Concise Dictionary Of Science E-Book

• Herausgeber: V&S Publishers
• Kategorie: Bildung
• Sprache: Englisch
• Veröffentlichungsjahr: 2018

Seitenzahl: 620

Beschreibung

Terms frequently used in the study of Science and their accurate explanation

Leseprobe

Published by:

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© Copyright: ISBN 978-935-05733-2-7

DISCLAIMER

While every attempt has been made to provide accurate and timely information in this book, neither the author nor the publisher assumes any responsibility for errors, unintended omissions or commissions detected therein. The author and publisher make no representation or warranty with respect to the comprehensiveness or completeness of the contents provided.

All matters included have been simplified under professional guidance for general information only without any warranty for applicability on an individual. Any mention of an organization or a website in the book by way of citation or as a source of additional information doesn't imply the endorsement of the content either by the author or the publisher. It is possible that websites cited may have changed or removed between the time of editing and publishing the book.

Results from using the expert opinion in this book will be totally dependent on individual circumstances and factors beyond the control of the author and the publisher.

It makes sense to elicit advice from well informed sources before implementing the ideas given in the book. The reader assumes full responsibility for the consequences arising out from reading this book. For proper guidance, it is advisable to read the book under the watchful eyes of parents/guardian. The purchaser of this book assumes all responsibility for the use of given materials and information. The copyright of the entire content of this book rests with the author/publisher. Any infringement/ transmission of the cover design, text or illustrations, in any form, by any means, by any entity will invite legal action and be responsible for consequences thereon.

Contents

Publisher's Note

Introduction

        A

        B

        C

        D

        E

        F

        G

        H

        I

        J

        K

        L

        M

        N

        O

        P

        Q

        R

        S

        T

        U

        V

        W

        X

        Y

        Z

AppendicesAppendix – I

Appendix – II

Appendix – III

Appendix – IV

Appendix – V

Appendix – VI

Appendix – VII

Appendix – VIII

Appendix – IX

Publisher's Note

Innumerable books are available in the market on science and its allied branches, like, physics, chemistry, and biology et al, both as textbook and reference manual. Written for different age-groups and class, quite a number of these books come replete with jargon-filled terms; and just fail to connect with readers’ inclination and curiosity level. On top of that, new words keep finding their way into the books every other day. Every new addition contributes to difficulty in comprehending the matter.

An average reader is interested only in knowing what a specific word means without getting lost with heavy sounding inputs.

Following an open-ended discussion with a cross-section of students and other stakeholders we realised that many books on science (physics, chemistry and biology) take readers’ understanding of scientific terms for granted and make short passing references while alluding to the term in the text. Presentations of this nature in no way assist readers in understanding the subject properly.

You need to suffer no longer.

V&S Publishers has come out with four dictionaries of terms; in science, physics, chemistry and biology. These have been compiled to help readers grasp the meaning of popular scientific terms. For easy reference terms have been arranged alphabetically. Terms that have come into the reckoning even in the early 2012 have been incorporated and suitably explained in such a way that an average secondary and senior secondary student can grasp them easily. High resolution images, illustrations and examples, where appropriate, have been added for reader's convenience. For all readers, who have not made a special study of any science subject, explanations of terms will be found to be easily comprehensible.

An attempt has been made to include important scientific charts, tables, constants, conversion tables as appendices to make this dictionary more useful. A glossary of Nobel Prize winners and their contributions is an added attraction.

We would be happy to have your views and comments about the book.

Introduction

Why Study Science?

Let's look at why we must have a working knowledge of science in everyday life.

Science is the study of the world around us – we learn all about the world that we live in – how things work, what living things there are, how things happen, etc. Science is the study supported by logic and reasoning. Learning science is all about examining properties of a thing in a systematic manner, endorsed by validation of the theoretical knowledge through the scientific experimentation and research, etc.

Science helps us, so to say, to separate grain from the chaff – there are a lot of misrepresentations on the television, the internet, and by word of mouth. If we arrive at the truth by learning science, we won't fall for all those inaccuracies!

Scope

Studying science equips us with the essential skills that make us employable, be that in a scientific or non-scientific arena. Science enables us to become more confident, gain proficiency with figures and calculations that prove invaluable when it comes to future employment. The ‘mathematical application within science’ is more than just putting numbers into formulae; it involves analysing data and understanding trends in the same way that businessmen might examine market data or sales figures. Problem solving is another key skill that needs to be mastered within science.

How is Science Classified?

Science can be classified in the following broad categories:

Biology – Biology is the study of anything that is alive; there are many sub-categories like microbiology, botany, and zoology.

Learning how living things work helps us to understand our own body and our health

Learning how living things survive helps us to understand why people act the way they do

Learning how living things are connected helps us to see why we should preserve our planet

Physical Science – Physical Science includes those sciences that study living and non-living things. These sciences are physics, chemistry, earth sciences (geology, meteorology, oceanography, etc), and astronomy (studying the stars and other planets).

Learning how the universe works helps us to understand why things happen

Learning how the earth came into existence helps us to understand why the world is the way it is

Learning how the earth works helps us to survive earthquakes, tornadoes, and tsunamis

Learning how the universe works helps us to see connections between all things

Social Science – These are sciences dealing with human beings. Some examples of social sciences include anthropology, geography, economics, and history.

Learning how people interact helps us to get along with others better

Learning how the world works helps us to be more successful

Learning what people have done in the past helps us to avoid making the same mistakes

Learning how people in different cultures live helps us to understand them and avoid conflicts

Application

Everything around us concerns about science…

Cooking involves process like condensation, evaporation, boiling… Inner metabolism of our body can be understood through study of biology which is part of science… The transportation, navigation, constructions and many others involves calculations, physics, logical and critical thinking – part of science. Geologists study about the ages of our World and fossils, shifting of continental shelves, occurrences of natural phenomenon all related to Science. Science starts with observation and most ends with a theory, prediction, anything which improves our daily lives.

Employability

The skills acquired by studying science are versatile and are applicable to any profession; a foundation in science can lead to a huge variety of career options in all sectors. Study of science is obviously relevant to many science-related jobs, such as engineering, information technology, medicine, psychology, sports science, biotechnology, animal health, forensics or astronomy, but they are also significant to working in banking, journalism, teaching, television, marketing, law, photography, art restoration, media and film production, and so on.

Benefits

In addition to providing students with useful skills and making them highly employable, it has been shown that achieving further qualifications in science brings greater rewards in monetary terms in future employment when compared to other subjects. The research carried out by PricewaterhouseCoopers in 2005 showed that students of chemistry and physics earn on average 30% more than those studied other subjects.

Without science we wouldn't have all the great inventions that we have amongst us today.

It makes one understand nature and how they exist.

Scientific conclusions are arrived through trials and errors. By trials and errors we make new inventions. Those precious cell phones to teenagers, those cars we rely on, the understanding of animals, the rainforests we study, the understanding of our need for trees to create oxygen, that's all science.

Science helps our understanding of nature and needs. Our cutting of rainforests might have continued at a higher rate than it is now if it wasn't for science discovering how we need those trees for oxygen or for animals. Our understanding of the world we live in is important for our survival and our knowledge of what is to come.

Scientific understanding has taken the world out of the dark ages and turned humanity into a culture that can control its own destiny.

Medical science has extended the human life expectancy nearly four times in the last 300 years.

Physics perpetuates the ground works understanding of the world and universe as a whole.

Chemistry is responsible for every industrial material you can name.

Biology has vastly improved all understanding of the way life was created, perpetuates and thrives; thus fuelling all medical and life research.

Engineering has brought everything from bridges, buildings, roads, planes to computers, satellites, space stations and nanotechnology from the grasp of the ever inquisitive scientist and into the home of the common person.

Astronomy has been the foreground of every great discovery in fundamental physics since the dawn of civilisation.

The most elementary advantage of studying science is that we can satisfy ourselves by getting answers to all the questions coming in our mind such as why it works like this… What is this…??? How it works…??? And many other different questions.

Great Physicists of All Time

Archimedes (Greek) – Archimedes described concept of buoyancy and developed formulae for the areas and volumes of spheres, cylinders, parabolas, and several other solids. He worked extensively with levers. He also invented the Archimedes screw to raise water. In warfare he developed several siege engines that served to hamper the Roman invasion of his home city of Syracuse.

Galileo Galilei (Italian) – Galileo discovered the law of uniformly accelerated motion. He improved on the refracting telescope and discovered the four largest satellites of Jupiter. He also described projectile motion and the concept of weight. He is however best known for his championing of the Copernican theory of heliocentricity against church opposition.

Michael Faraday (English) – Faraday showed how a changing magnetic field can be used to generate an electric current. He also described the principles of electrolysis. Faraday is the early pioneer in the field of low temperature study.

Johannes Kepler (German) – Kepler outlined three fundamental laws of planetary motion and described elliptical motion of planets around the sun. His work served as the precursor to that of Newton's.

Isaac Newton (English) – Newton described laws of motion and gravity. He explained the concept of light dispersion and co-invented the Calculus. He also invented the reflecting telescope.

Albert Einstein (German/Swiss/American) – Einstein developed Theories of Special and General Relativity. He worked on the photoelectric effect and described mass-energy equivalence.

Great Chemists of All-time

Dmitri Mendeleyev (Russian) – Mendeleyev devised the Periodic table of elements and predicted that several more elements would be discovered.

Antoine Lavoisier (French) – Lavoisier showed that air is a mixture of oxygen (O) and nitrogen (N). He disproved the old Theory of phlogiston and determined the nature of combustion. Lavoisier wrote the first modern book on chemistry and explained the law of conservation of matter.

Henry Cavendish (English) – Cavendish showed that water could be produced from two gases and discovered hydrogen (H).

Amedeo Avogadro (Italian) – Avogadro was the first to distinguish molecules from atoms he developed Avogadro's Constant (The number of particles of a substance in a mole) and studied the effect of combining volumes.

Jons Jakob Berzelius (Swedish) – Berzelius developed the symbols for many of the chemicals. He also calculated the atomic weights accurately of many of them and discovered Selenium, Silicon and Thorium.

John Dalton (English) – Developed an atomic theory of matter and explained the laws of partial pressure.

Robert Boyle (Irish) – Boyle studied gases and showed how pressure and volume at a constant mass were indirectly proportional to one another.

Great Biologists of All-time

Aristotle – Greek philosopher and scientist. He is sometimes called the father of biology. He was able to describe plant and animal specimens received from all parts of the far-flung Alexandrian empire. Out of 400 treatises that Aristotle wrote only 30 survive. Of these, most important in connection with biology are his Enquiry into Animals, Motion of Animals, Gait of Animals, Parts of Animals and Generation of Animals.

Charles Robert Darwin – An English naturalist. He established that all species of life have descended over time from common ancestors, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection. Darwin published his theory with compelling evidence for evolution in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species.

Walther Flemming – German biologist and a founder of cytogenetics. Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis. His discovery of mitosis and chromosomes is considered one of the 100 most important scientific discoveries of all times.

Oswald Avery – an American physician and medical researcher. He was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for his discovery in 1944, with his co-workers Colin MacLeod and Maclyn McCarty, that DNA is the material of which genes and chromosomes are made.

Gregor Mendel – An Austrian scientist who gained fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns. This theory is now referred to as the laws of Mendelian inheritance. Although the significance of Mendel's work was not recognised until the turn of the 20th century, the independent rediscovery of these laws formed the foundation of the modern science of genetics.

Louis Pasteur – French chemist and microbiologist. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. He created the first vaccines for rabies and anthrax. He is best known for inventing a method to stop milk from causing sickness, a process that came to be called pasteurisation. He is regarded as one of the founders of microbiology. Pasteur also made many discoveries in the field of chemistry, most notably the molecular basis for the asymmetry of certain crystals

Linus Carl Pauling – An American chemist, biochemist, peace activist. He was one of the most influential chemists in history and among the first scientists to work in the fields of quantum chemistry and molecular biology. He is one of only two people awarded Nobel Prizes in different fields (chemistry and peace prizes). Besides being the greatest architect of chemistry, Pauling was a founder of molecular biology and a pioneer in quantum mechanics. Pauling combined chemistry and physics to solve various puzzles related to the nature of chemical bonding which now are fundamental to modern theories of molecular structure. Pauling determined crystal structure by X-ray crystallography and the structure of gas molecules by electron diffraction.

Future of Science

Science is omnipresent in modern society. Due to the unsustainable demands we make on the world's resources and the impact we have on our environment, the contribution of science is vital to ensure the survival of our planet by developing new or alternative solutions for everything we do from fuel production to waste disposal. With current issues such as gene therapy, nuclear power, oil exploration, genetically modified foods, bird flu and global warming, future scientists have a fascinating and crucial role to play, be it developing new communications solutions or contributing to make the world a better place. Studying science provides an excellent foundation, keeps options open and offers a good progression route either directly into employment or to higher education to study them or other related subjects further. By opting for science, students could find themselves contributing to ensuring the future of the planet as well as safeguarding their own secure future in the world of employment.

A

Aberration

Property of an optical system that causes an image to have certain easily recognisable flaws. Aberrations are caused by geometrical factors such as the shapes of surfaces, their spacing, and alignments. Image problems caused by factors such as scratches or contamination are not called aberrations.

Abiotic

Pertaining to nonliving properties, including light, air, water, nutrients and other physical and chemical properties of an environment.

Absolute date

An estimate of the true age of a mineral or rock based on the rate of decay of radioactive minerals.

Absolute pressure

The measurement of pressure relative to the pressure in a vacuum. It is equal to the sum of the pressure shown on a pressure gauge and atmospheric pressure.

Absolute pressure transducer

A transducer which measures pressure in relation to zero pressure (a vacuum on one side of the diaphragm).

Absolute risk

The probability that an individual will develop a particular condition, based on family history and/or test results.

Absolute zero

The lowest temperature ever reached in the Universe: 0 Kelvin (0K), equivalent to minus 273 degrees Celsius (-273 °C). In laboratories on Earth physicists can get very close to that temperature, but have not been able to achieve the absolute zero.

Absorption

Decrease in intensity of radiation, when it crosses a material medium, as a consequence of an interaction between the radiation and the material medium.

Abundance

Relative number of atoms of a particular element, or isotope of an element, in the chemical composition of a single substance or object.

Abundant centre distribution

The highest population densities are observed in the range core, but the species becomes increasingly rare towards its range margin.

Ac

Alternating current; an electric current that reverses its direction at regularly recurring intervals.

Acarology

Branch of Zoology dealing with ticks & mites.

Acceleration

A change in the velocity of a body or particle with respect to time. The parameter that an accelerometer measures (dv/dt). Units expressed in “g”.

Accelerometer

A device which converts the effects of mechanical motion into an electrical signal that is proportional to the acceleration value of the motion. A sensor. A transducer.

Acceptable use policy

This is a policy set up by the network administrator or other school leaders in conjunction with their technology needs and safety concerns. This policy restricts the manner in which a network may be used, and helps provide guidelines for teachers using technology in the classroom.

Acceptor arm

The arm in tRNA to which an amino acid attaches.

Accessory chromosome

Any extra chromosome in the karyotype of an organism.

Accretion (disk, zone)

Process whereby small particles of matter accumulate and create larger bodies under the influence of their mutual gravitational attraction or as a result of chance col lisions.

Accumulators

Plants containing intermediate concentrations of certain chemical elements (frequently metals or metallic compounds).

Accuracy

The closeness of an indication or reading of a measurement device to the actual value of the quantity being measured. Usually expressed as ± percent of full scale output or reading.

Acentric chromatid

Lacks a centromere; produced when crossing over takes place within a paracentric inversion. The acentric chromatid does not attach to a spindle fiber and does not segregate in meiosis or mitosis, so it is usually lost after one or more rounds of cell division.

Acequia

acequias are gravity driven waterways, similar in concept to a flume. Most are simple ditches with dirt banks, but they can be lined with concrete. They were important forms of irrigation in the development of agriculture in the American Southwest. The proliferation of cotton, pecans and green chile as major agricultural staples owe their progress to the acequia system.

Acetylation

An enzymatic reaction that results in the addition of an acetyl group to a biochemical.

Acid

a substance that has a pH of less than 7, which is neutral. Specifically, an acid has more free hydrogen ions (H+) than hydroxyl ions (OH−).

Acidic activation domain

Commonly found in some transcriptional activator proteins, a domain that contains multiple amino acids with negative charges and stimulates the transcription of certain genes.

Acoustics

The degree of sound. The nature, cause, and phenomena of the vibrations of elastic bodies; which vibrations create compressional waves or wave fronts which are transmitted through various media, such as air, water, wood, steel, etc.

Acre-foot (acre-ft)

the volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic metres.

Acrobatics

The art of performing acrobatic feats (gymnastics)

Acrocentric chromosome

Chromosome in which the centromere is near one end, producing a long arm at one end and a knob, or satellite, at the other end.

A chromosome in which the centromere is located close to one end.

Across the flats

Measurement between 2 parallel faces on a nut. Indicates the size of spanner or socket required to tighten or loosen the nut.

Action potential

An electrical signal that carries information from the sensory organ to the brain via the nervous system.

Activation domain

Part of a transcription factor that is modular and independent from the DNA-binding activity. An activation domain stimulates activity at the locus.

Activation energy

The energy required to initiate a chemical reaction.

Activator

Protein in eukaryotic cells that binds to consensus sequences in regulatory promoters or enhancers and affects transcription initiation by stimulating or inhibiting the assembly of the basal transcription apparatus.

Active galactic nucleus (AGN)

Central region of a galaxy in which considerable energy is generated by processes other than those present in normal stars. The energy generated by the nucleus may outshine all the other stars in the galaxy. Most astronomers believe that at the centre of an AGN lies a supermassive black hole.

Active galaxy

A galaxy which releases large amounts of energy from its centre, the active galactic nucleus. The central engine of an active galaxy probably is a supermassive black hole. Seyfert galaxies, quasars and blazars are active galaxies.

Active restoration

Accelerating the process or attempting to change the trajectory of succession. For example, mine tailings would take so long to recover passively that active restoration is usually appropriate.

Active volcano

A volcano that is erupting; or one that, while not erupting at the present, has erupted within (geologically) recent time and is considered likely to do so in the (geologically) near future.

Activity (ai)

A thermodynamic term for the apparent or active concentration of a free ion in solution. It is related to concentration by the activity coefficient.

Activity coefficient (fi)

A ratio of the activity of species i(ai) to its molality (C). It is a correction factor which makes the thermodynamic calculations correct. This factor is dependent on ionic strength, temperature, and other parameters. Individual ionic activity coefficients, f+ for cation and f- for an anion, cannot be derived thermodynamically. They can be calculated only by using the Debye-Huckel law for low concentration solutions in which the interionic forces depend primarily on charge, radius, and distribution of the ions and on the dielectric constant of the medium rather than on the chemical properties of the ions. Mean ionic activity coefficient (f±) or the activity of a salt, on the other hand, can be measured by a variety of techniques such as freezing point depression and vapour pressure as well as paired sensing electrodes. It is the geometric mean of the individual ionic activity coefficients:

Adaptation

A process of genetic change in a population whereby, as a result of natural selection, the average state of a character becomes improved with reference to a specific function, or whereby a population is thought to have become better suited to some feature of its environment. Also, a feature that has become prevalent in a population because of a selective advantage conveyed by that feature in the improvement in some function.

A phenotypic trait that has evolved to help an organism cope with an environmental challenge or to increase its mating success.

Adapter

A mechanism or device for attaching non-mating parts.

Adaptive

A behaviour or trait that contributes either directly or indirectly to an individual.s fitness.

Adaptive evolution

The adjustment of an organism to its environment, or the process by which it enhances such fitness.

Adaptive immunity

A slow, specific immune response that develops after exposure to a foreign antigen.

Adaptive landscape

A three-dimensional depiction of population mean fitness as a function of genotype or phenotype, in which the horizontal axes are allele frequencies at two loci or two phenotypic traits, and the vertical axis is population mean fitness.

Adaptive mutation

Process by which a specific environment induces mutations that enable organisms to adapt to the environment.

Adaptive peak

A population mean fitness maximum, defined by values of allele frequencies or phenotypic traits.

That allele frequency, or combination of allele frequencies at two or more loci, at which the mean fitness of a population has a (local) maximum. Also, the mean phenotype (for one or more characters) that maximizes mean fitness.

Adaptive radiation

Evolutionary divergence of members of a single phylogenetic lineage into a variety of different adaptive forms; usually the taxa differ in the use of resources or habitats, and have diverged over a relatively short interval of geological time. The term “evolutionary radiation” describes a pattern of rapid diversification without assuming that the differences are adaptive.

Adaptive topography

A three-dimensional depiction of population mean fitness as a function of genotype or phenotype, in which the horizontal axes are allele frequencies at two loci or two phenotypic traits, and the vertical axis is population mean fitness (synonym: adaptive topography).

Adaptive valley

A set of allele frequencies at which mean fitness has a minimum.

Adaptive zone

A set of similar ecological niches occupied by a group of (usually) related species, often constituting a higher taxon.

Adc

Analogue-to-Digital Converter: an electronic device which converts analog signals to an equivalent digital form, in either a binary code or a binary-coded-decimal code. When used for dynamic waveforms, the sampling rate must be high to prevent aliasing errors from occurring.

Addition rule

States that the probability of any of two or more mutually exclusive events occurring is calculated by adding the probabilities of the individual events.

Additive effect

The magnitude of the effect of an allele on a character, measured as half the phenotypic difference between homozygotes for that allele compared with homozygotes for a different allele.

Additive genetic correlation

A measure of the degree to which two traits are affected by the same genes (pleiotropy) or pairs of genes (linkage disequilibrium). Selection on one trait produces an evolutionary change in all traits that have an additive genetic correlation with the selected trait.

Additive genetic variance

That component of the genetic variance in a character that is attributable to additive effects of alleles.

The magnitude of the phenotypic (and genotypic) variance that is due to additive effects of genes and that determines the degree to which the average phenotype of the parents is reflected in the average phenotype of their progeny.

Additive genetic variance-covariance matrix

A square matrix with additive genetic variances for the traits on the diagonal and additive genetic covariances on the off-diagonal.

Additivity

The type of gene action in which the alleles at a locus do not affect each other's expression or the expression of alleles at other loci; in other words, gene action with no dominance or epistasis.

Address

The label or number identifying the memory location where a unit of information is stored.

Adenine

A purine base in DNA and RNA.

Adenosine-3′,5′-cyclic monophosphate

Modified nucleotide that functions in catabolite repression. Low levels of glucose stimulate high levels of cAMP; cAMP then attaches to CAP, which binds to the promoter of certain operons and stimulates transcription.

Adiabatic rate

The rate of temperature change in the atmosphere due to the raising or lowering of an air mass. The “dry adiabatic rate” is 5.5 deg. F. per 1000 feet, while the “wet” rate is 3.5 deg. F. per 1000 feet.

Adiabatic system

A system that neither gains or looses heat.

Adjacent-1 segregation

Type of segregation that takes place in a heterozygote for a translocation. If the original, nontranslocated chromosomes are N1 and N2 and the chromosomes containing the translocated segments are T1 and T2, then adjacent-1 segregation takes place when N1 and T2 move toward one pole and T1 and N2 move toward the opposite pole.

Adjacent-2 segregation

Type of segregation that takes place in a heterozygote for a translocation. If the original, nontranslocated chromosomes are N1 and N2 and the chromosomes containing the translocated segments are T1 and T2, then adjacent-2 segregation takes place when N1 and T1 move toward one pole and T2 and N2 move toward the opposite pole.

A-dna

Right-handed helical structure of DNA that exists when little water is present.

Adult-onset

Describes a condition in which the phenotype does not manifest itself until later in life. The physical manifestation of such a condition is not present until after puberty.

Aerodynamics

The branch of mechanics that deals with the motion of air and other gases.

The study of the motion and control of solid bodies like aircraft, missiles, etc. in air.

Aeronautics

The science or art of flight.

Aeronomy

The study of the atmosphere of a planet, with particular attention to the composition, properties and motion of atmosphere constituents.

Aerosol

A gaseous suspension of ultramicroscopic particles of a liquid or a solid.

Aerosol collector

An instrument that collects aerosols and analyzes their composition.

Aerostatics

The branch of statics that deals with gases in equilibrium and with gases and bodies in them.

Aesthetics

The philosophy of fine arts.

Aetiology

The science of causation.

Affinity chromatography

A method of separating biochemical components based on specific interactions between the components of the biochemical mixture and other molecules (e.g., antigen-antibody or receptor-ligand).

Aflp

Genetic markers detected by cleaving DNA with one or more restriction enzymes and then amplifying some of these fragments by PCR using primers with random nucleotide sequences.

African sleeping sickness

A vector-borne disease caused by parasites from the genus Trypanosoma.

Ageing

The decline in organismal fitness that occurs with increasing age.

Agrobiology

The science of plant life and plant nutrition.

Agronomic

The science of managing land or crops.

Agronomy

The science of soil management & production of field crops.

Agrostology

The study of grasses.

Alara

Most often used in reference to chemical or radiation exposure levels.

Alarp

It is applied to the reduction of risk by taking measures to reduce risk until the cost of further measures is grossly disproportionate to the benefits they would deliver.

Alchemy

Chemistry in ancient times.

Alcohol

Organic compound used in gums, resins, dyes and perfumes. Fermentation produces ethanol not alcohol.

Alder

A common flowering plant along the successional chain of species for a forest.

Algol

Best known variable star, varying in brightness from about 2.2 to 3.5 magnitudes over a period of approximately 69 hours. It is in fact a binary system in which the two stars regularly cross in front of each other as viewed from Earth.

Alias

A file that points to another item, such as a programme, document, folder, or disk. When an alias is opened, the original item that the alias points to is opened. This helps in the organizing and accessing of files. Alias is purely a Mac term. The equivalent term for Windows-based computers is a shortcut.

Aliasing

If the sample rate of a function (fs) is less than two times the highest frequency value of the function, the frequency is ambiguously presented. The frequencies above (fs/2) will be folded back into the lower frequencies producing erroneous data.

Alignment

Process of mounting optical elements and adjusting their positions and orientations so that light follows exactly the desired path through the instrument and each optical element performs its function as planned.

Alkali

A base that is soluble in water.

Alkaline

Sometimes water or soils contain an amount of alkali (strongly basic) substances sufficient to raise the pH value above 7.0 and be harmful to the growth of crops.

Alkalinity

the capacity of water for neutralizing an acid solution.

Alkaptonuria

A single-gene disorder identified by Archibald Garrod that is characterized by dark urine. Garrod first coined the term “inborn error in metabolism” to describe this and other congenital, inherited disorders that affect metabolic pathways.

Allele

Alleles are alternate forms of a gene.

Allele frequency

The allele frequency represents the incidence of a gene variant in a population.

Alleles

Alternative versions of genes that are located at a specific position on a specific chromosome.

Allelopathy

Biochemical production by a plant which alters growth and survival of other plants or itself.

Alliance contract

A contract that generally relates to a specific and discrete set of services such as design or maintenance.

Allometric coeffient

Allometric equations

An equation to aid in the calculation of the change in proportion of various parts of an organism as a consequence of growth.

Allometric growth

Growth of a feature during ontogeny at a rate different from that of another feature with which it is compared.

Allometry

Biological scaling relationships, be it for morphological traits, physiological traits or ecological traits; the study of the relationship between size and shape.

Allopatric

Of a population or species, occupying a geographic region different from that of another population or species.

Allopatric speciation

An evolutionary process in which one species becomes two usually due to a physical barrier.

Allopolyploid

A polyploid in which the several chromosome sets are derived from more than one species.

Allosteric protein

Protein that changes its conformation on binding with another molecule.

Allotrope

Element with more than one natural form.

Alloy

A substance formed by the combination of two or more elements, at least one of which must be a metal.

Alloy 11

A compensating alloy used in conjunction with pure copper as the negative leg to form extension wire for platinum-platinum rhodium thermocouples Types R and S.

Alloy 200/226

The combination of compensating alloys used with tungsten vs. tungsten 26% rhenium thermocouples as extension cable for applications under 200°C.

Alloy 203/225

The combination of compensating alloys used with tungsten 3% rhenium vs. tungsten 150 rhenium thermocouples as extension cable for applications under 200°C.

Alloy 405/426

The combination of compensating alloys used with tungsten 5% rhenium vs. tungsten 26% rhenium thermocouples as extension cable for applications under 870°C.

Alluvium

deposits of clay, silt, sand, gravel, or other particulate material that has been deposited by a stream or other body of running water in a streambed, on a flood plain, on a delta, or at the base of a mountain.

Alpha diversity

Within-habitat diversity.

Alphanumeric

A character set that contains both letters and digits.

Alternate segregation

Type of segregation that takes place in a heterozygote for a translocation. If the original, nontranslocated chromosomes are N1 and N2 and the chromosomes containing the translocated segments are T1 and T2, then alternate segregation takes place when N1 and N2 move toward one pole and T1 and T2 move toward the opposite pole.

Alternation of generations

Complex life cycle in plants that alternates between the diploid sporophyte stage and the haploid gametophyte stage.

Alternative processing pathway

One of several pathways by which a single pre-mRNA can be processed in different ways to produce alternative types of mRNA.

Alternative splicing

Process by which a single pre-mRNA can be spliced in more than one way to produce different types of mRNA.

Splicing of different sets of exons from mRNA to form mature transcripts that are translated into different proteins (thus allowing the same gene to encode different proteins).

Altitude

Height in space of an object or point relative to sea level or ground level.

Altruism

Conferral of a benefit on other individuals at an apparent cost to the donor.

Altruistic

Behaviour by an individual that may reduce its immediate direct fitness but increases the fitness of another.

Alu

Arithmetic Logic Unit. The part of a CPU where binary data is acted upon with mathematical operations.

Alu

Part of a family of short, interspersed repeats, these are the most abundant sequence repeats in the human genome (making up 5%.10% of the total). Alu sequences can be propagated by retrotransposition, although most are sterile, or DNA “fossils.”

Alumel

An aluminum nickel alloy used in the negative leg of a Type K thermocouple (Trade name of Hoskins Manufacturing Company).

Amanitin

A highly poisonous polypeptide that selectively inhibits the activity of mammalian RNA polymerase.

Ambient compensation

The design of an instrument such that changes in ambient temperature do not affect the readings of the instrument.

Ambient conditions

The conditions around the transducer (pressure, temperature, etc.).

Ambient pressure

Pressure of the air surrounding a transducer.

Ambient temperature

The average or mean temperature of the surrounding air which comes in contact with the equipment and instruments under test.

American national standards institute

A private non-profit organization that administers and coordinates the U.S. voluntary standardisation and conformity assessment system.

American wire gauge

A standarised method for specifying the properties – including diameter – of electrical and electronic wire.

Ames test

Test in which special strains of bacteria are used to evaluate the potential of chemicals to cause cancer.

Amino acids

Carbon, hydrogen, oxygen and nitrogen compounds the composition of which are determined by genes.

Aminoacyl (A) site

One of three sites in a ribosome occupied by a tRNA in translation. All charged tRNAs (with the exception of the initiator tRNA) first enter the A site in translation.

Aminoacyl-trna synthetase

Enzyme that attaches an amino acid to a tRNA. Each aminoacyl-tRNA synthetase is specific for a particular amino acid.

Ammeter

An instrument used to measure current.

Amniocentesis

Procedure used for prenatal genetic testing to obtain a sample of amniotic fluid from a pregnant woman. A long sterile needle is inserted through the abdominal wall into the amniotic sac to obtain the fluid.

Ampere (amp)

A unit used to define the rate of flow of electricity (current) in a circuit; units are one coulomb (6.28 x 1018 electronics) per second.

Amphibian

Animal with smooth, moist skin; it has gills when young and then develops lungs when older. Frogs, toads, and salamanders are amphibians.

Amplifier

A device which draws power from a source other than the input signal and which produces as an output an enlarged reproduction of the essential features of its input.

Amplitude

A measurement of the distance from the highest to the lowest excursion of motion, as in the case of mechanical body in oscillation or the peak-to-peak swing of an electrical waveform.

Amplitude span

The Y-axis range of a graphic display of data in either the time or frequency domain. Usually a log display (dB) but can also be linear.

Anagenesis

Evolution of a feature within a lineage over an arbitrary period of time.

Analogue output

A voltage or current signal that is a continuous function of the measured parameter.

Analogue-to-Digital Converter (A/D or ADC)

A device or circuit that outputs a binary number corresponding to an analogue signal level at the input.

Analysis of variance

Statistical technique for testing for differences among the means of several groups with respect to a continuous variable.

Analytical model

A model in which the relationships among variables are defined using equations.

Anaphase

Anaphase is the fourth phase of mitosis, which is a process that separates the duplicated genetic material carried in the nucleus of a parent cell into two, identical daughter cells.

Anaphase I

Stage of meiosis I. In anaphase I, homologous chromosomes separate and move toward the spindle poles.

Anaphase II

Stage of meiosis II. In anaphase II, chromatids separate and move toward the spindle poles.

Anatomy

The science dealing with the structure of animals, plants or human body.

Ancestral species

A species at the root of a clade of related organisms.

Andesite

Intermediate volcanic rocks containing 54 to 62 percent silica and moderate amounts of iron and magnesium. Andesite minerals commonly include plagioclase and hornblende, with lesser amounts of mica, pyroxene, and various accessory minerals. Andesites are aphanitic in texture and are usually medium dark in colour. They occur with composite volcanic cones associated with convergent plate margins.

Anemology

The science of wind.

Anemometer

An instrument for measuring and/or indicating the velocity of air flow.

Aneuploidy

Change from the wild type in the number of chromosomes; most often an increase or decrease of one or two chromosomes.

Angiology

The science of blood & lymph vessels.

Angstrom

Ten to the minus tenth metres (10−10) or one millimicron, a unit used to define the wave length of light. Designated by the symbol ‰.

Angular frequency

The motion of a body or a point moving circularly, referred to as the circular frequency O which is the frequency in cycles per second (cps) multiplied by the term (2) and expressed in radians per second (2pf).

Animal

A living thing that can move from place to place, has a body covering, and eats other animals or plants for food. Monkeys and ocelots are two kinds of animals found in a tropical rain forest.

Animal development

The process whereby a fertilized egg undergoes cell division and cellular differentiation to generate the different tissue types of a fully functional complex organism.

Animal production

A subcategory of secondary production, the production of an animal population.

Anion

A negatively charged ion (Cl-, NO3-, S2- etc.)

Anisotropy, lnhomogeneity (in the cosmic microwave background)

Very small patches in the sky where the temperature of the cosmic microwave background is slightly different to the average; these temperature variations are of the order of microkelvin.

Anneal

The process of using heating and slow cooling to toughen steel (or glass) by reducing its brittleness and internal stresses.

Annubar

A device that uses Pitot tubes to measure the gas flow rate within a pipeline.

Ansi

American National Standards Institute.

Antagonistic interaction

An interaction between two organisms that benefits one to the detriment of the other.

Antagonistic relationships

Relationships in which organisms compete for resources, spread disease to their neighbors, or consume each other.

Antagonistic selection

A source of natural selection that opposes another source of selection on a trait.

Antenna (high gain, low gain)

An aerial for receiving or transmitting radio signals. A high gain antenna is highly focused, whereas a low gain antenna receives or transmits over a wide angle.

Antennapedia complex

Cluster of five homeotic genes in fruit flies that affects development of the adult fly's head and anterior thoracic segments.

Antennapedia homeodomain

A sequence-specific transcription factor from Drosophila melanogaster. The wild-type Antennapedia homeodomain complex works to initiate a series of transcription events that results in anterior-posterior polarity in the organism.

Anthropogenic

Processes or materials derived from human activities, in contrast to those produced by natural processes

Anthropology

The science that deals with the origin and physical and cultural development of mankind.

Antibiotic resistance

Heritable changes in bacteria that allow them to withstand antibiotic treatments that would normally kill them.

Antibody

Produced by a B cell, a protein that circulates in the blood and other body fluids. An antibody binds to a specific antigen and marks it for destruction by making it easier for a phagocytic cell to ingest the antigen.

Anticipation

Increasing severity or earlier age of onset of a genetic trait in succeeding generations. For example, symptoms of a genetic disease may become more severe as the trait is passed from generation to generation.

Anticodon

Sequence of three nucleotides in tRNA that pairs with the corresponding codon in mRNA in translation.

Antifeedants

A substance that inhibits normal feeding behaviour.

Antigen

Substance that is recognized by the immune system and elicits an immune response.

Antigenic drift

A process by which circulating influenza viruses are constantly changing, which allows the viruses to cause annual epidemics of illness. Antigenic drift occurs when mutations accumulate in the hemagglutinin and neuraminidase genes that alter the antigenicity of these proteins such that the “drifted” strains are no longer neutralized by antibodies that were specific for previously circulating strains.

Antigenic shift

A process by which a new influenza A virus hemagglutinin subtype (with or without an accompanying new neuraminidase subtype) is introduced into the human population, which lacks prior experience of and immunity to the subtype. Antigenic shift can occur as a result of the direct introduction of an influenza virus from an animal or avian host into humans, or by the exchange or reassortment of gene segments between human and non-human influenza viruses when they co-infect animals or humans.

Antimatter

The ‘opposite’ to ordinary matter. For every particle of ordinary matter there is an almost identical antiparticle of antimatter: protons and antiprotons; electrons and positrons…the particle's mass is exactly the same as its antiparticle's mass, but their electrical charges and other fundamental properties are opposite. When a particle meets its antiparticle, they annihilate each other.

Antiparallel

Refers to a characteristic of the DNA double helix in which the two polynucleotide strands run in opposite directions.

Anti-reset windup

This is a feature in a three-mode PID controller which prevents the integral (auto reset) circuit from functioning when the temperature is outside the proportional band.

Antisense RNA

Small RNA molecule that base pairs with a complementary DNA or RNA sequence and affects its functioning.

Antiterminator

Protein or DNA sequence that inhibits the termination of transcription.

Aperture

Opening that allows light to fall onto an instrument's optics.

Aphelion

The point on a planet's elliptical orbit at which it is furthest from the Sun.

Apocentre

The point on a spacecraft's orbit at which it is furthest away from the body it is orbiting.

Apogee

The most distant point from Earth on a satellite's orbit.

Apomixis

Parthenogenetic reproduction in which an individual develops from one or more mitotically produced cells that have not experienced recombination or syngamy.

Apomorphic

Having a derived character or state, with reference to another character or state. See also synapomorphy.

Apoptosis

Programmed cell death, in which a cell degrades its own DNA, the nucleus and cytoplasm shrink, and the cell undergoes phagocytosis by other cells without leakage of its contents.

Aposematic

Coloration or other features that advertise noxious properties; warning coloration.

Aposematic coloration

Antipredator adaptation in which conspicuous markings on an animal that is poisonous or unpalatable serve to discourage potential predators.

Application

A software programme that lets you complete a task, such as writing a paper, creating a poster, designing an image, or viewing a Web page.

Application programme

A computer programme that accomplishes specific tasks, such as word processing.

Applied restoration

A multi-step process, which may include some or all of these stages: assessing the site, formulating project goals, removing sources of disturbance, restoring processes/disturbance cycles, rehabilitating substrates, restoring vegetation, and monitoring and maintenance.

Appropriation doctrine

The system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid west as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of “First in Time, First in Right.” The first person to take a quantity of water and put it to Beneficial Use has a higher priority of right than a subsequent user. Under drought conditions, higher priority users are satisfied before junior users receive water. Appropriative rights can be lost through nonuse; they can also be sold or transferred apart from the land.

Aptamer

Nucleic acid that binds to a specific target molecule.

Aquaculture

farming of plants and animals that live in water, such as fish, shellfish, and algae.

Aqueduct

a pipe, conduit, or channel designed to transport water from a remote source, usually by gravity.

Aquiclude

An impermeable geologic formation or stratum which will not hold or transmit fluid.

Aquifer

a geologic formation(s) that is water bearing. A geological formation or structure that stores and/or transmits water, such as to wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people's uses.

Aquifer (confined)

Soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.

Aquifer (unconfined)

An aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall.

Aquifer, confined (or Artesian)

An aquifer overlain by a non-permeable layer or layers, in which pressure will force water to rise above the aquifer.

Aquifer, perched

An aquifer containing unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone.

Aquifer, principal

The aquifer or combination of related aquifers in a given area that is the important economic source of water to wells.

Aquifer, secondary

Any aquifer that is not the main source of water to wells in a given area.

Aquifer, unconfined (or Water Table)

An aquifer in which the upper surface is the water table.

Aquitard

A geologic formation or stratum that significantly retards fluid movement.

Arboriculture

Cultivation of trees & vegetables.

Archaea

One of the three primary divisions of life. Archaea consist of unicellular organisms with prokaryotic cells.

Archaeology

The study of antiquities.

Arcmin, arcsec

The size of an object in the sky can be measured by the angle that it covers when viewed from Earth. The full circle has 360 degrees. An arcmin is 1/60 of a degree; an arcsec is 1/60 of an arcmin or 1/3600 of a degree. The diameter of the full Moon is about one-half of a degree or 30 arcmin.

Area effect

The larger a place is, the more species it can support.

Argon

A chemical element, (symbol Ar, atomic number 18).

Ariane (4, 5) rockets

European launcher family (Ariane 4 and Ariane 5) developed by the European Space Agency. Launched from Kourou, French Guiana, flights are commercialised and operated by the Arianespace company.

Armour

A type of protective covering for the body. A hard covering of armor could protect a dinosaur from sharp teeth.

Array comparative genomic hybridization

Similar to conventional comparative genomic hybridization (CGH), but during hybridization, cloned chromosomal DNA fragments (about 200 kb in size) replace the metaphase chromosomes. This method offers greater sensitivity and resolution than conventional CGH in detecting copy number changes.

Artesian water

Ground water that is under pressure when tapped by a well and is able to rise above the level at which it is first encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer.

Artesian well

A well in an aquifer where the groundwater is confined under pressure and the water level will rise above the top of the confined aquifer.

Artificial recharge

The unnatural addition of surface waters to groundwater. Recharge could result from reservoirs, storage basins, leaky canals, direct injection of water into an aquifer, or by spreading water over a large land surface.

Artificial selection

The process of selective breeding of organisms by humans to produce domesticated animals with more desirable traits; also used by evolutionary biologists to test for genetic variation and covariation.

Selection by humans of a deliberately chosen trait or combination of traits in a (usually captive) population; differing from natural selection in that the criterion for survival and reproduction is the trait chosen, rather than fitness as determined by the entire genotype.

Ascii

American Standard Code for Information Interchange. This international standard contains 128 codes that correspond to all upper and lower-case Latin characters, numbers, and punctuation marks. Each code is represented by a seven-digit binary number: 0000000 through 1111111.

Asexual

Pertaining to reproduction that does not entail meiosis and syngamy.

Ash

Fine particles of rock material ejected during an explosive volcanic eruption (commonly intermediate to felsic events). Ash may be either solid or molten when first erupted, and generally measures less than 0.10 inch in size (larger particles have other names).

Ash flow

A turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure. The mass of pyroclastics is normally of very high temperature and moves rapidly down the slopes, or even along a level surface.

Ashfall (subaerial)

Volcanic ash that has fallen through the air. The resulting deposit is usually well sorted and exhibits a finely layered structure.

Asme

American Society of Mechanical Engineers. The professional organisation focused on technical; educational and research issues of the engineering and technology community.

Aspect

Whether north or south facing.

Assemblages

Species that share an attribute of habitat or taxonomic similarity.

Assembler

A programme that translates assembly language instructions into machine language instructions.

Assembly language

A machine oriented language in which mnemonics are used to represent each machine language instruction. Each CPU has its own specific assembly language.

Assisted reproductive technologies

Procedures that replace a gamete or the uterus to help people with fertility problems have children.

Association study

A case-control study in which genetic variation, often measured as single-nucleotide polymorphisms that form haplotypes, is compared between people with a particular condition and unaffected individuals.

Assortative mating

Nonrandom mating on the basis of phenotype; usually refers to positive assortative mating, the propensity to mate with others of like phenotype.

Asteroid

One of billions of rocky objects, less than 1000 km in diameter, which orbit the Sun. Also known as minor planets. Thought to be planetesimals leftover from the formation of the planets. The first asteroid (Ceres) was discovered by Giuseppe Piazzi in 1801. More than 10 000 asteroids have so far been discovered and given permanent identification numbers. The largest asteroid is 2001 KX76 with a diameter of at least 1200 km.

Asteroid belt

Region between the orbits of Mars and Jupiter which is populated by billions of asteroids.

Astigmatism

Failure of an optical system, such as a lens or a mirror, to image a point source of light as a single point.

Astm

American Society for Testing and Materials.

Astrology

The ancient art of predicting the course of human destinies with the help of indications deduced from the position and movement of heavenly bodies.

Astrometry

The branch of astronomy concerned with measuring the positions of celestial bodies, such as stars and galaxies, and their real and apparent motions.

Astronautics

The science of space travel.

Astronomical unit (au)

Astronomy

The study of space and the heavenly bodies. Galileo's study of Earth's orbit around the sun is astronomy.

Astrophysics

Study of the physical nature of the Universe, its objects and the composition of the space between them.

Asymmetrical response

A common result in artificial selection experiments in which there is a greater response to selection in one direction than there is in the opposite direction for the same trait.

Asymmetry potential

The potential developed across the glass membrane with identical solutions on both sides. Also a term used when comparing glass electrode potential in pH 7 buffer.

Asynchronous

A communication method where data is sent when it is ready without being referenced to a timing clock, rather than waiting until the receiver signals that it is ready to receive.

Atavism

The reappearance in an organism of characteristics that are present in the organism's remote ancestors.

Atc

Automatic temperature compensation.

Atmosphere

Layer of gases surrounding a star or planet.

Atomic number

The number of protons in an atom.

Atomic symbol

The letters representing each of the elements.

Atomic weight

The average weight of an atom.

Atoms

Composite particles of protons, neutrons and electrons. The smallest part of a substance that can take part in a chemical reaction.

Atp

Adenosine 5-triphosphate, or ATP, is the principal molecule for storing and transferring energy in cells.

Attached-X

A pair of X chromosomes in Drosophila melanogaster that are connected together at one end and inherited jointly.

Attachment site

Special site on a bacterial chromosome where a prophage may insert itself.

Attenuation

Type of gene regulation in some bacterial operons, in which transcription is initiated but terminates prematurely before transcription of the structural genes.

Attenuator

Secondary structure that forms in the 5′ untranslated region of some operons and causes the premature termination of transcription.

Attitude

Orientation of the spacecraft's axes relative to Earth.

Aurora

Illumination of the night sky, caused when electrons and protons from space collide with atoms and molecules of air in the Earth's upper atmosphere. Satellite observations usually show them as rings centred on the planet's magnetic poles. Popularly known as the Northern and Southern Lights. Various types of aurora are also found on Jupiter, its moon Ganymede, and Saturn.

Autoantibodies

Antibodies that attack the body's own cells.

Autoimmune disease

Characterized by an abnormal immune response to a person's own (self) antigen.

Automatic reset

A feature on a limit controller that automatically resets the controller when the controlled temperature returns to within the limit bandwidth set.

The integral function on a PID controller which adjusts the proportional bandwidth with respect to the set point to compensate for droop in the circuit, i.e., adjusts the controlled temperature to a set point after the system stabilizes.

Autonomous element

Transposable element that is fully functional and able to transpose on its own. DNA sequence that confers the ability to replicate; contains an origin of replication.

Autopolyploidy

Condition in which all the sets of chromosomes of a polyploid individual possessing more than two haploid sets are derived from a single species.

Autoradiography

Method for visualizing DNA or RNA molecules labeled with radioactive substances. A piece of X-ray film is placed on top of a slide, gel, or other substance that contains DNA labeled with radioactive chemicals. Radiation from the labeled DNA exposes the film, providing a picture of the labeled molecules.

Autosomal

A chromosome that is not a sex chromosome; there are equal numbers of copies of autosomes in males and females of a given species.

Autosomal dominant

The inheritance pattern of a dominant allele on an autosome. The phenotype can affect males and females and does not skip generations.

Autosomal inheritance

Genetic transmission of genes on autosomes (nonsex chromosomes).

Autosomal recessive

The inheritance pattern of a recessive allele on an autosome. The phenotype can affect males and females and can skip generations.

Autosome

An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females.[1] For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y. So, humans have 23 pairs of chromosomes.

Autotrophs

Organisms that obtain energy from the sun or from the oxidation of inorganic substance and convert it into their food through a series of chemical reactions.

Auto-zero

An automatic internal correction for offsets and/or drift at zero voltage input.

Auxillary chromosome

Former name for an unpaired sex chromosome. Used today to indicate an artificial “extra” (i.e., engineered) chromosome.

Auxotroph

Bacterium or fungus that possesses a nutritional mutation that disrupts its ability to synthesize an essential biological molecule; cannot grow on minimal medium but can grow on minimal medium to which has been added the biological molecule that it cannot synthesize.

Avalanche

A large mass of material falling or sliding rapidly due to the force of gravity. In many cases, water acts as a catalyst and/or lubricant. Avalanches often are classified by what is moving, such as a snow, ice, soil, or rock avalanche. A mixture of these materials is commonly called a debris flow.

Axis of rotation (spin axis)

The axis of rotation (spin axis) is that straight line about which a body rotates.