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External Genitalia



















Ovaries | Genital Tract | External Genitalia | Female Sexual Response & Hormone Control | Mammary Glands |









The external genitalia are the accessory structures of the female reproductive system that are external to the vagina. They are also referred to as the vulva or pudendum. The external genitalia include the labia majora, mons pubis, labia minora, clitoris, and glands within the vestibule.



The clitoris is an erectile organ, similar to the male penis, that responds to sexual stimulation. Posterior to the clitoris, the urethra, vagina, paraurethral glands and greater vestibular glands open into the vestibule.

The external genitalia are the accessory structures of the female reproductive system that are external to the vagina. They are also referred to as the vulva or pudendum. The external genitalia include the labia majora, mons pubis, labia minora, clitoris, and glands within the vestibule.



The clitoris is an erectile organ, similar to the male penis, that responds to sexual stimulation. Posterior to the clitoris, the urethra, vagina, paraurethral glands and greater vestibular glands open into the vestibule.





















Reproductive System Morphology










Diagram of the female reproductive system of N. eichhorniae



This is an illustration of the female reproductive system of N. eichhorniae. The female reproductive system is composed of two ovaries. Each ovary is comprised of two tubular ovarioles where the follicles (i.e., developing eggs) are formed and mature. The ovarioles are separated into two main parts; the more distal, germarium, where the follicles are formed and the more proximal portion, the vitellarium, where the follicles develop and mature.















B/W photomicrograph of the female reproductive system of N. eichhorniae



This is a black and white photomicrograph of the female reproductive system of N. eichhorniae. The female reproductive system is composed of two ovaries. Each ovary is comprised of two tubular ovarioles where the follicles (i.e., developing eggs) are formed and mature. The ovarioles are separated into two main parts; the more distal, germarium, where the follicles are formed and the more proximal portion, the vitellarium, where the follicles develop and mature.











Color photomicrograph of the female reproductive system of N. bruchi, a closely related species to N. eichhorniae.



This is a color photomicrograph of the female reproductive system of N. bruchi. N. bruchi is a closely related species to N. eichhorniae. No significant differences can be seen in the structure of the reproductive system for N. bruchi in comparison to N. eichhorniae. As in N. eichhorniae, the female reproductive system is composed of two ovaries. Each ovary is comprised of two tubular ovarioles where the follicles (i.e., developing eggs) are formed and mature. The ovarioles are separated into two main parts; the more distal, germarium, where the follicles are formed and the more proximal portion, the vitellarium, where the follicles develop and mature.











The female reproductive system in N. eichhorniae is similar to that reported for the boll weevil, Anthonomus grandis (Burke 1959, Grodowitz and Brewer, 1986). As documented for boll weevil, the type of ovariole exhibited by N. eichhorniae is of the meroistic type where specialized nurse cells or trophocytes are present within the ovarioles (Chapman 1971). The ovarioles are also considered to be telotrophic. Telotrophic ovaries have the trophic tissue, oogonia, and oocytes housed in the germarium and not within the follicle. Each developing oocyte within the ovariole is connected with the trophocytes via a nutritive cord. It is through the trophocytes that the developing follicles receive nutrition for growth and maturation.







The reproductive system in female N. eichhorniae is typically of the telotrophic type. It is composed of two ovaries, with each ovary comprised of two, tube-like ovarioles where the follicles develop and mature. The tube-like structures, called ovarioles, are partitioned into two main areas; the more distal, somewhat enlarged portion being called the germarium and the remaining more proximal portion called the vitellarium. The germarium contains the nurse cells and prefollicular tissue while the vitellarium houses the developing follicles .











The photomicrograph on the left (black and white) is of the more distal portion of a single ovariole of N. eichhorniae. Note the developing follicles become more mature (i.e., larger) as you move away from the germarium. N. eichhorniae has a telotrophic ovariole type where nurse cells are contained within the germarium and do not reside directly with each developing follicle. This is in contrast to Hydrellia pakistanae (photomicrograph on the right), a leaf-mining fly introduced from India for use as a biocontrol agent for hydrilla. H. pakistanae has a polytrophic ovariole where nurse cells reside directly with each follicle. Note the cluster of cells directly above each follicle. These are the nurse cells or trophocytes.







The youngest, least mature follicles are located closest to the germarium while the more mature follicles are found in the more proximal portion of the vitellarium. Hence, a succession of follicle maturity is established within the vitellarium.







The ovarioles are connected to one another via the lateral oviduct. The two lateral oviducts from each ovariole then combine to form the common oviduct. Connected to the common oviduct is a small sclerotized, roughly C-shaped pouch called the spermatheca .











Connected to the common oviduct is a small sclerotized, roughly C-shaped pouch called the spermatheca. Sperm is stored within the spermatheca and used for the fertilization of each egg as it passes through the common oviduct.







Sperm is stored within the spermatheca and used for the fertilization of each egg as it passes through the common oviduct.







The follicles (or developing eggs) are composed of a large central ova and a surrounding layer of follicular epithelium .











In this photomicrograph a series of developing follicles have been removed from the ovariole sheath to better view the follicle structure. Note the thin layer of cells surrounding the ova which is called the follicular epithelium. Within the ova is a small, lighter colored circular area. This is the germinal vesicle or nucleus of each ova. The combination of the ova and its surrounding follicular epithelium is called the follicle.







The entire set of developing follicles is housed within a thin layer of tissue called the ovariole sheath .











This is a photomicrograph of the ovarioles of N. eichhorniae. Note the thin transparent membrane surrounding the follicles called the ovariole sheath.







When the follicle passes through to the lateral oviduct (i.e., ovulation) the follicular epithelium sloughs off and accumulates in the lateral oviduct, forming the follicular relics. The quantity and appearance of the follicular relics are indicative of past and present reproductive activity and are the primary basis for this physiological age-grading procedure, especially the parous stages (see section on Follicular Relic Formation)













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Label Heart Interior Anatomy Diagram Human Anatomy

The heart is a fist-sized, muscular organ that pumps blood through the body. Oxygen-poor blood enters the right atrium of the heart (via veins called the inferior vena cava and the superior vena cava). The blood is then pumped into the right ventricle and then through the pulmonary artery to the lungs, where the blood is enriched with oxygen (and loses carbon dioxide). The oxygen-rich (oxygenated) blood is then carried back to the left atrium of the heart via the pulmonary vein. The blood is then pumped to the left ventricle, then the blood is pumped through the aorta and to the rest of the body. This cycle is then repeated. Every day, the heart pumps about 2,000 gallons (7,600 liters) of blood, beating about 100,000 times.
Label the heart anatomy diagram below using the heart glossary. Note: On the diagram, the right side of the heart appears on the left side of the picture (and vice versa) because you are looking at the heart from the front.





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Label Me! Printout Skeleton Information/Coloring Printout EnchantedLearning.com Human Skeleton Human Anatomy The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. These bones support your body and allow you to move. Bones contain a lot of calcium (an element found in milk, broccoli, and other foods). Bones manufacture blood cells and store important minerals. The longest bone in our bodies is the femur (thigh bone). The smallest bone is the stirrup bone inside the ear. Each hand has 26 bones in it. Your nose and ears are not made of bone; they are made of cartilage, a flexible substance that is not as hard as bone. Joints: Bones are connected to other bones at joints. There are many different types of joints, including: fixed joints (such as in the skull, which consists of many bones), hinged joints (such as in the fingers and toes), and ball-and-socket joints (such as the shoulders and hips). Differences between males and females: Males and females have slightly different skeletons, including a different elbow angle. Males have slightly thicker and longer legs and arms; females have a wider pelvis and a larger space within the pelvis, through which babies travel when they are born.
SCIENCE IN PHYSICS

Glossary of Nuclear Science Terms



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

- A -

Absorber
Any material that stops ionizing radiation. Lead, concrete, and steel attenuate gamma rays. A thin sheet of paper or metal will stop or absorb alpha particles and most beta particles.
Alpha particle (alpha radiation, alpha ray)
A positively charged particle (a Helium-4 nucleus) made up of two neutrons and two protons. It is the least penetrating of the three common forms of radiation, being stopped by a sheet of paper. It is not dangerous to living things unless the alpha-emitting substance is inhaled or ingested or comes into contact with the lens of the eye.
Atom
A particle of matter indivisible by chemical means. It is the fundamental building block of elements.
Atomic number
The number assigned to each element on the basis of the number of protons found in the element's nucleus.
Atomic weight (atomic mass)
Approximately the sum of the number of protons and neutrons found in the nucleus of an atom.
- B -

Background radiation
The radiation of man's natural environment originating primarily from the naturally radioactive elements of the earth and from the cosmic rays. The term may also mean radiation extraneous to an experiment.
Beta particle (beta radiation, beta ray)
An electron of either positive charge (ß+) or negative charge (ß-), which has been emitted by an atomic nucleus or neutron in the process of a transformation. Beta particles are more penetrating than alpha particles but less than gamma rays or x-rays.
- C -

Contamination
Radioactive material deposited or dispersed in materials or places where it is not wanted.
Cow
A radioisotope generator system.
Curie (Ci)
The basic unit used to describe the intensity of radioactivity in a sample of material. One curie equals thirty-seven billion disintegrations per second, or approximately the radioactivity of one gram of radium.
- D -

Daughter
A nucleus formed by the radioactive decay of a different (parent) nuclide.
Decay (radioactive)
The change of one radioactive nuclide into a different nuclide by the spontaneous emission of alpha, beta, or gamma rays, or by electron capture. The end product is a less energetic, more stable nucleus. Each decay process has a definite half-life.
Decontamination
The removal of radioactive contaminants by cleaning and washing with chemicals.
Density
That property of a substance which is expressed by the ratio of its mass to its volume.
Dose
A general term denoting the quantity of radiation or energy absorbed in a specific mass.
- E -

Electromagnetic radiation
Radiation consisting of electric and magnetic waves that travel at the speed of light. Examples: light, radio waves, gamma rays, x-rays.
Electron
An elementary particle with a unit electrical charge and a mass 1/1837 that of the proton. Electrons surround the atom's positively charged nucleus and determine the atom's chemical properties.
Electron capture
A radioactive decay process in which an orbital electron is captured by and merges with the nucleus. The mass number is unchanged, but the atomic number is decreased by one.
Eluant
Washing solution (The solution that is introduced into the cow).
Eluate
The washings obtained by elution (the solution that comes out of the cow).
Elute
To separate by washing (to milk).
Excited state
The state of an atom or nucleus when it possesses more than its normal energy. The excess energy is usually released eventually as a gamma ray.
- F -

Fission
The splitting of a heavy nucleus into two roughly equal parts (which are nuclei of lighter elements), accompanied by the release of a relatively large amount of energy in the form of kinetic energy of the two parts and in the form of emission of neutrons and gamma rays.
Fission products
Nuclei formed by the fission of heavy elements. They are of medium atomic weight and almost all are radioactive. Examples: strontium-90, cesium-137.
- G -

Gamma ray
A highly penetrating type of nuclear radiation, similar to x-radiation, except that it comes from within the nucleus of an atom, and, in general, has a shorter wavelength.
Geiger counter
A Geiger-Müller detector and measuring instrument. It contains a gas-filled tube which discharges electrically when ionizing radiation passes through it and a device that records the events.
Generator
A cow-a system containing a parent-daughter set of radioisotopes in which the parent decays through a daughter to a stable isotope. The daughter is a different element from that of the parent, and, hence, can be separated from the parent by elution (milking).
- H -

Half-life
The time in which half the atoms of a particular radioactive nuclide disintegrate. The half-life is a characteristic property of each radioactive isotope.
Health physics
That science devoted to recognition, evaluation, and control of all health hazards from ionizing radiation.
- I -

Induced radioactivity
Radioactivity that is created by bombarding a substance with neutrons in a reactor or with charged particles produced by particle accelerators.
Ion
An atomic particle that is electrically charged, either negative or positive.
Ionizing radiation
Radiation that is capable of producing ions either directly or indirectly.
Irradiate
To expose to some form of radiation.
Isomer
One of several nuclides with the same number of neutrons and protons capable of existing for a measurable time in different nuclear energy states.
Isometric transition
A mode of radioactive decay where a nucleus goes from a higher to a lower energy state. The mass number and the atomic number are unchanged.
Isotope
Isotopes of a given element have the same atomic number (same number of protons in their nuclei) but different atomic weights (different number of neutrons in their nuclei). Uranium-238 and uranium-235 are isotopes of uranium.
- K -

K-capture
The capture by an atom's nucleus of an orbital electron from the first K-shell surrounding the nucleus.
keV
One thousand electron volts.
- L -

- M -

MeV
One million electron volts.
Microcurie (µCi)
One millionth of a curie (3.7 x 104 disintegrations per second).
Milk
To elute a cow.
Minigenerator
A trademark of Union Carbide Corporation that is used to identify radioisotope generator systems for educational use.
- N -

Neutrino
An electrically neutral particle with negligible mass. It is produced in many nuclear reactions such as in beta decay.
Neutron
One of the basic particles which make up an atom. A neutron and a proton have about the same weight, but the neutron has no electrical charge.
Nuclear reactor
A device in which a fission chain reaction can be initiated, maintained, and controlled. Its essential components are fissionable fuel, moderator, shielding, control rods, and coolant.
Nucleon
A constituent of the nucleus; that is, a proton or a neutron.
Nucleonics
The science, technology, and application of nuclear energy.
Nucleus
The core of the atom, where most of its mass and all of its positive charge is concentrated. Except for hydrogen, it consists of protons and neutrons.
Nuclide
Any species of atom that exists for a measurable length of time. A nuclide can be distinguished by its atomic weight, atomic number, and energy state.
- O -

- P -

Parent
A radionuclide that decays to another nuclide which may be either radioactive or stable.
Photon
A quantity of electromagnetic energy. Photons have momentum but no mass or electrical charge.
Proton
One of the basic particles which makes up an atom. The proton is found in the nucleus and has a positive electrical charge equivalent to the negative charge of an electron and a mass similar to that of a neutron: a hydrogen nucleus.
- Q -

- R -

Rad
Radiation Absorbed Dose. The basic unit of an absorbed dose of ionizing radiation. One rad is equal to the absorption of 100 ergs of radiation energy per gram of matter.
Radioactive dating
A technique for estimating the age of an object by measuring the amounts of various radioisotopes in it.
Radioactive waste
Materials which are radioactive and for which there is no further use.
Radioactivity
The spontaneous decay of disintegration of an unstable atomic nucleus accompanied by the emission of radiation.
Radioisotope
A radioactive isotope. A common term for a radionuclide.
Radionuclide
A radioactive nuclide. An unstable isotope of an element that decays or disintegrates spontaneously, emitting radiation.
Rate meter
An electronic instrument that indicates, on a meter, the number of radiation induced pulses per minute from radiation detectors such as a Geiger-Muller tube.
- S -

Scaler
An electronic instrument for counting radiation induced pulses from radiation detectors such as a Geiger-Muller tube.
Scintillation counter
An instrument that detects and measures gamma radiation by counting the light flashes (scintillations) induced by the radiation.
Secular equilibrium
A state of parent-daughter equilibrium which is achieved when the half-life of the parent is much longer than the half-life of the daughter. In this case, if the two are not separated, the daughter will eventually be decaying at the same rate at which it is being produced. At this point, both parent and daughter will decay at the same rate until the parent is essentially exhausted.
Shielding
A protective barrier, usually a dense material, which reduces the passage of radiation from radioactive materials to the surroundings.
Source
A radioactive material that produces radiation for experimental or industrial use.
Spill
The accidental release of radioactive materials.
Stable
Non-radioactive.
- T -

Tracer
A small amount of radioactive isotope introduced into a system in order to follow the behavior of some component of that system.
Transmutation
The transformation of one element into another by a nuclear reaction.
-







Glossary of Physics Terms



The following are glossary entries compiled from the Light and Matter series of free introductory physics textbooks.
Each entry has a link to the volume that contains it.
You can also browse the tables of contents of the books:
- Contents of book 1, Newtonian Physics
- Contents of book 2, Conservation Laws
- Contents of book 3, Vibrations and Waves
- Contents of book 4, Electricity and Magnetism
- Contents of book 5, Optics
- Contents of book 6, The Modern Revolution in Physics

Absorption. What happens when wave passes through a medium and gives up some of its energy. See textbook.

Acceleration. The rate of change of velocity; the slope of the tangent line on a v-t graph. See textbook.

Alpha decay. The radioactive decay of a nucleus via emission of an alpha particle. See textbook.

Alpha particle. A form of radioactivity consisting of helium nuclei. See textbook.

Ammeter. A device for measurin electrical current. See textbook.

Ampere. The metric unit of current, one coulomb pe second; also "amp." See textbook.

Amplitude. The amount of vibration, often measured from the center to one side; may have different units depending on the nature of the vibration. See textbook.

Angular magnification. The factor by which an image's apparent angular size is increased (or decreased). Cf. magnification. See textbook.

Angular momentum. A measure of rotational motion; a conserved quantity for a closed system. See textbook.

Atom. The basic unit of one of the chemical elements. See textbook.

Atomic mass. The mass of an atom. See textbook.

Atomic number. The number of protons in an atom's nucleus; determines what element it is. See textbook.

Attractive. Describes a force that tends to pull the two participating objects together. Cf. repulsive, oblique. See textbook.

Axis. An arbitrarily chosen point used in the definition of angular momentum. Any object whose direction changes relative to the axis is considered to have angular momentum. No matter what axis is chosen, the angular momentum of a closed system is conserved. See textbook.

Beta decay. The radioactive decay of a nucleus via the reaction n -> p + e- + or p -> n + e+ + n; so called because an electron or antielectron is also known as a beta particle. See textbook.

Beta particle. A form of radioactivity consisting of electrons. See textbook.

Cathode ray. The mysterious ray that emanated from the cathode in a vacuum tube; shown by Thomson to be a stream of particles smaller than atoms. See textbook.

Center of mass. The balance point of an object. See textbook.

Charge. A numerical rating of how strongly an object participates in electrical forces. See textbook.

Circuit. An electrical device in which charge can come back to its starting point and be recycled rather than getting stuck in a dead end. See textbook.

Coherent. A light wave whose parts are all in phase with each other. See textbook.

Collision. An interaction between moving objects that lasts for a certain time. See textbook.

Component. The part of a velocity, acceleration, or force that is along one particular coordinate axis. See textbook.

Concave. Describes a surface that is hollowed out like a cave. See textbook.

Convex. Describes a surface that bulges outward. See textbook.

Coulomb (C). The unit of electrical charge. See textbook.

Current. The rate at which charge crosses a certain boundary. See textbook.

Damping. the dissipation of a vibration's energy into heat energy, or the frictional force that causes the loss of energy.See textbook.

Diffraction. The behavior of a wave when it encounters an obstacle or a nonuniformity in its medium; in general, diffraction causes a wave to bend around obstacles and make patterns of strong and weak waves radiating out beyond the obstacle. See textbook.

Diffuse reflection. Reflection from a rough surface, in which a single ray of light is divided up into many weaker reflected rays going in many directions. See textbook.

Displacement. (avoided in this book) A name for the symbol delta-x . See textbook.

Driving force. An external force that pumps energy into a vibrating system. See textbook.

Electric dipole. An object that has an imbalance between positive charge on one side and negative charge on the other; an object that will experience a torque in an electric field. See textbook.

Electric field. The force per unit charge exerted on a test charge at a given point in space. See textbook.

Electrical force. One of the fundamental forces of nature; a noncontact force that can be either repulsive or attractive. See textbook.

Electron. Thomson's name for the particles of which a cathode ray was made; a subatomic particle. See textbook.

Energy. A numerical scale used to measure the heat, motion, or other properties that would require fuel or physical effort to put into an object; a scalar quantity with units of joules (J). See textbook.

Equilibrium. A state in which an object's momentum and angular momentum are constant. See textbook.

Field. A property of a point in space describing the forces that would be exerted on a particle if it was there. See textbook.

Fission. The radioactive decay of a nucleus by splitting into two parts. See textbook.

Fluid. A gas or a liquid. See textbook.

Fluid friction. A friction force in which at least one of the object is is a fluid (i.e. either a gas or a liquid). See textbook.

Focal length. A property of a lens or mirror, equal to the distance from the lens or mirror to the image it forms of an object that is infinitely far away. See textbook.

Frequency. The number of cycles per second, the inverse of the period (q.v.). See textbook.

Fusion. A nuclear reaction in which two nuclei stick together to form one bigger nucleus. See textbook.

Gamma ray. Aform of radioactivity consisting of a very high-frequency form of light. See textbook.

Gravitational field. The force per unit mass exerted on a test mass at a given point in space. See textbook.

Gravity. A general term for the phenomenon of attraction between things having mass. The attraction between our planet and a human-sized object causes the object to fall. See textbook.

Half-life. The amount of time that a radioactive atom has a probability of 1/2 of surviving without decaying.See textbook.

Heat. The energy that an object has because of its temperature. Heat is different from temperature (q.v.) because an object with twice as much mass requires twice as much heat to increase its temperature by the same amount. There is a further distinction in the terminology, not emphasized in this book, between heat and thermal energy. See the entry under thermal energy for a discussion of this distinction. See textbook.

Image. A place where an object appears to be, because the rays diffusely reflected from any given point on the object have been bent so that they come back together and then spread out again from the image point, or spread apart as if they had originated from the image. See textbook.

Index of refraction. An optical property of matter; the speed of light in a vacuum divided by the speed of light in the substance in question. See textbook.

Independence. The lack of any relationship between two random events.See textbook.

Induction. The production of an electric field by a changing magnetic field, or vice-versa. See textbook.

Inertial frame. A frame of reference that is not accelerating, one in which Newton's first law is true. Seetextbook.

Kinetic friction. A friction force between surfaces that are slipping past each other. See textbook.

Invariant. A quantity that does not change when transformed.See textbook.

Ion. An electrically charged atom or molecule. See textbook.

Isotope. One of the possible varieties of atoms of a given element, having a certain number of neutrons. See textbook.

Kinetic energy. The energy an object possesses because of its motion. Cf. potential energy. See textbook.

Light. Anything that can travel from one place to another through empty space and can influence matter, but is not affected by gravity. See textbook.

Lorentz transformation. The transformation between frames in relative motion.See textbook.

Magnetic dipole. An object, such as a current loop, an atom, or a bar magnet, that experiences torques due to magnetic forces; the strength of magnetic dipoles is measured by comparison with a standard dipole consisting of a square loop of wire of a given size and carrying a given amount of current. See textbook.

Magnetic field. A field of force, defined in terms of the torque exerted on a test dipole. See textbook.

Magnification. The factor by which an image's linear size is increased (or decreased). Cf. angular magnification. See textbook.

Magnitude. The "amount" associated with a vector; the vector stripped of any information about its direction. See textbook.

Mass. A numerical measure of how difficult it is to change an object's motion. (In the context of relativity, some books use the word "mass" to mean what we refer to as mass multiplied by gamma.) See textbook.

Mass number. The number of protons plus the number of neutrons in a nucleus; approximately proportional to its atomic mass. See textbook.

Matter. Anything that is affected by gravity. See textbook.

Millirem. A unit for measuring a person's exposure to radioactivity; cf rem. See textbook.

Mks system. The use of metric units based on the meter, kilogram, and second. Example: meters per second is the mks unit of speed, not cm/s or km/hr. See textbook.

Molecule. A group of atoms stuck together. See textbook.

Momentum. A measure of motion, equal to mv for material objects. See textbook.

Neutron. An uncharged particle, the other types that nuclei are made of. See textbook.

Noninertial frame. An accelerating frame of reference, in which Newton's first law is violated. See textbook.

Nonuniform circular motion. Circular motion in which the magnitude of the velocity vector changes. See textbook.

Normal force. The force that keeps two objects from occupying the same space. See textbook.

Normalization. The property of probabilities that the sum of the probabilities of all possible outcomes must equal one.See textbook.

Oblique. Describes a force that acts at some other angle, one that is not a direct repulsion or attraction. Cf. attractive, repulsive. See textbook.

Ohm. The metric unit of electrical resistance, one volt per ampere. See textbook.

Ohmic. Describes a substance in which the flow of current between two points is proportional to the voltage difference between them. See textbook.

Open circuit. A circuit that does not function because it has a gap in it. See textbook.

Operational definition. A definition that states what operations should be carried out to measure the thing being defined. See textbook.

Parabola. The mathematical curve whose graph has y proportional to x2. See textbook.

Period. The time required for one cycle of a periodic motion (q.v.). See textbook.

Periodic motion. Motion that repeats itself over and over. See textbook.

Photon. A particle of light.See textbook.

Photoelectric effect. The ejection, by a photon, of an electron from the surface of an object.See textbook.

Potential energy. The energy having to do with the distance between to objects that interact via a noncontact force. Cf. Kinetic energy. See textbook.

Power. The rate of transferring energy; a scalar quantity with units of watts (W). See textbook.

Probability. The likelihood that something will happen, expressed as a number between zero and one.See textbook.

Probability distribution. A curve that specifies the probabilities of various random values of a variable; areas under the curve correspond to probabilities.See textbook.

Proton. A positively charged particle, one of the types that nuclei are made of. See textbook.

Quality factor. The number of oscillations required for a system's energy to fall off by a factor of 535 due to damping. See textbook.

Quantized. Describes quantity such as money or electrical charge, that can only exist in certain amounts. See textbook.

Quantum number. A numerical label used to classify a quantum state.See textbook.

Radial. Parallel to the radius of a circle; the in-out direction. Cf. tangential. See textbook.

Real image. A place where an object appears to be, because the rays diffusely reflected from any given point on the object have been bent so that they come back together and then spread out again from the new point. Cf. virtual image. See textbook.

Reflection. What happens when light hits matter and bounces off, retaining at least some of its energy. See textbook.

Refraction. The change in direction that occurs when a wave encounters the interface between two media. See textbook.

Rem. A unit for measuring a person's exposure to radioactivity; cf millirem. See textbook.

Repulsive. Describes a force that tends to push the two participating objects apart. Cf. attractive, oblique. See textbook.

Resistance. The ratio of the voltage difference to the current in an object made of an ohmic substance. See textbook.

Resonance. The tendency of a vibrating system to respond most strongly to a driving force whose frequency is close to its own natural frequency of vibration. See textbook.

Rest mass. Referred to as mass in this book; written as m0 in some books. Cf. mass.See textbook.

Scalar. A quantity that has no direction in space, only an amount. Cf. vector. See textbook.

Short circuit. A circuit that does not function because charge is given a low-resistance "shortcut" path that it can follow, instead of the path that makes it do something useful. See textbook.

Significant figures. Digits that contribute to the accuracy of a measurement. See textbook.

Simple harmonic motion. Motion whose x-t graph is a sine wave. See textbook.

Sink. A point at which field vectors converge. See textbook.

Source. A point from which field vectors diverge; often used more inclusively to refer to points of either convergence or divergence. See textbook.

Specular reflection. Reflection from a smooth surface, in which the light ray leaves at the same angle at which it came in. See textbook.

Speed. (avoided in this book) The absolute value of or, in more then one dimension, the magnitude of the velocity, i.e. the velocity stripped of any information about its direction Spring constant. The constant of proportionality between force and elongation of a spring or other object under strain. See textbook.

Spin. The built-in angular momentum possessed by a particle even when at rest.See textbook.

Stable equilibrium. One in which a force always acts to bring the object back to a certain point. See textbook.

Static friction. A friction force between surfaces that are not slipping past each other. See textbook.

Steady state. The behavior of a vibrating system after it has had plenty of time to settle into a steady response to a driving force. In the steady state, the same amount of energy is pumped into the system during each cycle as is lost to damping during the same period. See textbook.

Strong nuclear force. The force that holds nuclei together against electrical repulsion. See textbook.

Systeme International. Fancy name for the metric system. See textbook.

Tangential. Tangent to a curve. In circular motion, used to mean tangent to the circle, perpendicular to the radial direction Cf. radial. See textbook.

Temperature. What a thermometer measures. Objects left in contact with each other tend to reach the same temperature. Roughly speaking, temperature measures the average kinetic energy per molecule. For the distinction between temperature and heat, see the glossary entry for heat. See textbook.

Thermal energy. Careful writers make a distinction between heat and thermal energy, but the distinction is often ignored in casual speech, even among physicists. Properly, thermal energy is used to mean the total amount of energy possessed by an object, while heat indicates the amount of thermal energy transferred in or out. The term heat is used in this book to include both meanings. See textbook.

Torque. The rate of change of angular momentum; a numerical measure of a force's ability to twist on an object. See textbook.

Transformation. The mathematical relationship between the variables such as x and t, as observed in different frames of reference.See textbook.

Uniform circular motion. Circular motion in which the magnitude of the velocity vector remains constant.See textbook.

Vector. A quantity that has both an amount (magnitude) and a direction in space. Cf. scalar. See textbook.

Unstable equilibrium. One in which any deviation of the object from its equilibrium position results in a force pushing it even farther away. See textbook.

Velocity. The rate of change of position; the slope of the tangent line on an x-t graph. See textbook.

Virtual image. Like a real image, but the rays don't actually cross again; they only appear to have come from the point on the image. Cf. real image. See textbook.

Volt. The metric unit of voltage, one joule per coulomb. See textbook.

Voltage. Electrical potential energy per unit charge that will be possessed by a charged particle at a certain point in space. See textbook.

Voltmeter. A device for measuring voltage differences. See textbook.

Wave-particle duality. The idea that light is both a wave and a particle.See textbook.

Wavefunction. The numerical measure of an electron wave, or in general of the wave corresponding to any quantum mechanical particle.See textbook.

Weak nuclear force. The force responsible for beta decay. See textbook.

Weight. The force of gravity on an object, equal to mg. See textbook.

Work. The amount of energy transferred into or out of a system, excluding energy transferred by heat conduction. See textbook



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Glossary Of Biology


BIOCHEMISTRY

alginate -- component of the cell walls of many rhodophytes and kelps. Alginates have an affinity for water, and so help to slow dessication when the algae are exposed to the air; they are commercially important in the production of paper, toothpaste, beer, and frozen foods.

amino acid -- unit molecule from which proteins are constructed by polymerization.

ATP -- "adenosine triphosphate". A relatively stable, high energy molecule used to fuel chemical reactions within cells.

biochemistry -- the study of those molecules used and manufactured by living things.

bioluminescence -- the production of light by a chemical reaction within an organism. The process occurs in many bacteria and protists, as well as certain animals and fungi.

brevitoxin -- neurotoxin produced by the dinoflagellate Ptychodiscus brevis.

calcite -- A common crystalline form of natural calcium carbonate, CaCO3, that is the basic constituent of limestone, marble, and chalk. Also called calcspar.

calcium carbonate -- a "salt" used by many marine invertebrates, such as corals and echinoderms, and by protists, such as coccolithophorids, to construct their exoskeletons.

carbohydrates -- class of biochemical compounds which includes sugars, starch, chitin, and steroids.

cellulose -- carbohydrate polymer of the simple sugar glucose. It is found in the cell walls of plants and green algae, as well as dinoflagellates. Cellulose is the most abundant compound on earth that is manufactured by living things.

chitin -- n. A carbohydrate polymer found in the cell walls of fungi and in the exoskeletons of arthropods, which provides strength for support and protection; chitinous- adj.

chlorophyll -- n. The green-colored pigment that absorbs light during photosynthesis, often found in plants, algae, and some bacteria; it includes a porphyrin ring, and often has a long hydrophobic tail. More info?

collagen -- long proteins whose structure is wound into a triple helix. The resulting fibers have a high tensile strength. Collagen is a primary component of mammalian hair.

dinosteranes/dinosteroids -- chemicals found in dinoflagellates, which have been useful in documenting their existence early in the fossil record.

DNA -- "deoxyribonucleic acid". The nucleic acid which carries the genetic code of an organism. It is the primary component of chromosomes. MORE?

enzyme -- complex protein which helps to speed biochemical reactions. Enzymes are important in the construction and degradation of other molecules.

flagellin -- protein which is the primary component of prokaryotic flagella.

fucoxanthin -- yellowish-brown pigment found in some members of the Chromista, including kelps and diatoms.

glucose -- simple sugar, and the primary product of photosynthesis. It is polymerized to make cellulose and chitin.

glycoprotein -- a membrane-bound protein which has attached branching carbohydrates. These may function in cell-cell recognition, such as in human blood groups and immune system response, as well as in resisting compression of cells.

hemoglobin -- protein complex found in the blood of most chordates and the roots of certain legumes. It binds oxgen molecules, and in chordates serves as the means by which the oxygen is supplied to the cells of the body.

histones -- proteins attached to the DNA of eukaryotes which allows it to be packaged into chromosomes.

hydrophilic -- "water loving". Hydrophilic compounds dissolve easily in water, and are usually polar.

hydrophobic -- "water fearing". Hydrophobic compounds do not dissolve easily in water, and are usually non-polar. Oils and other long hydrocarbons are hydrophobic.

integrin -- adhesive protein of the extracellular matrix in animals.

ion -- an atom or small molecule which carries a positive or negative charge.

laminarin -- a beta-glucan polysaccharide produced by many chromists through photosynthesis.

lipids -- a class of biochemical compounds which includes fats, oils, and waxes.

luciferase -- enzyme which activates luciferin to produce bioluminescence.

luciferin -- compound whose activated form emits light.

neurotoxin -- poison which interferes with nerve function, usually by affecting the flow of ions through the cell membrane.

nucleic acid -- class of biochemical compounds which includes DNA and RNA. They are among the largest molecules known. MORE?

nucleotide -- unit from which nucleic acids are constructed by polymerization. It contains a sugar, a phosphate group, and an organic base. ATP is a nucleotide.

peptidoglycan -- carbohydrate polymer cross-linked by proteins. It is found in the cell wall of Gram positive bacteria, where it stains with the dye crystal-violet.

peridinin -- carotenoid pigment found in dinoflagellates.

phosphate -- an ion consisting of a phosphorus atom and four oxygen atoms. Among other things, it is used in the constuction of nucleic acids.

photosynthesis -- biochemical process in which light energy is absorbed by chlorophyll, and is used to fuel the building of sugar molecules.

phycocyanin -- blue, water-soluble pigment found in the cyanobacteria and the red algae.

phycoerythrin -- red, water-soluble pigment found in the cyanobacteria and red algae.

pigment -- any colorful compound, used by living things to absorb or block sunlight, and in sexual displays. More info?

polymer -- a large molecule constructed from many smaller identical units. These include proteins, nucleic acids, and starches.

protein -- class of biochemical compounds constructed from amino acids. Proteins may be structural, such as those that make up hair and cartilage, or they may be reactive, such as the enzymes.

proteinaceous -- describes any structure which is composed of protein.

proteoglycan --

rbcL -- a gene which is located in the chloroplast of photosynthetic organisms. It codes for the large subunit of the protein rubisco, and its sequence has been useful in plant phylogenies.

RNA -- "ribonucleic acid". The nucleic acid which carries the DNA message into parts of the cell where it is interpreted and used. The 18S ribosomal RNA sequence has been used in many groups of organisms to reconstruct phylogeny.

rubisco -- protein which fixes carbon in photosynthetic organisms. It binds molecules of carbon dioxide to a five-carbon molcule. Rubisco is the most common protein on earth.

saxitoxin -- neurotoxin found in a variety of dinoflagellates. If ingested, it may cause respiratory failure and cardiac arrest.

silica -- amorphous silicon dioxide (glass). It is a structural component in many organisms, such as diatoms and horsetails.

spongin -- proteinacous compound of which the spicules in Demospongiae are composed.

starch -- a complex polymer of glucose, used by plants and green algae to store surplus sugar for later use.

sugar -- any of several small carbohydrates, such as glucose, which are "sweet" to the taste.



ZOOLOGY

abdomen -- Region of the body furthest from the mouth. In insects, the third body region behind the head and thorax.

ambulacra -- Row of tube feet of an echinoderm.

amniotic egg -- n. An egg that can be laid on land due to the presence of a fluid-filled amniotic sac (amnion) that cushions and protects the developing embryo; amniote- n. Any of a group of land-dwelling vertebrates that have an amnion during embryonic development, including reptiles, birds, and mammals.

anapsid -- n. A vertebrate distinguished by a skull with no openings in the side behind the eyes, e.g. turtles.

anus -- End of the digestive tract, or gut, through which waste products of digestion are excreted, as distinct from the mouth.

bipedal -- adj. Describes an animal that walks on two legs.

biramous -- Arthropod appendages that are biramous have two branches, an outer branch and an inner branch. These branches may have separate functions; in crustaceans, for instance, the inner branch of a leg is used for walking, while the outer branch may be paddle-shaped or feathery and often functions as a gill. Contrast with uniramous.

blood -- Fluid which circulates throughout the body of an animal, distributing nutrients, and often oxygen as well.

book lung -- A set of soft overlapping flaps, covered up by a plate on the abdomen, through which oxygen is taken up and carbon dioxide given off. Characteristic of many terrestrial arachnids such as scorpions and spiders.

brain -- Collection of nerve cells usually located at the anterior end of an animal, when present at all. The nerves coordinate information gathered by sense organs, locomotion, and most internal body activities.

cephalon -- In trilobites, the head shield bearing the eyes, antennae, and mouth. More info?

chaetae -- Stiff bristles characteristic of annelids.

chela -- The claw of an arthropod.

chelicera -- The first pair of appendages of a chelicerate arthropod. Originally a short clawed appendage, the chelicerae of many arachnids are highly modified for feeding; in spiders, for instance, they are modified into poisonous fangs.

chordate -- n. An animal with a notochord (a cartilaginous rod that extends the length of the body), dorsal hollow nerve cord (a fluid-filled tube that runs the length of the body), gill slits or pouches, and a tail at some stage in its life cycle.

clitellum -- In annelids, a swelling of the body towards the head of the animal, where the gonads are located. Both oligochaetes and leeches have a clitellum.

cnidocyst -- The "stinging cell" of a cnidarian.

coelom -- Fluid-filled cavity within the body of an animal; usually refers to a cavity lined with specialized tissue peritoneum in which the gut is suspended. The structure and development of the coelom is an important character for recognizing major groups of animals.

compound eye -- Found in many but not all arthropods, a compound eye is composed of a large number of small, closely packed simple eyes (ommatidia), each with its own lens and nerve receptors.

cuticle -- 1) In animals, a multilayered, extracellular, external body covering, usually composed of fibrous molecules such as chitin or collagen, and sometimes strengthened by the deposition of minerals such as calcium carbonate. 2) A waxy layer which seals the outer surface of land plants, helping to retain moisture.

diapsid -- n. A vertebrate distinguished by a skull with two pairs of openings in the side behind the eyes, e.g., lizards, snakes, crocodiles, dinosaurs, and pterosaurs.

ectoderm -- The outer basic layer of tissue in those animals with true tissues. In vertebrates, for instance, the embryonic ectoderm differentiates into the skin and also the nervous system.

endoderm -- The innermost basic layer of tissue in those animals with true tissues. Forms the gut and its derivatives: in vertebrates, these include the liver, trachea, and lungs.

epidermis -- The outermost layer of cells or skin. This tissue often contains specialized cells for defense, gas exchange, or secretion.

epithelium -- Layer of cells which lines a body cavity; cells may be ciliated or unciliated, and may be squamous (flat, scale-shaped), cuboidal (cube-shaped), or columnar (column-shaped). Your stomach and cheeks are lined with epithelium.

esophagus -- That portion of the gut which connects the pharynx to the stomach.

exoskeleton -- n. An external, often hard, covering or integument that provides support and protection to the body.

gastrodermis -- In cnidarians, the endodermis which lines the gut cavity. The term is often used instead of endodermis since cnidarians only have two tissue layers instead of three.

genus -- n. A category in the classification of plants and animals between species and family; genera- pl.

gill -- In aquatic animals, highly vascularized tissues with large surface area; these are extended out of the body and into the surrounding water for gas exchange.

gill arches -- Stiffenings which support the flesh between the gill slits of chordates. In most vertebrates, the first gill arches have been modified to form the jaw, and in tetrapods, the inner ear bones.

gill slit -- A slitlike or porelike opening connecting the pharynx of a chordate with the outside of the body. Gill slits may contain the gills and be used for gas exchange, as in most fish, but may also be used for filter-feeding, or may be highly modified in land-dwelling vertebrates.

gnathobase -- The expanded and hardened base of the appendage of many arthropods, notably trilobites, crustaceans, and marine cheliceramorphs. Used to macerate food items before ingestion.

gut (enteron) -- Body cavity formed between the mouth and anus in which food is digested and nutrients absorbed; it consists of the mouth, pharynx, esophagus, stomach, intestine, and anus, though some animals do not have all these regions.

head -- That part of the body at the "front" end, where the brain, mouth, and most sensory organs are located.

heart -- Muscular pump which circulates the blood.

intestine -- The portion of the digestive tract between the stomach and anus; it is the region where most of the nutrients and absorbed.

jaw -- Often loosely applied to any movable, toothed structures at or near the mouth of an animal, such as the scolecodonts of annelids. In vertebrates, the jaw is derived from the first gill arch.

jointed -- When stiff body parts are connected by a soft flexible region, the body is said to be jointed.

librigenae -- The "free cheeks"; separate, detachable portions of the trilobite cephalon. More info?

lophophore -- Complex ring of hollow tentacles used as a feeding organ. The tentacles are covered by cilia, which generate a current to bring food particles into the mouth. The structure is only found in the brachiopods, phoronids, and bryozoans. More info?

marsupial -- n. (adj.) A mammal whose young are born while still embryos, and must crawl into its mother’s external pouch (called the marsupium) to finish development.

mesoderm -- In animals with three tissue layers (i.e. all except sponges and cnidarians), the middle layer of tissue, between the ectoderm and the endoderm. In vertebrates, for instance, the mesoderm forms the skeleton, muscles, heart, spleen, and many other internal organs.

mesogloea -- Jellylike material between the outer ectoderm and the inner endoderm of cnidarians. May be very thin or may form a thick layer (as in many jellyfish).

mouth -- Front opening of the digestive tract, into which food is taken for digestion. In flatworms, the mouth is the only opening into the digestive cavity, and is located on the "belly" of the worm.

mucus -- Sticky secretion used variously for locomotion, lubication, or protection from foreign particles.

muscle -- Bundle of contractile cells which allow animals to move. Muscles must act against a skeleton to effect movement.

myotome -- Segment of the body formed by a region of muscle. The myotomes are an important feature for recognizing early chordates.

nematocyst -- Older name for a cnidocyst.

nerve -- A bundle of neurons, or nerve cells. More properly, it is a bundle of axons.

nerve cord -- Primary bundle of nerves in chordates, which connects the brain to the major muscles and organs of the body.

neuron -- A specialized cell that can react to stimuli and transmit impulses. A neuron consists of a body which contains the nucleus; dendrites, which are short branches off the body that receive incoming impulses; and a long axon which carries impulses away from the body and to the next neuron.

notochord -- Characteristic of chordates, the notochord is a stiff rod of tissue along the back of the body. In vertebrates, the backbone is deposited around the notochord and nerve cord.

organ -- Collection of tissues which performs a particular function or set of functions in an animal or plant's body. The heart, brain, and skin are three organs found in most animals. The leaf, stem, and root are three organs found in most plants. Organs are composed of tissues, and may be organized into larger organ systems.

organ system -- Collection of organs which have related roles in an organism's functioning. The nervous system, vascular system, and muscle system are all organ systems.

osculum -- The main opening through which filtered water is discharged. Found in sponges.

papilla(e) -- Cellular outgrowths. These look like little bumps or fingers on the surface of cells.

parapodia -- A sort of "false foot" formed by extension of the body cavity. Polychaetes and some insect larvae have parapodia in addition to their legs, and these provide extra help in locomotion.

pedipalps -- The second pair of appendages of cheliceromorphs. In many arachnids, such as spiders, the pedipalps are enlarged in the male and used for copulation.

pharyngeal slits -- Characteristic of chordates, pharyngeal slits are openings through which water is taken into the pharynx, or throat. In primitive chordates the pharyngeal slits are used to strain water and filter out food particles; in fishes they are modified for respiration. Most terrestrial vertebrates have pharyngeal slits only in the embryonic stage.

pharynx -- Cavity in the digestive tract just past the mouth itself. May be muscularized for sucking or swallowing in various animals.

phylum -- n. A category in the hierarchy of animal classification between class and kingdom; phyla- pl.

placenta -- n. In mammals, a tissue formed within the uterus through which nutrients are passed from the mother to the embryo (and later the fetus) and its wastes are removed; placental- n. (adj.) A mammal whose young form a placenta as they develop in the mother’s uterus.

pleurae -- In trilobites and other arthropods, pleurae are elongated flat outgrowths from each body segment, that overlie and protect the appendages.

pore -- Any opening into or through a tissue or body structure.

proboscis -- Elongated organ, usually associated with the mouth. The proboscis is an important feeding appendage in echiurans.

pygidium -- In trilobites, the posterior division of the body, formed by fusion of the telson with one or more posterior pleurae.

segmentation -- In many animals, the body is divided into repeated subunits called segments, such as those in centipedes, insects, and annelids. Segmentation is the state of having or developing a body plan in this way.

septum -- Partition which divides up a larger region into smaller ones, such as in the central body cavity of some anthozoa.

siphon -- Opening in molluscs or in urochordates which draws water into the body cavity. In many molluscs, the siphon may be used to expel water forcibly, providing a means of propulsion.

skeleton -- Support structure in animals, against which the force of muscles acts. Vertebrates have a skeleton of bone or cartilage; arthropods have one made of chitin; while many other invertebrates use a hydrostatic skeleton, which is merely an incompressible fluid-filled region of their body.

spicule -- Crystalline or mineral deposits found in sponges, sea cucumbers, or urochordates. They are structural components in many sponges, and may serve a protective function in other organisms.

spiracle -- In insects and some other terrestrial arthropods, a small opening through which air is taken into the tracheae. Insects have several spiracles, arranged along the sides of the abdomen.

spongocoel -- Central body cavity of sponges. More Info?

synapsid -- n. A vertebrate distinguished by a skull with one pair of openings in the sidebehind the eyes, e.g., mammals and their close relatives.

telson -- The last segment of the abdomen in many arthropods. May be flat and paddlelike, buttonlike, or long and spiny, as in the horseshoe crabs.

tentacles -- Appendages which are flexible, because they have no rigid skeleton. Cnidarians and molluscs are two kinds of orgnaisms which may have tentacles.

tetrapod -- n. A vertebrae that has (or whose close relatives have) four limbs with digits, not fins.

thorax -- In insects, the second body region, between the head and thorax. It is the region where the legs and wings are attached.

tissue -- A group of cells with a specific function in the body of an organism. Lung tissue, vascular tissues, and muscle tissue are all kinds of tissues found in some animals. Tissues are usually composed of nearly identical cells, and are often organized into larger units called organs.

tracheae -- Internal tubes through which air is taken for respiration. Vertebrates with lungs have a single trachea carrying air to the lungs, while insects and some other land-living arthropods have a complex network of tracheae carrying air from the spiracles to all parts of the body.

tube feet -- Extensions of the water-vascular system of echinoderms, protruding from the body and often ending in suckers. May be used for locomotion and/or for maintaining a tight grip on prey or on the bottom.

tubercle -- Any small rounded protrusion. In pycnogonids and some cheliceramorph arthropods, the central eyes are carried on a tubercle.

uniramious -- Among arthropods, uniramous refers to appendages that have only one branch. Insects, centipedes and millipedes, and their relatives are uniramous arthropods; land-living chelicerates such as scorpions, spiders,and mites are also uniramous but probably descended from ancestors with biramous appendages. Contrast with biramous.

vascular -- Refers to a network of tubes which distribute nutrients and remove wates from the tissues of the body. Large multicellular animals must rely on a vascular system to keep their cells nourished and alive.

vertebra -- A component of the vertebral column, or backbone, found in vertebrates.

zooxanthellae -- Symbiotic dinoflagellates in the genus Symbiodinium that live in the tissues of a number of marine invertebrates and protists, notably in many foraminiferans, cnidarians, and some mollusks.



BOTANY



adventitious roots -- A root that grows from somewhere other than the primary root, for example, roots that arise from stems or leaves.

alternation of generations -- Life cycle in which haploid and diploid generations alternate with each other.

anemophily -- Seed plants which are pollinated by wind are said to be anemophilous.

angiosperm -- n. A group of plants that produce seeds enclosed within an ovary, which may mature into a fruit; flowering plants.

anther -- The pollen producing tip of a stamen; part of a flower. More info?

antheridium -- The organ on a gametophyte plant which produces the sperm cells.

anthophyte -- A flowering plant, or any of its closest relatives, such as the Bennettitales, Gnetales, or Pentoxylales.

apical meristem -- Group of cells at the growing tip of a branch or root. It divides cells to create new tissues.

archegonium -- The organ on a gametophyte plant which produces the egg cell, and nurtures the young sporophyte.

axil -- The angle formed between a leaf stalk and the stem to which it is attached. In flowering plants, buds develop in the axils of leaves.

bipinnate -- Describing a pinnate leaf in which the leaflets themselves are further subdivided in a pinnate fashion.

bisporangiate -- When a flower or cone produces both megaspores and microspores, it is said to be bisporangiate. Most flowers are bisporangiate.

blade -- Any broad and flattened region of a plant or alga, which allows for increased photosynthetic surface area.

bract -- Any reduced leaf-like structure associated with a cone or flower.

bryophyte -- Plants in which the gametophyte generation is the larger, persistent phase; they generally lack conducting tissues. Bryophytes include the Hepaticophyta (liverworts), Anthocerotophyta (hornworts), and Bryophyta (mosses).

carpel -- A unit of the pistil; it is evolutionarily a modified leaf.

cataphyll -- In cycads, a scale-like modified leaf which protects the developing true leaves.

columella -- A small column of tissue which runs up through the center of a spore capsule. It is present in hornworts, mosses, and some rhyniophytes.

compound leaves -- n. Leaves with two or more leaflets attached to a single leaf stem.

cotyledon -- n. The "seed leaves" produced by the embryo of a seed plant that serve to absorb nutrients packaged in the seed, until the seedling is able to produce its first true leaves and begin photosynthesis; the number of cotyledons is a key feature for the identification of the two major groups of flowering plants.

elater -- A cell or part of a cell which assists in dispersing spores. The elaters change shape as they lose or acquire water, and they will then push against surrounding spores.

embryophyte -- Synonym for the Plantae, as here defined. It includes all green photosynthetic organisms which begin the development of the sporophyte generation within the archegonium.

enations -- Flaps of tissue such as those found on psilophytes.

endodermis -- Literally "inner skin", this is a layer of cells which surrounds the central core of vascular tissue, and which helps to regulate the flow of water and dissolved substances.

entomophily -- Seed plants which are pollinated by insects are said to be entomophilous.

epiphyte -- A plant which grows upon another plant. The epiphyte does not "eat" the plant on which it grows, but merely uses the plant for structural support, or as a way to get off the ground and into the canopy environment.

eustele -- When a plant's vascular tissue develops in discrete bundles, it is said to have a eustele. See also protostele and siphonostele.

fiber -- Elongated and thickened cell found in xylem tissue. It strengthens and supports the surrounding cells.

flower -- Collection of reproductive structures found in flowering plants. More info?

fruit -- In flowering plants, the structure which encloses the seeds. True fruits develop from the ovary wall, such as bananas and tomatoes, though not all fruits are edible, such as the dry pods of milkweed or the winged fruits of the maple.

grain -- (1) The texture of wood, produced by the kinds of xylem cells present. (2) The fruit of a member of the grasses.

guard cells -- Pair of cells which surround a stomate and regulate its size by altering their shape.

gymnosperm -- n. A plant that produces seeds, which are not enclosed; includes any seed plant that does not produce flowers.

gynostemium -- The central reproductive stalk of an orchid, which consists of a stamen and pistil fused together.

habit -- The general growth pattern of a plant. A plant's habit may be described as creeping, trees, shrubs, vines, etc.

herb -- Generally any plant which does not produce wood, and is therefore not as large as a tree or shrub, is considered to be an herb.

heterosporangiate -- Producing two different kinds of sporangia, specifically microsporangia and megasporangia. Compare with heterosporous.

heterosporous -- Producing two different sizes or kinds of spores. These may come from the same or different sporangia, and may produce similar or different gametophytes. Contrast with homosporous, and compare with heterosporangiate.

holdfast -- Anchoring base of an alga.

homosporous -- Producing only one size or kind of spore. Contrast with heterosporous.

hypha -- n.Threadlike filaments that form the mycelium (body) of a fungus; hyphae- pl.

inflorescence -- A cluster of flowers.

internode -- The region of a stem between two nodes, when there is no branching of the vascular tissue.

lamina -- Any broad and flattened region of a plant or alga, which allows for increased photosynthetic surface area.

leaf -- An organ found in most vascular plants; it consists of a flat lamina (blade) and a petiole (stalk). Many flowering plants have additionally a pair of small stipules near the base of the petiole.

leaf trace -- The strand of vascular tissue which connects the leaf veins to the central vascular system of the stem.

leaflet -- In a compound leaf, the individual blades are called leaflets.

magnoliid -- Any member of the basal assemblage of flowering plants.

mannoxylic -- Wood in which there is a great deal of parenchyma tissue among the xylem is called mannoxylic. Cycads and pteridosperms have mannoxylic wood. Contrast with pycnoxylic.

megaspore -- In plants which are heterosporous, the larger kind of spore is called a megaspore; it usually germinates into a female (egg-producing) gametophyte. Contrast with microspore.

meristem -- Group of undifferentiated cells from which new tissues are produced. Most plants have apical meristems which give rise to the primary tissues of plants, and some have secondary meristems which add wood or bark.

merophytes -- Group of cells which have all been produced from the same initial cell. Leaves and stems in particular are often built from specific patterns of merophytes.

microphyll -- A kind of leaf, specifically one which has a single, unbranched vein in it. Microphylls are only found in the lycophytes.

microspore -- In plants which are heterosporous, the smaller kind of spore is called a microspore; it usually germinates into a male (sperm-producing) gametophyte. Contrast with megaspore.

mycorrhizae -- Symbiotic association between a fungus and the roots or rhizoids of a plant. More info?

node -- The region of a stem between two internodes, where there is branching of the vascular tissue into leaves or other appendages.

ovary -- In flowering plants, the part of the flower which encloses the ovules. When the ovary matures, it becomes the fruit.

ovule -- In seed plants, the structure which gives rise to the seed.

paleoherb -- Any member of a group of basal flowering herbs which may be the closest relatives of the monocots. They include the water lilies, Piperales, and Aristolochiales.

parenchyma -- A generalized cell or tissue in a plant. These cells may manufacture or store food, and can often divide or differentiate into other kinds of cells.

perennial -- A plant which continues to grow after it has reproduced, usually meaning that it lives for several years.

perianth -- The sepals and petals of a flower are together called the perianth; literally "around the anthers". More info?

peristome -- A set of cells or cell parts which surround the opening of a moss sporangium. In many mosses, they are sensitive to humidity, and will alter their shape to aid in spore dispersal.

petal -- One of the outer appendages of a flower, located between the outer sepals and the stamens. Petals often display bright colors that serve to attract pollinators. More info?

phloem -- Nutrient-conducting tissue of vascular plants.

phragmoplast -- The cell plate formed during cell division.

phytomelanin -- a papery "sooty" black layer over the seed of plants in the Asparagales, which includes agaves, aloes, onions and hyacinths. It is an important character for defining the group.

pinnately compound -- Leaves which are divided up like a feather are said to be pinnately compound.

pistil -- The central set of organs in a flower; it is composed of one or more carpels. More info?

pith -- To severely damage the brain of a frog, also any central region of parenchyma tissue within a plant stem.

pits -- Thin regions of the cell wall in xylem conducting cells. Their structure is an important characteristic for recognizing different kinds of wood.

plasmodesmata -- Cytoplasmic connections between neighboring cells in plant tissues.

platyspermic -- Having seeds which are flattened and disc-like. Contrast with radiospermic.

plicate -- Folded like a paper fan, as in the leaves of palms, cyclanthoids, and some orchids.

pollen -- The microspore of seed plants.

pollen tube -- In seed plants, the extension of the male gametophyte as it emerges from the pollen grain in search of the female gametophyte.

pollination -- Process of transferring the pollen from its place of production to the place where the egg cell is produced. This may be accomplished by the use of wind, water, insects, birds, bats, or other means. Pollination is usually followed by fertilization, in which sperm are released from the pollen grain to unite with the egg cell.

pollinia -- A mass of fused pollen produced by many orchids.

protostele -- When a plant's vascular tissue develops in a solid central bundle, it is said to have a protostele. See also siphonostele and eustele.

pseudoelaters -- Moisture-sensitive cells produced in the sporangium of hornworts.

pteridophyte -- Plant in which the sporophyte generation is the larger phase and in which the gametophyte lives an existence independent of its parent sporophyte. Pteridophytes are almost all vascular plants, and include the lycophytes, trimerophytes, sphenophytes, and ferns.

pteridosperm -- An extinct group of seed plants which bore fern-like leaves.

pycnoxylic -- Wood in which there is little or no parenchyma tissue among the xylem is called pycnoxylic. Conifers and flowering plants have pycnoxylic wood. Contrast with mannoxylic.

radicle -- The end of a plant embryo which gives rise to the first root.

radiospermic -- Having seeds which are round or ovoid. Contrast with platyspermic.

reticulate -- Interconnecting, like a network.

rhizoid -- n. A cellular outgrowth of a plant that usually aids in anchoring to the surface and increasing surface area to acquire water or nutrients; found in mosses, liverworts, and hornworts.

rhizome -- n. A horizontal underground stem, such as found in many ferns, where only the leaves may stick up into the air; sphenophytes (horsetails and their relatives) spread via rhizomes, but also produce erect stems.

root -- Usually the below ground portion of a plant. Contrast with shoot.

rosette -- A series of whorls of leaves or leaf-like structure produced at the base of the stem, just above the ground.

secondary growth -- Growth in a plant which does not occur at the tips of the stems or roots. Secondary growth produces wood and bark in seed plants.

sepal -- The outermost structures of a flower. More info?

shoot -- Usually, the above ground portion of a plant, bearing the leaves. Contrast with root.

siphonostele -- When a plant's vascular tissue develops as a central cylinder, it is said to have a siphonostele. See also protostele and eustele.

spermatophyte -- A seed plant.

sporangiophore -- A stalk to which sporangia are attached.

sporangium -- A chamber inside of which spores are produced through meiosis.

sporophyll -- Any leaf which bears sporangia is called a sporophyll.

stamen -- Part of a flower, the tip of which produces pollen and is called the anther. More info?

stigma -- The sticky tip of a pistil. Or, the dense region of pigments found in many photosynthetic protists which is sensitive to light, and thus functions somewhat like a miniature eye.More info?

stipe -- A scientific term for "stalk".

stipules -- Paired appendages found at the base of the leaves of many flowering plants.

stomata -- Openings in the epidermis of a stem or leaf of a plant which permit gas exchange with the air. In general, all plants except liverworts have stomata in their sporophyte stage.

streptophytes -- The clade consisting of the plants plus their closest relatives, the charophytes.

strobilus -- A tightly clustered group of sporophylls arranged on a central stalk; commonly termed a "cone" or "flower".

style -- The narrow stalk of the pistil, located above the ovary but below the stigma.

synangium -- A cluster of sporangia which have become fused in development.

tepal -- When the sepals and petals of a flower are indistinguishable, they are referred to as tepals. Tepals are common in many groups of monocots. More info?

thalloid -- Plants which have no roots, stems, or leaves are called thalloid, such as liverworts and hornworts.

tracheophyte -- Any member of the clade of plants possessing vascular tissue; a vascular plant.

tree -- Any tall plant, including many conifers and flowering plants, as well as extinct lycophytes and sphenophytes.

tuber -- An underground stem which has been modified for storage of nutrients, such as a potato.

turgor pressure -- Force exerted outward on a cell wall by the water contained in the cell. This force gives the plant rigidity, and may help to keep it erect. More info?

vegetative growth -- Growth of a plant by division of cells, without sexual reproduction.

venation -- The arrangement and pattern of veins in a leaf.

whorl -- An arrangement of appendages, such as branches or leaves, such that all are equally spaced around the stem at the same point, much like the spokes of a wheel or the ribs of an umbrella.

wood -- A secondary tissue found in seed plants which consists largely of xylem tissue.

xylem -- Water-conducting tissue of vascular plants.

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