charge, it undergoes a technical screening generally
referred to as a completeness review and is evaluated to
ensure that sufficient data and information have been
submitted in each area to justify the filing.
Neanderthal An early type of human (Homo sapiens
neanderthalensis) that evolved in Europe about
250,000 years ago and spread to the Middle East. By
the last Ice Age, fossil remains reveal a people with
faces that had distinct eyebrow ridges, flattened noses,
and heavy jaws. Their bodies were short and well built,
all features that may have been adaptations to the cold
conditions of the last Ice Age. They appear to have sur-
vived in parts of Europe until some time after 30,000
years ago and lived for a time side by side with present-
day-type humans.
See alsoCRO-MAGNON.
Nearctic Biogeographic region including arctic, tem-
perate, and subtropical North America, reaching south
to the northern border of the tropical rain forest in
Mexico.
necrosis Condition describing dead plant or animal
tissue due to injury, disease, or treatment.
negative feedback Describes a situation where an
action produces a consequence that affects, or feeds
back on, the action. In negative feedback, the conse-
quence stops or reverses the action. In biology, for
example, the stopping of the synthesis of an enzyme by
the accumulation of the products of the enzyme-medi-
ated reaction is a negative feedback reaction.
nematocyst Asmall harpoonlike structure or sting-
ing capsule located in a cnidoblast that coils out; used
by coelenterates (e.g., jellyfish) to deliver a toxin to
stun or kill its prey.
nematode Roundworms, simple worms of micro-
scopic size, consisting of an elongate stomach with a
reproduction system inside a resistant outer cuticle or
outer skin. Most feed on bacteria, fungi, and other soil
organisms; however, some are parasitic, obtaining their
nutrients from animals (dog heartworm), humans (pin-
worm), and plants. There are 15,000 known species.
They are related to the arthropods and are part of a
newly recognized group, the Ecdysozoa, which includes
the arthropods and nematodes.neo-Darwinism SeeDARWINISM.neoteny The retention of immature features in the
adult stage.
See alsoPAEDOGENESIS.Neotropic Geographical region including the West
Indies, South America, and Central America north to
the northern edge of tropical forests in Mexico.nephron A microscopic coiled tubular structure
found in each kidney that consists of a GLOMERULUS, a
mass of capillaries that filters the blood, and a renal
tubule that produces urine for elimination. Each kidney
is estimated to contain about 1 million nephrons.neritic zone The part of ocean that covers all water
to a depth of 600 feet. The entire ocean is called the
pelagic zone and is divided into two major zones, the
oceanic and neritic. The oceanic covers depths below
600 feet, while the neritic zone covers depths from 0 to
600 feet.net primary productivity(NPP) The primary pro-
ductivity of any community is the total amount of
biomass that is produced through photosynthesis per
unit area and time by the primary producers—plants. It
is usually expressed in units of energy or in units of dry
organic matter. The annual primary production around
the world is more than 240 billion metric tons of dry
plant biomass. Productivity is further divided into gross
and net primary productivity. Gross primary productiv-
ity (GPP) is the total energy fixed by plants in a com-
munity through photosynthesis. However, a portion of242 Neanderthal