Lion Science Scientia non habet inimicum nisp ignorantem		Northwest High School Jefferson County, MO

Obligate aerobes - Bacteria that cannot survive without atmospheric oxygen.
Obligate anaerobes - Bacteria that cannot survive in the presence of atmospheric oxygen.
Occipital lobe - Part of the brain controling vision.
Ockham's razor - If there are two possible explanations for something, and one explanation is simpler than the other, the simpler explanation should be preferred.
Octet Rule - The maximum number of electrons in the outer electron energy level of an atom is eight.
Ohm - A measure of the resistance to the flow of electric current.
Ohm's Law - The current in a wire is equal to voltage divided by resistance.
Olfactory lobes - The part of the brain of lower vertebrates that respond to smell.
Oligotrophic - Refers to an environment with a low nutrient content.
Omnivores - Consumers that eat both plants and animals.
Oncogene - A gene that causes cancer or other uncontrolled cell division.
Opaque - Light does not pass through a material.
Open circulatory system - A system in which the blood is not always contained in vessels.
Operculum - The gill cover of a fish.
Optic lobes - The part of the brain of lower vertebrates responsible for processing visual and auditory information.
Optimal foraging - Behaviors that bring a predator the maximum net food energy gain.
Orbital - An area in a sublevel that can hold up to two electrons.
Orbital-filling diagram - A way to represent the spin of electrons in the outer energy level of an atom.
Orbital motion - One object orbiting another has both a horizontal and vertical velocity.
Organ - A group of tissues with a common function.
Organism - Any complete living thing.
Organic acids - Organic compounds containing the carboxyl group.
Origin - The point of stationary attachment of a skeletal muscle.
Osmoregulation - The removing of excess water in freshwater species and conserving of water in marine and terrestrial species.
Osmosis - The movement of particles through a membrane from an area of high concentration to an area of low concentration.
Ossification - The gradual transition from a soft template to bone.
Ostwald process - The chemical process used for the commercial production of nitric acid.
Output - Changes which exit a system and which activate/modify a process.
Ovary - The female structure in both plants and animals that produces egg cells.
Oviparous - Eggs hatch outside the body of the female.
Ovoviviparous - Fertilized eggs carried inside female body until hatched.
Ovules - Structures in plant ovaries that produce an egg cell.
Oxidation - The combination of oxygen with other substances; the loss of electrons from an atom or ion.
Oxidation number - The number of electrons gained or lost by an atom to comply with the octet rule; valance.
Oxidizer - A chemical that promotes combustion in other materials.
Oxidizing agent - The reactant that gains electrons during a chemical reaction.
Oxygen - The most abundant element in the earth's crust and in your body.
Ozone - A relatively unstable molecule composed of three oxygen atoms, O₃.

Panicle - An elongated inflorencence with branched branches along the central axis.
Parallel circuit - An electric circuit with more than one path for the electrons to take.
Paraphyletic - A phylogenetic group of animals including an ancestral form and some of its recognized descendant species.
Parasitism - A symbiotic relationship in which one organism obtains its nutrition from another organism to the harm of the host.
Paratype - Any specimen, other than the holotype, referred to in the original publication of the taxon.
Parenchyma - Large, loosely packed, rectangular plant cells with thin cell walls.
Parietal lobe - Part of the brain that controls the feeling of touch, pressure, temperature, and pain
Pascal - A unit of pressure equal to one Newton/m².
Pauli Exclusion Principle - No two electrons in an atom have the same set of four quantum numbers.
Pectoral girdle - Bone structure supporting the forelimbs.
Pedigree - A history of the traits of several generations.
Pedipalps - Appendages in arachnids that hold and chew food.
Peduncle - The main supporting stalk of an inflorescence.
Pelagic zone - The open ocean.
Pelvic girdle - Bone structure supporting the hindlimbs.
Penicillin - An antibiotic that interferes with cell wall synthesis in bacteria.
Pentadactyl - Having five digits.
Pepo - A fleshy fruit with a leathery-skin and one carpel with 3 lines of ovules.
Percentage composition - The percentage of the formula mass represented by each element in a compound.
Perennials - Herbaceous plants that live for an indefinite period of years, and bloom every year after the first.
Perfect flower - A flower with both stamens and pistils.
Perianth - A flower's sepals and petals together.
Pericarp - The plant fruit wall.
Perigynous - A flower with the ovary situated within (and free from) a floral cup or hypanthium.
Period - A horizontal row on the Periodic Table.
Periodic Law - The physical and chemical properties of the elements are periodic functions of their atomic numbers.
Periodic table - A chart of the known elements arranged by increasing atomic number.
Peripheral nervous system - Nerves that connect the central nervous system to the rest of the body.
Peristalsis - Muscular contractions that push food through parts of the alimentary canal.
Permanent magnets - Materials that are hard to magnetize, but tend to stay magnetized.
Petiole - The leaf stalk connecting the leaf blade to the plant stem.
pH - A measure of the H₃O ⁺ concentration in a solution.
Pharynx - A muscular organ at the back of the throat.
Phase change - The physical change of matter from one state to another because of particle motion.
Phase diagram - A graph showing the phases of a substance as they relate to temperature and pressure.
Phenolphthalein - A common liquid acid/base indicator.
Phenotype - The external appearance of an organism.
Pheromones - A type of chemical messenger produced by some organisms.
Phloem - Straw-like tubes conducting food downward in a plant.
Photoautotrophs - Organisms that use sunlight as a source of energy.
Photoelectric effect - The production of electrons by the photons of light.
Photon - The massless, electromagnetic force carrier.
Photoperiodism - Plant response to changes in the length of days and nights.
Photoreceptors - Function as eyes in earthworms and some other organisms by detecting differences in light intensity.
Photosynthesis - The chemical process by which green plants use light energy to produce food.
Photosynthetic unit - A unit of several hundred antenna pigment molecules plus a reaction center.
Phototropism - A plant growth response to light.
Phylogenetic tree - A hypothetical model of an animal's evolutionary history.
Phylogeny - Inferred evolutionary relationships amoung organisms.
Physical digestion - Breaking large pieces of food into smaller ones.
Physical property - Any characteristic of a material that can be observed without changing the substances that make up the material.
Physical state symbols - Letters written as subscripts in a chemical equation to indicate physical state.
Physics - The study of the relationships between matter and energy.
Phytoplankton - Microscopic plants and animals that are the foundation of aquatic food chains.
Pia mater - The inner layer of the three protective tissues of the brain, consisting of blood vessels and nerves.
Pigments - Chemicals that reflect certain wavelengths of light and absorb the others.
Pion - A subatomic particle composed of a quark and an antiquark.
Placenta - A region of attachment of seeds on a plant fruit wall; the nutritive sac surrounding a developing mammal embryo.
Pili - Short, hairlike protein structures on the surface of some bacteria that help them stick to host cells.
Pion - A particle composed of quarks found only in cosmic rays.
Pioneer species - The first species to colonize a new haitat.
Pipet - A piece of glassware used for exact measurement of liquid volumes.
Pistil - The female organ of a flower.
Pitch - Refers to the frequency of sound waves.
Pith - A central core of parenchyma tissue in a herbaceous plant stem.
Planck's constant - A fundamental constant, denoted by h, which relates the energy of a photon to its frequency.
Plant - A multicellular, eukaryotic, autotrophic organism.
Plasma - The straw-colored liquid part of blood; a special form of gas that has a charge.
Plasmid - A ring of DNA.
Plastid - Pigment producing organelle in cells.
Plastron - The ventral shell of turtle-like animals.
Platelets - The part of the blood involved in clotting.
pOH - A measure of the OH ^- concentration in a solution.
Point defect - A change in a crystal unit cell.
Polar molecule - A molecule whose charge is not equally balanced over its surface.
Polarized light - Light with all waves vibrating in the same plane.
Pollen grain - The male gametophyte of Gymnosperms and Angiosperms.
Pollen tube - A pathway for the sperm cells to reach the ovule of a flower.
Pollination - The transfer of pollen from anther to stigma.
Pollution - Impurities producing an undesirable change in an ecosystem.
Polyatomic ion - A group of covalently bonded atoms with an overall charge.
Polygenic trait - A trait controled by two or more genes.
Polymer - A very large molecule made up of small, repeating units.
Polyp - A vase-shaped body form, specialized for a sessile life.
Polypeptide - A very long chain of bonded amino acids.
Polyphyletic - A phylogenetic group of animals including the descendants of more than one ancestral form.
Polyprotic acid - An acid with more than one ionizable hydrogen.
Polysaccharide - A complex molecule composed of three or more monosaccharides.
Pome - A fleshy accessory fruit with a cartilaginous core.
Pons - Part of the brain stem that relays signals between the cerebrum and cerebellum.
Population - A group of interacting individuals of the same species.
Portfolio - A collection of student work.
Posterior - Refers to the back end of an organism.
Potential energy - Energy stored in an object due to its position.
Power - The rate at which work is done.
PPE - Personal protective equipment.
Precipitate - An insoluble substance that crystallizes out of solution.
Precision - Refers to how close a set of measurements for a quantity are to one another.
Precocial - Birds that lay many eggs and incubate them for a long period.
Predation - Refers to the relationship between a predator and its prey.
Pressure - A force that acts over a certain area; the force of particles striking a surface.
Prefix - an affix placed before a base word that modifies the base meaning, i.e., milli-, centi-, deci-.
Primary colors - The three colors of light that can be mixed to produce white light.
Primary consumers - Herbivores that eat only primary producers.
Primary growth - The growth in length of a plant stem produced by the apical meristem.
Primary producers - Green plants, the foundation of all ecosystems.
Primary root - The first root to grow out of a seed.
Principle of Priority - The first validly published name of a species, or other taxon, becomes its accepted scientific name.
Prism - An object that forms a spectrum as light passes through it.
Producers - Autotrophic organisms that use solar or chemical energy to produce all the organic nutrients for an ecosystem.
Productivity - The rate of assimilation of chemical energy into organic matter within an ecosystem.
Proglottids - The body segments of a tapeworm.
Projectile - Any object thrown in the air.
Prokaryotes - Cells with no nucleus or organells with membranes.
Pronation - Rotating the palm of the hand downward.
Prophage - A segment of virus DNA that becomes part of the host cell's genome.
Prophase - The first stage of mitosis, when DNA condenses into chromosomes.
Protective coloration - The coloring of organisms to match their environment.
Protein - An organic compound composed of carbon, hydrogen, oxygen, and nitrogen.
Protocells - Cell-like organisms believed to the the ancestors of organized cells.
Proton - A positive subatomic particle found in the nucleus of atoms.
Proto-oncogene - A gene that, when altered by mutation, becomes an oncogene.
Protozoa - Single-celled microorganisms noted for their ability to move independently.
Pseudopods - Cytoplasmic streaming used for locomotion in amoeba.
Puberty - The physical and psychological changes caused by sex hormones.
Pulley - A belt, rope, or chain wrapped around a wheel.
Pulmonary - Refers to the lungs.
Punnett square - A chart drawn to determine the probable results of a genetic cross.
Pupa - A stage of metamorphosis in which a larva changes into the adult form.
Pupil - The opening through which light enters the eye
Pure science - The gathering of information that adds to the body of human knowledge.
Purines - The double carbon ring nitrogen bases in DNA and RNA.
PVC - Polyvinyl chloride, a plastic used for packaging and pipes.
Pyloric sphincter - The valve at the bottom of the stomach that regulates the passage of food.
Pyrimidines - The single carbon ring nitrogen bases in DNA and RNA.
Pyrophoric material - A substance that will ignite spontaneously in air at a temperature below 130 ^oF.