Glossary ❮ 331plasmodium This word has two meanings in this
book. It can be the causative agent of malaria, or it
can be the clumped unicellular mass that fungi
form under certain feeding conditions.
plasmolysis The shriveling of the cytoplasm of a
cell in response to loss of water in hypertonic
surroundings.
plateletBlood cell involved in the clotting of blood.
pleiotropy A single gene has multiple effects on an
organism.
PNSSeeperipheral nervous system.
polar A molecule that has an unequal distribution of
charge, which creates a positive and a negative side
to the molecule.
polar body Castaway cell produced during female
gamete formation that contains only genetic
information.
pollenSperm-bearing male gametophyte of gymno-
sperms and angiosperms.
polygenic traitsTraits that are affected by more
than one gene (e.g., eye color).
polymerase chain reaction Technique used to
create large amounts of a DNA sequence in a short
amount of time.
polyp Cylinder-shaped cnidarian that lives attached
to a surface (e.g., sea anemone).
polyploidy A condition in which an individual
has more than the normal number of sets of
chromosomes.
polysaccharide A carbohydrate usually composed of
hundreds or thousands of monosaccharides, which
acts as a storage form of energy, and as structural
material in and around cells. Starch and glycogen
are storage polysaccharides; cellulose and chitin are
structural polysaccharides.
pond successionProcess by which a hole filled with
water passes through the various succession stages
until it has become a swamp, forest, or grassland.
population A collection of individuals of the same
species living in the same geographic area.
population cycleWhen a population size dips below
the carrying capacity, it will later come back to the
capacity and even surpass it. However, the popula-
tion could dip below the carrying capacity as a
result of some major change in the environment
and equilibrate at a new, lower carrying capacity.
population density The number of individuals per
unit area in a given population.
population ecology The study of the size, distribu-
tion, and density of populations and how they
change with time.
positive feedback Occurs when a hormone acts to
directly or indirectly cause increased secretion of a
hormone.
posterior pituitary gland Structure that produces
only two hormones: ADH and oxytocin.
potometer Lab apparatus used to measure transpira-
tion rates in plants.
predation Scenario in which one species, the preda-
tor, hunts another species, the prey.
primary consumers The consumers that obtain
energy through consumption of the producers of
the planet. Known as herbivores.
primary immune response When a B cell meets and
attaches to the appropriate antigen, it becomes
activated and undergoes mitosis and differentia-
tion into plasma cells and memory cells.
primary oocytes Cells that begin the process of
meiosis and progress until prophase I, where they
sit halted until the host female enters puberty.
primary plant growth Increase in the length of a
plant.
primary productivityRate at which carbon-
containing compounds are stored.
primary sex characteristics The sexual organs that
assist in the vital process of procreation; include
the testes, ovaries, and uterus.
primary spermatocytes Produced by mitotic
division, these cells immediately undergo meiosis
I to produce two secondary spermatocytes,
which undergo meiosis II to produce four
spermatids.
primary structureThe sequence of the amino acids
that make up a protein.
primary succession Succession that occurs in an area
that is devoid of life and contains no soil.
primer sites DNA segments that signal where repli-
cation should originate.
prion Incorrectly folded form of a brain cell protein
that works by converting other normal host pro-
teins into misshapen proteins. Prion diseases tend
to cause dementia, muscular control problems,
and loss of balance.
progesterone Hormone involved in menstrual cycle
and pregnancy.
prokaryotic cell Asimplecell with no nucleus, or
membrane-bound organelles; divides by binaryhttp://www.ebook3000.com