Biology 1030 Glossary
Copyright © Michael Shaw 2007 (Images and Text)
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abdomen
The part of the body of vertebrates containing the viscera, that is the kidneys,
liver, stomach, and intestines. In arthropods the abdomen is the part of the
body directly behind the thorax, and in many other invertebrates it is divided
into segments.
aboral,
or dorsal
Toward the back, or upper surface.
acoelomate
A solid-bodied animal lacking a cavity between the gut and outer body wall.
adductor muscle
1. a muscle which pulls something towards the main part of the body.
2. a muscle which pulls two structures together, like the two valves of a shell.
adrenal
gland
An endocrine gland located adjacent to the kidney in mammals; composed of two
glandular portions: an outer cortex, which responds to endocrine signals in
reacting to stress and effecting salt and water balance, and a central medulla,
which responds to nervous inputs in reacting to stress.
adventitious roots
Roots that have differentiated from the kinds of tissue other than root tissue.
agranulocyte
A type of leukocyte (white blood cell) with nongranular cytoplasm and a large
spherical nucleus. They are produced either in the lymphatic system or in the
bone marrow.
albumen
(egg white) A solution of protein in water that is secreted by the oviduct of
birds and some reptiles. Albumen surrounds the embryo and yolk, which it cushions
within the shell of the egg. It is eventually absorbed by the embryo as food.
alimentary canal
A tubular passage which extends from the mouth to the anus. Found in organisms
with complete digestive systems.
Covered in:
allantois
One of four extraembryonic membranes; serves as a repository for the embryo's
nitrogenous waste.
allele
an alternative form of a gene.
alpha male
the dominant male in a pack.
amictic egg
A thin shelled diploid egg which cannot be fertilized. Instead, it develops
by parthenogenesis. It is produced by rotifers
when living conditions are optimal, and will develop to produce amictic females.
amnion
The innermost of four extraembryonic membranes; encloses a fluid-filled sac
in which the embryo is suspended.
amniotic fluid
Watery-fluid that bathes the fetus keeping it suspended to act as a protective
cushion.
ampulla
Any small vesicle or sac-like offshoot. Some examples include the dilation at
the end of the semicircular canal of the ear, or the internal expansion of the
echinoderm tube foot.
Anabaena
a genus of filamentous cyanobacteria in which filaments when viewed
under the microscope resemble strings of beads. Thick-walled, clear heterocysts
can be seen at intervals along or at the ends of the filaments.
anabolism
Metabolic reactions that require energy and result in the biosynthesis of needed
compounds. An example of this is photosynthesis, in which solar energy is incorporated
into complex compounds such as glucose and its derivatives.
Angiosperm
Any plant that is a member of the class Angiospermae, in which the seeds are
enclosed in an ovary. Each member of the class is either a monocotyledon (grasses,
tulips) or a dicotyledon (apple, primrose).
annulus
The ring of cells in the moss or fern capsule that splits and allows liberation
of spores.
antenna
(pl. antennae)
Usually one of a pair of many-jointed, whip-like structures present on the head
of many arthropods, particularly insects (first appendage on head) and crustaceans(second
appendage). Antennae have a sensory function, though in some crustaceans they
are used for attachment or swimming.
antennule
The foremost of two pairs of antennae that occurs in some crustaceans. Most
antennae in other arthropods are homologous with the antennules of crustaceans.
anther
The terminal pollen sac of a stamen, inside which pollen grains with male gametes
form in the flower of an angiosperm.
antheridium (pl. antheridia)
The male sex organ or gametangium, within which male gametes are formed, in
algae, fungi, bryophytes
(mosses, liverworts, etc.), and pteridophytes
(ferns).
antipodal
The three haploid nuclei which are formed during megasporogenesis in plants.
They are all located opposite the micropyle end of an ovule.
anus
The terminal opening of the gut; the solid residues of digestion are eliminated
through the anus.
aorta
The major artery of vertebrate systemic blood circulation. It carries oxygenated
blood from the left ventricle of the heart around the trunk, giving rise to
several branches to individual body organs.
aortic
arch
one of up to six paired arteries that join the ventral and dorsal aorta in vertebrates
or their embryos.
apical
meristem
A group of plant cells that are found at the growing tip of a root or a stem.
These cells are capable of dividing indefinitely and their main function is
the production of new growth.
Apicomplexa
members of this phylum were formerly called sporozoans, and are parasites of
animals, some of which cause dangerous human diseases. Most apicomplexans have
intricate life cycles with both sexual and asexual stages, often requiring two
or more different host species for completion.
aponeurosis
A tough, flat sheet of connective tissue that distributes the tension of a muscle.
Arachnida
the class contains scorpions,
spiders,
ticks, mites, and king crabs. They lack antennae, usually have four pairs of
walking legs and with the exception of the king crab, Limulus, are air-breathing.
archegonium (pl. archegonia)
The female sex organ of liverworts, mosses,
ferns,
and most gymnosperms.
It is usually a flask-shaped organ, comprising a swollen base or venter containing
a single egg-cell and a slender elongated neck containing one or more layers
of cells.
archenteron
The endoderm-lined cavity formed during the gastrulation process that develops
into the digestive tract of an animal.
arterial
system
Blood vessels that carry oxygenated blood to tissues from the heart , forming
part of the blood circulatory system.
Ascaris
a genus of parasitic roundworm, phylum Nematoda, that occasionally inhabit the
small intestine of man.
Ascomycotina
a subdivision of fungi in which sexually produced spores are contained within
asci and are called ascospores.
asexual reproduction
A type of reproduction involving only one parent that produces genetically identical
offspring by budding or by the division of a single cell or the entire organism
into two or more parts.
ATP
(Adenosine TriPhosphate) A molecule consisting of adenosine (adenine plus a
ribose sugar) and three phosphate groups. The last two phosphates are joined
by high energy bonds which provide energy used in chemical reactions such as
respiration and glycolysis. In plants, ATP is formed in the chlorplasts during
photosynthesis.
atrium
A chamber in the heart which receives blood from the body.
autotrophs
An organism able to build all the complex organic molecules that it requires
as its own food source, using only simple inorganic compounds. Plants, and some
bacteria are autotrophs.
axon
a typically long outgrowth, or process, from a neuron that carries nerve impulses
away from the cell body toward target cells.
Bacillus
a bacterial cell that is rod-shaped (i.e. longer than it is wide).
bacteriophages
a type of virus that infects bacteria. Infection with a bacteriophage may or
may not lead to the death of the bacterium, depending on the phage and sometimes
on conditions. Each bacteriophage is specific to one form of bacterium.
bark
The living tissue outside the vascular cambium in a woody stem. It is composed
of phloem tissues, which occur as living inner and dead outer zones.
basidium
a reproductive appendage that produces sexual spores on the gills of mushrooms.
The fungal division Basidiomycota is named for this structure.
belly
The central portion of a muscle.
biceps
A group of muscles present in the upper forelimb of tetrapods, which are flexors
of the elbow joint. In the hind limb, the biceps femoris is a flexor of the
knee and an elevator of the femur.
bilateral
symmetry
An animal body structure in which the right and left halves of an organism are
approximately mirror images of each other. Most higher invertebrates and all
vertebrates have members which are bilaterally symmetrical.
bile
a mixture of substances containing bile salts, which emulsify fats and aid in
their digestion and absorption.
binary fission
the type of cell divisions by which prokaryotes reproduce; each dividing daughter
cell receives a copy of the single parental chromosome.
blastema
An undifferentiated mass of animal cells that later forms a structure or organ
either embryologically if through regeneration, for example the head of a flatworm.
blastocoel
The central cavity of the blastula stage of vertebrate embryos.
blastoderm
The layer of cells formed by cleavage of the fertilized egg in the presence
of large amounts of yolk.
blastomeres
Any cell that occurs in the blastula.
blastopore
The opening of the gastrula that develops into the mouth in protostomes and
the anus in deuterostomes.
blastula
The hollow ball of cells marking the end stage of cleavage during early embryonic
development.
blood vascular system
the mechanism by which blood is moved through the body. This includes the arteries,
veins, capillaries, and heart.
bone
cell
Also referred to as an Osteoblast.
Bowman's
Capsule
Found at the end of a kidney nephron, it contains the glomerulus and functions
in filtration.
brachial
of or relating to the arm or to an arm-like structure.
bract
A modified leaf with a single flower growing in its axil.
branch
primordia
A lateral stem that is in its earliest stage of differentiation.
branchial chamber
A chamber or cavity containing the gills of fish.
brush border
Formed by epithelial cells with microscopic projections called microvilli, that
extend into the intestinal lumen
buccal
cavity
Mouth cavity.
bud
An immature shoot, which the stems, leaves, or flowers may develop from.
budding
A method of asexual reproduction common in some lower animal groups in which
part of the body wall bulges outward and eventually forms a new individual,
which becomes detached from the parent. Budding can also occur in single-celled
organisms such as yeast.
caecum
(pl. caeca)
a blind-ending sac in the digestive system, which occurs in mammals at the junction
of the small and large intestines. In herbivores the caecum contains bacteria
that produce cellulase, enabling breakdown of cellulose cell walls.
calcareous algae
algae that contains calcium carbonate.
calyx
A collective term for all the sepals of a flower.
canines
Four pointed teeth present in the jaw between the incisors and the premolars
in mammals, being particularly prominent in the Carnivora and having a stabbing
function.
cannibalistic
The act of an animal feeding on its own kind.
cap
(also pileus)
The fleshy or leathery structure upon which the spore-bearing structures occurs
in a fungal fruit body.
capillaries
One of the many minute blood vessels that connect arterioles and venules in
vertebrate tissues, allowing a high level of exchange of materials between blood
and tissues via the interstitial fluid.
capitulum
In animals it is the rounded rib head that articulates with the centrum of the
vertebra. In plants it is a head of flowers.
capsid
the protein shell that encloses the viral genome; rod-shaped, polyhedral, or
more completely shaped.
capsule
a containing structure with a strong outer covering, found in many different
groups.
carapace
The part of a Crustacean that spreads over the head and thorax.
carbohydrate
A family of organic molecules with the general formula (CH20)x,
ranging from simple sugars, such as glucose and fructose, to complex molecules,
such as starch and cellulose.
cardiac
muscle
A type of muscle that forms the contractile wall of the heart; its cells are
joined by intercalated discs that relay each heartbeat.
Covered in:
cardiac portion
Of or relating to the heart.
cardiac stomach
Front portion of the stomach.
carpel
The female reproductive organ of a flower, consisting of the stigma, style and
ovary.
catabolism
A type of metabolism in which biochemical processes taking place in a cell result
in the breaking down of complex compounds into simpler ones to release energy.
catalase
An enzyme found in tissues, such as the liver, whose function is to catalyze
the breakdown of toxic hydrogen peroxide into water and oxygen.
caudal
Relating to or in the position of the tail.
cell
membrane
the outer boundary of cells, the structure of which is visible only under the
electron microscope.
cellulose
A type of unbranched polysaccharide carbohydrate that is composed of glucose
sugars.
cell vacuole
a membrane-bound sac that is found in many cells, normally acting as a storage
organ of various types. A large central vacuole is a particular feature of many
plant cells, where it can occupy 80-90% of the total cell volume.
cell
wall
Unique to plant cells, a wall formed of cellulose fibers embedded in a polysaccharide-protein
matrix. The primary cell wall is thin and flexible, whereas the secondary cell
wall is stronger and more rigid and the primary constituent of wood.
cellular
respiration
the most prevalent and efficient catabolic pathway for the production of ATP,
in which oxygen is consumed as a reactant along with the organic fuel
central
cell
Found in the central region of the megagametophyte, it contains two polar nuclei.
centriole
One of two structures in the center of animal cells, composed of cylinders of
nine triplet microtubules in a ring. Centrioles help organize microtubule assembly
during cell division.
centromere
The centralized region joining two sister chromatids.
cephalic
Pertaining to the head.
cephalization
The evolution of a head (anterior) end with sensory structures and a highly
specialized brain to process sensory input; a feature of bilaterally symmetric
animals, especially the vertebrates.
cephalothorax
The fused head and thorax occurring in many Arthropods, particularly Crustaceans.
cerebellum
part of the vertebrate hind-brain (rhombencephalon) located dorsally; it is
responsible for unconscious coordination of movement and balance.
cerebrum
the dorsal portion, composed of right and left hemispheres, of the vertebrate
forebrain; the integrating center for memory, learning, emotions, and other
highly complex functions of the central nervous system.
cervical
Referring to the neck.
Cestoda
a phylum of Platyhelminthes containing the parasitic tapeworms, the adults of
which are intestinal parasites of vertebrates.
chalazae
ZOOLOGICAL
- Either of two spiral bands in the white of a bird's egg that extend from the
yolk and attach to opposite ends of the lining membrane.
BOTANICAL - the basal part of a plant ovule where the nucellus is fused to the
surrounding integument and to which the funiculus is usually attached.
cheliped
(aka chelicerae)
Clawlike feeding appendages characteristic of the chelicerate group.
chitin
A structural polysaccharide of an amino sugar found in many fungi and in the
exoskeletons of all Arthropods.
chloragogue
cells
Yellow cells which surround the gut of earthworms. These cells break loose into
the coelom and absorb wastes.
chlorenchyma
plant parenchyma cells that contain chloroplasts in their cytoplasm.
Chlorophyta
the green algae, which constitute the largest division of algae. They are terrestrial,
found in damp places, such as tree trunks, in fresh water, and in the marine
environment.
chloroplast
A subcellular organelle which contains chlorophyll and enzymes necessary to
perform photosynthesis. Has an inner and outer membrane, as well as a third
membrane bound sac, the thylakoid. Stacks of thylakoids are called grana, where
the Light Reaction occurs. The cytoplasm of the chlorplast is called the stroma,
and the Light Independant Reaction (carbon fixation) occurs here.
chordate
a member of a diverse phylum of animals that possess a notochord; a dorsal,
hollow nerve cord; pharyngeal gill slits; and a postanal tail as embryos.
chromatid
One of a pair of duplicated chromosomes produced during the S phase of the cell
cycle, which are joined together at the centromere.
chromatin
the aggregate mass of dispersed genetic material formed of DNA and protein and
observed between periods of cell division in eukaryotic cells.
chromosome
a long, threadlike association of genes in the nucleus of all eukaryotic cells
and most visible during mitosis and meiosis. Chromosomes consist of DNA and
protein.
cilium
(plural, cilia)
A short cellular appendage specialized for locomotion.
Ciliophora
a very large subphylum of Protozoans, including the Ciliata and Suctoria, that
at some time during the life cycle possess cilia and usually a micro- and meganucleus.
circular
muscle fiber
The layer of muscles found just below the epidermis.
cleavage
The process of cytokinesis in animal cells, characterized by pinching of the
plasma membrane; also, the succession of rapid cell divisions without growth
during early embryonic development that converts the zygote into a ball of cells.
cloaca
A common opening for the digestive, urinary, and reproductive tracts in all
vertebrates except most mammals.
Covered in:
clone
A lineage of genetically identical individuals.
closed circulatory system
A type of internal transport in which blood is confined to vessels.
coarse
adjustment knob
knob located on the arm of a microscope used to obtain an approximate focus
coelom
The main body cavity, which is lined with mesoderm, and found in annelids, molluscs,
arthropods, echinoderms, and chordates.
Covered in:
collateral
a minor side branch of a blood vessel or nerve.
collecting tubules
That part of the renal tubule in a kidney in which water absorption takes place
under the control of ADH, producing urine of variable concentration depending
on overall water levels in the body.
collenchyma
A supporting plant tissue similar to parenchyma cells, but have cellulose wall
thickenings.
colon
A part of the large intestine in mammals which functions in the reabsorption
of water from feces.
columella
The sterile central column in the sporangia of mosses and liverworts.
columnar epithelial cells
A layer of covering cells that is normally one cell thick and usually covers
connective tissue embryologically derived from the ectoderm. Columnar refers
to their shape.
companion cells
A type of plant cell that is connected to a sieve-tube member, making up the
phloem tissue.
complete
metamorphosis
The change in an organism from larval to adult from where the larval stages
look entirely different from the adult stage.
compound
eye
a type of multi-faceted eye in insects and crustaceans consisting of up to several
thousand light-detecting, focusing ommatidia; especially good at detecting movement.
compound pistil
Made up of several pistils to form one structure
conaliculi
Fine passages that radiate from the lacunae of the lamellae.
condenser
concentrates light from the illuminator below.
conjugation
A recombination mechanism that results in the transfer of genetic, material
between two cells that are temporarily joined.
conjugation
tube
Connecting tube that allows two individuals to fuse together temporarily in
order to exchange micronuclear material.
contractile
vacuole
An organelle that pumps excess water out of many freshwater protist cells.
cork
cambium
A cylinder of meristematic tissue in plants that produces cork cells to replace
the epidermis during secondary growth.
cork
cell
A secondary tissue produced by the cork cambium, and forms the outer part of
the periderm in a woody plant.
corolla
A collective term for all the petals of a flower. The petals are often brightly
coloured and attract pollinating animals. The corolla encloses the reproductive
organs, and is itself protected by the sepal.
corpus luteum
Formed from a follicle that has ruptured due to hormonal regulation. The corpus
luteum secretes progesterone, which prepares the reproductive organs for pregnanacy
and maintains the uterine lining. If the egg is fertilized the corpus luteum
will persist during pregnancy, otherwise it will degenerate.
cortex
The region of the root between the stele and epidermis filled with ground tissue.
cortex
The outer zone of an organ, ex. kidney.
cotyledons
The one (monocot) or two (dicot) seed leaves of an angiosperm embryo.
cranium
The skull of vertebrates.
crista (plural, cristae)
An infolding of the inner membrane of a mitochondrion that houses the electron
transport chain and the enzymes catalyzing the synthesis of ATP.
crop
In vertebrates, it is an expanded part of the esophagus where food is stored
while in invertebrates it is an expansion of the anterior part of the gut system
where food is either digested or stored.
crossing over
the reciprocal exchange of genetic material between non-sister chromatids during
synapsis of meiosis I.
Crustacea
class in the phylum Arthropoda. Most members of this class are aquatic, although
a few are terrestrial.
cuboidal epithelial cells
a layer of covering cells that is normally one cell thick and usually covers
connective tissue embryologically derived from the ectoderm. Cuboidal refers
to their shape.
cutaneous
maximus
Muscle that originates in the region of the armpit and the outer surface of
the latissumus dorsi muscle. The cutaneous maximus muscle inserts on the skin
and it is used for shaking the skin.
cuticle
(1) a waxy covering on the surface of stems and leaves that acts as an adaptation
to prevent desiccation in terrestrial plants. (2) the exoskeleton of an arthropod,
consisting of layers of protein and chitin that are variously modified for different
functions.
Covered in:
cyanobacteria
a large and varied group of bacteria which possess chlorophyll a and
which carry out photosynthesis in the presence of light and air with concomitant
production of oxygen.
cytokinesis
the division of the cytoplasm to form two separate daughter cells immediately
after mitosis.
cytoplasm
the entire contents of the cell, exclusive of the nucleus, and bounded by the
plasma membrane.
dehiscent
will spontaneously burst open to release it's contents, usually spores or seeds.
dendrite
one of usually numerous, short, highly branched processes of a neuron that conveys
nerve impulses toward the cell body.
depressors
muscles which produce the down stroke in birds flight and run from the humerus
to the sternum.
determinate growth
A type of growth characteristic of animals, in which the organism stops growing
after it reaches a certain size.
deuterostome
An evolutionary line of coelomates (ex. echinoderms and chordates) that are
characterized by radial, indeterminate cleavage and development of the anus
from the blastopore.
diaphragm
A sheet of muscle that forms the bottom wall of the thoracic cavity in mammals;
active in ventilating the lungs.
diastema
A gap between teeth.
dicot
A subdivision of flowering plants whose members possess two embryonic seed leaves,
or cotyledons. Dicots also differ from monocots in terms of structure of the
roots and shoots.
differentiation
Divergence in structure and function of cells as they become specialized during
a multicellular organism's development; depends on the control of gene expression
(cell differentiation).
digitigrade
Walking on the toes or fingers, as in most fast-running animals, such as dogs
and cats.
digit
Any part of the pentadactyl limb of vertebrates that contains a linear group
of phalanges. A primate finger or toe.
dimorphism
An occurance of an organism in two forms. Sexual dimorphism refers to males
and females. Dimorphism may occur in, for example, body form or colour.
dioecious
Possesses male and female flowers or other reproductive organs on separate,
unisexual, individual plants.
diploid
Refers to a cell nucleus containing two of each type of chromosome. Refers to
an organism in the main life stage having cell nuclei having two of each type
of chromosome, written as 2N.
Covered in :
distal
Farthest from the body in any structure, or farthest from the center of the
system concerned. For example, the finger is at the distal end of the human
arm.
dorsal
Referring to the top (or back) half of a bilaterally symmetric animal.
dorsal
aorta
an artery of the mammalian blood circulatory system that carries oxygenated
blood from the heart down the length of the trunk, giving rise to several branches
to individual body organs.
dorsal
horn of gray matter
the gray matter of the spinal cord that is internally arranged in an H shape
in cross section.
dorsal
lip
The upper edge of the blastopore produced by invagination during gastrula formation
in amphibian embryos; the site toward which surface cells of the gastrula converge
and migrate inward along the roof of the blastocoel in the process of involution.
dorsal
root ganglion
a nerve trunk containing only sensory axons that enters the spinal cord near
the dorsal surface.
dorsoventrally
flattened
Flattened along the length of it's back ex. platyhelminths.
double circulation
A circulation scheme with separate pulmonary and systemic circuits, which ensures
vigorous blood flow to all organs.
double
stranded
two adjacent strands. For example DNA has two adjacent polynucleotide strands
wound into a spiral shape.
duodenum
Part of the small intestine connecting the stomach to the ileum.
Covered in:
ectoderm
The outermost of the three primary germ layers in animal embryos; gives rise
to the outer covering and, in some phyla, to the nervous system, inner ear,
and lens of the eye.
ectotherm
An animal, such as a reptile, fish, or amphibian, that must use environmental
energy and behavioral adaptations to regulate its body temperature.
effector cell
A muscle cell or gland cell that performs the body's responses to stimuli; responds
to signals from the brain or other processing center of the nervous system.
elevators
muscles which produce the upstroke for flight and are attached to the upper
surface of the humerus by a tendon that runs through the pectoral girdle to
the sternum.
embryo sac
The female gametophyte of angiosperms, formed from the growth and division of
the megaspore into a multicellular structure with eight haploid nuclei.
endoderm
The innermost of the three primary germ layers in animal embryos; lines the
archenteron and gives rise to the liver, pancreas, lungs, and the lining of
the digestive tract.
endodermis
The innermost layer of the plant cortex which surrounds the stele in plants.
It functions in controlling the transport of substances within the plant.
endoplasmic
reticulum
a series of interconnected, flattened cavities lined with a membrane about 4
nm thick, which is continuous with the nuclear membrane.
endosperm
A nutrient-rich tissue formed by union of a sperm cell with two polar nuclei
during double fertilization, which provides nourishment to the developing embryo
in angiosperm seeds.
endotherm
An animal that uses metabolic energy to maintain a constant body temperature,
such as a bird or mammal.
enteron
The tubular passage that extends from mouth to anus.
epidermis
(1) the dermal tissue system in plants. (2) the outer covering of animals.
epididymis
The long, coiled narrow tube running from the testis to the vas deferens in
the higher vertebrates. It functions to store sperm.
epiglottis
A thin flexible structure, made of cartilage with a leaf-like shape, which guards
the entrance to the larynx (the glottis) and prevents food material from entering
the trachea during swallowing.
erythrocyte
A red blood cell; contains hemoglobin, which functions in transporting oxygen
in the circulatory system. These are the most common cell type of the blood.
esophagus
The part of the alimentary canal of vertebrates that lies between the pharynx
and the stomach.
Covered in:
eukaryotes
Any member of a group of organisms that contains all plants and animals apart
form bacteria and blue-green algae. Their cells possess a membrane-bound nucleus
containing the genetic material.
Eustachian tubes
A tube passing from the pharynx to the middle ear in higher vertebrates, serving
to equalize pressure on either side of the tympanic membrane.
exoskeleton
A skeleton present on the outside of an organism, as in Arthropods or Mollusks.
exponential phase
Rapid increase resulting in a J-shaped curve through time.
extensor
a muscle that extends of straightens a limb.
external
nares
An external opening of the nose leading into the nasal cavity.
external oblique
Muscle that inserts on the linea alba and border of the pubis and its action
is to constrict the abdominal region.
eye-piece
or ocular, one of the magnifying elements of a microscope.
eyespots
a light-sensitive organelle present in unicellular organisms, green algae, zoospores,
and some gametes.
Fallopian Tube
upper part of the oviduct in mammals, which is ciliated and where the egg passes
from the coelom.
fascia
sheets of connective tissue.
fat
(triacylglycerol)
a biological compound consisting of three fatty acids linked to one glycerol
molecule.
femur
The thigh bone of tetrapods.
fermentation
a catabolic process that makes a limited amount of ATP from glucose without
an electron transport chain and that produces a characteristic end-product,
such as ethyl alcohol or lactic acid.
fiber cell
A type of plant cell which has a thickened cell wall that performs a structural
role. (ex. cortex, phloem, and xylem.)
fibroblast
a type of cell in loose connective tissue that secretes the protein ingredients
of the extracellular fibers.
fibula
A bone present in the posterior limb of tetrapods lying slightly posterior to
and parallel with the tibia.
flagellum (pl. flagella)
A long cellular appendage specialized for locomotion, ensheathed in an extension
of plasma membrane.
Covered in:
flame cell
A cell specialized for excretion found in platyhelminths.
flexor
any muscle that brings about the bending of a limb.
flower
A structure involved in sexual reproduction. It consists of the androecium (male
organs) and gynoecium (female organs), surrounded by a corolla and a calyx.
The male and female parts may or may not be in the same flower.
foliose
Leaf-like; made up of thin flat lobes, as are the thalli of certain types of
lichen.
follicles
Microscopic structures in the ovary that contain developing ova and secrete
estrogens.
foot
The molluscian organ of locomotion.
frond
A big compound leaf applied to those of palms and ferns.
fructose
a simple carbohydrate (monosaccharide) that is a structural isomer of glucose
and considered to be an atypical ketose.
funiculus
The stalk by which a developing angiosperm ovule attaches to the carpel wall.
gametangium (pl. gametangia)
The reproductive organ of bryophytes, consisting of the male antheridium
and female archegonium;
a multichambered jacket of sterile cells in which gametes are formed.
gametes
Haploid egg or sperm cells that unite during sexual reproduction to produce
a diploid zygote.
gametogenesis
The process where haploid gametes are produced from diploid cells via meiosis.
In animals the two processes are spermatogenesis
and oogenesis.
gametophyte
The part of the life cycle of plants having haploid nuclei and giving rise to
the sex cells that on fusing produce a diploid stage, usually the sporophyte.
ganglion (plural, ganglia)
A cluster (functional group) of nerve cell bodies in a centralized nervous system.
gastric
of or relating to the stomach.
gastric
caeca
Out pockets of the gut. For example they are found in starfish.
gastrulation
The formation of a gastrula from a blastula.
generative
cell
One of two haploid nuclei found within pollen grains of flowering plants, which
enters the pollen tube when it is produced, divides by mitosis, and becomes
the male gamete nucleus that fuses with the female egg cell at fertilization.
gene
one of many discrete units of hereditary information located on the chromosomes
and consisting of DNA.
germinal disc
A small mass of active protoplasm found directly under the vitelline membrane.
gill
The respiratory organ of aquatic animals.
glomerulus
A ball of capillaries surrounded by the Bowman's capsule in the nephron and
serving as the site of filtration in the vertebrate kidney.
glottis
Opening of the larynx (windpipe).
glucose
(C6H12O6) An important monosaccharide (simple
carbohydrate) that acts as a primary energy supply for both plant and animal
cells.
glycolysis
The splitting of glucose into pyruvate. Glycolysis is the one metabolic pathway
that occurs in all living cells, serving as the starting point for fermentation
or aerobic respiration.
glycogen
An extensively branched glucose storage polysaccharide found in the liver and
muscle of animals; the animal equivalent of starch.
goblet cells
a wineglass-shaped cell, which is present in the columnar epithelium of the
mammalian intestine and secretes mucin.
Golgi
apparatus
An organelle in eukaryotic cells consisting of stacks of membranes that modify,
store, and route products to the endoplasmic reticulum.
gonads
The male and female sex organs; the gamete-producing organs in most animals.
granum
(plural, grana)
A stacked portion of the thylakoid membrane in the chloroplast. Grana function
in the light reactions of photosynthesis.
granulocyte
A type of white blood cell (leucocyte) that possesses granules in the cytoplasm
and is formed in the bone marrow. Granulocytes form about 70% of all leucocytes.
guard
cell
A specialized epidermal plant cell that forms the boundaries of the stomata.
gymnosperm
A vascular plant that bears naked seeds not enclosed in any specialized chambers.
gynoecium
The female reproductive organs of a flower, consisting of one or more carpels.
habituation
a simple kind of learning involving loss of sensitivity to unimportant stimuli,
allowing an animal to conserve time and energy.
haemocoel
The body cavity of invertebrates, arthropods, and mollusks. As to the coelom,
the haemocoel never opens to the exterior and it does not contain germ cells.
haploid
Referring to a cell nucleus it contains one of each type of chromosome. Referring
to an organism it is one in which the main life stage has cell nuclei with one
of each type of chromosome, written as n.
haploid
gametophyte
The part of the life cycle of plants having haploid nuclei and giving rise to
the sex cells that on fusing produce a diploid stage, usually the sporophyte.
Haversian
canal
One of many channels formed within bone by the development of osteoblasts in
concentric rings around them, and whose function is to facilitate linking of
the living parts.
heart
The muscular pump of the blood circulatory system.
hepatic
caeca
A blind-ending sac in the digestive system, which occurs in mammals at the junction
of the small and large intestines. In herbivores the cecum contains bacteria
that produce cellulase, enabling breakdown of cellulose cell walls.
hepatic
portal system
The part of the blood circulatory system of vertebrates in which blood from
the alimentary canal is taken through capillaries in the liver before transport
to the heart.
Covered in:
hepatic portal vein
A vein which enables some materials absorbed from the gut to be stored or filtered
out during passage through the liver.
hepatocytes
A liver cell.
hermaphrodite
Plants which possess both stamens and carpels in the same flower, while in animals
it is organisms which possess both male and female sex organs
heterocyst
A specialized cell that engages in nitrogen fixation on some filamentous cyanobacteria.
heterodont
Possessing teeth of different kinds, such as incisors or molars.
heterosporous
The formation of more than one sort of spore, usually microspores and megaspores
in ferns and seed plants, giving rise to distinct male and female gametophyte
generations.
heterotroph
An organism dependent on obtaining organic food from the environment because
it is unable to synthesize organic material. They (animals, fungi, many bacteria,
and a few flowering plants) obtain almost all their organic material either
directly or indirectly from the activity of autotrophs.
homeothermic
Any warm-blooded animal (mammal or bird that can maintain its body temperature
within a narrow range, usually above that of its surroundings despite large
variations in environmental temperature. It may be maintained continually or
for limited periods only.
homologous
chromosomes
chromosome pairs of the same length centromere position, and staining pattern
that possess genes for the same traits at corresponding loci. One homologous
chromosome is inherited from the organism's father, the other from the mother.
homology
similarity in characteristics resulting from a shared ancestry.
homospory
The possession of only one form of spore. This gives rise to a single gametophyte
generation carrying both male and female reproductive organs.
humerus
The bone of the vertebrate forelimb, or arm, nearest to the body, to which it
is attached at the shoulder. It is attached distally to the radius and ulna
at the elbow.
hypha
(plural, hyphae)
A filament that collectively makes up the body of a fungus.
ileum
The part of the intestine lying between the duodenum and the colon, where digestion
is completed by enzymes that break down carbohydrates, fates, and proteins.
Absorption of food also occurs here.
iliac
artery
Arise at the posterior end of the abdominal cavity, where they form the two
major terminal branches off the aorta supplying the legs with oxygenated blood.
iliolumbar
artery
arise form the aorta posterior to the genital arteries and send branches to
the dorsal musculature of the body wall.
illuminator
light source found at the base of the microscope.
imprinting
an aspect of learning in which there is rapid development of a response to a
particular stimulus at an early stage of development. Young animals recognize
the first object they see, such as a mother figure, and they can be imprinted
on objects other that their own species.
incisor
A front, chisel-shaped tooth in mammals, normally used for cutting or gnawing.
In some species incisors continue to grow throughout life.
incomplete
metamorphosis
The change in an organism from larval to adult form where there is a gradual
development of a nymph to an adult.
indehiscent
Will not spontaneously burst open to release it's contents, usually spores or
seeds.
independent assortment
the random arrangement and separation of chromosomes during meiosis, giving
all possible combinations in equal frequency. This process explains the random
distribution in the gametes of genes or homologous chromosomes.
indeterminate cleavage
Characteristic of deuterostomes, each cell produced by early cleavages retains
the ability to develop into a complete embryo.
inferior vena cava
Drains blood from the abdominal region and brings it back to the heart via the
right atrium.
inflorescence
A specialized branching stem bearing more than a single flower, for example,
a male catkin.
infundibulum
the part of the pituitary gland that is produced by a down growth of the posterior
region of the forebrain.
innominate
artery
A short artery arising from the aorta that gives rise to the subclavian and
carotid arteries.
Insecta
class of organisms that are small air-breathing arthropods. This class contains
organisms that in the adult normally have six legs, three distinct regions to
the body (head, thorax, and abdomen), one pair of antennae, and one or two pairs
of wings.
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
insertion
The more movable attachment point of a muscle.
integument
The outermost layer or layers of tissue that serve in protection.
intercalated
disc
A specialized region in cardiac muscle which allows the action potential to
spread to all cardiac muscle cells, causing the whole heart to contract.
intercostal
muscles
The muscles lying between the ribs of vertebrates that, with the ribs, form
the walls of the thorax.
internal nares
two small openings in the roof of the buccal cavity.
internal oblique
Muscle that inserts on the linea alba and its action is to compress the abdominal
region.
internode
The segment of a plant stem between the points where leaves are attached.
interphase
A stage of growth in the cell cycle in which metabolism occurs without visible
evidence of nuclear division. Interphase is the phase between divisions (meiosis
and mitosis).
interstitial cells
Cells scattered among the seminiferous tubules of the vertebrate testis that
secrete testosterone and other androgens, the male sex hormones.
intestinal
villi
folds and projections on the internal surface if the intestine that greatly
increases the surface area for digestion and absorption.
intestine
The part of the alimentary canal that lies between the stomach and anus. It
is usually coiled, and the internal surface is greatly increased by the presence
of folds and projections (villi) to enable efficient digestion and absorption.
iris
diaphragm control
small lever that allows the size of the opening to change in order to regulate
the amount of light passing through it.
jejunum
Found in the small intestine, it is located between the duodenum and the ileum.
jointed
appendages
Where the bones that make up the appendage have contacts between them
karyokinesis
the division of the cell nucleus.
kidney
Paired vertebrate organs that regulate
fluid balance in the body and filter out wastes from the blood in the form of
urine. The functional unit of the kidney is the nephron.
Wastes are filtered from the blood by nephrons, which drain into the ureters
(muscular tubes that connect each kidney to the bladder).
labium
The lower lip of insects, found immediately behind the maxillae.
labrum
A cuticular plate at the front of the insect head, forming an upper lip.
lacunae
One of many small cavities uniformly spaced along the lamellae of bones. In
living bone, each lacuna contains one bone cell known as an osteocyte. Small
canals (canaliculi) radiate from the lacunae and in these are small protoplasmic
processes that conn ect with the osteoblast in other lacunae.
lag phase
The stage of growth of microbial cells in which nucleic acids and proteins are
synthesized, but in which there is no cell division.
lamellae
(a) the sheet-like membrane that occurs within the chloroplast, each of which
consists of a pair of membranes with a narrow space between. (b) the gills of
a basidiomycete fungus that radiate out from the stalk beneath the cap of the
fruit and bear the spores.
larynx
(the voice box) A dilation of the upper part of the trachea (windpipe) of tetrapods
(Adam's apple in humans), occurring in the front part of the neck containing
the vocal cords
lateral
At the side of
lateral meristem
Consisting of the vascular cambium and the cork cambium, it produces the secondary
tissues which make up the secondary plant body.
lateral (secondary) roots
The branches that develop from deep inside the plant root. This type of branching
is initiated by the plant hormone, auxin.
latissimus
dorsi muscle
This muscle originates on the thoracic and lumbar vertebrate and inserts on
the shaft of the humerus. Its action is to pull the arm backward and upward.
leaf
A thin organ arising from the node on the stem of a plant. The main site of
phtosynthesis.
Covered in:
leaflets
the "leaves" that make up a compound leaf.
leaf
primordia
The early, precursor cells of a leaf.
lenticel
A small pore found on the surface of stems and roots in higher plants through
which gas exchange can take place.
leucocyte
A white blood cell; typically functions in immunity, such as phagocytosis or
antibody production.
limb
An articulated (jointed) projection from the body of an animal that is used
for locomotion, such as a leg or wing.
linea
alba
A narrow, longitudinal, whitish band of tendonous tissue found along the mid-ventral
line.
lipid
One of a family of compounds, including fats, phospholipids, and steroids, that
are insoluble in water.
liver
The largest organ in the vertebrate body, performing such functions as producing
bile, preparing nitrogenous wastes for disposal, and detoxifying poisonous chemicals
in the blood.
liverworts
Belong to the class Bryophyta and are found in damp and wet conditions.
lobule
One of several lobes or divisions of the liver.
locus
(pl. loci)
a particular place along the length of a certain chromosome where a given gene
is located.
log (logarithmic) phase
The exponential phase of growth in a bacterial culture.
longitudinal axis
a lengthwise axis from head to tail end of an animal.
longitudinal
muscle fiber
Arranged in a feather-like pattern, this thick layer of muscles is found below
the circular muscle fibers.
loop of Henle
The long hairpin turn, with a descending and ascending limb, of the renal tubule
in the vertebrate kidney; functions in water and salt reabsorption.
lower
epidermis
the tissue in plants, usually one cell thick, that is on the bottom of the leaves.
lumbar
Vertebrae present between the thoracic vertebrae and the sacral vertebrae, in
the region of the waist in mammals.
lumen
Any cavity enclosed within a cell or structure, such as the lumen of the gut.
lung
The organ that enables an animal to breathe air. In mammals the paired lungs
are each supplied by a bronchus that divides, treelike, into bronchioles. Each
bronchiole ends in an atrium from which arise numerous alveoli that contact
a vast capillary system.
lymphatic system
A system of tubules in vertebrates that drains excess tissue fluid (lymph) from
the tissue spaces to the blood system. Lymph are blind-ending in the tissue
spaces, gradually joining up to larger and larger vessels with two major lymphatic
ducts entering the venous system in the upper thoracic cavity. Lymph is moved
by the action of skeletal muscles.
lysosome
a membrane-enclosed bag of hydrolytic enzymes found in the cytoplasm of eukaryotic
cells.
macromere
A large cell from the vegetative pole of a developing egg. Such a cell contains
yolk and gives rise to the endoderm of the embryo.
macronucleus
The larger of two nuclei found in some Protozoans and concerned with cell division.
It appears to have mainly vegetative functions.
madreporite
The porous opening to the hydrocele in echinoderms.
Malpighian
tubule
A unique excretory organ of insects that empties into the digestive tract, removes
nitrogenous wastes from the blood, and functions in osmoregulation.
mammary gland
A gland present in female mammals that produces milk used to suckle the young.
It probably evolved from a modified sweat gland and at least two are normally
present, although in many mammals more than two are developed, usually concentrated
on the underbelly beneath the pelvic girdle. In most mammals the size of the
gland is determined by the state of the estrous cycle.
mandibles
The mouthparts of an animal that does most of the crushing of food materials.
In vertebrates, the term usually denotes the lower jaw.
mandibular
abductor muscle
Muscle in the crayfish that pulls up the mandible.
mantle
The part of the epidermis of a mollusk that secretes the shell and covers the
dorsal and lateral surfaces.
masseter
Large muscle that elevates the jaw.
mature ovum
a functional egg cell of an animal.
maxilla
In vertebrates it is the bone of the upper jaw, carrying all teeth except the
incisors. In invertebrates (arthropods) it is part of the mouthparts lying behind
the jaws.
maxillipede
Any limb modified for feeding, normally found immediately in front of the legs,
particularly in crustaceans.
median
describing a location along the line of bilateral symmetry (median plane).
medulla
The central part of an organ. Ex. kidney.
medulla
oblongata
The lowest part of the vertebrate brain; a swelling of the hind-brain dorsal
to the anterior spinal cord that controls autonomic, homeostatic functions,
including breathing, heart and blood vessel activity, swallowing, digestion,
and vomiting.
medusa
the floating, flattened, mouth-down version of the cnidarian body plan. The
alternate form is the polyp.
megagametophyte
Female gametophyte in seed plants.
megasporangium
The organ in which megaspores are formed.
megaspore
The larger of two types of spores produced by many ferns and seed plants. The
megaspore gives rise to a female gametophyte in ferns and in seed plants, and
in flowering plants becomes the embryo sac.
megasporocyte
Special cell of the megasporangium called the megaspore mother cell.
meiosis
A type of nuclear division associated with sexual reproduction, producing four
haploid cells from a single diploid cell, the process involving two cycles of
division.
meristem
A region of a plant in which active cell division occurs, the cells of the meristem
being undifferentiated into a specialized form. Meristematic tissues occur at
the root and shoot tips giving growth in length.
mesentery
The layers of peritoneum that attach the gut system and its associated organs,
for example, the spleen, to the dorsal surface of the peritoneal cavity in mammals.
mesoderm
The middle primary germ layer of an early embryo that develops into the notochord,
the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the
circulatory system.
mesophyll
The ground tissue of a leaf, sandwiched between the upper and lower epidermis
and specialized for photosynthesis.
metabolism
The totality of an organism's chemical processes, consisting of catabolic and
anabolic pathways.
metaphase
a stage of nuclear division in eukaryote cells, occurring once in mitosis and
twice in meiosis. This phase begins when all of the centromeres line up at the
equatorial plane.
microgametophyte
Pollen grains.
micromere
Any of the small blastomeres formed at the animal pole of a developing egg.
These eventually give rise to the ectoderm.
micronucleus
The smaller of the two nuclei found in some Protozoans that is concerned with
cell division.
micropyle
A small canal in the integument surrounding the ovule of a flowering plant,
through which the pollen tube usually enters the ovule on the way to the embryo
sac. Water enters the seed via the micropyle prior to germination.
microsporangium
The sporangium from which the microspores are formed, which in higher plants
is the pollen sac.
microspore
The smaller of the two types of spore produced by ferns and higher plants, giving
rise to the male gametophyte. In Tracheophytes the microspore is the pollen
grain.
microsporocytes
Thousands of cells (pollen mother cells) found within a young microsporangium.
microvillus
(plural, microvilli)
collectively, fine, finger-like projections of the epithelial cells in the lumen
of the small intestine that increase its surface area.
mictic egg
A thin shelled haploid egg. If not fertilized, they will produce males by parthenogenesis.
If fertilized, they will accumulate a large amount of yolk and secrete a heavier,
resistant shell. These eggs are now dormant and can survive harsher environmental
conditions until they develop into a diploid amictic female.
mitochondrion
(plural, mitochondria)
An organelle in eukaryotic cells that serves as the site of cellular respiration.
mitosis
A process of cell division in eukaryotic cells conventionally divided into the
growth period (interphase) and four stages: prophase, metaphase, anaphase, and
telophase. The stages conserve chromosome number by equally allocating replicated
chromosomes to each of the daughter cells.
mitospores
Spores resulting from meiosis.
molar
teeth
The crushing teeth that occur at the back of the jaw of mammals. Each molar
has a complicated pattern of cusps and ridges and several roots. The molars
have no preceding milk teeth.
monocot
A subdivision of flowering plants whose members possess one embryonic seed leaf,
or cotyledon. The grasses are a classic example of monocots.
monoecious
Referring to a plant species that has both staminate and carpellate flowers
on the same individual.
morphogenesis
The development of body shape and organization during ontogeny.
moss
Any bryophyte of the class Musci. Usually these are small plants (less than
5 cm high) attached to moist or wet substrates by rhizoids; this is the sporophyte
generation. The sexual organs are borne on a gametophyte generation, and the
antheridia and archegonia are on separate leaf rosettes.
mouth
The anterior opening of the alimentary canal of animals through which food is
taken into the body. It is often surrounded by mouthparts or tentacles that
facilitate feeding.
mucosa
Any epithelium that secretes mucus, such as the mucous membrane lining the alimentary
canal.
Mullerian duct
The duct from the embryonic pronephros, which in later development in mammals
becomes the oviduct in females and disappears in males.
muscularis
The fleshy part of any animal that consists of tissue made up of highly contractile
cells serving to move parts of the body relative to each other.
mushroom
gills
A tissue of radiating strips found on the lower surface of the mushroom cap.
mycelium
The densely branched network of hyphae in a fungus.
myelin
a sheath of fatty substance associated with protein that surrounds larger nerve
fibers of vertebrates. The sheath permits a greater current flow and thus speeds
transmission of nerve impulses.
myofibrils
Fibrils arranged in longitudinal bundles in muscle cells (fibers); composed
of thin filaments of actin and a regulatory protein and thick filaments of myosin.
myotome
A muscle block that is repeated in each metameric segment.
nare
An external opening of the nose that leads into the nasal cavity.
nasal cavity
A system of chambers above the hard palate of mammals through which air passes
from the nostrils to the pharynx and on to the lungs. During inspiration, air
is filtered, warmed, moistened, and smelled.
nasal septum
A dividing wall of partition that occurs between the nasal cavities.
naso-pharynx
Above the palate where the nasal cavities open into.
nectary (pl. nectaries)
An area in the tissue in a flower that secretes sugary nectar, serving as an
attraction for visiting insects. Nectaries are frequently deep inside the corolla
so that the pollinator both deposits and carries off pollen.
neoblast
Are undifferentiated cells arising from the parenchyma, which are rich in RNA.
Thse cells form the blastema, which preceeds regeneration of planarians.
nephridium
(pl. nephridia) A primitive excretory organ present in many invertebrates, for
example, the earthworm, in the form of a tube that opens at one end to the exterior.
The other end may open into the coelom or may terminate in a flame cell.
nephron
The functional unit of the vertebrate kidney.
neural
Relating to the nerves or to the nervous system.
neuron
(nerve cell) the structural unit of the nervous system, usually consisting of
the cell body and cytoplasmic extensions.
neurula
The stage of a vertebrate embryo when gastrulation is largely finished and a
neural plate is forming, ending with formation of the neural tube.
nictitating membrane
A third eyelid that occurs in birds, reptiles, sharks, amphibians, and some
mammals. It is transparent and flicks over the eyeball without shutting out
the light.
nodes
A point along the stem of a plant at which leaves are attached.
nodes
of Ranvier
the small gaps in the myelin sheath between successive ganglia cells along the
axon of a neuron; also, the site of high concentration of voltage-sensitive
ion channels.
Nostoc
a blue-green algae.
nostril
(nares) An external opening of the nose leading into the nasal cavity.
notochord
A longitudinal, flexible rod formed from dorsal mesoderm and located between
the gut and the nerve cord in all chordate embryos.
nucleolus
(plural, nucleoli)
A specialized structure in the nucleus, formed from various chromosomes and
active in the synthesis of ribosomes.
nucleus
An organelle of eukaryotic cells that is bounded by a nuclear membrane and contains
the chromosomes whose genes control the structure of proteins within the cell.
objective
A magnifying element found on the revolving nosepiece of a microscope.
ocelli
A type of eye found in threes in insects that detects light and dark, used primarily
in flight.
ocular
the eye-piece of a microscope which serves to magnify the object.
olfactory
bulb
a projection of the frontal lobe of a cerebral hemisphere that is well developed
in most vertebrates, but reduced in humans, from which arises the olfactory
nerve. It is associated with the sense of smell.
olfactory
nerve
arises from the olfactory bulb and is associated with receiving and transmitting
signals concerning the sense of smell.
omentum
(pl. omenta)
A membrane that joins one internal organ to another.
oogenesis
The process in the ovary that results in the production of female gametes.
ootid
(ovum) Produced when a haploid secondary ooctye undergoes meiosis.
operculum
(1) the lid of a moss capsule. (2) the hard bony flap covering the gills of
fishes. (3) the plate of exoskeletal material on the foot of a gastropod mollusk
with which it closes off the entrance to the shell.
opposite
arrangement
leaves located at the same height on the plant but at opposite sides of the
stem.
optic
chiasma
a point under the hypothalamus of the brain where the two optic nerves meet
and cross over, so that a stimulus from either eye is interpreted in the optic
lobe of the opposite side of the brain.
optic
lobes
one of a pair of lobes found as swellings on the dorsal side of the midbrain
of some lower vertebrates. The lobes integrate sensory information from the
eyes and certain auditory reflexes.
oral
groove
A depression leading to the mouth in some invertebrates.
organ
any multicellular structural or functional unit of an animal of plant, often
composed of different tissues that perform specific roles, such as the liver
and leaf.
organogenesis
An early period of rapid embryonic development in which the organs take form
from the primary germ layers.
origin
The less movable attachment point of a muscle.
origin of life
the process by which biomolecules, subcellular structures, and living cells
have come into existence.
oro-pharynx
Part of the pharynx found behind the buccal cavity and is shared by the respiratory
and digestive systems
Oscillatoria
blue-green algae without any heterocysts.
osteocyte
A cell located in lacunae of vertebrate bone, that deposits a matrix of collagen
and calcium phosphate that forms a mineralized connective tissue.
ostia
An opening in the heart where blood enters. Found in open circulatory systems.
ostium
Any of numerous openings present in sponges through which water is drawn in.
ovarian
artery
Arise from the abdominal aorta just posterior to the kidneys and supplies the
ovaries with oxygenated blood.
ovary
(1) in flowers,
the portion of a carpel in which the egg-containing ovules develop. (2) in animals,
the structure that produces female gametes and reproductive hormones.
Covered in:
oviduct
A tube passing from the ovary to the vagina in invertebrates or to the uterus
in vertebrates.
ovule
A structure found in higher plants that contains an egg cell and develops into
a seed after fertilization.
ovuliferous
scales
A spiral series of overlapping scales making up the female or ovulate cone with
each scale producing two ovules on the upper surface.
ovum
(pl. ova)
A functional egg cell of an animal, produced by gametogenesis. Ova are frequently
packed with nutritive yolk granules and are usually immobile.
Covered in:
oxidation
A chemical process in which either electrons are lost from an atom, or oxygen
is added to a molecule. Oxidation may also occur without the addition of oxygen
if hydrogen is removed (dehydrogenation.)
oxygen
A colourless, tasteless gas forming about 21% of Earth's atmosphere and capable
of combining with all other elements except the inert gases.
oxygenated blood
blood that has become enriched with oxygen as it exchanges with the lungs.
palate
The roof of the mouth in vertebrates formed anteriorly by a bony projection
of the upper jaw and posteriorly by the fold of connecitve tissue (soft palate).
palisade
chlorenchyma
the upper internal tissue of a plant leaf which are stacked side by side and
contain chloroplasts for photosynthesis. The chloroplasts lie close to the edge
of the cell in order to gain maximum light and gas supply.
palisdae
mesophyll
the upper internal tissue of a plant leaf which are stacked side by side resembling
columns.
pancreas (Frog,
Rat)
A gland situated in the mesentery of the duodenum of jawed vertebrates that
has both an exocrine and an endocrine function.
papilla (pl. papillae)
A projection from the surface of a structure, such as tongue papillae, which
carry the taste buds.
Paramecium
a genus of freshwater protozoan, having an oval body covered with cilia and
a ventral ciliated groove for feeding.
paramylum
A starch-like substance that occurs as a food reserve in flagellate Protozoans
and algae, such as Euglena.
parasite
An organism that absorbs nutrients from the body fluids of living hosts.
parenchyma cells
A relatively unspecialized plant cell type that carries on most of the metabolism
synthesizes and stores organic products, and develops into more differentiated
cell types.
parietal peritonium
A thin layer of connective tissue which originated from the mesoderm. It lines
the abdominal cavity, as opposed to the internal organs.
parthenogenesis
The development from an egg without fertilization by a sperm. The egg cell may
be haploid or diploid.
pectoral
girdle
The skeletal support for the anterior limbs of vertebrates that transmits power
from limbs to the body and also serves to protect and support the organs in
the thorax.
pectoralis
major
A muscle that originates on the sternum and inserts on the humerus.
pelvic
girdle
The skeletal support for posterior limbs of vertebrates that transmits power
in locomotion from the hind limbs to the body.
pentadactyl
Bearing five digits (fingers or toes), which is present in amphibia, reptiles,
birds, and mammals.
pereiopod
The walking legs of a crayfish.
pericardial cavity
The part of the coelom surrounding the heart in vertebrates or the part of the
hemocoel surrounding the heart in arthropods.
pericardial sinus
A cavity which contains the heart.
pericardial membrane
The membrane surrounding the heart.
pericardium
A sac-like envelope surrounding the vertebrate heart and the pericardial cavity
in arthropods and mollusks.
pericycle
A layer of cells just inside the endodermis of a root that may become meristematic
and begin dividing again.
periderm
The protective coat that replaces the epidermis in plants during secondary growth,
formed of the cork and cork cambium.
peripheral
of or relating to the outside or extreme edge of a structure.
peripheral nervous system
The sensory and motor neurons that connect to the central nervous system.
peritoneum
The thin membrane of meosdermal origin that lines the body cavity, covers the
heart, and forms mesenteries.
petal
Any of the separate parts of the corolla of a flower. Often brightly colored,
the petal is a modified leaf and is important in flowers pollinated by insects.
petiole
the stalk of a leaf, which joins the leaf to a node of the stem.
Phaeophyta
a division of algae, comprising the brown algae.
phagocytosis
A type of endocytosis involving large, particulate substances.
pharynx
An area in the vertebrate throat where air and food passages cross; in flatworms,
the muscular tube that protrudes from the ventral side of the worm and ends
in the mouth.
phloem
The portion of the vascular system in plants consisting of living cells arranged
into elongated tubes that transport sugar and other organic nutrients throughout
the plant.
photosynthesis
The conversion of light energy into chemical energy that is stored in glucose
or other organic compounds; occurs in plants, algae, and certain procaryotes.
photoautotroph
A type of autotroph that uses light as an energy source to synthesize organic
compounds from inorganic materials. Green plants are photoautotrophs.
pileus
the cap of certain groups of fungi.
See also Cap
pinna
1. the primary division of a leaf. 2. a wing or fin. 3. the projecting part
of the external ear of mammals.
pistil
The flask-shaped female reproductive unit of a flower, composed of ovary, style,
and stigma.
pith
The core of a dicotyledon stem, containing parenchyma cells that have a storage
function.
pituitary gland
An endocrine gland at the base of the hypothalamus; consists of a posterior
lobe (neurohypophysis), which stores and releases two hormones produced by the
hypothalamus, and an anterior lobe (adenohypophysis), which produces and secretes
many hormones that regulate diverse body functions.
plantigrade
Walking on the entire sole of the foot, as in humans and bears.
plaque
A clear area in a lawn of a bacterial colony, where the bacteria have undergone
lysis due to bacteriophage infection.
plasma
membrane
The outer boundary of cells which is only visible with an electron microscope.
plasmalemma
the cell membrane that also lines the connecting plamsodesmata between living
cells.
plateau
A period or level at which something is stabilized for a time, represented on
a graph as a horizontal line.
pleopod
A biramous (forked) abdominal appendage of the crayfish. They may be used for
swimming or carrying eggs, in the females case. In the male, the first two pairs
are modified for copulation.
pleura
The membrane that covers the lung and lines the innermost wall of the thorax.
poikilothermic
(Ectotherm) Any animal whose body temperature follows that of the surrounding
environment.
polar
body
A small haploid cell, produced during oogenesis in female animals, that does
not develop into a functional ovum. A similar situation arises in the development
of the egg cell of higher plants, in which only one fertile gamete is produced
from meiosis.
polar
nuclei
The two nuclei that are formed at each pole of the angiosperm embryo sac. They
will fuse with a male nucleus to form a primary endosperm nucleus.
pollen
grain
A small structure of higher plants that contains haploid male gamete nuclei
and is surrounded by a double wall, the exine and intine. Pollen grains are
transported from the male stamen to the female stigma in a process called pollination.
pollen tube
A slender structure produced from a pollen grain after pollination.
polyp
The asexual reproducing, normally sedentary form of coelenterates such as the
sea anemone.
polysaccharide
A large carbohydrate molecule with a chainlike or branched structrure composed
of many monosaccharides. Functions in storage (ex. starch, insulin, glycogen)
or structre (ex. cellulose, chitin.)
posterior
situated behind; back; hind.
premolars
The cheek teeth in mammals that occur between the molars and the canines. They
have a grinding function.
primary growth
Growth that takes place relatively close to the tips of roots and stems. It
is intiated by the apical meristems, and primarily involves extending the length
of the plant body.
primary
oocyte
A diploid cell formed after a diploid oogonium underwent mitosis. The primary
oocyte is arrested in Prophase of Meiosis I. It will complete meiosis to form
a haploid primary oocyte and the haploid first polar body.
primary root
The first root of the plant. It develops in continuation from the root tip.
primary
spermatocyte
A diploid cell formed after a diploid spermatogonium underwent mitosis. The
primary spermatocyte is arrested in Prophase of Meiosis I. It will complete
meiosis to form two haploid secondary spermatocytes.
primitive
streak
A line of cells in the center of the embryonic disk of reptiles, birds, and
mammals that forms the future axis of the embryo.
proboscis
The elongated mouthparts of some insects and other invertibrates.
prokaryotes
an organism that is either a bacterium or a blue-green alga, its main characteristic
being prokaryotic cells lacking a membrane-bound nucleus and no mitosis or meiosis.
proglottid
A reproductive division of a tapeworm.
prostate gland
a gland of male animals that produces substances that are added to the semen.
protein
A three-dimensional biological polymer constructed from a set of 20 different
monomers called amino acids.
Protozoan
(plural, protozoa)
A protist that lives primarily by ingesting food, an animal-like mode of nutrition.
proximal
Pertaining to the region near the body.
pubic symphysis
Joint where the pubic bones come together.
pulmonary veins
Veins that carry the oxygenated blood from the lungs back to the heart.
pyloric portion
Of or relating to the end of the vertebrate stomach that opens into the intestine.
pyloric sphincter
A ring of smooth muscle surrounding the opening of the pyloric portion of the
stomach into the intestine. The sphincter prevents premature escape of food
from the stomach into the intestine before the food is properly digested.
pyrenoid
A region of starch formation found in the chloroplasts of various algae, for
example, Chlamydomonas.
pyruvic
acid
An important 3-carbon molecule formed from glucose and glycerol in glycolysis.
radial
canal
Part of the water vascular system, it extends into each arm of the starfish
and ends in a small external tentacale at the tip of each arm.
radial
symmetry
Characterizing a body shaped like a pie or barrel, with many equal parts radiating
outward like the spokes of a wheel; present in cnidarians and echinoderms.
radius
The anterior bone in the lower part of the forelimb of vertebrates.
receptacle
1. in flowering plants, the end of the stalk becoming the flower parts. 2. in
ferns, the mass of tissue that becomes the sporangium. 3. in liverworts, the
cup containing a gemma. 4. in algae, the swollen tip of a branch carrying the
reproductive organs.
rectum
The terminal part of the intestine of an animal, opening into the anus or cloaca.
rectus abdominis
Muscle that originates on the pelvic girdle (pubis) and inserts on the cartilage
of the first and second ribs.
reducing agent
any substance capable of removing oxygen from a molecule or of adding hydrogen,
that is, it is capable of contributing electrons to a process.
renal
Pertaining to the kidneys.
renal portal system
The system of veins in fish and amphibians taking blood from the region of the
tail or hind limbs directly to the kidneys.
replication
the production of exact copies of complex molecules during the growth of living
organisms.
respiration
A process by which gaseous exchange -oxygen and carbon dioxide-takes place between
an organism and the surrounding medium.
rhizoid
A hair-like structure that functions as a root in lower organisms, such as certain
fungi and mosses. Rhizoids are important in penetrating a substance, giving
anchorage and absorbing nutrients.
rhizome
A horizontal underground stem, with leaves and buds, that serves as a storage
organ and a means of vegetative propagation.
Rhizopoda
subclass which includes the amebiod protozoans that feed by means of pseudopodia
and lack cilia or flagella.
Rhodophyta
members of the Thallophyta division Rhodophyta, in which the chlorophyll is
masked by phytocoerythrin. Rhodophytes vary from filamentous forms to those
with an extensive thallus and have non-motile gametes.
ribosome
a cell organelle constructed in the nucleolus, consisting of two subunits and
functioning as the site of protein synthesis in the cytoplasm.
root
The part of a plant that usually grows below ground. The root provides anchorage
for aerial parts, absorbs water and mineral salts from the soil, conducts water
and nutrients to other parts of the plant, and often stores food materials over
winter.
root
apical meristem
A group of plant cells found at the growing end of a root which are capable
of dividing indefinetly. Their main function is the production of new root.
root
cap
A structure found at the apex of roots, except those of many water plants, produced
by the apical meristem. As the root pushes its way through the soil, the outer
(older) cells of the root cap are sloughed off and replaced by new cells from
the meristem.
rosette
arrangement
an arrangement in which the structures (leaves, petals, etc.) are spread in
a horizontal plane from a short axis at ground level.
rostrum
Anterior point of Arthropod head.
rough
endoplasmic reticulum
Endoplasmic reticulum when it is covered with ribosomes is referred to as rough
ER.
rumin
A branch of the esophagus where unchewed food is temporarily stored until it
is regurgitated tothe mouth for chewing.
sagittal section
a longitudinal section through the median vertical plane.
saprophytes
Any plant of microorganism that obtains its nutrition from dead or decaying
organic materials in the form of organic substances in solution. Such organisms
are important in breaking down dead organic material.
sarcolemma
The thin connective tissue sheath that occurs around a muscle fiber and extends
and contracts with the contractile material enclosed.
sarcoplasm
The cytoplasm of a muscle cell.
scale
Any plate-like outgrowth of the integument, each in the form of a flat calcified
or horny structure on the surface of the skin.
scapula
The shoulder blade.
Schwann cells
a chain of supporting cells enclosing the axons of many neurons and forming
an insulating layer called the myelin sheath.
sciatic
nerve
composed of spinal nerves VII, VIII, IX united to send impulses to the hind
leg.
sciatic
plexus
the uniting of spinal nerves VII, VIII, IX to form the sciatic nerve to the
hind leg.
scolex
The head of a tapeworm, found at the anterior end. It has hooks and suckers
for attachment to it's host.
scrotum
a sac containing the testes of male mammals that is situated outside the posteriorly
ventral part of the abdomen. The external location ensures that the testes are
cooled to below body temperature, since heat can adversely affect development
of sperm.
secondary
growth
The increase in girth of the stems and roots of many plants, especially woody,
perennial dicots.
secondary
oocyte
A haploid cell whose chromosome number was reduced when a diploid primary oocyte
underwent meiosis. A secondary oocyte will undergo a second round of meiosis
to produce a haploid ovum and the haploid second polar body.
secondary
spermatocyte
A haploid cell whose chromosome number was reduced when a diploid primary spermatocyte
underwent meiosis. A secondary spermatocyte will undergo a second round of meiosis
to produce two haploid spermatids.
secondary root
(Lateral root.) A root that arises from another, older primary root. Initiated
by the plant hormone, auxin.
secondary
phloem
Tissue produced by vascular cambium and composed of both sieve tubes and companion
cells.
secondary
xylem
Tissue produced by vascular cambium and composed of both tracheids and vessel
elements.
secondary
palate
the roof of the mouth in vertebrates formed anteriorly by a bony projection
of the upper jaw forms the hard palate.
seed
Formed from a fertilized ovule, it is the body from which a new plant develops.
It is comprised of an outer coat enclosing a food source (which may be stored
in the cotyledon), and an embryo.
seed coat
A protective coat around the seed, formed from the integuments of the ovule.
seed plant
any plant that bears seeds. Most seed plants, have flowers and produce seeds
in fruits; some, such as the pines, form seeds on cones.
segment
a division; a section.
segregation
the separation of homologous chromosomes during anaphase 1 of meiosis, producing
gametes containing only one allele of each gene. Such an occurrence is the physical
mechanism underlying the first law of Mendelian genetics and is particularly
important when the two separated alleles are different.
seminal vesicles
Apart of the male reproductive tract that stores sperm in invertebrates and
produces semen in vertebrates.
seminiferous
tubules
Highly coiled tubes in the testes in which sperm are produced.
sepal
A whorl of modified leaves in angiosperms that encloses and protects the flower
bud before it opens.
septum
(plural, septa)
Any dividing wall or partition that occurs between structures or in a cavity.
serosa
A serous membrane such as the peritoneum that secretes a serum.
seta
(plural, setae)
1. the erect aerial part of the spore-producing structure of mosses or liverworts.
2. a slender, straight prickle.
sex cells
gametes. In the male it is the sperm and in the female it is the egg.
sexual
reproduction
A type of reproduction in which two parents give rise to offspring that have
unique combinations of genes inherited from the gametes of the two parents.
shell
Any hard outer covering, such as the carapace of turtles and tortoises, the
exoskeleton of crustaceans, the calcareous plates of echinoderms, the outermost
membranes of an egg, the skeleton of Forminifera, and the mantle secretions
of mollusks.
shell
membrane
The membranes of an egg that surround the yolk (ovum).
shoot
The part of a vascular plant above the ground, consisting of stem and leaves.
sieve tubes
A series of long cells lying end to end and forming a tube, found in the phloem
of Angiosperms.
simple
eye (ocellus)
a single eye with a single lens found in insects and some other invertebrates.
sinus venosus
1. in lower vertebrates it is the chamber of the heart to which veins return
blood. 2. in mammals it is a vessel of the embryonic heart, present in the transverse
septum, into which open the vitelline, allantoic, and cardinal veins.
siphon
Found at the posterior margin in the mantle of Bivalves where fresh water enters
the organism through the incurrent siphon, circulates through the mantle cavity
and over the gills, and leaves through the excurrent siphon.
skeleton
any structure present in an organism that maintains its shape and supports structures
associated with the body. It can take the form of an internal bony skeleton
as in vertebrates, an external calcareous or chitinous exoskeleton as in arthropods,
a hydrostatic skeleton as in jellyfish , or that of a subcellular system of
support.
smooth endoplasmic reticulum
Endoplasmic reticulum that is not covered with ribosomes and gives rise to the
Golgi Apparatus.
smooth
muscle
A type of muscle lacking the striations of skeletal and cardiac muscle because
of the uniform distribution of myosin filaments in the cell.
soft palate
the posterior section of the roof of the mouth that is characterized by a fold
of connective tissue.
somatic cell
any of the cells of a plant or animal except the reproductive cells.
somite
A serial segment of the animal body.
sorus
(pl. sori)
A group of sporangia developed on the underside of sporophylls (spore-bearing
leaflets) of the sporophyte generation of a fern.
sperm
Spermatozoon; a small, usually motile male gamete.
spermatic artery
Arise from the abdominal aorta just posterior to the kidneys and supplies the
testes with oxygenated blood.
spermatids
A haploid stage in male gametogenesis.
spermatogenesis
the continuous and prolific production of mature sperm cells in the testis via
meiosis.
spermatogonium
(plural, spermatagonia)
An early diploid stage of male gametogenesis.
spermatozoon
(plural, spermatozoa)
The male gamete; a haploid, usually small, flagellated cell.
sphincter
a ring-like valve, consisting of modified muscles in a muscular tube, such as
a digestive tract; closes off the tube like a drawstring.
spinal
cord
A more or less uniform tube extending the full length of the body in vertebrates
behind the head. It is enclosed in the backbone.
spinal
nerve
any of numerous nerves that leave the spinal cord, one pair in each segment,
each being connected with the cord by a dorsal and a ventral root.
spiracles
Minute pores distributed over the surface of an insect's body that serve as
entrances to the tracheal system.
spleen (Frog,
Rat)
An important part of the mononuclear phagocyte system, make up of lymphoid tissue.
It stores excess red blood cells, destroys old cells, and is capable of acting
as a reservoir holding 20-30% of all blood cells. It produces lymphocytes and
serves to regulate the volume of blood cells elsewhere in the blood system.
spongy
mesophyll
The internal tissue layer of a leaf found below the palisade mesophyll. Lacks
a regular organization due to irregularly shaped cells and many air spaces.
sporangium
(pl. sporangia)
A capsule in fungi and plants in which meiosis occurs and haploid spores develop.
sporangiophore
A fungal hypha bearing one or more sporangia.
spore
In the life cycle of a plant or alga undergoing alternation of generations,
a meiotically produced haploid cell that divides mitotically, generating a multicellular
individual, the gametophyte, without fusing with another cell.
sporophyte
The multicellular diploid form in organisms undergoing alternation of generations
that results from a union of gametes and that meiotically produces haploid spores
that grow into the gametophyte generation.
sporozoan
any parasitic protozoan of the class Sporozoa, such as the Malaria parasite.
stalk
Holds up the cap of mushrooms.
stamen
The pollen-producing male reproductive organ of a flower, consisting of an anther
and filament.
stapes
The innermost of the three ear ossicles, which contacts the oval window of the
ear. It is stirrup-shaped.
starch
A polysaccharide carbohydrate consisting
of two forms of glucose units, amylose and amylopectin.
stele
The central vascular cylinder in roots where xylem and phloem are located.
stem
The part of the plant bearing the buds, leaves, and flowers. It forms the central
axis of the plant, and provides mechanical support. If present below ground,
it is usually called a rhizome.
sterile cell
A cell derived from the microgametophyte which does not divide further.
stigma
The part of the reproductive organs of flowers where pollen grains germinate.
stipe
The fruiting body of a fungus.
stipule
one of a pair of leaflets found at the base of a leaf where it joins the stem.
stolon
A long slender stem running along the surface of the ground, arising from the
axil of a leaf, whose function is to enable rapid vegetative propagation in
an area. Runners are found, for example, in strawberries and creeping buttercup.
stoma
(pl. stomata)
A microscopic pore surrounded by guard cells in the epidermis of leaves and
stems that allows gas exchange between the environment and the interior of the
plant.
stomach
The part of the vertebrate gut system that follows the esophagus. It is expanded
to form a chamber, and its walls secrete pepsinogen, giving rise to pepsin,
rennin, and hydrochloric acid. Gastric secretions also include mucin, which
lubricates the food mass that is passed a little at a time to the small intestine
via the pyloric sphincter.
storage material
any compound that accumulates naturally within a cell, for example, the starch
grains of potato tubers and glycogen in liver cells.
striate
in plant structures, marked with parallel ridges or depressions.
striated
muscle
Contractile tissue, in vertebrates consisting of fibrils with marked striations
at right angles to the long axis. The muscle is concerned with movement of skeletal
parts.
stroma
the fluid of the chloroplast surrounding the thylakoid membrane; involved in
the synthesis of organic molecules from carbon dioxide and water.
style
The slender, neck-like portion of the carpel that leads to the ovary.
suberin
A complex of fatty substances present in the wall of cork tissue that waterproofs
it and makes it resistant to decay.
submucosa
Located below the mucosal layer.
subsidiary cells
secondary or auxiliary cells
superficial
on or near the surface, for example, of an artery, vein or ovule.
superior
vena cava
Drains the anterior body regions, returning blood back to the heart via the
right atrium.
synapse
the locus where one neuron communicates with another neuron in a neural pathway;
a narrow gap between a synaptic terminal of an axon and a signal-receiving portion
(dendrite or cell body) of another neuron or effector cell. Neurotransmitters
released by synaptic terminals diffuse across the synapse, relaying messages
to the dendrite or effector.
syncytium
A cellular structure containing many nuclei.
synergid
Either of two small cells present in the embryo sac of seed plants near the
egg cell at the micropylar end.
syngamy
The process of cellular union during fertilization.
teat
Of female mammals, the nipple of a breast or udder, from which the young suck
milk.
telson
The terminal appendage of the last abdominal segment of some arthropods.
tendon
A bunch of parallel collagen fibers making up a bank of connective tissue that
serves to attach a muscle to a bone.
testis
(plural, testes)
The male reproducitve organ, or gonad, in which sperm and reproductive hormones
are produced.
tetrad
the four homologous chromatids that associate during prophase and metaphase
of meiosis and are involved in crossing over. A tetrad is also the four haploid
cells produced by one complete meiotic division.
tetrapod
Any vertebrate with two pairs of pentadactyl
limbs. Ex. rats, frogs.
thallus
The vegetative part of simple plants, ranging from unicellular structures to
large seaweeds. It shows no differentiation into root, stem, and leaves.
thoracic
cavity
The space within the thorax.
thorax
1. in vertebrates it is the part of the body that contains the lungs and heart,
and in mammals is divided from the abdomen by the diaphragm. 2. in arthropods
it is the part of the body directly behind the head and in front of the abdomen.
3. in insects it is the three segments bearing the legs and wings.
thylakoid
a flattened membrane sac inside the chloroplast, used to convert light energy
to chemical energy.
tibia
The anterior of the two long bones articulating in the hind limb. In humans,
the tibia is the shinbone.
tissue
A large group of cells of similar structure in plants or animals that performs
a specific function. (ex. muscle, phloem, etc.)
tongue
A muscular organ on the floor of the mouth in most higher vertebrates that carries
taste buds and manipulates food. It may act as a tactile or prehensile organ
in some species.
trachea
(pl. tracheae)
1. the windpipe; that portion of the respiratory tube that has C-shaped cartilaginous
rings and passes from the larynx to two bronchi. 2. tiny air tubes that ramify
throughout the insect body for gas exchange. 3. in plants they make up part
of the xylem tissue.
Tracheophyte
any plant of the division Tracheophyta, comprising all forms of vascular plants,
Pteridophytes and Spermatophytes.
transverse
Lying or placed across or crosswise
traverse muscles
Fibers run ventrally and slightly posteriorly, originates from cartilage of
the floating ribs, the lumbar vertebrae and the border of the ilium and inserts
on the linea alba. Its action is to constrict the abdominal region.
trematode
any parasitic flatworm of the class Trematoda, including the flukes.
triceps
muscle
Found on the back side of the arm, it is an antagonist to the biceps. It originates
from the humerus and the scapula and inserts on the ulna. The triceps extends
the forearm.
tripartite
Having three parts.
tube
cell nucleus
one of two haploid nuclei within a developing pollen tube, whose function may
be control of tube growth.
tube
feet
The locomotory organs of Echinoderms, which are protruded from the body by,
and are retracted by, fluid pressure from the water vascular system.
tunica
Any layer of tissue or membrane that encloses a structure or organ in either
an animal or plant.
turbellarian
any aquatic free-swimming platyhelminth of the class Turbellaria, the body of
which is covered with cilia.
tympanic
membrane
The eardrum. A membrane situated at the end of the external auditory meatus
at the junction of the outer and middle ears. Vibrations are set up in the membrane
by sound waves, and these are transmitted by the ear ossicles to the oval window.
typhlosole
A dorsal unfolding of the earthworm's intestine along its entire length that
increases its surface area for digestive purposes.
ulna
The posterior of two bones of the forearm of tetrapods. The ulna articulates
proximally with the humerus and distally with the carpals.
umbo
The pointed centre of an oyster shell. It is the oldest part and surrounded
by concentric lines of growth.
unicellular
made up of one cell.
upper
epidermis
the tissue in plants, usually one cell thick, that is on the top surface of
the leaf.
ureter
A duct leading from the kidney to the urinary bladder.
urethra
A tube that releases urine from the body near the vagina in females or through
the penis in males; also serves in males as the exit tube for the reproductive
system.
urinary bladder
An elastic, muscular sac located in the pelvic cavity, in which urine is collected
before excretion.
uropod
The flattened, sixth pair of pleoplods that, together with the telson, forms
the tail fin of crayfish.
uterus
The enlarged posterior portion of the oviduct in which the embryo implants a
develops in viviparous species. It is also called the womb of female humans.
vacuole
A membrane-enclosed sac taking up most of the interior of a mature plant cell
and containing a variety of substances important in plant reproduction, growth,
and development.
vagina
A thin-walled chamber that forms the birth canal and is the repository for sperm
during copulation.
vas deferens
The tube in the male reproductive system in which sperm travel from the epidiymis
to the urethra.
vascular
bundle
A structure of vascular plants that runs up through the roots, into the stems,
and out into the leaves, and whose function is transport of water, ions and
dissolved organic solutes within the plant.
vascular
cambium
A continuous cylinder of meristematic cells surrounding the xylem and pith that
produces secondary xylem and phloem.
vascular system
1. in animals the blood circulatory system and the water vascular system in
echinoderms that manipulate the tube feet. 2. in plants the tissue that serves
to conduct water throughout plants.
veins
Vessels which carry blood back to the heart from the tissues. Veins are thin
walled and will collapse if empty. They have a series of one-way valves to prevent
blood from flowing backwards.
vena
cava
One of the major veins of the blood circulatory system.
venous
system
The part of the blood circulatory system carrying blood back to the heart from
the tissues.
venter
The swollen base of the archegonium that contains the egg cell.
ventral
Of or relating to the underside of an organism, or the side normally directed
downward in the usual stance or resting position.
ventral
root
any of the nerve roots issuing from the ventral side of the vertebrate brain
or spinal cord, containing the motor nerves.
ventricle
(1) a chamber that pumps blood out of the vertebrate heart. (2) a space in the
vertebrate brain filled with cerebrospinal fluid.
venules
Vessels into which capillaries converge and that empty into veins.
vertebral
column
Spinal cord or backbone; the series of vertebrae surrounding the spinal cord.
vessel cell
An empty tube formed from longitudinal fusion of several cells with strong walls
reinforced with lignin, whose function is mass transport of water for transpiration.
vestigial
organ
any organ over the course of evolution had become reduced in function and usually
in size.
vibrissa
(plural, vibrissae)
Any of the stiff sensitive hairs found around the mouths of mammals; whiskers.
villus
(plural, villi)
A finger-like outgrowth, as in the lining of the small intestine. Villi effectively
increase the surface area of the gut wall
viriod
a plant pathogen composed of molecules of naked RNA only several hundred nucleotides
long.
virus
the smallest organism known, ranging in size from about 0.025-0.25 um. Viruses
infect cells of bacteria, plants , and animals, and while they carry out no
metabolism themselves, they are able to control the metabolism of the infected
cell.
viscera
The internal organs of the body cavity.
visceral peritonium
A thin layer of connective tissue which originated from the mesoderm. It lines
the internal organs, as opposed to the abdominal cavity.
vital stains
the staining of cells while alive, which has been used particularly for studying
the movements of parts of embryos.
vitelline membrane
Delicate membrane that surrounds the yolk of an egg.
vomerine
teeth
found on the roof of the buccal cavity, medial to the internal nares, on either
side of the midline in frogs.
walking
legs
Pereiopods of Crustaceans. Posterior jointed, thoracic appendages.
whorled
arrangement
a circular set (two or more) of leaves or sepals arising at the same level on
the plant.
Wolffian duct
The duct from the mesonephros in vertebrates. In fish and amphibians, it forms
the urinary duct in females and the genitourinary duct in males. In reptiles,
birds, and mammals, it forms the vas deferens in males and it degenerates in
females.
xylem
The tube-shaped, nonliving portion of the vascular system in plants that carries
water and minerals from the roots to the rest of the plant.
yolk
The food store in the eggs of the majority of animals, made up mainly of fat
and protein granules. Where yolk is present in the egg, as in chickens, there
is meroblastic cleavage, but where it is absent, or nearly so, cleavage is holoblastic,
as in Amphioxus.
yolk
plug
In amphibians, when the opening of the archenteron, the blastopore, is filled
with yolk-rich cells, it is called the yolk plug.
zygospore
A thick-walled resting spore that is formed from the union of similar gametes.
zygote
The diploid product of the union of haploid gametes in conception; a fertilized
egg.
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