Download narcotic natural resources natural selection nebula negative

narcotic
type of pain-relief drug that affects the central nervous system.
natural resources
Resources provided by Earth, including air, water, land, all
living organisms, nutrients, rocks, and minerals.
natural selection
mechanism for change in popula tions; occurs when organisms
with favorable variations survive, reproduce, and pass their
variations to the next generation.
nebula
Large cloud of interstellar gas and dust that collapses on itself,
due to its own gravity, and forms a hot, condensed object that
will become a new star.
negative feedback system
internal feedback mechanism in which a substance is fed back
to inhibit the original include hormones in the endocrine system.
nephron
individual filtering unit of the kidneys.
net force
The vector sum of all the forces on an object.
neurons
basic unit of structure and function in the nervous system;
conducts impulses throughout the nervous system; composed of
dendrites, a cell body, and an axon.
neurotransmitters
chemicals released from an axon that diffuse across a synapse
to the next neuron’s dendrites to initiate a new impulse.
neutral
An atom whose positively charged nucleus exactly balances the
negative charge of the surrounding electrons.
neutron
A neutral subatomic particle in an atom’s nucleus that has a
mass nearly equal to that of a proton.
neutron star
Collapsed, dense core of a star that forms quickly while its
outer layers are falling inward, has a radius of about 10 km, a
mass 1.5 to 3 times that of the Sun, and contains only neutrons.
Newton’s first law
States that an object at rest will remain at rest, and a moving
object will continue moving in a straight line with constant
speed, if and only if the net force acting on that object is zero.
Newton’s second law
States that the acceleration of an object is proportional to the net
force and inversely proportional to the mass of the object being
accelerated.
Newton’s second law for
rotational motion
States that the angular acceleration of an object is directly
proportional to the net torque and inversely proportional to the
moment of inertia.
Newton’s third law
States that all forces come in pairs and that the two forces in a
pair act on different objects and are equal in strength and
opposite in direction.
niche
role or position a species has in its environment; includes all
biotic and abiotic interactions as an animal meets its needs for
survival and reproduction.
nitrogen fixation
The process that converts nitrogen gas into biologically useful
nitrates.
noble gas
An extremely unreactive group 8A element.
node
The stationary point where two equal wave pulses meet and are
in the same location, having a displacement of zero.
nonmetals
Elements that are generally gases or dull, brittle solids that are
poor conductors of heat and electricity.
nonrenewable resource
Resource that exists in Earth’s crust in a fixed amount and can
be replaced only by geological, physical, or chemical processes
that take hundreds of millions of years.
normal
The line in a ray diagram that shows the diretion of the barrier
and is drawn at a right angle, or perpendicular, to the barrier.
normal force
The perpendicular contact force exerted by a surface on another
object.
normals
Standard values for a location, including rainfall, wind speed,
and temperatures, based on meteorological records compiled for
at least 30 years.
nuclear equation A type of
equation that shows the atomic
number and mass number of
the particles involved.
nuclear reaction
A reaction that involves a change in the nucleus of an atom.
nucleic acid
A nitrogen-containing biological polymer that is involved in
the storage and transmission of genetic information.
nucleotides
subunits of nucleic acid formed from a simple sugar, a
phosphate group, and a nitrogenous base.
nucleus
The extremely small, positively charged, dense center of an
atom that contains positively charged protons, neutral neutrons,
and is surrounded by empty space through which one or more
negatively charged electrons move.
nymph
stage of incomplete metamorphosis where an insect hatching
from an egg has the same general appearance as the adult insect
but is smaller and sexually immature.