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96 Cards in this Set

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obligate aerobe aorganism that needs oxygen in order to live
obligate aerobe
obligate anaerobe an organism that needs the absence of oxygen in order to live
obligate anaerobe
observation the process of obtaining information by using the senses; the information obtained by using the senses
observation
occluded front a front that forms when a cold air mass overtakes a warm air mass and lifts the warm air mass off the ground and over another air mass
occluded front
ocean current a movement of ocean water that follows a regular pattern
ocean current
ocean floor the surface of the ocean basin
ocean floor
ocean floorthe 7 to 10 km thick layer of sediment and igneous rock that makes up the ocean floor
ocean floor
oceanography the scientific study of the ocean, including the properties and movements of ocean water, the characteristics of the ocean floor, and the organisms that live in the ocean
oceanography
ocean thermal energy conversion the use of temperature differences in ocean water to produce electricity (abbreviation, OTEC)
ocean thermal energy conversion
ocean trench a long, narrow, and steep depression on the ocean floor that forms as when one tectonic plate subducts beneath another plate; trenches run parallel to volcanic island chains or to the coastlines of continents; also called a trench or a deep-ocean trench
ocean trench
octane number a measure of a fuel’s burning efficiency and antiknock properties
octane number
octet rule a concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty valence shells or full valence shells of eight electrons
octet rule
oil reserves oil deposits that are discovered and are in commercial production
oil reserves
olfactory bulb the part of the brain that is found at the end of the olfactory nerve and that serves as the center of the sense of smell in vertebrates
olfactory bulb
olfactory cell one of the nerve cells that produce the sensation of smell
olfactory cell
olfactory nerve the nerve that carries impulses from the olfactory receptors to the brain
olfactory nerve
a cell found in the nasal passages that is stimulated by certain substances, produces nerve impulses, and gives rise to the sense of smell
olfactory receptor
oligotrophic lake a lake that lacks plant nutrients and that has a lot of oxygen dissolved in its lower layer
oligotrophic lake
omnivore an organism that eats both plants and animals
omnivore
oncogene a gene that induces cancer, or uncontrolled cell proliferation
oncogene
oogenesis the production, growth, and maturation of an egg, or ovum
oogenesis
oogonium a single-celled gametangium (female sex organ) in some algae and fungi
oogonium
Oort cloud a spherical region that surrounds the solar system, that extends from just beyond Pluto's orbit to almost halfway to the nearest star, and that contains trillions of comets
Oort cloud
ooze a soft mud at the bottom of a lake, river, or estuary
ooze
opaque describes an object that is not transparent or translucent; a material through which light cannot pass
opaque
open circulatory system a type of circulatory system in which the circulatory fluid is not contained entirely within vessels; a heart pumps fluid through vessels that empty into spaces called sinuses
open circulatory system
open cluster a group of stars that are close together relative to surrounding stars
open cluster
open-pit mining a method of mining that is used to remove ores and minerals near the surface and in which the ore is broken and loaded after the waste is removed
open-pit mining
open system a system that can exchange both matter and energy with its surroundings
open system
open-water zonethe zone of a lake or pond that extends from the littoral zone out across the top of the water and that is only as deep as light can reach through the water
open-water zone
operating system the software that controls a computer's activities
operating system
operator a short sequence of viral or bacterial DNA to which a repressor binds to prevent transcription (mRNA synthesis) of the adjacent gene in an operon
operator
operculum in fish, a hard plate that is attached to each side of the head, that covers gills, and that is open at the rear
operculum
operon a unit of gene regulation and transcription in bacterial DNA that consists of a promoter, an operator, and one or more structural genes
operon
opportunistic infection an infection caused by a microorganism that normally does not cause disease but that becomes pathogenic if the patient's immune system is weakened
opportunistic infection
optical fiber a transparent thread of plastic or glass that transmits light
optical fiber
optic nerve the nerve that connects the retina of the eye to the brain and that transmits impulses that contribute to the sense of sight
optic nerve
oral groove a depressed region around the mouth of some ciliate protozoans, such as Paramecium
oral groove
oral surface the surface of a radially symmetrical animal, such as an echinoderm, on which the mouth is located
oral surface
orbit the path that a body follows as it travels around another body in space
orbit
orbital a region in an atom where there is a high probability of finding electrons
orbital
orbital period the time required for a body to complete a single orbit
orbital period
orbital velocity the speed and direction that an object must have to remain in an orbit
orbital velocity
order in chemistry, a classification of chemical reactions that depends on the number of molecules that appear to enter into the reaction
order
order the taxonomic category below the class and above the family
order
order numberthe number assigned to interference fringes relative to the central bright fringe
order number
ore a natural material whose concentration of economically valuable minerals is high enough for the material to be mined profitably
ore
ore mineral a mineral that contains one or more elements of economic value
ore mineral
organ a collection of tissues that carry out a specialized function of the body
ore mineral
organelle one of the small bodies that are found in the cytoplasm of a cell and that are specialized to perform a specific function
organelle
organic compound a covalently bonded compound that contains carbon, excluding carbonates and oxides
organic compound
sedimentary rock that forms from the remains of plants or animals
organic sedimentary rock
organism a living thing; anything that can carry out life processes independently
organism
organ of Corti in the ear, a structure that is located in the cochlea and that contains hair cells that are the sensory receptors for hearing
organ of Corti
organ system a group of organs that work together to perform body functions
organ system
origin in anatomy, the point at which a muscle attaches to a stationary bone
origin
ornithologist a person who specializes in the scientific study of birds
ornithologist
osculum an opening in a sponge's body through which water exits
osculum
osmosis the diffusion of water or another solvent from a more dilute solution (of a solute) to a more concentrated solution (of the solute) through a membrane that is permeable to the solvent
osmosis
osmotic pressure the external pressure that must be applied to stop osmosis
osmotic pressure
ossicle one of the small, calcium carbonate plates that make up the endoskeleton of an echinoderm
ossicle
ossification the process by which cartilage is converted into bone
ossification
osteoarthritisadegenerative joint disease
osteoarthritis
osteocyte a bone cell
osteocyte
ostium one of the small openings in a sponge’s body through which water enters
ostium
outcrop an area of exposed rock
outcrop
outer core the liquid layer of the Earth’s core that lies beneath the mantle and surrounds the inner core
outer core
outer ear the part of the ear that collects sound vibrations
outer ear
outwash plain a broad sheet of sand and gravel deposited in front of a glacier by meltwater streams
outwash plain
oval window the membrane that separates the middle ear from the inner ear
oval window
ovarian cycle a series of hormone-induced changes in which the ovaries prepare and release a mature ovum each month
ovarian cycle
ovary in the female reproductive system of animals, an organ that produces eggs
ovary
ovaryin flowering plants, the lower part of a pistil that produces eggs in ovules
ovary
overgrazing the depletion of vegetation due to the continuous feeding of too many animals
overgrazing
overharvesting catching or removing from a population more organisms than the population can replace
overharvesting
overpopulationa condition that occurs when the number of individuals within an environment becomes so large that there are not enough resources to support them all
overpopulation
oviduct the tube that leads from an ovary to the uterus
oviduct
oviparous describes organisms that produce eggs that develop and hatch outside the body of the mother
oviparous
ovipositor in many female insects, a structure that is at the end of the abdomen and that is used to lay eggs
ovipositor
ovoviviparous describes organisms that produce eggs that develop and hatch inside the body of the mother
ovoviviparous
ovulation the release of an ovum from a follicle of the ovary
ovulation
ovule a structure in the ovary of a seed plant that contains an embryo sac and that develops into a seed after fertilization
ovule
ovum a mature egg cell
ovum
oxbow lake a lake that forms when a stream cuts a new channel across the narrow neck of a meander
oxbow lake
oxidation a reaction that removes one or more electrons from a substance such that the substance's valence or oxidation state increases; in geology, the process by which a metallic element combines with oxygen
oxidation
oxidation number the number of electrons that must be added to or removed from an atom in a combined state to convert the atom into the elemental form
oxidation number
oxidation reactioa chemical reaction in which a reactant loses one or more electrons such that the reactant becomes more positive in charge
oxidation reaction
reaction oxidation-reductionany chemical change in which one species is oxidized (loses electrons) and another species is reduced (gains electrons); also called redox reaction
reaction oxidation-reduction
oxidation state the condition of an atom expressed by the number of electrons that the atom needs to reach its elemental form
oxidation state
oxidized describes an element that has lost electrons and that has increased its oxidation number
oxidized
oxidizing agentthe substance that gains electrons in an oxidation-reduction reaction and that is reduced
oxidizing agent
oxygen debt the extra oxygen taken in by the body while recovering from exercise
oxygen debt
oxytocin a hormone that stimulates milk production and uterine contractions
oxytocin
ozone a gas molecule that is made up of three oxygen atoms
ozone
ozone hole a thinning of stratospheric ozone that occurs over the poles during the spring
ozone hole
ozone layer the layer of the atmosphere at an altitude of 15 to 40 km in which ozone absorbs ultraviolet solar radiation
ozone layer