A common bacterium that has been studied intensively by geneticists because it has a small genome and is usually harmless and easy to grow.

2. E1A
Definition:

An early gene (a gene of a virus which is expressed early in the viral life cycle) found in adenoviruses associated with cancer which is responsible for their cancer-causing aspects.

3. ear
Author: Guo Li
Definition:

The ear consists of three parts: external, middle, and internal ear and serves two functions: hearing and equilibrium.

4. early development
Definition:

An early stage in the life cycle of a bacteriophage (a virus which infects bacteria) that occurs after infection but before replication of the bacteriophage genome.

5. early genes
Definition:

The genes of a virus which are expressed first, soon after the virus infects its host. Generally, they replicate the viral genome and signal expression of the late genes of the virus at a later point in the viral life cycle.

6. Eaton-Lambert syndrome (Lambert-Eaton syndrome, myasthenic syndrome)
Author: Guo Li
Definition:

Eaton-Lambert syndrome is characterized by weakness of the proximal muscles of the limbs, often associated with small cell carcinoma (of the lung) and some autoimmune diseases. This condition is caused by the body creating antibodies against its own motor nerve axon terminals.

7. ebb
Author:
Definition:

Falling stage or outward flow, especially of tides.

8. Ebola virus
Definition:

An RNA-containing virus in the family Filoviridae that causes an acute, fatal type of hemorrhagic fever characterized by massive bleeding. This virus is native to the Zaire and Sudan areas of Africa.

9. ecchymosis
Author: Guo Li
Definition:

Ecchymosis is the discoloration due to hemorrhage under the skin. It can be a sign of bleeding tendency secondary to poor nutrition or liver dysfunction.

10. ecdysone
Image: View the chemical structure
Definition:

Any of several insect hormones that triggers the expression of critical genes during larval development; these hormones are being researched as safer alternatives to pesticides.

11. ECF (extracellular fluid)
Author: Guo Li
Definition:

ECF is the abbreviation often used to indicate extracellular fluid. It is the volume of body fluid exclusive of that in the cells (intracellular fluid, ICF). Therefore ECF includes fluid in the blood vessels, and in the interstitial space (the space between cells). About 20 percent of body weight is ECF: 5 percent is plasma, and 15 percent is interstitial fluid.

12. echinate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Bearing stiff, stout, prickly hairs.

13. echocardiogram
Author: Guo Li
Definition:

An echocardiogram is a method of studying the heart ventricular size, function, wall thickness, motion, and valves by using Doppler ultrasound.

14. eclampsia
Author: Guo Li
Definition:

Eclampsia is a complication of pregnancy characterized by four conditions: elevated blood pressure, proteinuria (protein in the urine), edema (fluid buildup in the tissues) and seizure.

15. ECn
Definition:

This is the commonly used abbreviation for the exposure concentration of a poisonous substance causing a defined effect on n% of a test population; for instance, the EC₅₀ would affect 50% of the population.

16. eco-
Definition:

A prefix which indicates that the word has to do with the environment or with ecology.

17. eco-organ
Definition:

An ecological feature which mirrors environmental conditions. A type of vegetation based on such a feature.

18. ecological protection
Author:
Definition:

Protection consists of measures undertaken to protect and preserve elements of an ecosystem's structure and functions against future degradation.

19. ecological restoration
Author: Society for Ecological Resoration
Definition:

1. The process of renewing and maintaining ecosystem health.
2. Ecological restoration is the process of intentionally altering a site to establish a defined, indigenous, historic ecosystem. The goal of this process is to emulate the structure, function, diversity, and dynamics of the specified ecosystem.

20. ecology
Definition:

The scientific study of the relationship of organisms to each other and to their environment.

21. economic botany
Definition:

The study of plants and plant products that can be used for profit, such as in the field of agriculture or medicine.

22. economic entomology
Definition:

The study of insects which are able to cause economic losses by destroying plants or animals that are commercially valuable.

23. ecophene
Definition:

The variety of phenotypes (visible physical characteristics or behaviors), from a single genotype (a specific combinations of alleles in a gene), that can be observed in a population within a particular habitat.

24. ecophenotype (adj. ecophenotypic)
Definition:

A phenotype (visible physical characteristics or behaviors) that is a result of environmental or ecological conditions rather than genetic expression (nurture instead of nature).

25. EcoRI methylase
Definition:

An enzyme that will methylate (attach a methyl group (-CH₃ group) to the nitrogenous base adenine on DNA molecules) the cutting site (the sequence GAATTC) of the EcoRI restriction enzyme (an enzyme which will cleave DNA at specific nucleotide sequences).

26. EcoRI restriction enzyme
Definition:

A commonly-used restriction enzyme (enzyme which will cleave the phosphodiester bonds of DNA at specific nucleotide sequences) that came from the bacteria Escherichia coli and recognizes the sequence GAATTC. The enzyme will make a staggered cut of the double-stranded DNA molecule by cutting between the G and A on both strands.

27. ecospecies
Definition:

A species consisting of different subspecies, or breeds, of an organism which despite being adapted to slightly different environments and/or having distinctly different appearances and behaviors, can still successfully interbreed.

28. ecosphere
Definition:

1. In astronomy: the region of space around a star that is considered able to support life.
2. In ecology: the Earth, all of the organisms living on it, and all of the environmental factors which act on the organisms.

29. ecosystem (ecological system, holocoen)
Author:
Definition:

1. An ecosystem is the dynamic and interrelating complex of plant and animal communities and their associated non-living environment.
2. The physical and climactic features and all the living and dead organisms in an area that are interrelated in the transfer of energy and material.
3. An interacting complex of a community and its environment functioning as an ecological unit in nature. Differs from "system" in being a more rigorous definition that encompasses and requires assumptions of energetics, ecological interactions, species adaptations and so forth.

30. ecosystem altering
Author:
Definition:

Any activity that modifies the biota including species composition, distribution, and abundance and any activity that modifies the physical environment, including soils and the water cycle.

31. ecosystem dynamics
Author:
Definition:

Those intrinsic ecological functions through which an ecosystem becomes self-regulating, self-sustaining, and capable of recovery from external forces (e.g., damaging storm events). These intrinsic processes may cause continual change in biotic composition and structure at specific localities. Collectively, these changes represent internal flux, rather than substantive and permanent alteration of the ecosystem regionally.

32. ecosystem function
Definition:

1. The collective intraspecific and interspecific interactions of the biota, such as primary and secondary production and mutualistic relationships.
2. The interactions between organisms and the physical environment, such as nutrient cycling, soil development, water budgeting, and flammability.

33. ecosystem structure
Author:
Definition:

The physical and spatial aspects of an ecosystem that are contributed by the biotic composition. Biotic composition is generally determined by the collective physiognomy of the dominant plants, including life forms, vertical stratification, and size.

34. ecotone
Definition:

A transition area between two distinct habitats, where the ranges of the organisms in each bordering habitat overlap, and where there are organisms unique to the transition area.

35. ecotoxicology
Definition:

Ecotoxicology is the scientific study of harmful effects caused by manmade chemicals to the natural environment, especially effects on populations, communities, and ecosystems; an essential part of ecotoxicology is the study of the movement of potentially toxic substances through food webs and through the water cycle, etc.

36. ecotropic
Definition:

A retrovirus (virus which uses RNA instead of DNA to encode its genome) that can reproduce only in the host of the species in which it originated.

37. ecotype (adj. ecotypic)
Definition:

A subspecies, or breed, that has adapted to its local environment and as a result is distinctive from other members of the species, but can still successfully interbreed with other members of the species.

38. ecto-
Definition:

A prefix which indicates that the word has to do with "external" or "outer."

39. ectocommensal organism
Definition:

An organism that benefits from living on the outer surface of another organism without harming the other organism. A type of commensalism.

40. ectoderm (ectoblast, epiblast)
Definition:

The outermost layer of tissue in a developing animal embryo which will eventually become the skin and/or other outer surface of the organism, the outermost parts of the nervous system, and various other outer and external organs, structures, and systems (depends on the organism). Occurs in all animals except for sponges and placozoans.

41. ectoenzyme
Definition:

An enzyme that is secreted to the outside of the cell and acts extracellularly (between cells, outside of all cells). Compare endoenzyme.

42. ectogenesis
Definition:

Developing an embryo or embryonic tissue in vitro, or within an artificial environment.

43. ectogenous (exogenous)
Definition:

Originating from or due to influences from outside of the organism or cell.

44. ectomere
Definition:

A blastomere (one of the cells formed during the first few divisions of the zygote) which takes part in forming the ectoderm (the outermost tissue layer of an embryo).

45. ectoparasite
Definition:

A parasite that lives on the outside of its host rather than within the host's body. Fleas and lice are examples.

46. ectophyte (epiphyte)
Definition:

A plant that lives and grows on the outer surface of another organism, such as moss on trees.

47. ectopia
Definition:

An organ or other structure which is positioned abnormally within the body.

48. ectopic
Definition:

A biological event or process (such as a pregnancy) that occurs in an abnormal location or position within the body.

49. ectopic pairing
Definition:

Pairing of heterochromatin randomly, without regard to whether they are homologous.

50. ectopic pregnancy
Definition:

Implantation of an embryo and its subsequent development outside the uterus, most commonly in a fallopian tube.

51. ectopic pregnancy
Author: Guo Li
Definition:

Ectopic pregnancy is a pregnancy implanted at a site which does not permit development of the embryo. 98 percent of ectopic pregnancies are implanted in one of the fallopian tubes. The incidence of ectopic pregnancy is increased in the following conditions:

1. pelvic inflammatory disease;
2. the use of an intrauterine device as birth control;
3. the use of progestin-only oral contraceptives.

Aside from the fallopian tubes, ectopic pregnancies can occur in an ovary, the abdominal cavity, and in the broad ligament. Ectopic pregnancy is a medical emergency as a ruptured ectopic pregnancy can often result in severe hemorrhage leading to death. Other complications are: chronic salpingitis, sterility, intestinal obstruction and fistulae formation.

52. ectoplasm
Definition:

Cytoplasm embedded with microfilaments (to give it rigidity) and lacking organelles that is found just under the cytoplasmic membrane in ciliates (one-celled organisms with cilia).

53. ectosymbiont
Definition:

An organism which is participating in ectosymbiosis (a form of symbiosis in which the organisms involved are physically separated).

54. ectosymbiosis
Definition:

Symbiosis between two organisms which are physically separated from each other. Compare endosymbiosis.

55. ectotherm
Definition:

An organism that does not generate its own body heat and must use an external source of heat to warm itself. A cold-blooded organism.

56. ectothermic
Definition:

Able to maintain a constant body temperature with an external heat source.

57. ectotrophic
Definition:

Describes an organism that gets its nutrients from the outside surface of its host.

58. ectrogeny
Definition:

An organ or bodily structure which is flawed or missing from the body as a congenital condition.

59. eczema (adj.: eczematous)
Definition:

A noncontagious skin condition where red and itchy blisters appear, then crusty and thickened skin. The condition can be acute (occurs suddenly and once) or chronic (is present for a long time) and has numerous causes.

60. edaphic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pertaining to the soil.

61. edaphic community
Definition:

A community of plants which results from or is influenced by factors about the soil, for example amount of drainage, level of salinity (salt concentration), or amount of sediment movement. Marsh environments often have edaphic communities of plants specially adapted to marsh conditions.

62. edaphon
Definition:

An organism (nematode worm, fungus, bacterium, etc.) that lives in the soil.

63. EDC (estimated date of confinement)
Author: Guo Li
Definition:

EDC is the abbreviation often used to indicate the "estimated date of confinement" in pregnancy. This is the date when child birth is most likely to take place. Many tables and charts are available to obtain the EDC.

Nagele's rule is a mathematical formula to obtain the EDC assuming a normal 28-day cycle of menstruation:

• to obtain the month of EDC, subtract 3 from the month of the last normal menstrual period
• to obtain the day of EDC, add 7 to the first day of the last normal menstrual period

64. eddy (eddy current)
Author:
Definition:

1. Rotational flow around a vertical axis.
2. Circular current of water, sometimes quite strong, diverging from the main current. (It usually forms where the flow passes some obstruction or at the inside of river bends, and often forms backwater pools or pocket water in riffles.)
3. A circular water movement that develops between the main flow and the bank. (An eddy usually forms downstream of a structure or an abrupt change in the shape of the bank. Eddies are often the cause of bank erosion.)

65. edema
Definition:

Abnormal buildup of watery fluid in the tissues.

66. edentulous
Definition:

A medical term meaning "lacking teeth."

67. Edman degradation
Definition:

A lab technique used to find out the order of amino acids in a polypeptide (chain of amino acids). It involves using the Edman reagent, phenyl isothiocyanate (PITC), to react one by one with each amino acid, in order. The technique is used in machines which automatically sequence (determine the order of subunits) polypeptides.

68. EDn
Definition:

This is the commonly used abbreviation for the dose of a toxicant causing a defined effect on n% of a test population; for instance, the ED₅₀ would affect 50% of the population.

69. Edward's Syndrome ( Edwards' syndrome, trisomy 18, trisomy E)
Definition:

A congenital disorder caused by a baby having an extra copy of chromosome 18 (three instead of the normal two). Characteristics of the disorder include a large number of different malformed organs and malformed physical features of the face and skeletal structure. In most cases, the child dies before it is born; 90% of babies born live die within a year of birth. Symptoms may be less severe when the trisomy occurs after fertilization during mitosis in the zygote (10% of cases), than when the trisomy occurs during the meiosis which produced the egg or sperm (90% of cases).

For more information, visit http://www.icondata.com/health/pedbase/files/TRISOMY2.HTM.

70. effacement
Author: Guo Li
Definition:

Effacement is the thinning out of the cervix during the first stage of labor from 0 percent to 100 percent when it is less than 0.25 centimeters thick.

71. effectively drained
Author:
Definition:

A condition where ground or surface water has been removed by artificial means to the point that an area no longer meets the wetland hydrology criterion.

72. effector
Definition:

A molecule, chemical, or structure that regulates a pathway by increasing or decreasing the pathway's reaction rate.

73. efferent
Definition:

Moving or carrying outward or away from a central part. Refers to vessels, nerves, etc. For example, blood vessels carrying blood away from the heart or nerves carrying signals from the brain. Compare afferent.

74. effervescence (adj.: effervescent)
Author: Guo Li
Definition:

Effervescence is the formation of bubbles in a solution.

75. efficacious (efficacy)
Definition:

Having the ability or power to produce a desired effect.

76. effluent
Definition:

Liquid waste from sewage treatment or industrial processes, especially such liquid waste that is released into a river or other waterway.

77. effusion
Author: Guo Li
Definition:

Effusion is the abnormal accumulation of fluids in a body cavity.

78. egg
Definition:

A structure which the females of certain animal species lay as a means of reproduction; it contains a fertilized zygote and nutrition in the form of yolk for the developing offspring, sometimes contains other substances (eg., the "white" of a hen's egg), sometimes surrounded by a protective outer shell.

79. egg coat
Definition:

A layer of glycoproteins and other stuff which surrounds an egg (ovum), just outside of the egg's cell membrane. The coat protects the egg, and for organisms which practice external fertilization (fertilization outside of the parents' bodies) it can help prevent the sperm of other species from entering the egg. For the eggs of mammals, the egg coat is called the zona pellucida and for sea urchins (a popular study organism for developmental biologists) it is called the vitelline layer.

80. egg donation
Definition:

Donation of an ovum by one woman to another who attempts to become pregnant by in vitro fertilization.

81. eglandular
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Without glands.

82. Ehlers-Danlos syndrome
Author: Guo Li
Definition:

Ehlers-Danlos syndrome is characterized by a collagen abnormality resulting in hyperelasticity and fragile tissues. It is inherited as an autosomal dominant condition.

83. eicosanoid
Definition:

A type of hormone which forms when the body breaks down arachidonic acid. Examples include the leukotrienes, lipoxins, prostaglandins, and thrombaxanes.

84. Eisenmenger's syndrome
Author: Guo Li
Definition:

Eisenmenger's syndrome is characterized by pulmonary hypertension and a right-to-left or bi-directional shunt. The shunt can be atrial or ventricular. Most patients can not survive beyond age 40 and demise occurs when the fraction of right-to-left shunt increases.

85. ejaculation
Author: Guo Li
Definition:

Ejaculation is a two-part spinal reflex that involves:

1. movement of semen into the urethra in response to signals from the internal pudendal nerves (afferent), and hypgastric nerves (efferent), and
2. propulsion of the semen out of the urethra by contraction of the bulbocavernosus muscle in response to signals from the sacral roots and the internal pudendal nerves.

86. elaiosome
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An appendage of a seed, usually rich in oil, not essential for the viability of the seed but attractive to animals (especially ants) as a food for larvae etc. and hence an aid to dispersal by such animals.

87. elater
Definition:

An elongated, spirally thickened, water-attracting cell in the capsule of a liverwort, derived from sporogenous tissue and assisting in spore dispersal.

88. elective surgery
Definition:

Surgery which is not needed immediately; i.e., one for a non-life-threatening disorder.

89. electroblotting
Definition:

The use of an electric field to transfer proteins or nucleic acids from the electrophoresis gel to the blotting membrane as a part of Southern blotting, Northern blotting, or Western blotting.

90. electrocardiogram (EKG, ECG)
Author: Guo Li
Definition:

This is a recording of the electrical signals from the heart. From an EKG, it is possible to identify arrythmias, myocardial ischemia or infarction, the type and timing of damage, ventricular hypertrophy and some abnormalities of serum electrolytes.

91. electrocautery
Definition:

Cauterization via the use of an electrical current.

92. electrocautery
Author: Guo Li
Definition:

Electrocautery is the destruction of tissue by means of electric current. In surgery, high frequency electric current is used to cauterize small blood vessel to stop bleeding.

93. electrochemical potential
Definition:

The energy needed to maintain separate concentrations and charges on each side of a membrane.

94. electroconductivity (EC)
Author:
Definition:

A measure of the total dissolved ions in a substance, which indicates the material's ability to conduct electricity. Soil EC's are determined from distilled water extracts of saturated soil pastes.

95. electrode
Definition:

A terminal of an electric source through which electricity passes when the circuit is completed.

96. electrodialysis
Definition:

The use of an electric field to speed up the dialysis process. The electric field is applied across the dialysis membrane.

97. electrodiffusion
Definition:

The use of an electric field to induce substances with positive or negative charges to move in a particular direction.

98. electroejaculation
Author: Fertilitext
Definition:

Controlled electrical stimulation, usually applied to the prostate gland with a probe, to induce ejaculation in a man who has nerve damage that prevents him from ejaculating normally.

This technique is also used in veterinary medicine, especially by zoo vets who are trying to increase the populations of endangered mammal species by artificially inseminating females of the species in question.

99. electroencephalogram
Definition:

A graph of very tiny changes in the electrical potential associated with neural activity in the cerebral cortex. The graphed electrical activity is picked up by scalp electrodes.

100. electroencephalogram (EEG)
Author: Guo Li
Definition:

This is the recording of electrical signals of the brain. It identifies epileptic activities (paroxysmal abnormalities containing spikes or sharp waves), and is used during surgery to localize the epileptogenic source for excision.

101. electroendosmosis
Definition:

1. The effect of an electric field on the diffusion of water through or into a membrane or gel.
2. The movement of the liquid medium of a colloid solution towards an electrode.

102. electrogenic
Definition:

Refers to a substance that contributes to an electrical potential across a membrane.

103. electrolysis
Definition:

1. The process where an electric current is passed through an electrolytic solution or other appropriate medium, causing a chemical reaction. Similar to what happens within a battery.
2. In medicine, the process where an electric current is used to destroy tumors. 
3. In cosmetology, the removal of unwanted body hair by electrocuting the hair roots with an electrified needle.

104. electrolyte
Author: Guo Li
Definition:

"Electrolyte" refers to ionized salts in the body fluids. The major electrolytes are made from sodium, potassium, magnesium, calcium, chloride, bicarbonate, phosphate and protein.

105. electrolyte solution
Definition:

A solution containing charged atoms or molecules.

106. electromagnetic wave (electromagnetic radiation)
Definition:

A wave of electric and magnetic fields that can move through space. Particles which make up the waves are called photons.

107. electromyogram
Definition:

A graphical representation of the electrical activity in a muscle.

108. electromyograph
Definition:

A device that senses and graphs on paper the electrical activity in a muscle.

109. electron
Definition:

A stable atomic particle that has a negative charge; the flow of electrons through a substance constitutes electricity.

110. electron acceptor
Definition:

A molecule or compound that gets electrons during an oxidation-reduction reaction.

111. electron carrier
Definition:

A protein which can either accept or donate electrons in oxidation-reduction reactions.

112. electron donor
Definition:

A molecule or compound that gives up electrons in an oxidation-reduction reaction.

113. electron microscope
Definition:

A microscope (device used to magnify small objects) which beams electrons at and through the object of interest instead of light beams. Instead of a glass lens to bend the light, a powerful magnet is used to bend the electron beam. The microscope can only be operated in a vacuum. This type of microscope provides the greatest resolution of extremely small details available and has been used to see individual atoms in an object or substance.

114. electron microscopy
Definition:

The use of an electron microscope (a microscope that uses electron beams instead of light beams) to magnify extremely fine details of an object or substance. Since the microscope can only be operated in a vacuum, biological specimens of interest must first be protected by coating it with a thin metal layer, which also outlines the structural features of the specimen.

115. electron transport
Definition:

The transport of electrons through a number of electron carriers in a set sequence.

116. electron transport chain
Definition:

A group of electron carriers in mitochondria (energy-making organelles found in eukaryotes) which transports electrons to and from each other in a set sequence, for the purpose of generating the energy needed to convert ADP and inorganic phosphate into ATP (used to store energy in units by all living things).

117. electron-transport phosphorylation (oxidative phosphorylation)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Synthesis of ATP involving a membrane associated electron transport chain and the creation of a proton-motive force.

118. electronegativity
Definition:

1. The likelihood that an atom or molecule will attract electrons; the strength of the attraction.
2. The tendency of an atom or molecule to become negatively charged.

119. electronic potential
Definition:

The measure (in volts) of electron pressure. A measure of the difference in electron concentrations between two compartments, such as either side of a cell membrane.

120. electrophile
Definition:

A molecule or group that doesn't have enough electrons and will tend to take them from a molecule or group with an excess of elecrons (nucleophile).

121. electrophoresis (ionophoresis)
Definition:

A method of separating large molecules (such as DNA fragments or proteins) from a mixture of similar molecules. An electric current is passed through a medium containing the mixture, and each kind of molecule travels through the medium at a different rate, depending on its electrical charge and size. Separation is based on these differences. Agarose and acrylamide gels are the media commonly used for electrophoresis of proteins and nucleic acids. Specific electrophoretic methods include Northern blot, Southern blot, and Western blot.

122. electroporation
Definition:

The exposure of cells to rapid pulses of high-voltage current which renders the plasma membrane of the cells permeable and thus allowing transfection.

123. elimination half-life
Author: PharmInfoNet
Definition:

The time it takes for the body to eliminate or breakdown half of a dose of a pharmacologic agent.

124. ELISA
Author: Guo Li
Definition:

ELISA is the abbreviation for "enzyme-linked immunosorbent assay" which is a method of measuring the antigen titer.

125. ELISA (enzyme-linked immunosorbent assay)
Definition:

A highly sensitive technique for detecting and measuring antigens or antibodies in a solution; the solution is run over a surface to which immobilized antibodies specific to the substance have been attatched, and if the substance is present, it will bind to the antibody layer, and its presence is verified and visualized with an application of antibodies that have been tagged in some way.

126. elliptic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Oval in outline, widest at the center.

127. elongation factors
Definition:

Certain proteins that ribosomes need to make polypeptide chains longer.

128. eluant
Definition:

The term for the fluid (such as a buffer solution) that is used in column chromatography to separate the components of a mixed sample. The fluid is run through the column and brings out the separated substances (separately). Also see elution.

129. eluate
Definition:

The waste liquid produced during chromatography.

130. elution profile
Definition:

A graph made to show how much material is being carried out of the column by the eluant in column chromatography over time. The graph will show a number of different peaks; each peak represents a different separated material from the original mixed substance.

131. elution volume
Definition:

The amount of eluant which has passed through the column in column chromatography before a particular peak in an elution profile appears, or before a specific substance of interest comes out with the eluant, separated out of the original mixed substance.

132. emaciated
Definition:

Extremely thin or physically wasted.

133. emarginate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having a broad, shallow notch at the top.

134. embankment
Definition:

A structure made of packed soil built above the natural ground.

135. Embden-Meyerhof-Parnas pathway (Embden-Meyerhof pathway; EMP pathway)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A pathway that degrades glucose to pyruvate; the six-carbon stage converts glucose to fructose-1,6-bisphosphate, and the three-carbon stage produces ATP while changing glyceraldehyde-3-phosphate to pyruvate. Compare with Entner-Doudoroff pathway.

136. embeddedness
Author:
Definition:

Degree to which large particles (boulders, rubble, gravel) are surrounded or covered by fine sediment, usually measured in classes according to percent coverage.

137. embolectomy
Author: Guo Li
Definition:

An embolectomy is the surgery to remove the obstruction in a blood vessel, aiming at improving circulation.

138. embolism
Definition:

Obstruction in a blood vessel; can be caused by a blood clot or mass of bacteria or other material.

139. embolism
Author: Guo Li
Definition:

An embolism is the disorder of lodging a substance in a blood vessel so that blood flow is totally or partially obstructed. The substance could be air, a blood clot, tumor fragments, fat, amniotic fluid, bacteria, or parasites.

140. embryo
Definition:

1. A stage of development in a multicelled organism between the time that the zygote is fertilized and the point at which the organism developing from that zygote becomes free-living.
2. Specifically, in vertebrate animals, the developmental stage from after the long axis appears until all major anatomical structures form.
3. In human development, this is from about two weeks after fertilization until the seventh or eighth week of pregnancy.
4. In higher plants, this is the rudimentary plant encased in a viable seed before germination; a plant embryo usually consists of an epicotyl, hypocotyl, radicle and one or two cotyledons.
5. In primitive plants, the young sporophyte that develops from the union of male and female sex cells.

141. embryo transfer
Author: Fertilitext
Definition:

The placement of a laboratory-fertilized egg into the uterus.

142. embryogenesis
Author: ForBio Ltd.
Definition:

1. A process of differentiation which results in the formation of embryo-like structures from undifferentiated cells.
2. Process which leads to the formation of embryos.

143. embryologist
Author: Fertilitext
Definition:

A specialist in embryo development.

144. embryology
Definition:

The study of the embryo and its development from a one-celled zygote (fertilized ovum) to the establishment of form and shape (at which point, if it is an animal, it becomes a fetus). A subfield of developmental biology.

145. embryotoxin (embryotoxic)
Definition:

This describes any chemical which is harmful to an embryo.

146. emerge
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

To rise out of a fluid or other covering.

147. emergence (fish emergence)
Author:
Definition:

Departure of fry from the incubation gravel into the water column.

148. emergency medicine
Definition:

This medical field encompasses:

1. clinical issues and techniques concerning the treatment of patients who are critically injured and need fast (and often extensive) treatment;
2. the management and administration of a hospital emergency room.

149. emergent
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Any of various plants (as a cattail) rooted in shallow water and having most of the vegetative growth above the water.

150. emersed
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Standing out of or rising above a surface as an aquatic plant with flower stalk emersed.

151. emersed plants
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Plants growing with their roots and a portion of the shoot below the water and the remainder of the shoot above the surface of the water.

152. emetogenic
Author: PharmInfoNet
Definition:

Induces vomiting.

153. emission standard
Definition:

This regulatory value is a quantitative limit on the emission or discharge of a potentially toxic substance from a source. The simplest form for regulatory purposes is a uniform emission standard (UES) where the same limit is placed on all emissions of a particular contaminant.

154. emphysema
Author: Guo Li
Definition:

Emphysema is the abnormal condition of air in the tissues. In pulmonary emphysema, the lung tissues are destroyed so that alveolar sacs are replaced with useless air space. Chronic tobacco smoking is a major cause of emphysema.

155. empyema
Author: Guo Li
Definition:

Empyema is the collection of pus in a body cavity.

156. emulsifier (emulsifying agent)
Definition:

A substance which can be used to produce an emulsion out of two liquids that normally cannot be mixed together (such as oil and water). Emulsifiers are common in foods to maintain consistency within puddings, powders, etc.

157. emulsion
Definition:

A mixture of two normally unmixable liquids (e.g., oil and water) in which one is colloidally suspended in the other (one exists as tiny particles within the other).

158. enantiomers
Definition:

A pair of chiral isomers that are direct, nonsuperimposable mirror images of each other.

159. enation
Definition:

An epidermal outgrowth.

160. encapsulation
Definition:

The coating or engulfing of particles within a continuous matrix.

161. encephalitis
Definition:

Inflammation of the brain; it's most often caused by a virus transmitted by a mosquito that has recently fed on an infected person, but bacteria, bleeding, or poison can cause the illness.

162. encephaloma
Definition:

Any swelling or tumor of the brain.

163. encephalopathy
Definition:

Any disease of the brain.

164. end plate (end-plate)
Definition:

The flat end of a part of the body, usually against another part. Most often refers to the end of a nerve fiber against a skeletal muscle fiber, to which it transmits nerve signals.

165. end point (end-point, endpoint)
Definition:

1. In analytical chemistry, it is the point during a titration reaction where there are equal amounts of titrant and whatever is being titrated. A color change in the sample usually indicates this point.
2. In immunology, it is the most dilute an antibody or antiserum solution can be while still detectably reacting with the antigen.

166. end product
Definition:

The final product of after a series of reactions with enzymes in a biochemical metabolic pathway has taken place.

167. end-filling
Definition:

The use of DNA polymerase to create a blunt end (both strands are the same length and end together) on double-stranded DNA that has a staggered end (one strand is longer than the other so there is a single-stranded section at the end of the molecule).

168. endangered species
Definition:

Any species which is in danger of extinction throughout all or a significant portion of its range.

169. endemic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having a natural distribution confined to a particular geographical region.

170. endemic
Definition:

Native to a particular region.

171. endergonic
Definition:

Refers to a chemical reaction that consumes energy.

172. endo-
Definition:

A prefix indicating that the word has to do with internal, inside, inner, or within.

173. endobiotic
Definition:

Describes an organism which is living in the tissues or cells of another, hosting organism.

174. endocarditis
Author: Guo Li
Definition:

Endocarditis is an inflammatory disorder of the heart valves or the mural endocardium (the innermost layer of the three layered walls of the heart). It can be caused by bacterial infection, or by other means. Libman-Sacks endocarditis is nonbacterial and is caused by systemic lupus erythematosus. In bacterial versions of this disorder, valvular lesions from previous infections or congenital heart disease are the predisposing factors.

175. endocardium
Author: Guo Li
Definition:

The endocardium is the innermost layer of the three layered walls of the heart.

176. endocarp
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The innermost layer of the wall of a fruit; in a drupe, the stony layer surrounding the seed.

177. endocrine gland
Definition:

A gland, such as the pituitary or thyroid, that secretes its products directly into the bloodstream. Compare exocrine gland.

178. endocrinologist
Author: PharmInfoNet
Definition:

A doctor who treats people who have problems with their endocrine glands. diabetes is an endocrine disorder.

179. endocrinology
Definition:

The scientific study of the function and pathology of the endocrine glands (e.g. the thyroid gland, pituitary gland, etc.)

180. endocytic vesicle
Definition:

The vesicle (membrane-bound bubble within the cell) which is formed during the process of endocytosis and which contains substances being imported from outside of the cell.

181. endocytosis
Definition:

Process by which extracellular materials are taken up by a cell. Compare exocytosis. A blanket term for phagocytosis and pinocytosis.

182. endodeoxyribonuclease
Definition:

A hydrolase enzyme that hydrolyzes the interior bonds of deoxyribonucleotides and strings them together into oligonucleotides or polynucleotides.

183. endoderm (entoderm, endoblast, entoblast, hypoblast)
Definition:

The innermost layer of tissue in a developing animal embryo which will eventually become the digestive tract, respiratory tract, and various other things depending on the organism. Occurs in all animals except for sponges and placozoans.

184. endoenzyme
Definition:

1. An enzyme which is not secreted or exported out of the cell, but is kept and used by the cell which made it. Compare ectoenzyme.
2. An enzyme that makes bonds within polymers (chains of similar units).

185. endogamy
Definition:

The opposite of exogamy:

1. Sexual reproduction between organisms which are closely related to each other.
2. Production of a zygote (an egg that has been fertilized by a sperm) by a simultaneous hermaphrodite (an organism which produces both sperm and eggs) using only its own gametes (eggs and sperm) without gamete contributions from other individuals.
3. Marriage between members of the same restricted group, class, or caste.

186. endogenote
Definition:

The original complete genome of a bacterium, before addition of new genetic material (an exogenote) from a donor by the process of genetic recombination or by genetic engineering.

187. endogenous
Definition:

1. In general, means anything developing or growing from within.
2. In immunology, it means a disease or illness that is caused by a problem within the organism.

188. endogenous pyrogen
Definition:

A protein which produces a fever when the body has been invaded by foreign antigens.

189. endogenous retrovirus
Definition:

A retrovirus that has become dormant and exists as DNA copies in every cell in the body of its host and is passed down from generation to generation.

190. endogenous virus
Definition:

1. A virus with the ability to integrate into the genome of its host and become dormant, so that it exists as DNA copies in every cell in the body of the host and is passed down from generation to generation.
2. A virus that causes a persistent infection.

191. endometrial biopsy
Author: Fertilitext
Definition:

The removal of a fragment of the lining of the uterus for study under a microscope.

192. endometriosis
Definition:

Growth of the tissue lining the uterus (the endometrium) outside the uterus, usually in the lower abdomen. This mislocated tissue bleeds during the woman's period, causing pain and inflammation.

193. endometritis
Definition:

Inflammation of the endometrium (the tissue lining the uterus), often due to infection by bacteria, which can occur after childbirth or abortion and which can result in lesions, tubercles, or the sloughing off of tissue.

194. endometrium (adj.: endometrial)
Definition:

The tissue lining the uterus; it is sloughed off during the woman's menstrual period, and afterward grows back and slowly gets thicker and thicker until the next period.

195. endomitosis
Definition:

Replication of the DNA in a cell's nucleus without subsequent mitosis (nuclear division).

196. endomixis
Definition:

1. Self-fertilization; the union of an egg and a sperm which are both from the same individual.
2. In certain ciliated protozoans, a process of nuclear division and reorganization.

197. endomysium
Definition:

A sheath of connective tissue that surrounds muscle fibers.

198. endoneural
Definition:

Having to do with a nerve.

199. endonuclease
Definition:

An enzyme that cleaves its nucleic acid substrate at internal sites (the phosphodiester bonds) in the nucleotide sequence.

200. endonuclease S1
Definition:

A nuclease enzyme from the fungus Aspergillus oryzae which cuts the phosphodiester bonds between nucleotides in single-stranded DNA or RNA, producing individual nucleotide molecules.

201. endopeptidase
Definition:

A hydrolase enzyme that cleaves peptide bonds between amino acids in a polypeptide (chain of amino acids) by hydrolyzing them.

202. endoplasm
Definition:

The portion of the cell's cytoplasm which is closest to the cell's nucleus.

203. endoplasmic reticulum
Definition:

A system of double-membraned, tubular organelles that aid in protein synthesis in eukaryotic cells.

204. endopolyploidy
Definition:

Many multiple copies of the chromosomes of a cell which has been repeatedly duplicating and dividing them without undergoing cell division afterwards.

205. endoribonuclease
Definition:

A hydrolase enzyme which makes oligonucleotides and polynucleotides by hydrolyzing the interior bonds of ribonucleotides.

206. endorphin
Image: View the chemical structure
Definition:

Any of several morphine-like peptides naturally produced in the brain which bind to certain neuron receptors and have the effect of diminishing pain.

207. endoscope
Definition:

A medical instrument used to view inside the body.

208. endoskeleton (neural skeleton)
Definition:

A skeleton, or support structure, which is on the inside of the organism's body. All vertebrates possess one that is made of either bone or cartilage. (Note: teeth are not counted as part of the endoskeleton.) Compare exoskeleton.

209. endosmosis
Definition:

The movement of liquid from outside the cell to its interior by osmosis through the cell membrane. The opposite of exosmosis.

210. endosome (receptosome)
Definition:

A large membrane-bound structure that is the result after several coated vesicles fuse together following endocytosis. The structure contains the combined contents of all of the former vesicles.

211. endosperm (albumen)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Nutritive tissue in a seed; in angiosperms it's triploid and is formed in the embryo sac after fertilization. In gymnosperms, it's haploid and is derived from the sterile portion of the female gametophyte. Compare perisperm.

212. endospore
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A differentiated cell formed within the cells of certain Gram-positive bacteria and extremely resistant to heat as well as to other harmful agents.

213. endosulfan
Definition:

A toxic chemical used as an insecticide; it has the chemical formula of C₉H₆Cl₆O₃S. At room temperature, endosulfan is composed of brown crystals. It cannot be dissolved in water, but can be dissolved in most organic solvents. In pure form, it melts at 106°C.

214. endosymbiont
Definition:

An organism which lives within the body of another organism (its host) as part of an endosymbiotic relationship.

215. endosymbiosis
Definition:

A symbiotic relationship between two organisms in which one of the two organisms (the endosymbiont) lives inside the body of the other one (the host). Compare ectosymbiosis.

216. endosymbiosis theory
Definition:

The scientific theory that the organelles of eukaryotic cells arose when free-living procaryotic cells began living within other, larger free-living procaryotic cells and formed mutualistic symbiotic relationships with them.

217. endosymbiotic infection (endosymbiosis)
Definition:

A situation where a cell that has been infected by a virus is prevented from dividing but is not immediately killed.

218. endothelial cell
Definition:

A thin, flattened cell; a layer of them lines the inside surfaces of body cavities, blood vessels, and lymph vessels, making up the endothelium.

219. endothelin
Definition:

A polypeptide (chain of amino acids) that induces the smooth muscles of the blood vessel walls to contract. It is made by the endothelial cells which line the inner surface of the blood vessels.

220. endothelioma
Definition:

A tumor (usually benign) which is formed from tissues of the endothelium.

221. endotheliotoxin
Definition:

A poison that causes hemorrhages (internal bleeding) by attacking the endothelium (inner lining) of small blood vessels.

222. endothelium (endothelial)
Definition:

A layer of cells (called endothelial cells) that lines the inside surfaces of body cavities, blood vessels, and lymph vessels.

223. endotherm
Definition:

1. An organism which is capable of generating its own body heat and maintaining a constant body temperature; a warm-blooded organism.
2. A graph which shows the difference in temperature between a test compound and a reference compound that is thermally inert, when the compounds are both heated at the same rate.

224. endothermic
Definition:

Describes a chemical reaction that absorbs or requires energy (usually in the form of heat).

225. endotoxin
Definition:

Any of a group of poisonous lipopolysaccharides found in the outer membranes of Gram-negative bacteria. These toxins cause illnesses such as diarrhea and hemorragic shock.

226. endotracheal tube
Definition:

In surgery, a tube which is passed through the mouth or nose into the trachea to provide a free passage for air into the lungs.

227. energy coupling
Definition:

The tranfer of energy produced in one reaction to another.

228. energy dissipater
Author:
Definition:

A device which fits on the downstream end of a culvert pipe or sluiceway which reduces the hydraulic energy of high velocity water flows. Arranging for the discharge to strike a large rock, log, etc., can also dissipate the energy of the flow. This is sometimes used in the absence of a downspout on the downstream end of a culvert or sluiceway to prevent severe erosion of a stream bank where the outlet is high above natural stream grade.

229. enhancement
Author:
Definition:

Altering an object, substance or site for the improvement of a specific value.

230. enhancement flow
Author:
Definition:

An improvement of flow that provides improvement over natural conditions for the aquatic, terrestrial, and other recreation resources.

231. enhancers
Definition:

1. DNA sequences that positively influence the expression of a gene and which may be some distance from that gene.
2. A protein which binds to such a sequence of DNA.

232. enriched medium
Definition:

A growth medium which contains extra unusual nutrients or contains higher concentrations of regular nutrients than a standard medium. It is used to grow auxotrophs (organisms which lack the ability to make something essential for growth).

233. enrichment culture
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Use of selective culture media and incubation conditions to isolate microorganisms directly from nature.

234. ensiform
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Having sharp edges and tapering to a slender point; having a shape suggesting a sword.

235. enteric bacteria
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A large group of Gram negative rod-shaped bacteria characterized by a facultatively aerobic metabolism. Many of them are commonly found in the intestines of animals.

236. enteric coating (enteric-coated)
Definition:

A coating put on a capsule or pill so that it doesn't dissolve until it reaches the small intestine.

237. enteric organism
Definition:

A microorganism that lives in the intestines.

238. enterics
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The common name for bacteria in the family Enterobacteriaceae.

239. enteritis
Definition:

Inflammation of the intestine, particularly of the small intestine.

240. Enterobacteriaceae
Definition:

A family of bacteria which are gram-negative, shaped like rods, and are facultative anaerobes. They live in soil, water, plants, and animals (especially the intestines), and can cause diseases in vertebrate animals.

241. enterotoxin
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A toxin affecting the intestine.

242. enthalpy (H)
Definition:

The heat in a system.

243. enthalpy change (�H)
Definition:

In a reaction, this is more or less equal to the the difference between the energy put into breaking bonds and the enery gained from new bond formation.

244. entire
Definition:

1. Complete; not missing parts.
2. Having a smooth margin, not dissected or toothed.

245. entisols
Author:
Definition:

Soils of slight and recent development; common along rivers and flood plains.

246. Entner-Doudoroff pathway (ED pathway)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A pathway that converts glucose to pyruvate and glyceraldehyde-3 phosphate by producing 6-phosphogluconate and then dehydrating it.

247. entomology
Definition:

The scientific study of insects.

248. entomophilous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pollinated by insects.

249. entropy
Definition:

The amount of disorder in a system.

250. enuresis
Author: Guo Li
Definition:

Enuresis is the involuntary urinary incontinence (involuntary urination) in a child 5 years or older when there exists no physical abnormality to account for this condition.

251. env genes
Definition:

One of three retrovirus genes which codes for the env glycoproteins.

252. env glycoproteins
Definition:

An important protein component of the mature retrovirus protein outer coat (the capsid). It is coded for by the env genes.

253. environment
Author:
Definition:

1. The complex of climatic, edaphic and biotic factors that act upon an organism or an ecological community and ultimately determine its form and survival.
2. Califonia state law defines environment as "the physical conditions which exist within the area which will be affected by a proposed project, including land, air, water, mineral, flora, fauna, noise, and objects of historic or aesthetic significance."

254. environmental output
Author:
Definition:

Environmental outputs are the desired or anticipated measurable products or results of restoration measures and plans.

255. Environmental Protection Agency (EPA)
Author: Susan A.Hagedorn
Definition:

The U.S. regulatory agency for biotechnology of microbes. The major laws under which the agency has regulatory powers are the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA); and the Toxic Substances Control Act (TSCA).

256. environmental quality objective (EQO)
Definition:

This is a regulatory value defining the quality to be aimed for in a particular aspect of the environment. Unlike an environmental quality standard, an EQO is not usually expressed in quantitative terms and cannot be enforced legally.

257. environmental quality standard (EQS, ambient standard, air quality standard)
Definition:

This regulatory value defines the maximum concentration of a potentially toxic substance which can be allowed in an environmental compartment, usually air (air quality standard - AQS) or water, over a defined period.

258. environmental tobacco smoke
Author: Stephen J. Jay, MD
Definition:

A complex mixture of chemical constituents and particulates released into the atmosphere from the burning tip of a cigarette, pipe or cigar or from smoke exhaled by the smoker.

259. environmental variance
Definition:

Within a population, the measure of how much of the variation of a particular phenotype is due to environmental factors (as opposed to variations in genotype - see genetic variance). An example might be the height of a human as determined by such factors as nutrition or infectious diseases during childhood.

260. enzyme derepression
Definition:

Removing or turning off the inhibitor or inhibitors (molecules which repress or prevent other molecules from acting) enzyme so that enzyme activity can resume.

261. enzyme immobilization
Definition:

The attachment of an enzyme to a solid matrix so that it cannot escape but can still act on its substrate.

262. enzyme inactivation
Definition:

The disappearance of an enzyme’s activity during in vitro conditions, such as during a lab preparation of the enzyme, where the enzyme is exposed to conditions not normally found within its environment inside a living cell (like different pH, excess or too little salt, temperature changes, etc.)

263. enzyme kinetics
Author: ForBio Ltd.
Definition:

Quantitative characteristics of enzymatic reactions.

264. enzyme replacement therapy
Definition:

A type of medical treatment for patients who lack an important enzyme; the missing enzyme is injected into the patient.

265. enzyme stabilization
Definition:

Reducing the chances that an enzyme will inactivate in vitro (see enzyme inactivation) by changing the environmental conditions (such as pH, temperature, concentration of salt, etc.) or by attaching organic groups to it or changing some of its amino acid subunits.

266. enzymes
Definition:

Proteins that act as catalysts, speeding the rate at which biochemical reactions proceed but not altering the direction or nature of the reactions.

267. enzymic process (enzymatic process)
Definition:

Any chemical reaction or series of reactions catalysed by an enzyme.

268. eosin
Definition:

1. A red, fluorescent, bromine-containing, water-insoluble dye used mainly in toner and cosmetics.
    
2. A red or brown potassium or sodium salt of the above dye; it is used as a biological stain and in pharmaceuticals.

269. eosinophil
Definition:

A type of granular leukocyte that is an amoeba-like scavenger that disposes of cellular debris. This cell takes its name from the fact that it can be stained with eosin. People with parasitic infections typically have increased numbers of these cells in their bloodstream.

270. ephemeral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Short-lived.

271. ephemeral stream
Author:
Definition:

A stream that flows briefly and only in direct response to local precipitation, and whose channel is always above the water table.

272. epibenthic
Author:
Definition:

Living on the surface of bottom sediments in a water body.

273. epicalyx
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A whorl of bracts, just below a flower, looking like a second calyx.

274. epicarp
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The outer layer of the wall of a fruit, i.e. the 'skin'.

275. epicormic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of buds, shoots or flowers, borne on the old wood of trees (applied especially to shoots arising from dormant buds after injury or fire).

276. epicortical
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

On top of the bark, i.e. outside the bark.

277. epicotyl
Definition:

The part of the stem of an embryonic plant which is above the cotyledons but below the first true leaves (which are attached to the apex of the epicotyl). The epicotyl develops into the shoot of the plant upon germination of the seed. (The rest of the embryonic stem, which is below the cotyledons, is called the hypocotyl).

278. epidemic
Definition:

A virulent, widespread disease in a human or animal population.

279. epidemiology
Definition:

The scientific study of diseases; includes analyzing the occurence and distribution of diseases and the factors that govern their spread.

280. epidermal growth factor (EGF)
Definition:

A polypeptide growth factor that stimulates the growth of epithelial cells. It was discovered by Stanley Cohen, and a part of the gene which codes for the receptor on the cells that heed its signals is extremely similar to the erb-b oncogene (proto-cancer gene).

281. epidermis
Definition:

1. The outer epitheial layer of the skin, consisting of a basal layer, a prickle-cell (spinous) layer, a a glandular layer, a clear layer, and a horny layer.
2. The outermost layer of parenchyma in plants which protects against water loss, abrasions, etc.

282. epididymis
Author: Fertilitext
Definition:

The tightly-coiled, thin-walled tube that conducts sperm from the testicles to the vas deferens.

283. epididymitis
Author: Fertilitext
Definition:

Inflammation of the epididymis.

284. epididymitis
Definition:

Epididymitis is inflammation/infection of the epididymis.

285. epifauna
Author:
Definition:

Animals living on the surface of the substrate.

286. epigeal
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of germination, having the cotyledon(s) emerging from the seed coat and becoming photosynthetic. Compare hypogeal.

287. epigenetic
Definition:

Describes something which influences the behavior of a cell without directly affecting its DNA or other genetic machinery, such as an environmental effect.

288. epigenetic changes
Definition:

Any changes in an organism brought about by alterations in the action of genes are called epigenetic changes. Epigenetic transformation refers to those processes which cause normal cells to become tumor cells without the occurrence of any mutations.

289. epigynous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of floral parts (especially stamens), attached above the level of insertion of the ovary, and arising from tissue that is fused to the ovary wall. Compare hypogynous, perigynous.

290. epilepsy
Author: Guo Li
Definition:

Epilepsy is a clinical condition characterized by recurrent attacks of seizures of sudden onset. The seizures may range in severity from a brief loss of consciousness (which may resemble simple daydreaming or dozing to the observer) to grand mal seizures that may involve several minutes of powerful convulsions.

291. epilithic
Author:
Definition:

Living on rocks or other stony matter.

292. epimer
Definition:

A stereoisomer of a compound that has at least two asymmetric centers that differs from its alternate form at a single asymmetric center.

293. epimerase
Definition:

An enzyme that catalyzes the reversible conversion of an epimer into its counterpart form.

294. epinephrine (adrenaline)
Definition:

A chemical produced and secreted by the adrenal glands. It can act as a stimulant, increasing blood pressure, heart rate, and other functions. It is a neurotransmitter, or substance which transmits nerve signals from neuron to neuron, and is also a hormone that helps break glycogen (a polysaccharide) down into glucose (a simple sugar). It has the chemical formula C₉H₁₃NO₃.

295. epipetalous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Borne on the petals.

296. epiphyllous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Growing on leaves, e.g. applied to vegetatively propagated plantlets in some members of the family Crassulaceae.

297. epiphyte
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A plant growing on, but not parasitic on, another plant (often loosely applied to plants, such as orchids, that grow on vertical rock faces). Compare parasite, saprophyte.

298. epiphytotic
Definition:

A virulent, widespread disease in a plant population. Often called an epidemic.

299. episome
Definition:

DNA in a bacterium that is not part of the bacterium’s chromosomes, so that it replicates separately and can have a different number of copies. Plasmids are an example.

300. epistasis (epistatic)
Definition:

The condition where one gene suppresses the expression of another gene (and therefore whatever phenotype it is responsible for), when the two genes are not alternate alleles of the same phenotype. The gene which does the suppressing is called the epistatic gene.

301. epistatic gene
Definition:

A gene which suppresses another gene when the two are not alternate alleles.

302. epistaxis
Definition:

This is the medical term for a nose bleed.

303. epithelium (epithelial)
Definition:

The covering of an organism or an organ. The layer(s) of cells between the organism or its tissues or organs and the environment. Examples include the skin cells, the inner linings of the lungs and the digestive tract, etc.

304. epitope
Definition:

The particular site within a macromolecule to which a specific antibody binds.

305. Epstein-Barr virus (mononucleosis)
Definition:

A virus in the family Herpesviridae which infects humans. It causes infectious mononucleosis, which is characterized by debility, fever, sore throat, enlarged lymph nodes, and an increase in white blood cell count. This virus is transmitted mainly via saliva and is associated with carcinomas of the nasal passages and throat and with Burkitt's lymphoma.

306. equatorial plate
Definition:

1. The plate or plane along which the chromosomes align during metaphase (an intermediate stage of mitosis or meiosis).
2. An unconnected cytoplasmic membrane which forms in the middle of a cell during early cytokinesis, when the cell is about to divide into two daughter cells.

307. equilateral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of stamens, with anthers regularly spaced around the style.

308. equilibrium
Definition:

1. Balance
2. A condition in which no further net change is occuring in a system, and free energy is minimimal.

309. equilibrium centrifugation
Definition:

A type of density gradient centrifugation used to separate proteins or nucleic acids from a mixture.

310. equilibrium potential
Definition:

The membrane potential at which a particular type of ion or other particle does not diffuse through the membrane in either direction.

311. equine
Definition:

Relating to, affecting, resembling or derived from a horse.

312. equitant
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of leaves, folded in half along the midline so that the adaxial surface disappears, and overlapping the edges of a similarly folded leaf on the opposite side of the stem.

313. Erb's palsy
Author: Guo Li
Definition:

Erb's palsy is an injury to the upper brachial plexus (mainly the fifth and sixth cervical roots) related to birth trauma of newborns. Its occurrence is about 0.1 percent in spontaneous delivery, 1.2 percent in breech delivery, and 1.3 percent in forceps delivery. The result is partial paralysis of the muscles of the shoulder and flexors of the elbow such that the arm hangs at the side and internally rotated at the shoulder.

314. erb-a
Definition:

One of two oncogenes (proto-cancer gene) found in the avian erythroblastosis retrovirus (a retrovirus which affects red blood cell formation in birds). It is incredibly similar to a gene which codes for the receptor protein that recognizes hormones from the thyroid gland for the cell.

315. erb-b
Definition:

One of two oncogenes (proto-cancer gene) found in the avian erythroblastosis retrovirus (a retrovirus which affects red blood cell formation in birds). It is incredibly similar to a gene which codes for the receptor protein that recognizes signals from the epidermal growth factor (EFG) for the cell.

316. ERCP (endoscopic retrograde cholangiopancreatography)
Author: Guo Li
Definition:

In this procedure, a fiberoptic endoscope is passed through the oral pharynx, esophagus, stomach, into the duodenum. A catheter is passed through the endoscope and canulates the Ampulla of Vater, the bile duct and the pancreatic duct. This procedure can identify gallstones and tumors.

317. erectile impotence
Author: Guo Li
Definition:

Erectile impotence is the failure of penile erection under any conditions. This includes failure of penile tumescence (swelling with accumulation of blood in the penile tissues) occurring during sleep often in association with rapid eye movement (REM) episodes. The decrease of penile tumescence with REM sleep has been reported to be associated with aging.

318. eremean
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pertaining to regions of low, irregular rainfall.

319. erg
Definition:

A measurement unit for energy. It is equal to 2.4 x 10^-8 gram calories or 0.624 x 10¹² electronvolts, or the amount of work done by a force of one dyne acting on a distance of one centimeter.

320. ergon
Definition:

A unit used to measure/represent the stability of a gene over the lifetime of a given organism. It is a function of the ratio of the adenine-thymine to the guanine-cytosine content of the gene, and is evidenced by the continual physical expression of the trait coded by the gene.

321. ergot
Definition:

A disease of cereal plants (rye, wheat, etc.) caused by the fungus Claviceps purpurea; this fungus produces toxic alkaloids that, if ingested, cause symptoms such as hallucinations, severe gastrointestinal upset, a burning sensation in the limbs and extremities (a.k.a. Saint Anthony's Fire) and a form of gangrene.

322. Erlenmeyer flask
Definition:

A piece of chemistry laboratory equipment, a container often made of glass, which has a narrow cylindrical mouth and a cone-shaped main body that ends in a wide, flat bottom. It may also have a smaller straight tube-shaped opening from the side of the cylindrical part, where tubes can be attached.

323. erose
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Margin irregularly incised.

324. erose
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of a margin: finely and irregularly eroded or toothed.

325. erosion
Author:
Definition:

1. The wearing away of the earth's surface by natural forces, such as water, wind and ice.
2. The loosening and transportation of rock and soil debris by wind, rain, or running water.
3. Wearing away of land by physical and chemical action in moving water or air.

326. error-prone repair (SOS repair)
Definition:

A type of DNA repair which occurs when both nucleotides in a base pair are missing, such that it is not possible to maintain accuracy. In general, the repair proteins replace the missing nucleotides randomly. The idea is that "bad" DNA is better than no DNA at all.

327. erysipelas
Author: Guo Li
Definition:

Erysipelas is a streptococcal infection of the dermis layer of the face.

328. erythema
Definition:

General term for redness of the skin due to capillary congestion; can be caused by anything from blushing to contact with a skin irritant to radiation damage.

329. erythema multiforme
Author: Guo Li
Definition:

Erythema multiforme is an acute inflammatory condition of the skin presenting in various types: urticarial, erythematous macular, papular, vesicular, and bullous. Although the exact cause is unknown, many precipitating factors are identified: infection, vaccination, x-ray therapy, certain medications, and pregnancy.

330. erythema threshold
Definition:

The amount of radiation that causes redness of the skin.

331. erythroblast
Definition:

A stem cell in bone marrow that gives rise to red blood cells.

332. erythroblastosis fetalis
Definition:

A type of anemia which can occur in newborns that have Rh⁺ blood and which are born to mothers with Rh^- blood (see Rh factor). Symptoms include lots of erythroblast cells which are circulating in the blood instead of being within bone marrow, liver and spleen enlargement, and edema (tissue swelling due to excessive fluid).

333. erythroblastosis fetalis
Author: Guo Li
Definition:

Erythroblastosis fetalis is the condition in which a pregnant women produces an antibody (IgG) to the red blood cells of the fetus she is carrying, which causes the destruction of her fetus' red blood cells. This condition is worse in successive at-risk pregnancies. The antigens could be Rh (most commonly RhD), Kell, Duffy, Lutheran, and Kidd. The mother whose pregnancy is at risk is negative for these antigens.

334. erythrocyte (red blood cell, RBC)
Image: red blood cell
Definition:

A red blood cell; erythrocytes carry oxygen in the blood via hemoglobin. RBCs are disk-shaped and indented on both sides and are about 7 micrometers in diameter. A red blood cell lives about 120 days.

335. erythrocyte ghost
Definition:

A red blood cell that has had its contents removed and replaced with drugs and other bioactive chemicals to be delivered to target cells. A type of delivery system.

336. erythrocyte sedimentation rate (ESR)
Author: Guo Li
Definition:

ESR is elevated in inflammation due to many clinical conditions such as tumor, infections, rheumatoid arthritis. As such, it is a non-specific test. However, it is useful for monitoring the progression of the disease. With more specific tests available, ESR is used less often now.

337. erythromycin
Image: View the chemical structure
Definition:

An antibiotic that disrupts bacterial protein synthesis by binding to their ribosomes and inhibiting translocation.

338. erythropoesis
Definition:

The process of turning erythroblasts (bone marrow stem cells) into erythrocytes (red blood cells) within the bone marrow.

339. erythropoetin
Definition:

A glycoprotein (a molecule combining sugar and protein) that induces erythropoesis (the making of red blood cells in the bone marrow). It is made by the kidneys.

340. erythropoiesis
Author: Guo Li
Definition:

Erythropoiesis is the process of red blood cell production (which occurs in red bone marrow).

341. erythropoietin
Author: Guo Li
Definition:

Erythropoietin is a hormone secreted by certain cells in the kidney in response to low oxygen levels. It stimulates red blood cell production (which occurs in bone marrow).

342. escapement
Author:
Definition:

That portion of an anadromous fish population that escapes the commercial and recreational fisheries and reaches the freshwater spawning grounds.

343. eschar
Definition:

In medical terminology, this is a dry scab that forms on skin that has been burned or exposed to corrosive agents.

344. esophagitis
Author: PharmInfoNet
Definition:

Inflammation of the esophagus.

345. esophagitis
Definition:

Inflammation of the esophagus.

346. esophagus (adj. esophageal)
Definition:

The tube-like upper portion of the digestive tract which carries food and fluid from the mouth to the stomach.

347. esotropia
Definition:

This is a misalignment of the eye in which the eye is turned inward.

348. essential amino acid
Definition:

Any amino acid that can't be synthesized by an organism and must be taken in as a nutrient; in humans, about half of the 20 amino acids we use for growth and metabolism are essential.

349. essential fatty acid
Definition:

Any polyunsaturated fatty acid involved in human physiologic processes that is synthesized by plants but not by the human body and is therefore a dietary requirement.

350. essential gene
Definition:

Any gene that, if it doesn't work correctly, kills the organism.

351. EST
Definition:

Expressed Sequence Tag. See sequence tagged site.

352. established cell line
Definition:

A stable culture of cells that can be maintained indefinitely. A lineage of cells that has become immortalized.

353. ester
Definition:

1. A general term for any organic molecule produced by combining an acid with an alcohol.
2. A derivative of carboxylic acid (acid with a carboxyl group -COOH) which has the general formula RCOOR, where the R's stand for the same or different aliphatic groups (alkyl groups), aromatic groups (aryl groups), or hydrogen ions.

354. esterase
Definition:

An enzyme that breaks ester linkages, especially the ones found in nucleic acids (phosphodiester bonds) and lipids.

355. estero
Author:
Definition:

Spanish for "estuary." The area where the waters of a river or stream mingle with the ocean into which it flows.

356. estivation (aestivation)
Author: Botany def. mirrored from Jim Croft's Flora of Australia
Definition:

In zoology, a dormant state involving vastly lowered metabolism which certain animals enter in order to survive hot weather.

In botany, refers to the arrangement of sepals and petals or their lobes in an unexpanded flower bud. Compare vernation.

357. estradiol
Author: Fertilitext
Definition:

Estradiol is the principal estrogen produced by the ovary.

358. estrogen (pl. estrogens)
Definition:

A steroid sex hormone that regulates female reproductive processes and creates feminine secondary sexual characteristics. Some types of cancer depend on estrogen for their growth, and modern-day increases in cancer rates are thought by many to be caused by the action of certain chlorinated organic chemicals (such as pesticides and herbicides) that mimic the action of this hormone.

359. estrus cycle (estrous cycle)
Definition:

A reproductive cycle in some female mammals (but not female humans, who instead have menstrual cycles). The cycle is characterized by a short period of intense sexual desire (called estrus or heat) when the animal is fertile, which often occurs only once or twice a year, and involves correlating physical changes of the reproductive tract.

360. estuary (pl. estuaries)
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

An inlet or arm of the sea; especially the wide mouth of a river, where the tide meets the current.

361. et
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "and".

362. Etard reaction
Definition:

In organic chemistry, this involves oxidizing methylated homologs of benzene into aromatic aldehydes. The reaction uses chromyl chloride.

363. ethanol (ethyl alcohol, grain alcohol)
Definition:

A type of alcohol created in some types of fermentation; it is the alcohol found in alcoholic beverages.

364. ethidium bromide
Author: Susan A.Hagedorn
Definition:

A fluorescent dye used to stain DNA and RNA. The dye fluoresces when exposed to UV light.

365. ethosuximide (Zarontin)
Definition:

This prescription drug is used to treat petit mal epilepsy. It can cause a wide range of adverse side effects and may cause some mental or physical impairment.

366. ethylene
Image: View the chemical structure
Definition:

A gas produced naturally by fruits (especially apples and bannanas), fungi and some bacteria which stimulates ripening and germination (though treating a plant with ethylene after it sprouts can inhibit its growth). Ethylene is also a by-product of natural gas combustion, and people with gas-heated homes may have problems growing their houseplants.

367. ethylene diamine tetra acetate (EDTA)
Definition:

A chemical that is used to remove all traces of magnesium and calcium ions from a solution because it binds tightly to them, in order to control unwanted side reactions with these metals during a laboratory process.

368. etiology
Definition:

The scientific study of the cause of diseases.

369. etiology
Author: PharmInfoNet
Definition:

The science of the causes and modes of operation of diseases.

370. ets oncogene
Definition:

A proto-cancer gene which causes leukemias (blood cancers) in chickens. It is carried and spread by the avian leukemia virus E26 (v-ets). The normal role of the oncogene is the making of a nuclear protein which can bind DNA and which may help activate and proliferate T lymphocyte cells.

371. eu-
Definition:

This prefix means "good" or "genuine."

372. euchromatin
Definition:

One of two types of chromatin seen during interphase of the cell cycle. It is genetically active (transcription occurs in it) and less condensed than heterochromatin (the other type of chromatin).

373. eugenics
Definition:

The scientific study of artificial selection towards a particular set of desired characteristics.

374. Euglena
Definition:

Euglena is a genus of flagellate freshwater protozoans. It contains chlorophyll and is therefore photosynthetic, but it can also be mobile and gather its own food when sunlight is absent. Because it has the characteristics of both plants and animals, it is thought to be related to/similar to the ancestral organism which gave rise to both plants and animals.

375. Eukarya
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The phylogenetic domain containing all eukaryotic organisms.

376. eukaryote (eucaryote, eukaryotic cell, eucaryotic cell)
Definition:

Cell or organism with a membrane-bound, structurally discrete nucleus and other well-developed subcellular compartments. Eukaryotes include all organisms except viruses, bacteria, and cyanobacteria (blue-green algae). Compare prokaryote.

377. euploid (euploidy)
Definition:

Describes a cell or individual which has the normal total number of chromosomes. Humans normally have 46 chromosomes per cell. Euploidy is the opposite of aneuploidy.

378. European Molecular Biology Lab gene bank (EMBL)
Definition:

A large database of DNA sequence data in Heidelberg, Germany, compiled from international sources. It is the European equivalent to the Genbank DNA sequence databank in the United States of America.

It can be found at http://www.embl-heidelberg.de/Services/index.html.

379. eusporangiate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of ferns, having sporangia with walls more than one cell thick. Compare leptosporangiate.

380. eutrophic
Author:
Definition:

Rich in dissolved nutrients, photosynthetically productive and often deficient in oxygen during warm weather. (Compare oligotrophic.)

381. eutrophication
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The gradual increase in nutrients in a body of water. Natural eutrophication is a gradual process, but human activities may greatly accelerate the process.

382. evapotranspiration
Author:
Definition:

Loss of water by evaporation from the soil and transpiration from plants.

383. even-pinnate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Said of compound leaves having an even number of leaflets; this is usually easily determined because there is a terminal pair.

384. even-year runs
Author:
Definition:

Populations of fish returning to spawning grounds in even-numbered years.

385. evergreen
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Bearing green leaves throughout the year.

386. evolution
Definition:

In biological terms: a change in the genetic composition of a population over time.

387. evolutionary computation (genetic algorithms, genetic programming)
Definition:

Evolutionary computation, genetic algorithms, and genetic programming are all computer disciplines involved with modeling genetic inheritance and/or biological evolution in computers.

For more information, visit The Hitch-Hiker's Guide to Evolutionary Computation.

388. evolutionary distance
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In phylogenetic trees, the sum of the physical distance on a tree separating organisms; this distance is inversely proportional to evolutionary relatedness.

389. ex
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "from".

390. ex modo prescripto (e.m.p.)
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "after the manner prescribed".

391. excelsior matting
Author:
Definition:

A layer of fine, curled wood shavings used to stabilize eroding soil or to filter sediment from flowing water.

392. excentric
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

To one side; off-center.

393. excision repair
Definition:

A DNA repair process where the damaged portion of DNA is excised, or removed, then the removed part is recopied from the other undamaged strand by DNA polymerase enzymes, and finally the replacement part is attached to the site by DNA ligase enzymes.

394. excitotoxin
Author: The Alzheimer's Association
Definition:

A chemical substance that can damage and kill nerve cells by overstimulating them.

395. exclosure
Author:
Definition:

An area from which livestock or other animals are excluded.

396. excrescence
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A normal outgrowth; a disfiguring addition.

397. excretion
Definition:

This is a general term for the discharge of substances from the body.

398. excurrent
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Projecting beyond the tip, as the midrib of a leaf or bract.

399. exergonic
Definition:

Describes a chemical reaction that releases energy in the form of heat, light, etc.

400. exfoliate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Peeling off in thin layers, shreds, or plates, as the bark of some trees.

401. exfoliate
Author: PharmInfoNet
Definition:

To shed cells from the skin or from mucous membranes.

402. exine
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The outer layer of the wall of a pollen grain or spore.

403. exit domain
Definition:

One of the two main binding sites on the ribosome molecule. The finished portion of the polypeptide being translated is attached to this site and leaves the ribosome from this site when the entire polypeptide is finished.

404. exocarp
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The outer layer or "skin" of a pericarp.

405. exocellular
Definition:

Refers to reactions or processes that are initiated inside a cell but actually take place outside it.

406. exocrine gland
Definition:

A gland that secretes its products through ducts or canals, such as sweat glands or mammary glands. Compare endocrine gland.

407. exocytosis
Definition:

Process by which cellular material is discharged from a cell. Compare endocytosis.

408. exodeoxyribonuclease
Definition:

A type of hydrolase enzyme that removes nucleotides one at a time from the end of a DNA molecule.

409. exogamy
Definition:

The opposite of endogamy:

1. Sexual reproduction between organisms which are completely unrelated to each other.
2. Marriage between members of different groups, classes, or communities.

410. exogenote
Definition:

The fragment of new genetic material that has been added to a bacterial genome by the process of genetic recombination or by genetic engineering. See also endogenote.

411. exogenous
Author: PharmInfoNet
Definition:

Grown or made outside the body; for instance, insulin made from pork or beef pancreas is exogenous insulin for people.

412. exogenous DNA
Definition:

DNA originating outside an organism.

413. exon shuffling
Definition:

A type of recombination where the exons of a gene are recombined to make new genes.

414. exon trapping (exon trap method)
Author: Vincent Van Buren
Definition:

A technique used to identify exons with a specialized vector. The vector has two exons that are normal, spliced together in a transcript. Fragments of DNA can be inserted into the intron, and when the insert is an exon, the exon is spliced into the transcript, thereby giving a longer transcript that can be detected by Northern blot analysis.

415. exons
Definition:

The protein-coding DNA sequences of a gene. Compare intron.

416. exonuclear gene
Definition:

A gene that is not located in the nucleus of the cell. Examples are the genes found in mitochondria and chloroplasts (organelles outside of the nucleus).

417. exonuclease
Definition:

An enzyme that cleaves nucleotides sequentially from the free ends of a linear nucleic acid substrate.

418. exonuclease III
Definition:

An exonuclease enzyme which removes nucleotides one at a time from the 5'-end of duplex DNA which does not have a phosphorylated 3'-end.

419. exonuclease lambda
Definition:

An exonuclease enzyme that removes nucleotides from the 5' end of duplex DNA which have 5'-phosphate groups attached to them.

420. exonuclease VII
Definition:

An exonuclease enzyme which makes oligonucleotides by cleaving chunks of nucleotides off of both ends of single-stranded DNA.

421. exopathogen
Definition:

A disease-causing virus or bacteria which causes plant diseases from outside of the plant, without having to invade the plant's tissues.

422. exopeptidase
Definition:

A hydrolase enzyme that removes the end amino acids of a polypeptide by cleaving peptide bonds.

423. exopeptidase
Definition:

This is an enzyme that sequentially removes the amino acids from the end of a chain of polypeptides.

424. exoskeleton
Definition:

1. A skeleton, or support structure, which supports the organism's body from the outside and is formed from the ectoderm. All arthropods (spiders, insects, crustaceans, horseshoe crabs, etc.) possess one. Compare endoskeleton.
2. Any structure that is formed from the ectoderm in vertebrates, like nails, claws, hair, fur, horns, or teeth. (Note: does not include skin, which is an organ.)

425. exosmosis
Definition:

The movement of liquid from inside the cell to the outside by osmosis through the cell membrane. The opposite of endosmosis.

426. exostosis
Definition:

A noncancerous growth on the surface of a bone, usually with a cartilage cap, that is due to long-term irritation as a result of osteoarthritis, infections, or trauma.

427. exotherm
Definition:

A graph showing how much heat is produced by a chemical reaction at different points in time by plotting temperature versus time.

428. exothermic
Definition:

Describes a chemical reaction that releases energy (usually in the form of heat).

429. exotic
Author:
Definition:

Not native to a given area; either intentionally transplanted from another region or introduced accidentally.

430. exotic species
Author:
Definition:

Plant or animal species introduced into an area where they do not occur naturally; non-native species.

431. exotoxin
Definition:

Any of many poisonous substances (toxins) secreted by disease-causing one-celled microbes into their immediate environment. Compare with endotoxin.

432. exotropia
Definition:

This is a misalignment of the eye in which the eye is turned outward.

433. expansive soils
Author:
Definition:

Soils that swell when they absorb water and shrink as they dry.

434. expectorant
Definition:

1. A drug or chemical substance which induces the ejection of mucus, phlegm, and other fluids from the lungs and air passages by coughing or spitting.
2. Any cough medicine.

435. experiment
Definition:

Noun: A procedure done in a controlled environment for the purpose of gathering observations, data, or facts, demonstrating known facts or theories, or testing hypotheses or theories.
Verb: To carry out such a procedure.

436. expert systems (knowledge-based systems, ES, KBS)
Definition:

Expert systems (ES), also known as knowledge-based systems (KBS), are computer programs designed to simulate the problem-solving behavior of human experts within very narrow domains or scientific disciplines (entomology, plant pathology, etc.)This discipline is a sub-set of Artificial Intelligence.

For more information, visit Introduction to Artificial Intelligence and Expert Systems.

437. explant
Author: ForBio Ltd.
Definition:

An organ, piece of tissue or cell which is taken for culture.

438. exponential growth
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Growth of a microorganism where the cell number doubles within a fixed time period.

439. exponential growth
Definition:

A rate of growth of an organism, a part of an organism, or a population of organisms which, when graphed, produces an exponential or logarithmic curve. Such a rate occurs, for example, during the exponential growth phase, when a population of bacterial (or other) cells divide at a constant rate so that the total number of cells doubles with each division.

440. export
Definition:

To transport substances from inside the cell, through the cell membrane, to the outside by a system specialized for the purpose. To secrete.

441. expressed gene
Definition:

See gene expression.

442. expression (gene expression)
Definition:

The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (e.g., transfer and ribosomal RNAs).

443. expression library
Definition:

A library of DNA fragments which was created with an expression vector so that any genes present in the library are expressed.

444. expression site
Definition:

The location in the genome of the gene for the "variable surface glycoprotein" that is currently being expressed (an expression-linked copy) by the trypanosome (a parasitic protozoan which causes the disease African sleeping sickness). Most of these sites are near the ends, or telomeres, of a chromosome.

445. expression system
Definition:

An expression vector, its cloned DNA, and the host for the vector.

446. expression vector
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A cloning vector that contains the necessary regulatory sequences to allow transcription and translation of a cloned gene or genes.

447. expression vector
Definition:

A cloning vector which is able to replicate and transcribe clone DNA.

448. expression-linked copy (ELC)
Definition:

One of many different versions of the "variable surface glycoprotein gene" of the trypanosome (a parasitic protozoan which causes the disease African sleeping sickness); refers to whichever one of them is currently being expressed on the outer surface of the trypanosome.

449. exserted
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Protruding, e.g. of stamens with respect to a corolla tube.

450. exstipulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Without stipules.

451. external ear
Author: Guo Li
Definition:

The external ear is composed of the visible parts of the ear and the canal leading to the eardrum.

452. extinction
Definition:

The death of an entire species.

453. extinction coefficient (absorptivity)
Definition:

A constant used in the Beer-Lambert Law which relates the concentration of the substance being measured (in moles) to the absorbance of the substance in solution (how well the substance in solution blocks light beamed through it from getting out on the other side).

454. extra-corporeal membrane oxygenation (ECMO)
Author: Guo Li
Definition:

ECMO is a method to provide oxygenation of a patient's red blood cells outside of the patient's body by means of a mechanical device.

455. extra-floral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of nectaries, not within the flower.

456. extracellular
Definition:

Refers to something outside the cell or cells.

457. extracellular fluid
Definition:

The fluid found outside of the cell or cells and between the cells in a tissue.

458. extracellular matrix
Definition:

A mixture of proteins on the outside of a cell which helps the cell attach to a surface on which it can grow. The composition of this matrix in cancerous tissue is drastically different from the matrix in normal tissue and, partly because of this, the composition is thought to influence the regulation of cell growth, division, and differentiation.

459. extractum (ext.)
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "an extract".

460. extrahepatic biliary tree
Definition:

Bile ducts that are located outside or beyond the liver.

461. extravaginal
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

1. Outside the vagina.
2. Of a shoot, arising from an axillary bud which breaks through the sheath of the subtending leaf.

462. extreme halophile
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An organism whose growth is dependent on large amounts (generally more than 10% in solution) of salt (sodium chloride, NaCl).

463. extrinsic protein
Definition:

A protein found in a cell or tissue which came from somewhere else (other than the cell or tissue in which it is found).

464. extrorse
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of anthers, opening away from the center of the flower. Compare introrse.

465. extrusion
Definition:

A process where a cell exports large particles or organelles (transports them through its cell membrane to the outside). Requires energy.

466. exudate
Author: Guo Li
Definition:

Exudate is fluid escaped from the blood vessels through the walls of the vessels, usually as a result of inflammation. Exudate is rich in protein.