absorption the process in which nutrients enter cells of the villi, then move across the cells and enter blood vessels.
acids compounds
that release hydrogen ions (H+) when the compounds are placed in water.
actin a
protein filament within the sarcomeres of muscle cells.
action potential occurs
when a neuron is displaying a nerve impulse.
active site the
portion of an enzyme that interacts with the substrate.
active transport the
movement of molecules across a membrane from a region of low concentration to a
region of high concentration that requires the expenditure of energy (ATP).
adenosine diphosphate
(ADP) a product of adenosine triphosphate (ATP) breakdown.
adenosine triphosphate
(ATP) the chemical substance that serves as the currency of
energy in cells.
adrenal glands two
glands lying atop the kidneys that produce a family of steroids.
aerobic organisms
that require oxygen for their metabolism.
algae a
large number of photosynthetic organisms that are generally unicellular and not
classified as plants.
alleles different
forms of the same gene.
alveoli microscopic
air sacs that are surrounded by a rich network of blood vessels in mammalian
lungs that function in gas exchange; the air sacs are at the end of the
bronchioles.
amino acids the
building blocks of proteins.
amoeba single-celled
organisms with no distinct shape; members of the phylum Sarcodina.
anabolism the
process of synthesizing large molecules by joining smaller molecules together.
anaerobic organisms
that thrive in an oxygen-free environment.
anaphase a
phase during mitosis in which chromatids separate to become visible chromosomes
and migrate to opposite poles.
anaphase I a
phase during meiosis in which homologous chromosomes separate.
anaphase II a
phase during meiosis II in which the centromeres divide and the chromosomes
separate from one another.
androgens hormones,
such as testosterone, produced from the testes that promote secondary male
characteristics.
Animalia the
kingdom that includes the animals.
antibodies proteins
synthesized by plasma cells that are released into the circulation to the
antigen site and destroy the microorganisms by chemically reacting with them.
antibody-mediated
immunity the process by which antibodies bind to antigens and
destroy the microorganisms in a highly specific manner.
anticodon the
complementary codon present on a tRNA molecule.
antigens the
immune-stimulating polysaccharides on the surface of cells.
aorta the
major artery of the human circulatory system that receives blood from the left
ventricle.
appendix a small
fingerlike process that may be a vestige of larger organs functional in human
ancestors.
archaebacteria ancient
bacteria that have a different ribosomal structure, membrane composition, and
cell wall composition than modern bacteria.
arteries the
channels through which fluid flows away from the heart.
atom the
smallest part of an element that can enter into various combinations with atoms
of other elements.
atrium a
thin-walled receiving chamber in which blood accumulates in fishes.
auditory nerve the
nerve within the ear that carries impulses to the brain for interpretation.
autonomic nervous system a
subdivision of the peripheral nervous system, which is divided into the
sympathetic and parasympathetic nervous systems.
autosomes the
22 pairs of human chromosomes that are not sex chromosomes.
autotrophic certain
bacteria that synthesize their own foods.
axon the
long extension of a neuron.
bacilli the
rod-shaped bacteria (singular, bacillus).
bark the
structure of vascular plants formed between the phloem and the cork.
bases compounds
that attract hydrogen atoms when placed in water.
basophils the
white blood cells that function in allergic responses.
bicuspid (mitral) valve the
valve that leads into the left ventricle of the human heart.
binomial name the
scientific name of an organism, which contains two elements.
biomass the
total dry weight of food at each level of the food pyramid.
biome a
group of communities dominated by a particular climax community, such as
deserts, forests, and prairies.
biosphere the
blanket of living things that surrounds the substratum of the earth.
blastocyst a
hollow ball of cells resulting after the morula has passed through the
Fallopian tubes and enters the female uterus.
blood clotting the
process in which platelets adhere to the walls of damaged blood vessels,
setting off a series of processes leading to the formation of a patchy mesh at
the injury site.
blue-green algae cyanobacteria;
members of the kingdom Monera that are photosynthetic and are found in the soil
and in freshwater or saltwater environments.
B lymphocytes white
blood cells within the lymph nodes; stimulated by microorganisms or other
foreign materials in the blood.
Bowman's capsule an
enlarged cuplike structure below the nephron in the human kidney.
bronchi two
large tubes at the lower end of the trachea (singular, bronchus).
bronchioles the
branches formed from the bronchi.
capillaries the
microscopic blood vessels between the arteries and the veins.
carbohydrates the
primary energy source for living things; composed of carbon, hydrogen, and
oxygen.
cardiac muscle the
involuntary muscle found in the heart; contains actin and myosin filaments.
carnivores animals
that eat other animals.
carrying capacity a
situation when a population has reached the maximum size that the environment
can support.
catabolism the
breakdown or digestion of large, complex molecules.
cecum a
blind sac that is the meeting point of the small and large intestines.
cerebellum a
portion of the hindbrain that serves as a coordinating center for motor
activity.
cell body the
main portion of the nerve cell.
cell cycle many
repetitions of cellular growth and reproduction; divided into interphase and
mitosis.
cell-mediated immunity the
process in which the T lymphocytes interact with the microorganisms
cell-to-cell and destroy them.
cells the
fundamental units of living things.
cellular respiration the
process by which animals and other organisms obtain the energy available in
carbohydrates.
cell wall a
strong membrane outside the plasma membrane present in certain cells, such as
bacteria and plants.
centriole a
cylinder-like organelle that assists in chromosomal migration during mitosis.
centromere the
place of attachment of the two homologous chromatids during prophase in
mitosis.
cerebrum the
portion of the forebrain that controls higher mental activity, such as
learning, memory, logic, creativity, and emotion.
cervix the
opening at the lower end of the uterus.
chemiosmosis the
subdivision of cellular respiration in which the energy given off by electrons
is used to pump protons across a membrane and synthesize ATP.
chemoreceptors the
specialized receptor cells that transmit smell and taste.
chlorophyll green
pigment that makes up a photosystem that absorbs energy from the sun during
photosynthesis.
chloroplast an
organelle within green plants in which photosynthesis occurs.
chordates animals
with rods along their backs, including reptiles, amphibians, birds, and
mammals.
chromatid homologous
chromosomes joined to each other at the centromere; present during the prophase
of mitosis.
chromatin compacted
DNA and protein.
chromosomes linear
units of DNA.
chyme a
soupy liquid formed in the stomach from the churning of the bolus with gastric
juices.
circulatory system the
transport system in animals.
class a
grouping of similar orders.
cocci spherical
bacteria (singular, coccus).
cochlea a
snail-like series of coiled tubes within the skull that assist hearing.
coenzymes organic
molecules that act as cofactors, such as NAD and FAD.
cofactors ions
or molecules that associate with enzymes and are required for enzymatic
reactions to take place.
commensalism a
relationship in which one population receives a benefit from an association
while the other is neither benefited nor harmed.
community a
situation in which populations of organisms each contain a habitat and a niche.
comparative anatomy comparing
the anatomical structures of modern day organisms with fossils to yield clues
to the type of organisms that roamed earth long ago.
comparative biochemistry the
comparison of biochemical processes of modern day organisms with fossils and
ancient species; modern biochemistry indicates there is a biochemical
similarity in all living things.
compound a
collection of molecules.
cone cells cells
of the eye that detect color.
consumers the
organisms within an ecosystem that meet their energy needs by feeding on the
producers.
cork a
tough tissue that combines with the phloem to become the bark of vascular
plants.
coronary arteries the
arteries that supply the heart muscle with blood.
corpus luteum the
mass of cells derived from the female follicle that secretes progesterone.
cortex the
outer portion of the adrenal gland.
corticosteroids the
steroids secreted from the adrenal glands.
cristae the
folds of the inner mitochondrial membrane.
crossing over a
process during prophase I in which segments of DNA from one chromatid in the
tetrad pass to another chromatid in the tetrad.
cyanobacteria see blue-green
algae.
cytochromes molecules
that accept and release electrons in an electron transport system.
cytokinesis the
process during mitosis in which the cytoplasm divides into two separate cells;
also called cytoplasmic division.
cytoplasm semiliquid
substance that composes the foundation of the cell and contains the organelles.
cytoskeleton an
organelle within cells consisting of an interconnected system of fibers,
threads, and interwoven molecules that give structure to the cell.
cytosol see cytoplasm.
decomposers the
organisms of decay; usually bacteria and fungi.
dendrites the
short extensions of the neuron.
deoxyribonucleic acid see DNA.
deoxyribose the
five-carbon carbohydrate attached to purine or pyrimidine bases within DNA
molecules.
dermal tissue the
tissue that functions to protect the plant from injury and water loss and
covers the outside of the plant.
diffusion the
movement of molecules through a membrane from a region of high concentration to
low concentration.
diploid cells
having two sets of chromosomes.
diploid nuclei contained
within a mass of cytoplasm within cellular slime molds.
disaccharides sugars
composed of two molecules.
division see phylum.
DNA deoxyribonucleic
acid; a double helix nucleotide molecule containing deoxyribose, nitrogenous
base, and a phosphate group; contains the genetic information from which amino
acids are determined.
DNA fingerprinting a
technique that uses electrophoresis to match DNA molecules to one another for
identification purposes.
DNA polymerase the
enzyme that joins all the nucleotide components to one another to form a long
strand of nucleotides.
DNA replication the
process by which cells replicate or synthesize their DNA; takes place during S
phase of the cell division cycle.
domestic breeding a
process of directed evolution that brings about new forms that differ from
ancestral stock.
dominant an
allele that expresses itself.
ductless glands glands
that have no ducts, such as the endocrine glands.
duodenum the
first 10 to 12 inches of the small intestine in which most of the chemical
digestion takes place.
eardrum the
tympanic membrane that receives vibrations from the outer ear.
ecosystems systems
formed from the interactions between communities and their physical
environments.
ectoderm one
of three germ layers that develops into the skin and nervous system.
egg the
haploid cell within the female ovary.
elements the
fundamental building blocks of matter within all living things.
embryo forms
when all the organs of the body have taken shape.
embryology the
study of embryonic development.
endergonic reaction chemical
reactions in which energy is obtained and trapped from the environment.
endocrine glands glands
throughout the animal body that secrete hormones, which help coordinate body
systems.
endocytosis the
process in which a small patch of plasma membrane encloses particles that are
near the cell surface.
endoderm one
of three germ layers that develops into the gastrointestinal tract.
endoplasmic reticulum
(ER) an organelle comprised of a series of membranes
extending throughout the cytoplasm; two types exist, rough and smooth ER.
endoskeleton an
internal support system in the echinoderms and most vertebrates that may
include a framework of bones and cartilage that serves as a point of attachment
for muscle.
endosperm the
female tissue that encloses the seed within the angiosperms.
entropy the
degree of disorder or randomness of a system.
environmental fitness an
individual's ability to adapt to an environment and reproduce.
enzymes proteins
that catalyze the chemical reactions within cells.
eosinophils white
blood cells whose functions are uncertain.
epididymis the
tube in which sperm cells mature.
epiglottis a
thin flap of tissue that folds over the opening to the mammalian trachea during
swallowing and prevents food from entering the trachea.
epinephrine a
hormone produced in the adrenal medulla that increases heart rate, blood
pressure, and the blood supply to skeletal muscle.
erythrocytes the
red blood cells; disk-shaped cells produced in the bone marrow that have no
nucleus; their cytoplasm is filled with hemoglobin to transport oxygen.
erythropoetin a
hormone produced by the kidney cells that functions in the production of red
blood cells.
esophagus a
thick-walled muscular tube located behind the windpipe that extends through the
neck and chest to the stomach.
estrogen a
hormone produced by the ovaries that stimulates the development of secondary
female characteristics.
eubacteria modern
bacteria.
eukaryotes cells
that contain a nucleus and internal cellular bodies called organelles.
evolution changes
that occur within populations and organisms that make individuals able to adapt
to their external environment.
exergonic reaction a
chemical reaction in which energy is released.
exocrine glands glands,
such as the salivary glands, that deliver their enzymes via ducts.
exoskeleton the
hard, protective, outer covering of arthropods and mollusks.
facilitated diffusion the
movement of molecules across a membrane from a region of high concentration to
a region of low concentration that is assisted by proteins.
Fallopian tubes the
passageways that egg cells enter after release from the ovaries; also called
oviducts.
family similar
genera classified together.
fats lipids
composed of a glycerol and fatty acids.
fatty acids long
chains of carbon atoms with carboxyl groups at one end.
feeding pattern the
pattern in which animals obtain their nutrients.
fermentation an
anaerobic process in which energy can be released from glucose even though
oxygen is not available; occurs in yeast cells.
fertilized egg cell an
egg cell that has been fertilized by a sperm cell.
fetus results
from a developing embryo at about eight weeks when the embryo is somewhat human
looking and the remaining development consists chiefly of growth and
maturation.
flavin adenine
dinucleotide (FAD) a coenzyme that
functions in the production of ATP.
food chain the
transfer of food energy from producers to consumers.
food pyramid a
way of expressing the availability of food in an ecosystem at a successive
number of trophic levels.
food web many
interwoven food chains.
forebrain a
portion of the brain that consists of the cerebrum, thalamus, hypothalamus, and
limbic system.
Fungi a
kingdom that includes the yeasts, molds, mildews, and mushrooms.
G1 phase a
phase within interphase of the cell division cycle that prepares cells for DNA
replication.
G2 phase a
phase within interphase of the cell division cycle that prepares cells for
mitosis.
gametes sex
cells of parent organisms; usually haploid cells.
gastrin a
hormone produced by digestive glands to influence digestive processes.
gene the
functional segment of chromosomes.
gene flow a
mechanism of evolution that results when individuals migrate from one group to
another and contribute their genes to the gene pool of the new population.
gene linkage the
concept of transfer of a linkage group.
gene linkage map a
map that pinpoints the location of genes based on their connection to certain
marker gene sequences.
gene pool the
collection of genes within a population; as changes in the gene pool occur, a
population evolves.
genetic drift a
mechanism of evolution that occurs when a small group of individuals leaves a
population and establishes a new one in a geographically isolated region.
genome the
set of all genes that specify an organism's traits.
genotype the
gene composition of a living organism.
genus a
grouping of similar species (plural, genera).
geographic distribution the
distribution of species in geographical areas.
geotropism the
turning of a plant away from or toward the earth.
gills structures
that allow fish to exchange gases with their environment.
glial cells the
cells of the nervous system that support, protect, and nourish the neurons.
glomerulus a
ball of capillaries that comprises Bowman's capsule in the human kidney.
glottis a
slitlike structure at the opening to the mammalian trachea.
glucagon a
hormone produced in the pancreas that stimulates the breakdown of glycogen to
glucose in the liver.
glucose a
carbohydrate with the chemical formula C6H12O6 that
serves as the primary carbon source of living things.
glycogen a
polysaccharide composed of thousands of glucose units that serves as the
storage form of glucose in the human liver.
glycolysis the
subdivision of cellular respiration in which glucose molecules are broken down
to form pyruvic acid molecules.
Golgi apparatus an
organelle within eukaryotic cells comprised of a series of flattened sacs; the
site of protein and lipid processing and packaging; also called Golgi bodies.
Graafian follicle a
cluster of cells within the ovary that is derived from egg cells and secretes
female hormones called estrogens.
ground tissue the
tissue of the vascular plant that is responsible for storing the carbohydrates
produced by the plant.
gymnosperms vascular
plants having naked seeds, such as the conifers.
haploid cells
containing one copy of each chromosome.
hemoglobin a
red pigment that binds oxygen and carbon dioxide molecules and carries them
through the bloodstream.
herbivores animals
that eat plants.
heterotrophic species
that acquire food from organic matter.
heterozygous two
different alleles that are present for a particular characteristic.
hindbrain the
portion of the brain that consists of the medulla, pons, and cerebellum.
histones nuclear
proteins that coil DNA molecules.
homeostasis the
process in which the internal environment exists at a steady-state equilibrium
despite changes in the external environment.
homeothermic animals
that can maintain a constant body temperature.
homozygous two
identical alleles that are present for a particular characteristic.
hormones biochemical
substances produced within plant or animal cells, or glands, that exert a
particular effect.
hydrostatic skeleton a
water-based skeleton present in many animals (such as the earthworm) that lack
structures, such as bone, for muscles to pull against.
hypothalamus the
portion of the forebrain that serves as the control center for hunger, thirst,
body temperature, and blood pressure.
hypothesis the
proposal of a solution to the question within the scientific method.
ileum the
final 12 feet of the small intestine.
immune response the
stimulation of B and T lymphocytes.
incomplete dominance an
allele combination in which two characteristics blend and both alleles can
express themselves; one example is red, white, and pink snapdragons.
inner cell mass a
group of cells that continues to develop at one end of the blastocyst.
interneuron a
type of neuron that connects sensory and motor neurons and carries stimuli in
the brain and spinal cord.
interphase the
cell division cycle phase in which the cell spends most of its time; includes G1,
S phase (DNA replication), and G2.
invertebrates the
most primitive of the chordates; lack a backbone.
involuntary muscle see smooth
muscle and cardiac muscle.
islets of Langerhans clusters
of cells that make up the endocrine portion of the pancreas.
jejunum the
second 10 inches of the small intestine.
kinetochore a
region of DNA that has remained undivided during prophase of mitosis; binds to
the spindle fibers that eventually pull apart the sister chromatids.
kingdom the
largest and broadest category of the classification system.
Krebs cycle the
subdivision of cellular respiration in which pyruvic acid is broken down and
the energy in its molecules is used to form high-energy compounds.
larynx the
voicebox of mammals, formed from several folds of cartilage at the upper end of
the trachea.
left atrium the
chamber of the human heart that receives oxygen-rich blood via the pulmonary
vein.
left ventricle the
chamber of the human heart in which oxygen-rich blood enters through the bicuspid
valve that leads into the aorta.
lens the
portion of the eye that focuses the light on the retina.
leukocytes the
white blood cells produced in the bone marrow that have various functions in
the body, such as immune reaction.
lichens associations
between the cyanobacteria and the fungi.
ligaments the
tough, fibrous tissues that link bones to one another.
limbic system a
collection of structures that ring the edge of the brain and apparently
function as centers of emotion.
lipid an
organic molecule used to form cellular and organelle membranes, the sheaths
surrounding nerve fibers, and certain hormones; includes fats as an energy
source.
liver the
organ that helps to process the products of human digestion and removes excess
glucose from the bloodstream, converting it to a polymer called glycogen for
storage.
loop of Henle the
segment of the human kidney after the proximal tubule.
lungs the
organ where oxygen diffuses into the blood to join with hemoglobin in the red
blood cells.
lymph a
watery fluid derived from plasma that seeps out of the blood system capillaries
and mingles with the cells.
lymph nodes capsule-like
bodies that contain cells that filter the lymph and phagocytize foreign
particles.
lymphatic system the
extension of the circulatory system consisting of capillaries called lymph
vessels, a fluid called lymph, and structures called lymph nodes.
lymphatic vessels a
series of vessels that return the lymph fluid to the circulatory system.
lymphocytes the
white blood cells that are essential components of the immune system.
lysosome an
organelle within eukaryotic cells; a droplike sac filled with enzymes used for
digestion within the cell.
mammals milk-producing
animals.
marsupials the
mammals whose embryos develop within the mother's uterus for a short period of
time before birth.
medulla the
inner portion of the adrenal glands; a swelling at the tip of the hindbrain
that serves as the passageway for nerves extending to and from the brain.
meiosis the
process by which the chromosome number is halved during gamete formation.
menstruation the
process by which the endometrium is released in females.
meristematic tissue the
growth tissue; the location of most cell division of vascular plants.
mesoderm one
of three germ layers that develops to become the muscles and other internal
organs.
metabolism the
rapid turnover of chemical materials; involves the release or use of chemical
energy.
metaphase the
stage during mitosis in which the pairs of chromatids line up on the equatorial
plate.
metaphase I the
phase during meiosis in which tetrads align on the equatorial plate (as in
mitosis).
metaphase II the
phase during meiosis II in which the chromatid pairs gather at the center of
the cell prior to separation.
midbrain a
portion of the brain that lies between the hindbrain and the forebrain that
consists of a collection of crossing nerve tracts.
minerals types
of nutrients that include phosphorus, sulfur, potassium, magnesium, and zinc.
mitochondrion the
organelle that is the site of energy production in eukaryotic cells.
molecule a
precise arrangement of atoms of different elements.
Monera the
kingdom that includes the bacteria and the cyanobacteria; prokaryotic
organisms.
monocytes some
of the white blood cells that function in phagocytosis.
monosaccharides sugars
that are composed of single molecules.
monotremes the
egg-laying mammals that produce milk.
morula a
solid mass of cells that develops about six days after fertilization of an egg
cell.
motor neuron a
type of neuron that transmits impulses from the brain and spinal cord to
muscles or glands.
mRNA messenger
RNA; the RNA molecules that receive the genetic code in the DNA and carry the
code into the cytoplasm where protein synthesis takes place.
multiple alleles a
condition in which more than two alleles exist for a characteristic; one
example is A, B, AB, and O blood types.
muscle contraction a
process in which actin and myosin proteins move within a sarcomere.
mutation a
random change in the gene pool of a population that gives rise to new alleles
and is the source of variation in a population.
mutualism a
living arrangement in which both partners benefit.
myelin sheath a
fatty layer of material that covers the axons of nerve cells.
myofibrils microscopic
filaments that make up a muscle cell.
myosin a
protein microfilament that comprises the sarcomere of muscle cells.
natural selection the
concept that random, small variations take place in living things that lead to
the gradual development of a species.
nephron the
functional and structural unit of the kidney that produces urine and is the
primary unit of homeostasis in the human body.
nerve chord also
called a spinal cord; a hollow structure that extends the length of the animal
just above the notochord.
nerve impulse an
electrochemical event that occurs within the neuron.
nerve roots the
31 pairs of projections that extend out along each side of the spinal cord; the
sites of axons of the sensory and motor neurons.
nerves bundles
of axons bound together.
neuroglia the
glial cells together with the extracellular tissue.
neuron a
nerve cell.
neurotransmitter a
chemical substance that accumulates in the synapse and increases the membrane
permeability of the next dendrite.
neutrophils the
white blood cells that function in phagocytosis.
nicotinamide adenine
dinucleotide (NAD) a coenzyme that
functions during respiration to produce ATP.
nicotinamide adenine
dinucleotide phosphate (NADP) a coenzyme that
functions during photosynthesis to produce ATP.
nitrogenous base the
nitrous molecules that make up DNA (and RNA) molecules; two major types are
purines and pyrimidines.
nonvascular plants the
plants that do not have specialized tissues to transport fluids.
norepinephrine a
hormone produced in the adrenal medulla that intensifies the effects of
epinephrine.
notochord a
flexible rod of tissue extending the length of an animal that provides internal
support.
nucleic acids large
molecules comprised of nucleotides.
nucleoli the
small organelles that make up the nucleus; the site for ribosomal synthesis,
assembly, and packaging (singular, nucleolus).
nucleotide the
unit that makes up nucleic acid; contains a nitrogen base, a phosphate group,
and a carbohydrate molecule.
nucleus the
organelle within eukaryotic cells that contains the genetic material, DNA.
Okazaki fragments new
sections of DNA that are placed along the lagging strand during DNA replication
and are joined together by DNA ligase to produce a new DNA strand.
olfactory nerve the
nerve that carries the impulse from the nose to the brain for interpretation.
omnivores animals
that consume both plants and animals.
oocytes the
developed oogonia in a female after the age of puberty.
oogonia primitive
egg cells that accumulate in the ovaries before a female is born.
optic nerve the
nerve that carries impulses from the eye to the brain.
order a
grouping of similar families.
organelles microscopic
bodies within the cytoplasm that perform distinct functions.
osmosis the
movement of water molecules across a membrane from a region of high
concentration to a region of low concentration.
ovary an
endocrine gland that secretes estrogens. In plants, the structure of the pistil
where the ovules are enclosed.
oviducts see Fallopian
tubes.
ovulation the
process by which an egg cell is released from the follicle and swept into the
Fallopian tube where it moves toward to uterus.
ovules the
protective structures that contain egg cells produced by the female.
Pacinian corpuscles the
touch and pain receptors on the skin, muscles, and tendons.
paleontology the
science of locating, cataloging, and interpreting the life forms that existed
in past millennia.
pancreas a
large, glandular organ lying near the stomach that produces many of the enzymes
used to digest food.
parasites organisms
that attack living things and cause disease.
parasitism a
type of symbiosis in which one population benefits while the other is harmed.
parasympathetic nervous
system a subdivision of the autonomic nervous system that
returns the body to normal after an emergency.
parathyroid glands glands
located on the posterior surfaces of the thyroid gland that produce parathyroid
hormone.
pathogenic organisms
that cause human disease.
PCR polymerase
chain reaction; a technique used to amplify a gene of interest.
peptides small
proteins.
peripheral nervous system a
collection of nerves that connect the brain and spinal cord to other parts of
the body and the external environment.
peristalsis a
rhythmic series of muscular contractions that propels the bolus along.
peroxisome cytoplasmic
body containing enzymes for digestion.
phagocytes cells
that attack and engulf invading microorganisms.
phagocytosis occurs
when the vesicle formed from endocytosis contains particulate matter; the
process by which cells or microorganisms are engulfed by another cell.
pharynx the
cavity at the rear of the mouth that the nasal chambers open into; the throat.
phenotype the
expression of genes and the physical characteristics that result.
phloem structures
of vascular plants that transport sugars and other nutrients from the leaves to
the other parts of the plant.
phosphate group a
group derived from a molecule of phosphoric acid that connects the DNA
molecules to one another.
phosphate ion a
product of adenosine triphosphate (ATP) together with ADP.
photosystem the
site within the chloroplast in which sunlight is captured; includes the pigment
molecules, proton pumps, enzymes, coenzymes, and cytochromes.
phototropism the
bending and turning of the plant stem toward a light source.
phyla related
classes grouped together (singular, phylum).
physical map a
map that locates a gene of interest precisely by showing the actual number of
base pairs between genes on a chromosome.
pineal gland a
human endocrine gland in the midbrain that regulates mating behaviors and
day-night cycles.
pinocytosis when
the vesicle formed from endocytosis contains droplets of fluid.
pistil the
structure of the flower that contains a stigma, a style, and an ovary.
pith the
structure at the center of the stem of vascular plants.
pituitary gland a
gland at the base of the brain consisting of the anterior and posterior lobes
that secretes several hormones.
placenta the
structure that supplies the fetus with nourishment.
placental mammals mammals
that have a nutritive connection between the embryo and the mother's uterine
wall.
plant hormones hormones
that regulate the growth and development of many plants.
plasma a
straw-colored liquid composed primarily of water; the fluid portion of blood.
plasma cells large
antibody-producing cells derived from B lymphocytes when stimulated.
plasma membrane also
called a cell membrane; a membrane composed of lipids, proteins, and
phospholipids.
plasmid small
circular DNA molecules often used as vectors to transform specific genes into
cells.
platelets small
disk-shaped blood fragments produced in the bone marrow that serve as the
starting material for blood clotting.
polygenic inheritance the
condition in which some characteristics are determined by an interaction of
genes on several chromosomes or at several places on one chromosome; one
example is human skin color.
polymerase chain reaction see PCR.
polysaccharides complex
carbohydrates formed by linking multiple monosaccharides.
pons the
portion of the hindbrain below the medulla and the midbrain that acts as a
bridge between various portions of the brain.
population an
interbreeding group of individuals of one species occupying a defined
geographic area.
predation a
relationship in which one population within a community may capture and feed
upon another population.
producers organisms
within an ecosystem that trap energy (by photosynthesis).
progesterone a
hormone produced by the corpus luteum that regulates the buildup of tissue in
the endometrium and inhibits the contractions of the uterus.
prokaryotes cells
that do not contain a nucleus or internal organelles; include bacteria,
cyanobacteria, and archaebacteria.
prophase the
first phase of mitosis; involves chromosomal condensation, nuclear membrane
breakdown, and the migration of centrioles to opposite poles.
prophase I the
first phase of meiotic division, during which crossing over takes place.
prophase II the
phase during meiosis II in which the chromatin material condenses and each
chromosome contains two chromatids attached by the centromere.
prostaglandins the
hormones secreted by various tissue cells that produce their effects on smooth
muscles, on various glands, and in reproductive physiology.
proteinoids the
primitive polymers formed by the unison of amino acids; able to act as enzymes
and catalyze organic reactions.
proteins long
chains of amino acid units that are the main molecules from which living things
are constructed.
Protista a
kingdom that includes protozoa, one-celled algae, and slime molds.
protocells the
first cells.
protons positively
charged particles within the nucleus of an atom.
pulmonary artery the
artery of the human circulatory system that pumps the blood from the right
ventricle to the lungs for gas exchange.
pulmonary vein the
vein of the human circulatory system that returns oxygen-rich blood from the
lungs to the left atrium.
purine a
type of nitrogenous base present in DNA molecules containing two fused rings of
carbon and nitrogen atoms; two examples in DNA are adenine (A) and guanine (G).
Purkinje fibers the
nerves that transfer amplified impulses to regions of the heart to control its
function.
pyrimidine a
type of nitrogenous base in DNA molecules that has one ring containing carbon
and nitrogen atoms; two examples in DNA are cytosine (C) and thymine (T).
recessive the
allele overshadowed by the dominant allele.
recombinant DNA DNA
molecules that have been altered in some way during the process of genetic
engineering or biotechnology.
red blood cells also
known as erythrocytes; cells that contain hemoglobin to transport oxygen.
reflex arc the
simplest unit of nervous activity; involved in the detection of a stimulus in
the environment by sensory nerve endings, followed by impulses that travel via
the sensory neurons to the spinal cord.
renal arteries arteries
in which blood enters the kidney.
renal veins veins
in which blood exits the kidney.
responsiveness the
ability of living things to respond to stimuli in the external environment.
resting potential the
inactive state of a neuron in which the cytoplasm is negatively charged with
respect to the outside of the cell.
restriction enzymes catalyze
the opening of a DNA molecule at a "restriction" point; many leave
dangling ends of DNA molecules at the point where the DNA has been opened.
retina a
single layer containing nerve cells within the eye.
RFLP restriction
fragment length polymorphism; a technique using small bits of DNA fragments
linked to various diseases.
rhodopsin a
light-sensitive pigment of the eye that functions in the detection of light.
ribonucleic acid see RNA.
ribosomes organelle
bodies that may be bound to the ER that are the sites of protein synthesis in
eukaryotic cells; the bodies in which amino acids are bound together to form
proteins.
right atrium the
chamber of the human heart in which oxygen-poor blood enters through a major
vein called the vena cava.
right ventricle the
pumping chamber of the human heart from which blood exits.
RNA ribonucleic
acid; a nucleic acid produced during transcription that is complementary to a
DNA strand; similar to DNA in structure but contains the carbohydrate ribose
and the pyrimidine uracil rather than thymine.
RNA polymerase the
enzyme that moves along the DNA strand, reads the nucleotides one by one, and
synthesizes a complementary mRNA molecule according to the principle of
complementary base pairing.
rod cells the
cells of the eye that permit vision in dim light.
roots the
structures of vascular plants that anchor them to the ground and take in water
and minerals from the soil.
rough endoplasmic
reticulum ER studded with ribosomes; the site of protein
synthesis in eukaryotic cells.
rRNA ribosomal
RNA; RNA molecules that function to manufacture ribosomes.
salivary glands the
parotid glands, the submaxillary glands, and the sublingual glands that secrete
saliva into the mouth.
sarcolemma the
muscle cell membrane.
sarcomere the
functional unit of the muscle that contains thin actin filaments and thick
myosin filaments.
scientific method an
orderly process of gaining information about the biological world.
scrotum a
pouch outside the male body that contains the testes.
secretin a
hormone produced by digestive glands that influences digestive processes.
seedless vascular plants the
division Pteridophyta that includes the ferns.
semen a
fluid secretion containing sperm and secretions from the prostate gland,
seminal vesicles, and Cowper's glands.
semilunar valves two
valves found in the pulmonary artery and the aorta.
seminiferous tubules coiled
passageways in which sperm production takes place.
sensory neurons neurons
that receive stimuli from the external environment.
sensory somatic system a
subdivision of the peripheral nervous system that carries impulses from the
external environment and the senses.
sepals modified
leaves that enclose and protect a growing bud in flowers.
serum plasma
from which clotting proteins have been removed.
sex chromosomes one
pair among the 23 pairs of human chromosomes; the X and Y chromosomes.
skeletal muscle see striated
muscle.
slime molds (cellular) amoebalike
cells that live independently and unite with other cellular slime molds to form
a single, large, flat cell with many nuclei.
slime molds (true) single,
flat, very large cells with many nuclei.
small intestine the
site of chemical digestion; includes the duodenum, jejunum, and ileum.
smooth endoplasmic reticulum ER
with no ribosomes attached.
smooth muscle found
in the linings of the blood vessels, along the gastrointestinal tract, in the
respiratory tract, and in the urinary bladder; contains few actin and myosin
filaments; also called involuntary muscle.
species a
group of individuals that share features and are able to interbreed under
natural conditions to yield fertile offspring.
spermatogonia primitive
cells within the seminiferous tubules that undergo a series of changes and then
meiosis to yield sperm cells.
sperm cells haploid
cells within the male testes.
S phase the
phase within the cell division cycle in which DNA is replicated.
spinal cord the
white cord of tissue passing through the bony tunnel made by the vertebrae.
spiracles a
series of openings on the body surface of terrestrial arthropods that open into
tiny air tubes that assist in gas exchange.
spirilla flexible
spiral bacteria (singular, spirillum).
spirochetes rigid
spiral bacteria.
spleen the
site where red blood cells are destroyed; a reserve blood supply for the body.
stamen the
structure of a flower that contains a thin, stemlike filament and an anther.
stomata the
pores within leaves surrounded by guard cells that regulate the rate of gas
exchange, which regulates the rate of photosynthesis. (Singular, stoma.)
striated muscle skeletal
muscle fiber that appears to be banded due to the presence of overlapping actin
and myosin filaments; also called voluntary muscle.
substrate the
substance changed or acted on by an enzyme.
survival of the fittest the
concept of natural selection that states that the fittest survive and spread
their traits through a population.
sutures the
immovable joints where bones come together within the skull.
symbiosis the
relationship between two populations that live together in a close, permanent,
and mutually beneficial association.
sympathetic nervous
system a subdivision of the autonomic nervous system that
prepares the body for an emergency.
synapse the
fluid-filled space separating the end of the axon from the dendrite of the next
neuron or from a muscle cell.
synergism a
type of relationship in which two populations accomplish together what neither
could accomplish on its own.
telophase a
phase during mitosis in which the chromosomes arrive at the opposite poles of
the cell.
telophase I the
phase during meiosis in which the nucleus reorganizes as the chromosomes become
chromatin; cytoplasmic division takes place, resulting in two cells.
telophase II the
phase during meiosis II in which the chromosomes gather at the poles of the
cells and form a mass of chromatin; the nuclear envelope develops, the nucleoli
reappear, and the cells undergo cytokinesis.
tendons the
connective tissue by which muscles are attached to bones.
testes endocrine
glands that secrete androgens; the male reproductive organs located in the
scrotum.
thalamus a
portion of the forebrain that integrates sensory impulses.
theory a
hypothesis that is confirmed through repeated experimentation.
thrombocytes the
starting material for blood clotting; also called platelets.
thylakoids membranes
that make up the grana in chloroplasts; the actual site of photosynthesis
within chloroplasts.
thymosins hormones
secreted by the thymus gland that influence the development of the T
lymphocytes of the immune system.
thymus gland an
endocrine gland in the neck tissues that secretes thymosins.
thyroid gland a
gland at the base of the neck that produces several hormones, such as thyroxine
and calcitonin.
T lymphocytes white
blood cells in the lymph nodes that are stimulated by microorganisms or other
foreign material in the blood.
trachea the
windpipe of mammals.
tracheae the
branching network that extends from holes to all parts of an anthropod body to
assist in gas exchange.
tracheids the
main conducting vessels of the xylem in most vascular plants.
tracheophytes vascular
plants composed of a xylem and phloem.
transcription the
process in which a complementary strand of mRNA is synthesized according to the
nitrogenous base code of DNA.
transgenic animals animals
in which one or more genes have been introduced into the nonreproductive cells.
translation the
process by which the genetic code is transferred to an amino acid sequence in a
protein.
tricuspid valve a
valve that passes blood from the right atrium into the right ventricle.
tRNA transfer
RNA; RNA molecules in the cytoplasm of a cell that carry amino acids to the
ribosomes for protein synthesis.
trophoblast a
layer of cells that forms after fertilization; projections from the trophoblast
form vessels, which merge with maternal blood vessels to form the placenta.
tropism the
bending or turning response of a plant caused by external stimuli.
turgor pressure the
pressure exerted on a plant's guard cells to open.
umbilical cord the
source of attachment of the fetus to the maternal blood supply.
urea a
component of urine that results from amino acid breakdown in the liver.
ureters tubes
that carry waste from the kidneys to the urinary bladder for storage or
release.
urethra the
path in which urine flows from the bladder to the exterior; the tube within the
penis that carries the sperm.
uric acid a
component of urine that results from nucleic acid breakdown.
urinary bladder the
site where waste products are shipped from the kidney for storage or for
release.
urine the
product of the kidney; a watery solution of waste products, salts, organic
compounds, uric acid, and urea.
uterus a
muscular organ in the pelvic cavity of female mammals; also called the womb.
vacuole an
organelle found in mature plant cells that stores nutrients and toxic waste.
vagina a
muscular organ in female mammals leading from the cervix to the exterior.
vascular bundles arrangements
of the xylem and phloem in vascular plants.
vascular plants plants
that contain specialized tissues to transport fluids.
vascular plants with
protected seeds angiosperms; the most developed
and complex vascular plants.
vascular plants with
unprotected seeds gymnosperms;
vascular plants that contain naked seeds, such as the conifers.
vectors the
carriers of DNA genes to be inserted into cells.
veins channels
through which fluid flows toward the heart.
vena cava the
major vein in the human heart; pumps oxygen-poor blood into the right atrium.
ventricle a
pumping chamber for blood to exit from the heart.
vertebrates animals
with backbones.
vessels the
main conducting vessels of the xylem found in the angiosperms.
virus fragments
of nucleic acid surrounded by a protein coat; may attack cells and replicate
within the cells, destroying them.
vitamins organic
nutrients essential in trace amounts to the health of animals.
voluntary muscle see striated
muscle.
white blood cells see leukocytes.
xylem the
structure of vascular plants that conducts water and minerals upward from the
roots.
No comments:
Post a Comment