high altitude.  See pulmonary edema.
conduction  click this icon to hear the preceding term pronounced
the movement of heat from one object to another by direct contact.  Example: the transmission of heat from your body to the chair on which you are sitting.  See convection and radiation.
convection  click this icon to hear the preceding term pronounced
the movement of heat from on object to the surrounding fluid (either gas or liquid).  Example: the transmission of heat from your body to water when you are swimming.  See conduction and radiation.
core body temperature
the temperature of the internal organs in the chest cavity, abdominal region, and head in animals.  See hyperthermia and hypothermia.
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developmental acclimatization
see developmental adjustment.
developmental adjustment
a change in the normal growth patterns and development of an individual that occurs in childhood as a result of specific cultural practices (e.g., foot binding) or other environmental processes.  The anatomical and physiological changes that result are mostly irreversible by adulthood.  Example: stunted growth and mild mental retardation due to severe, prolonged undernourishment.  Developmental adjustment is also referred to as "developmental acclimatization."
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- E -

endemic click this icon to hear the preceding term pronounced disease
a disease that remains at a more or less constant frequency of affected individuals in a population all of the time.  Examples: hypertension, tooth decay, and malaria.
enzymes  click this icon to hear the preceding term pronounced
proteins that cause or regulate specific chemical reactions within cells.
epidermis  click this icon to hear the preceding term pronounced
the outer most skin layer in humans and related animals.
eumelanin  click this icon to hear the preceding term pronounced
See melanin.
evaporative cooling
cooling of the skin resulting from the evaporation of sweat on its surface.  In hot dry environments, this is normally the most significant mechanism by which the human body loses excess heat.
evolution  click this icon to hear the preceding term pronounced
genetic change in a population of organisms that occurs over time.  The term is also frequently used to refer to the appearance of a new species.  More specifically, it is change in the frequencies of alleles in a population's gene pool from one generation to the next.  
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- F -

frostbite
the freezing of part of the body, especially soft tissue.  This may result in gangrene and the loss of appendages, such as toes and ears.
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- G -

gastrointestinal  click this icon to hear the preceding term pronounced
relating to the stomach and the intestines--the lower digestive tract.
gene pool
the sum of all of the alleles of genes in all of the individuals in a population.
genes  click this icon to hear the preceding term pronounced
units of inheritance usually occurring at specific locations, or loci, on a chromosome.  Physically, a gene is a sequence of DNA bases that specify the order of amino acids in an entire protein or, in some cases, a portion of a protein.  A gene may be made up of hundreds of thousands of DNA bases.  Genes are responsible for hereditary characteristics in plants and animals.
genotype  click this icon to hear the preceding term pronounced
the genetic makeup of an individual.  Genotype can refer to an organism's entire genetic makeup or the alleles at a particular locus.
Gloger's Rule  click this icon to hear the preceding term pronounced
within the same species of warm-blooded animals, there is a tendency for darker, more heavily pigmented skin to occur in animals near the equator and lighter pigmented skin farther from it.  This is because of the selective advantage the coloration provides.  Heavy pigmentation protects from skin cancer caused by ultraviolet radiation from the sun.  However, too much pigmentation can significantly reduce the skin's ability to produce vitamin D, which is necessary for the absorption of calcium and phosphorus from food.  Open country close to the equator typically experiences high amounts of intense ultraviolet radiation while temperate and arctic regions have relatively little.  Subsequently, heavy skin pigmentation is an advantage near the equator but a disadvantage farther away from it.  Gloger's Rule was named after Wilhelm Gloger, a 19th century naturalist. 
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- H -

hemoglobin  click this icon to hear the preceding term pronounced
a gas transporting protein molecule that makes up most of the contents of erythrocytes (red cells) in our blood.  There are usually about 270,000,000 hemoglobin molecules in each red cell.
hyperthermia  click this icon to hear the preceding term pronounced
unusually elevated core body temperature resulting from fever or prolonged exposure to a hot environment.   This can be a life threatening condition.  See hypothermia.
hypothalamus  click this icon to hear the preceding term pronounced
a small region near the base of the brain that controls the sympathetic nervous system, which in turn regulates the autonomic functions of the body, including beating of the heart, breathing, and body temperature control.
hypothermia  click this icon to hear the preceding term pronounced
unusually low core body temperature resulting from prolonged exposure to a cold environment.  This can be a life threatening condition.  See hyperthermia.
hypoxia  click this icon to hear the preceding term pronounced
oxygen deprivation. This condition can occur at high altitude.  Symptoms include a reduced ability to do work, fatigue, dizziness, nausea, and an inability to effectively perform memory intensive tasks.  Even moderate hypoxia results in the death of some individuals due to heart failure.  In very high mountain areas, hypoxia can cause pulmonary edema and/or cerebral edema, both of which are life-threatening conditions that are aspects of what is often referred to as acute mountain sickness.
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- K - 

kwashiorkor   click this icon to hear the preceding term pronounced
the disease of babies and very young children resulting from long-term severe protein deficiency in the diet.  There is usually an associated deficiency in the consumption of vitamin A and E as well as zinc and selenium.  Symptoms include edema (or swelling) due to water retention (especially in the abdomen), stick-like legs and arms with little fat or muscle mass, apathy, and loss of hair and skin pigmentation in patches.  As in the case of marasmus, children with kwashiorkor are likely to have their growth retarded.  Kwashiorkor usually results from a child being weaned too early and being forced to subsist mainly on a high carbohydrate and low protein diet.
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- L -

lactase  click this icon to hear the preceding term pronounced
an enzyme produced by mammals to break down lactose in milk that they consume.  Lactase is needed for the digestion of uncooked dairy products.  Lactase deficiency results in diarrhea and other symptoms of physical intolerance of most dairy products.
lactose  click this icon to hear the preceding term pronounced
a sugar normally present in milk.  Lactose intolerance is often due to lactase deficiency.  However, physical intolerance of dairy products can also result from an allergy to milk proteins.
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- M -

macroevolution  click this icon to hear the preceding term pronounced
major evolutionary changes in a population's gene pool, occurring over many generations, resulting in the evolution of new species.  See microevolution.
malaria  click this icon to hear the preceding term pronounced
a group of similar life threatening diseases found mostly in tropical and subtropical regions of the world.  Malaria is caused by any of four different microorganisms called plasmodia (Plasmodium falciparum, vivax, ovale, and malariae).  These single-celled organisms are transmitted from person to person mostly by anopheles mosquitoes as they extract blood.  Symptoms of malaria include chills, high fever, and sometimes fatal irregularities of the brain, liver, kidney, and/or blood.  There are at least 100,000,000 new cases of malaria reported annually around the world.  Approximately 1,500,000 people die from it each year (mostly children--3,000 children die of malaria every day).
malnourishment   click this icon to hear the preceding term pronounced
an inadequacy or an excess of some key element(s) in the diet, such as proteins, fats, or specific minerals and vitamins.  See undernourishment and overnourishment.
marasmus   click this icon to hear the preceding term pronounced
the medical condition resulting from prolonged famine.  Symptoms include extreme emaciation, diarrhea, anemia, and apathy.  Women with marasmus usually stop ovulating.  The loss of insulating body fat makes people with marasmus highly vulnerable to death resulting from a drop in core body temperature when the air falls below 60-65� F.  Children who survive marasmus usually develop short adult stature and some degree of permanent brain damage.  See kwashiorkor.
Melanesia  click this icon to hear the preceding term pronounced
  map of the Southwest Pacific Ocean with the islands of Melanesia highlighted
New Guinea and other nearby islands in the Southwest Pacific Ocean. Indigenous people from this region are referred to as Melanesians.
 
melanin  click this icon to hear the preceding term pronounced
a dark colored organic pigment produced in the skin.  There are two forms of melanin----pheomelanin click this icon to hear the preceding term pronounced, which is red to yellow in color, and eumelanin click this icon to hear the preceding term pronounced, which is dark brown to black.  People with light complexioned skin mostly produce pheomelanin, while those with dark colored skin mostly produce eumelanin.   High concentrations of melanin near the surface of the skin result in a darker complexion.   Suntanned skin also has higher concentrations of melanin.
melanocytes  click this icon to hear the preceding term pronounced
specialized cells that produce melanin in the skin.
melanoma  click this icon to hear the preceding term pronounced
A type of aggressive skin cancer.  Specifically, it is a cancer that begins in melanocytes and rapidly spreads to other parts of the body.
metabolism  click this icon to hear the preceding term pronounced
the chemical and physical processes continuously going on in the cells of living organisms.  These are the processes by which energy and matter are made available for use by the cells of an organism.  Heat is a byproduct of metabolism.
microevolution  click this icon to hear the preceding term pronounced
small changes in the frequency of alleles in a population's gene pool occurring over generations.  The accumulation of microevolutionary changes can result in macroevolution.
multiple sclerosis  click this icon to hear the preceding term pronounced
a genetically inherited progressive disease of the central nervous system.  Symptoms range from numbness and tingling to paralysis.  The gene(s) responsible for MS are incompletely penetrant in that the onset of the disease is apparently triggered by a virus.  There is also a correlation between the amount of sunlight that children are exposed to and the likelihood that they will develop MS later in life.  People who spend much of their first 16 years in tropical and subtropical parts of the world are much less likely to develop this disease than those who live in far northern and far southern regions.  It is believed that the lack of abundant sun exposure early in life is somehow responsible for the later onset of MS.
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- N -

natural selection
an evolutionary mechanism that occurs when some individuals of a population are better able to adapt to their environment and, subsequently, produce more offspring.  Nature, in effect, selects which members of a population are fit to survive long enough to reproduce.  Differential productive success between individuals is the key.  Those who produce more offspring have a greater influence on the gene frequencies of the next generation.  This mechanism of evolutionary change was first articulated by Charles Darwin. 
neural tube defects  click this icon to hear the preceding term pronounced
defective developments of a child's brain or spinal cord occurring before birth.  By the mid embryonic stage (5 weeks in humans), a neural tube extends from the top of the head to the lower end of the spinal column.  Later, this tube becomes the brain and spinal chord.  Spina bifida and anencephaly are examples of neural tube defects.
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- O -

osmosis   click this icon to hear the preceding term pronounced
diffusion of a liquid through a membrane.
osteoporosis   click this icon to hear the preceding term pronounced
a disease condition in which the bones lose significant amounts of calcium and phosphorous so that they are brittle.  It is now most common among postmenopausal women, but older men may experience this condition as well.
overnourishment  click this icon to hear the preceding term pronounced
regular consumption of too many calories.  Prolonged over nourishment can result in chronic obesity, which is associated with higher risks for type 2 diabetes, heart disease, and some kinds of cancer.   See malnourishment.
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- P -

pastoralists   click this icon to hear the preceding term pronounced
people who make their living by tending herds of large animals.  The species of animals vary with the region of the world, but they are all domesticated herbivores that normally live in herds and eat grasses or other abundant plant foods (e.g., cattle, horses, sheep, reindeer).
peripheral blood flow
blood flowing in vessels near the surface of the skin.
pheomelanin  click this icon to hear the preceding term pronounced
See melanin.
pheromones  click this icon to hear the preceding term pronounced
chemicals produced and secreted by an animal that can have a powerful affect on the behavior and development of other animals (usually in the same species).  Pheromones are common throughout the animal world, including humans.
physiology  click this icon to hear the preceding term pronounced
referring to the organic or bodily processes of an organism.   See anatomy.
physiological plasticity   click this icon to hear the preceding term pronounced
referring to the physical moldability of an organism as it is developing.  This flexibility allows environmental forces to alter the genetically predetermined shape of our bodies to some extent.  Example: permanent changes in the shape and position of foot bones resulting from the old Chinese practice of binding, or tightly wrapping, the feet of girls.
proteins   click this icon to hear the preceding term pronounced
any of a large number of organic molecules that are composed of one or more chains of amino acids.  Proteins can serve a wide variety of functions through their ability to bind to other molecules.  Proteins may be enzymes, hormones, antibodies, structural components, or gas transporting molecules.
pulmonary edema  click this icon to hear the preceding term pronounced
a pneumonia-like accumulation of fluid and swelling in the lungs.  Like cerebral edema, it can be caused by hypoxia at high altitude.  While pulmonary edema is potentially life threatening, it generally is less likely than cerebral edema to result in death if treated in time.
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- R -

radiation
electromagnetic energy that is given off by an object.  Our bodies lose heat by radiation.  More specifically, we give off infrared radiation like the heat from a light bulb.
rickets disease  click this icon to hear the preceding term pronounced
a disease of the skeletal system in which the bones are softened and often bent as a result of vitamin D deficiency in the diet that hinders the normal development of bones and teeth.  Rickets most frequently affects malnourished children.
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- S -

selectively permeable   click this icon to hear the preceding term pronounced
referring to a membrane that allows some kinds of substances to pass through it but not others.
selective pressure
environmental pressure that is placed on individuals within a population that results in change of the genetic makeup of the next generation.   Selective pressure is the driving force of natural selection.
sickle-cell trait  click this icon to hear the preceding term pronounced
a genetically inherited recessive condition in which some or all of the red blood cells are abnormally distorted to a sickle shape.  Symptoms include pain and severe anemia as well as heart, lung, and kidney problems.  People who are heterozygous for this trait rarely have these debilitating and ultimately fatal problems but do have a high degree of immunity to malaria.  Sickle cell trait is at its highest frequency among Central African populations and among people whose ancestors came from that region.  Sickle-cell trait is often referred to as sickle-cell anemia.
spina bifida   click this icon to hear the preceding term pronounced
a neural tube birth defect in which there are malformations of vertebrae and the protrusion of the spinal cord from the body.  This can result in paralysis of the legs, loss of bowel and bladder control, and "water" on the brain (hydrocephaly).   Spina bifida requires surgical correction.
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- U -

ultraviolet click this icon to hear the preceding term pronounced radiation
electromagnetic radiation ranging in wave length just beyond violet in the visible spectrum of light.  The human eye cannot detect u.v.  Our sun is the major source of u.v. radiation on earth.  Prolonged exposure to u.v. can result in destructive skin burns and can promote the onset of skin cancer.
undernourishment   click this icon to hear the preceding term pronounced
severe deficiency of calories in the diet. Prolonged undernourishment can result in marasmus which is a wasting away of the body.   See malnourishment.
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- V -

vascular click this icon to hear the preceding term pronounced network
the network of blood vessels throughout the body.
vasoconstriction  click this icon to hear the preceding term pronounced
constriction or narrowing of blood vessels so that a decrease in flow occurs.  See vasodilation.
vasodilation  click this icon to hear the preceding term pronounced
enlargement in the diameter of blood vessels so that an increased flow occurs.  See vasoconstriction.
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Copyright 1998-2012 by Dennis O'Neil. All rights reserved.
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