[noun] A preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a portion of the pathogen's structure that is used to stimulate immunity to a particular disease or antibody production.

• Appears in modules:

• Carlos J. Finlay
• David Ho
• DNA I
• Louis Tompkins Wright

[noun - chemical reactions, compounds, elements] The number of single bonds an atom can form, also measured as the number of hydrogen atoms that typically bond to an atom of an element. For example, in H₂O, oxygen has a valence of two; in CH₄, carbon has a valence of four.

• Appears in modules:

• Atomic Theory III
• Carbon Chemistry
• Chemical Bonding
• Nuclear Chemistry
• Santiago Ramón y Cajal and Camillo Golgi
• The Periodic Table of Elements

[noun - chemical reactions, elements] Electrons that can be actively involved in chemical change; usually electrons in the shell with the highest value of n (electrons in the "outermost" shell of an atom). For example, sodium's ground state electron configuration is 1s² 2s² 2p⁶ 3s¹; the 3s electron is the only valence electron in the atom. Valence electrons determine the chemical properties of an atom and are the only electrons that participate in chemical bonding.

• Appears in modules:

• Atomic Theory III
• Carbon Chemistry
• Chemical Bonding
• The Periodic Table of Elements

[noun - chemical reactions, elements] The outermost electron shell of an atom that contains electrons.

• Appears in modules:

• Carbon Chemistry
• Chemical Bonding

[verb - research methods] To establish the soundness or truth of something, often using an independent means of checking results. Validation of data, models, statistical analyses, etc. is a key component of the process of science.

• Appears in modules:

• Modeling in Scientific Research
• Peer Review in Scientific Publishing
• Scientific Ethics
• Statistics in Science

[noun - data] A number that is assigned based on measurement or a calculation. In mathematics, an unknown value that is commonly represented by x or y.

• Appears in modules:

• Acids and Bases I
• Atomic Theory I
• Atomic Theory III
• Atomic Theory IV
• Confidence Intervals
• Data Analysis and Interpretation
• Defining Minerals
• Diffusion I
• DNA III
• Energy Metabolism I
• Exponential Equations in Science I
• Exponential Equations in Science II
• Gravity
• History of Earth's Atmosphere II
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics
• Light and Electromagnetism
• Linear Equations in Science
• Measurement
• Modeling in Scientific Research
• Population Genetics
• Scientific Notation and Order of Magnitude
• The Mole and Atomic Mass
• The Nature of Scientific Knowledge
• Uncertainty, Error, and Confidence
• Wave Mathematics
• Waves and Wave Motion

[noun] A general term for all attractive forces that occur between electrically neutral molecules. Van der Waals forces include dipole-to-dipole interactions, hydrogen bonds, and other intermolecular forces.

• Appears in modules:

• Properties of Liquids

[noun - research methods, equations] In math, an expression that can be assigned any set of values. Variables are written as symbols, such as x, y or z, representing unspecified quantities or members of a set.

In science, the term refers to a condition or parameter that may be manipulated, fixed, measured, or observed in the course of scientific research. There are usually three categories of variables in science experiments; control, independent (experimental) and dependent (response). For more information, see our module Experimentation in Scientific Research.

• Appears in modules:

• Atomic Theory III
• Barbara McClintock
• Cell Division I
• Chemical Bonding
• Comparison in Scientific Research
• Composition of Earth's Atmosphere
• Confidence Intervals
• Description in Scientific Research
• Experimentation in Scientific Research
• Exponential Equations in Science I
• Exponential Equations in Science II
• Franklin Chang Díaz
• Introduction to Descriptive Statistics
• Introduction to Inferential Statistics
• Linear Equations in Science
• Modeling in Scientific Research
• Properties of Gases
• Properties of Solids
• Statistics in Science
• Uncertainty, Error, and Confidence
• Unit Conversion
• Using Graphs and Visual Data in Science

[noun - anatomy & physiology] One of the systems of branching vessels conveying deoxygenated blood from various parts of the body to the heart.

• Appears in modules:

• Absorption, Distribution, and Storage of Chemicals
• Adaptation
• The Silicate Minerals

[noun] The speed and direction in which a given object is traveling, measured in distance per unit time (for example meters per second or m/s). Compare to acceleration.

• Appears in modules:

• Atomic Theory I
• Charles Darwin I
• Charles Darwin II
• Data Analysis and Interpretation
• Description in Scientific Research
• Diffusion I
• Discovery and Structure of Cells
• DNA III
• Earth Structure
• Experimentation in Scientific Research
• Fabiola León-Velarde
• Factors that Control Earth's Temperature
• Factors that Control Regional Climate
• France Anne-Dominic Córdova
• Franklin Chang Díaz
• History of Earth's Atmosphere I
• Introduction to Descriptive Statistics
• Kinetic-Molecular Theory
• Light and Electromagnetism
• Light I
• Linear Equations in Science
• Measurement
• Membranes II
• Modeling in Scientific Research
• Origins of Plate Tectonic Theory
• Properties of Gases
• The Nature of Scientific Knowledge
• The Nitrogen Cycle
• The Phosphorus Cycle
• Theories, Hypotheses, and Laws
• Uncertainty, Error, and Confidence
• Unit Conversion
• Waves and Wave Motion

[person - genetics & inheritance] (born 1946) American geneticist and entrepreneur, renown for leading the charge to sequence the human genome. While a researcher at the National Institutes of Health (NIH), Venter developed a technique called expressed sequence tags (ESTs) that made rapid sequencing possible. In 1998, he started Celera Genomics, a privately funded company, to pursue genome projects.

• Appears in modules:

• Barbara McClintock

[noun - anatomy & physiology, organisms, taxonomy & systematics] Any organism with a backbone. Only ~5% of described animal species are vertebrates.

• Appears in modules:

• Cell Division II

[noun - anatomy & physiology, cells] A small, self-enclosed sac inside of cells containing fluid and other material. The vesicles organize the cell's metabolism, help store enzymes in the cell, and serve a transport function by moving molecules between locations within the cell. Vesicles are also used as containers to isolate damaging chemical reactions from occurring in the cytosol.

• Appears in modules:

• Blood Biology I
• Cellular Organelles I
• Discovery and Structure of Cells

[noun] (singular: villus) Small protrusions or bumps, usually on the surface of a membrane, that increase its surface area.

[person - seismology & plate tectonics] English geophysicist, born in London (1939-). With his advisor, Drummond Matthews, Vine wrote "Magnetic Anomalies Over Ocean Ridges," presenting ideas that helped the theory of plate tectonics gain widespread recognition and adherents. Vine also researched the history of Earth's magnetic field and studied the electrical conductivity of the lower continental crust.

[person - cells] Polish biologist, born in Scievelbein, Pommerania (today Swindin, Poland) (1821-1902). In 1858 he published his best-known work, The Foundation of Cellular Pathology on the Basis of a Physiological and Pathological Understanding of Tissue, formalizing the cell theory.

[noun] An ultramicroscopic infectious agent that can only replicate within the cells of living hosts, mainly bacteria, plants, and animals. Viruses have a very basic structure, consisting of an RNA or DNA core surrounded by a protein coat. More complex viruses also have an envelope surrounding the core and protein coat. Viruses have a wide range of effects on their hosts, from nearly harmless (such as toxoplasmosis in cats) to fatal (such as Ebola in humans).

• Appears in modules:

• César Milstein
• David Ho
• DNA I
• Exponential Equations in Science I
• Exponential Equations in Science II
• Future of Human Evolution
• Membranes I
• Properties of Minerals

[verb - anatomy & physiology, matter, physical & chemical properties, fluid mechanics & hydraulics, matter] The measurement of a fluid's resistance to shear or flow. Highly viscous fluids resist motion due to their molecular composition that produce internal friction. Honey, for example, is a fluid with a high viscosity. Low viscosity fluids, conversely, flow easily because their molecular composition results in very little friction.

• Appears in modules:

• Diffusion I
• Earth Structure
• Membranes II
• Plates, Plate Boundaries, and Driving Forces
• Properties of Liquids
• Scientists and the Scientific Community
• Water

[adjective - biomolecules, cells, organisms] Used to describe substances that are gluey in character and are in between a solid and fluid.

• Appears in modules:

• Plates, Plate Boundaries, and Driving Forces
• Properties of Liquids

[noun - atmospheric science, hydrology & fresh water, oceanography, weather & climate, natural resources, nutrient cycles, weather & climate] The distance the human eye can see through a given medium, such as air or water, under certain environmental conditions.

In aquatic sciences, visibility is usually measured in meters with a Secchi disc. Visibility in water can be an indication of water turbulence. As water moves within a given area, it stirs up sediment and nutrients that have settled onto the area’s bottom – an action similar to shaking a snow globe. Visibility can also be an indication of how much productivity is occurring in the aquatic system. For example, all other variables being equal, a pond that is rich in plant and animal life will likely have a lower visibility than a pond that has very little life. This is because there are more plankton and particulate matter in the water column of the pond rich in life – similar to the difference between looking down a crowded street and looking down the same street when it is empty of people.

• Appears in modules:

• Santiago Ramón y Cajal and Camillo Golgi
• The Phosphorus Cycle

[noun] The amount of space taken up by matter, commonly expressed in cubic centimeters (cm³) or milliliters (ml).

• Appears in modules:

• Acids and Bases I
• Atomic Theory III
• Blood Biology I
• Craig Lee
• Density
• Description in Scientific Research
• Diffusion I
• Early Ideas about Matter
• Introduction to Paleoanthropology
• Kinetic-Molecular Theory
• Lipids
• Luis Walter Alvarez
• Measurement
• Modeling in Scientific Research
• Properties of Solids
• Scientific Institutions and Societies
• Solutions, Solubility, and Colligative Properties
• States of Matter
• Temperature
• The Metric System
• The Mole and Atomic Mass
• Unit Conversion

[person] (November 15, 1871 – October 11, 1962) An Austrian agronomist whose research focused on developing disease-resistant crops, such as wheat-rye and oat hybrids. In 1900, von Seysenegg published a paper presenting his rediscovery of Gregor Mendel's work on genetics.

• Appears in modules:

• Mendel and Independent Assortment