F1 (first
filial generation)
The first
filial or hybrid offspring in a genetic cross-fertilization.
F2 (second
filial generation)
Offspring
resulting from interbreeding of the hybrid F1 generation.
F factor
A
fertility factor in bacteria, a DNA segment that confers the ability to form
pili for conjugation and associated functions required for the transfer of DNA
from donor to recipient. May exist as a plasmid or integrated into the
bacterial chromosome.
facilitated
diffusion
The
spontaneous passage of molecules and ions, bound to specific carrier proteins,
across a biological membrane down their concentration gradients.
facultative
anaerobe
(fak-ul-tay-tiv an-uh-robe)
An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
FAD
Abbreviation
of flavin adenine dinucleotide, a coenzyme that functions as an electron
acceptor in the Krebs cycle.
Fallopian
tube
See Oviduct.
family
A
taxonomic grouping of related, similar genera; the category below order and
above genus.
fat
(triacylglycerol)
(tri-ah-sil-glis-er-all)
A biological compound consisting of three fatty acids linked to one glycerol molecule.
A biological compound consisting of three fatty acids linked to one glycerol molecule.
fatty
acid
A long
carbon chain carboxylic acid. Fatty acids vary in length and in the number and
location of double bonds; three fatty acids linked to a glycerol molecule form
fat.
feedback
inhibition
A method
of metabolic control in which the end-product of a metabolic pathway acts as an
inhibitor of an enzyme within that pathway.
feedback
systems
Control
mechanisms whereby an increase or decrease in the level of a particular factor
inhibits or stimulates the production, utilization, or release of that factor;
important in the regulation of enzyme and hormone levels, ion concentrations,
temperature, and many other factors.
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.
fertilization
The union
of haploid gametes to produce a diploid zygote.
fetus
[L.
pregnant]
An unborn or unhatched vertebrate that has passed through the earliest developmental stages; a developing human from about the second month of gestation until birth.
An unborn or unhatched vertebrate that has passed through the earliest developmental stages; a developing human from about the second month of gestation until birth.
fiber
A lignified
cell type that reinforces the xylem of angiosperms and functions in
mechanical support; a slender, tapered sclerenchyma cell that usually occurs
in bundles.
fibril
[L. fibra, fiber]
Any minute, threadlike structure within a cell.
Any minute, threadlike structure within a cell.
fibrin
(fy-brin)
The activated form of the blood-clotting protein fibrinogen, which aggregates into threads that form the fabric of the clot.
The activated form of the blood-clotting protein fibrinogen, which aggregates into threads that form the fabric of the clot.
fibroblast
(fy-broh-blast)
A type of cell in loose connective tissue that secretes the protein ingredients of the extracellular fibers.
A type of cell in loose connective tissue that secretes the protein ingredients of the extracellular fibers.
fibrous
protein
Insoluble
structural protein in which the polypeptide chain is coiled along one
dimension. Fibrous proteins constitute the main structural elements of many
animal tissues.
filament
[L. filare, to
spin]
(1) A chain of cells. (2) In flowers, the stalk of a stamen.
(1) A chain of cells. (2) In flowers, the stalk of a stamen.
filtrate
Fluid
extracted by the excretory system from the blood or body cavity. The excretory
system produces urine from the filtrate after extracting valuable solutes from
it and concentrating it.
filtration
The first
stage of kidney function; blood plasma is forced, under pressure, out of the
glomerular capillaries into Bowman's capsule, through which it enters the renal
tubule.
first law
of thermodynamics
(thur-moh-dy-nam-iks)
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
fitness
The
genetic contribution of an individual to succeeding generations relative to the
contributions of other individuals in the population.
fixed
action pattern
A highly
stereotypical behavior that is innate and must be carried to completion once
initiated.
flaccid
(flas-id)
Limp; walled cells are flaccid in isotonic surroundings, where there is no tendency for water to enter.
Limp; walled cells are flaccid in isotonic surroundings, where there is no tendency for water to enter.
flagellum pl. flagella
(fla-jell-um)
[L. flagellum, whip]
A long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extension of plasma membrane.
A long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extension of plasma membrane.
flower
The
reproductive structure of angiosperms; a complete flower includes sepals,
petals, stamens (male structures), and carpels (female structures).
fluid-feeder
An animal
that lives by sucking nutrient-rich fluids from another living organism.
fluid
mosaic model
The
currently accepted model of cell membrane structure, which envisions the
membrane as a mosaic of individually inserted protein molecules drifting
laterally in a fluid bilayer of phospholipids.
follicle
(fol-eh-kul)
A microscopic structure in the ovary that contains the developing ovum and secretes estrogens.
A microscopic structure in the ovary that contains the developing ovum and secretes estrogens.
follicle-stimulating
hormone (FSH)
A protein
hormone secreted by the anterior pituitary that stimulates the production of
eggs by the ovaries and sperm by the testes.
food
chain
The
pathway along which food is transferred from trophic level to trophic level,
beginning with producers.
food web
The
elaborate, interconnected feeding relationships in an ecosystem.
fossil
[L. fossilis, dug
up]
The remains of an organism, or direct evidence of its presence (such as tracks). May be an unaltered hard part (tooth or bone), a mold in a rock, petrification (wood or bone), unaltered or partially altered soft parts (a frozen mammoth).
The remains of an organism, or direct evidence of its presence (such as tracks). May be an unaltered hard part (tooth or bone), a mold in a rock, petrification (wood or bone), unaltered or partially altered soft parts (a frozen mammoth).
founder
effect
A cause
of genetic drift attributable to colonization by a limited number of
individuals from a parent population.
fovea
[L. pit]
A small area in the center of the retina in which cones are concentrated; the area of sharpest vision.
A small area in the center of the retina in which cones are concentrated; the area of sharpest vision.
fragile X
syndrome
A
hereditary mental disorder, partially explained by genomic imprinting and the
addition of nucleotides to a triplet repeat near the end of an X chromosome.
frameshift
mutation
A mutation
occurring when the number of nucleotides inserted or deleted is not a multiple
of 3, thus resulting in improper grouping into codons.
free
energy
A
quantity of energy that interrelates entropy (S) and the system's total energy
(H); symbolized by G. The change in free energy of a system is calculated by
the equation G = ΔH – T ΔS, where T is absolute temperature.
free
energy of activation
The
initial investment of energy necessary to start a chemical reaction; also
called activation energy.
frequency-dependent
selection
A decline
in the reproductive success of a morph resulting from the morph's phenotype
becoming too common in a population; a cause of balanced polymorphism in
populations.
fruit
[L. fructus, fruit]
A mature ovary of a flower that protects dormant seeds and aids in their dispersal.
A mature ovary of a flower that protects dormant seeds and aids in their dispersal.
function
[L. fungor, to
busy oneself]
Characteristic role or action of a structure or process in the normal metabolism or behavior of an organism.
Characteristic role or action of a structure or process in the normal metabolism or behavior of an organism.
functional
group
A
specific configuration of atoms commonly attached to the carbon skeletons of
organic molecules and usually involved in chemical reactions.
