Bespoke Education SAT Biology - All Subjects

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Abiotic
Nonliving
Abscisic Acid
A plant hormone that generally acts to inhibit growth, promote dormancy, and help the plant tolerate stressful conditions
Acetylcholine
A prominent neurotransmitter; stimulates muscle cells
Adrenocorticotropic Hormone (ACTH)
A hormone produced in the pituitary gland that regulates the function of the adrenal cortex
Actin
A contractile protein of muscle
Activation Energy
The energy required to start a chemical reaction
Active Immunity
Immunity conferred by recovering from exposure to an antigen and creating memory B cells
Adaptive Radiation
The development of several new species from one species that enters a new ecosystem
Antidiuretic Hormone (ADH)
A hormone synthesized by the hypothalamus and secreted by the pituitary gland that promotes retention of water
Adrenal Glands
Endocrine glands located above the kidneys that secrete epinephrine, norepinephrine, and adrenocorticoids
Agglutination
Clumping of red blood cells or bacteria
Albinism
The absence of any pigmentation in a person, animal, or plant, resulting in white hair and pink eyes in mammals
Aldosterone
A hormone produced in the adrenal cortex that regulates salt and water balance
Allele
An alternative form of a gene
Allopatric
A mode of speciation induced when the ancestral population becomes segregated by a geographical barrier
Alveoli
The dead-end air sacs that constitute the gas exchange surface of the lungs
Amino Acid
An organic molecule possessing one carboxyl, one amino, and one variable group; the monomers of proteins
Ammonia
The highly toxic form in which many animals living in aquatic or aqueous environments excrete nitrogen
Amniote Egg
The embryos of reptiles, birds, and mammals with four membranes: the amnion, yolk sac, allantois, and chorion; adapted for birth on dry land
Amphibia
The class of chordates who lay their eggs and complete their first life stage in water, and can carry out limited breathing through their skin; e.g. frogs and salamanders
Amylase
A digestive enzyme secreted by the salivary glands in the mouth that breaks down starch
Analogous Structures
Structures in different species with similar functions but different structures; do not indicate common ancestry
Anaphase
The stage of mitosis in which sister chromatids are pulled apart
Angiosperms
Flowering plants
Annelid
A segmented worm, such as an earthworm, with a hydrostatic skeleton
Anther
The site of pollen production and release in a flower
Antibiotic
A drug that kills bacteria
Antibody
An antigen-binding protein, produced by plasma B-cells, that functions in an immune response
Antigen
A molecule that provokes an immune response
Aorta
The artery that carries oxygenated blood away from heart
Arachnida
The class of arthropods with eight legs; e.g. spiders and scorpions
Arteriole
One of the small terminal branches of an artery, especially one that connects with a capillary
Artery
A thick vessel that carries blood away from the heart
Arthropod
An animal with three segmented body regions, a jointed exoskeleton, and an open circulatory system; includes arachnids, insects, and crustaceans
Atmosphere
All the air between the surface of the earth and outer space
ATP
Adenosine triphosphate, the main source of readily usable energy for cells
Autosomal
Referring to a gene located on a chromosome not involved in the determination of sex
Autotroph
Organism that is able to utilize inorganic carbon (usually carbon dioxide) as a carbon source
Auxins
A class of plant hormones that stimulate primary growth and tropisms
AV (atrioventricular) Node
A patch of nodal tissue at the base of the wall separating the two atria that relays the signal from the SA node to the ventricles
Aves
The vertebrate class of birds, characterized by feathers, hollow bones, beaks, and a four-chambered heart
Axon
A long extension from a neuron that carries nerve impulses away from the cell body towards target cells
Bicarbonate/Carbonic Acid
The form in which carbon dioxide is transported in the bloodstream to the lungs; also acts as a pH buffer
Bile
An emulsifying fluid, stored in the gallbladder, that aids in the mechanical digestion of fats
Binary Fission
The type of asexual reproduction used by prokaryotic organisms
Biological Magnification
The increasing concentration of environmental toxins in higher trophic levels
Biomass
The dry weight of organic matter comprising a group of organisms in a particular habitat
Biosphere
The portion of the atmosphere that can support life
Blastula
The stage of embryonic development in animals with two layers of cells and a large central cavity
Bolus
A mass of chewed food
Bottleneck Effect
Genetic drift resulting from a drastic reduction in population size
Bryophytes
A group of plants that lack xylem and phloem; includes mosses
Budding
The type of asexual reproduction in which a new organism develops while still attached to the parent; used by yeast and hydra
Calcitonin
A hormone secreted by the thyroid gland that lowers the blood calcium level
Calvin Cycle
The chemical synthesis of G3P (a precursor to glucose), using CO2, ATP and NADPH; in the stroma
Cambium
Plant tissue responsible for secondary (lateral) growth; produces xylem and phloem (vascular cambium) or cork (cork cambium)
Capillary
A small blood vessel that allows nutrient exchange with its surroundings
Carnivore
An animal that eats other animals
Carrier
An organism that carries one allele for a particular recessive trait
Carrying Capacity
In a population, the number of individuals that an environment can sustain
Cartilage
A type of flexible connective tissue found the nose and ears of humans; composes the skeleton of cartilaginous fish
Cell Plate
Two membranes formed across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis
Cellular Respiration
The series of reactions necessary for the production of ATP within a cell
Cellulose
A structural polysaccharide that composes the cell walls of plants
Central Vacuole
The organelle in plants that functions in storage and maintenance of turgor
Centrifuge
A device that rotates at various speeds about a fixed central point; separates liquids from solids, or liquids of different densities from each other
Centrioles
Two structures in the center of animal cells that may help organize spindle assembly during cell division
Centromere
The region of the chromosome where the sister chromatids are joined; also the point of attachment of the spindle fibers during cell division
Cephalization
An evolutionary trend in the animal kingdom toward centralization of neural and sensory organs in the head or front of the body
Cerebellum
The part of the vertebrate brain that functions in unconscious coordination of movement and balance
Cerebrum
The part of the vertebrate brain that is the integrating center for memory, learning, emotions, and other highly complex functions of the central nervous system
Cervix
The neck of the uterus, which opens into the vagina
Chaparral
A scrubland biome of dense, spiny evergreen shrubs, characterized by mild, rainy winters and long, hot, dry summers
Chemiosmosis
The use of a proton gradient to drive ATP production; an element of both aerobic cellular respiration and photosynthesis
Chemosynthesis
Synthesis of carbohydrates from carbon dioxide and water using energy obtained from the oxidation of simple inorganic compounds
Chitin
A structural polysaccharide found in the cell walls of fungi and the exoskeletons of arthropods
Chloroplast
An organelle found only in plants and some protists that serves as the site of photosynthesis
Chordata
The phylum of animals having a notochord and pharyngeal gill slits at some point in their development; includes the vertebrates
Chromatography
Separation of a mixture based on the components' affinities for a medium that they pass through
Chromosomal Inversion
A mutation in which a part of a chromosome is reversed end-to-end
Chyme
A mixture of recently swallowed partially digested food and gastric juices
Cilia
Hair-like structures that sway back and forth to facilitate cellular movement or move liquid over the cell surface
Citric Acid Cycle
The chemical breakdown acetyl Co-A to carbon dioxide; supplies most of the NADH molecules that carry energy to the electron transport chain; in the mitochondrial matrix
Cladogram
A phylogenetic tree that branches repeatedly, suggesting a classification of organisms based on the time sequence in which evolutionary branches arise
Class
The taxonomic category of classification consisting of related orders
Cleavage
The pinching of the plasma membrane following mitosis, resulting in the separation of the two daughter cells; also, the succession of rapid cell divisions without growth during early embryonic development
Climax Community
A stable mature community in a successive series which has reached equilibrium after having evolved through stages and adapted to its environment
Cline
Variation in features of individuals in a population that parallels a gradient in the environment
Clone
A lineage of genetically identical individuals
Cnidaria
The phylum of aquatic animals with radial symmetry and two layers of cells, such as jellyfish and hydras
Cnidocytes
The stinging cells on the tentacles of members of the phylum Cnidaria; contains organelles called cnidocysts that produce toxins
Cochlea
The complex, coiled organ of hearing within the ear
Codominance
A phenotypic situation in which both alleles are expressed in the heterozygote
Codon
A three-nucleotide sequence of DNA or mRNA that codes for a particular amino acid or termination signal
Collagen
A protein that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom
Collenchyma
A flexible plant cell type that supports growing parts
Commensalism
A type of symbiosis in which one species benefits and the other is unaffected
Community
All the organisms that inhabit a particular area
Conditioning
A process of behavior modification by which a subject comes to associate a desired behavior with a previously unrelated stimulus
Conjugation
The transfer of plasmids between two bacteria through a sex pilus
Contractile Vacuole
An organelle found in freshwater protists that pumps excess water out of the cell
Convergent Evolution
The development of a similar trait in organisms with different evolutionary histories
Cornea
The transparent coating of the eye that admits light
Corpus Callosum
Bundle of nerves connecting the left and right sides of the brain
Cortex
Plant tissue between the epidermis and vascular tissue
Cotyledon
The one (monocot) or two (dicot) seed leaves of an angiosperm embryo
Covalent Bond
A type of strong chemical bond in which two atoms share one pair of electrons
Crop
A digestive organ used for food storage prior to digestion
Crustacea
The class of marine arthropods such as lobsters, shrimp, crabs, and barnacles
Cyanobacteria
Photosynthetic, oxygen-producing bacteria
Cytochrome
An iron-containing protein component of electron transport chains in mitochondria and chloroplasts
Cytokinesis
The division of cytoplasm between two daughter cells after mitosis, resulting in the formation of two distinct cells
Cytokinins
A class of plant hormones that affect root growth and differentiation, stimulate cell division and growth, germination, and flowering
Cytoplasm
Everything inside a cell between the plasma membrane and the nucleus
Cytoskeleton
A network of filaments that maintains cell shape and enables intracellular transport, cell movement, and cell division
Cytosol
The fluid portion of the cytoplasm
Cytotoxic T-Cells
A type of lymphocyte that attacks body cells infected with pathogens; also called killer T cells
Deciduous
Having leaves that fall off seasonally to avoid adverse weather conditions
Decomposer
An organism that derives its energy from organic wastes and dead organisms; also called detritovore
Dehydration Synthesis
A chemical process that covalently bonds two molecules coupled with the removal of water
Denaturation
The process in which a protein unravels and loses its shape, thereby becoming biologically inactive
Dendrite
A short, highly branched extension of a neuron that conveys nerve impulses toward the cell body
Denitrifying Bacteria
Bacteria that convert nitrogenous compounds into nitrogen gas
Depolarization
An electrical state in an excitable cell whereby the inside of the cell is made less negative relative to the outside than at the resting membrane potential
Desert
A dry, often sandy region of extreme temperatures and sparse rainfall
Desertification
The transformation of arable or habitable land to desert
Desmosome
A structure that binds one cell to another
Deuterostome
One of two distinct evolutionary lines of coelomates, consisting of echinoderms and chordates
Diaphragm
The muscle responsible for inflating and deflating the lungs
Dihybrid Cross
A cross of two individuals heterozygous for two traits; results in a 9:3:3:1 phenotypic ratio
Diploid
Containing two sets of chromosomes, one set inherited from each parent
Directional Selection
Natural selection that favors one extreme of a trait
Disruptive Selection
Natural selection that favors both extremes of a trait
DNA Ligase
An enzyme that joins two DNA molecules together
DNA Polymerase
An enzyme that catalyzes the elongation of new DNA by the addition of nucleotides to the existing chain during DNA replication
Dominant
The allele that is fully expressed in the phenotype of a heterozygous individual
Duodenum
The first section of the small intestine
Echinodermata
The phylum of sessile or slow-moving animals with radial symmetry, water vascular system and tube feet, such as sea stars
Ecosystem
All the organisms in a given area, along with the nonliving factors with which they interact
Ectoderm
The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye
Electron Transport Chain
A series of electron carrier molecules that shuttle electrons during the redox reactions that release energy used to make ATP; in the inner mitochondrial or thylakoid membrane
Electrophoresis
The separation of macromolecules on the basis of their rate of movement through a porous gel under the influence of an electric field
Emigration
Migration out of a population
Endergonic
Referring to a reaction in which free energy is absorbed from the surroundings
Endoderm
The innermost of the three primary germ layers in animal embryos; gives rise to the liver, pancreas, lungs, and the lining of the digestive tract
Endoplasmic Reticulum
An extensive membranous network in eukaryotic cells that either modifies proteins (rough ER) or synthesizes lipids (smooth ER)
Endorphin
A hormone produced in the brain and anterior pituitary that inhibits pain perception
Endosperm
Tissue in plant seeds that nourishes the developing embryo
Endosymbiotic Theory
The theory that mitochondria and chloroplasts were once free-living prokaryotes that were engulfed by other cells
Endothelium
The innermost layer of cells lining the blood vessels
Endothermy
The use of metabolic energy to maintain a constant body temperature
Enzyme
A class of proteins that change the rate of a reaction without being consumed
Epidermis
The outer covering of plants and animals
Epididymis
Convoluted tubule connecting the seminiferous tubules to the vas deferens; site of maturation and storage of sperm
Epiglottis
A cartilaginous flap that blocks the top of the larynx during swallowing, which prevents the entry of food or fluid into the respiratory system
Epinephrine
A hormone produced as a response to stress; also called adrenaline
Epistasis
A phenomenon in which one gene alters the expression of another gene that is independently inherited
Epithelium
Sheets of tightly packed cells that line organs and body cavities
Erythrocyte
A red blood cell; biconcave in shape, contains hemoglobin, a protein that carries oxygen; lack nuclei in mammals
Estrogen
The female steroid sex hormone, produced in the ovaries, that stimulates the development and maintenance of the female reproductive system and secondary sexual characteristics
Ethylene Gas
The only gaseous plant hormone; responsible for fruit ripening
Eutrophication
An increase in the mineral and organic nutrient content of a body of water, promoting a proliferation of algae, reducing the dissolved oxygen content of the water
Exergonic
Referring to a reaction in which free energy is released into the surroundings
Exon
The coding region of a eukaryotic gene that is expressed
Exoskeleton
A hard shell on the surface of an animal that provides protection and points of attachment for muscles; composed of chitin in arthropods
F1 Generation
The first generation of offspring in a genetic cross
F2 Generation
Offspring resulting from interbreeding of the F1 Generation
FAD
A molecule that carries electrons from the citric acid cycle to the electron transport chain; the reduced form is FADH2
Fallopian Tube
The tube that conveys egg cells away from an ovary; also called an oviduct
Family
The taxonomic category of classification consisting of related genera
Fat
A type of lipid composed of one glycerol molecule with three fatty acids attached
Fermentation
A cellular process that regenerates the NAD+ used in glycolysis and produces a characteristic byproduct, such as ethanol or lactic acid
Fertilization
The union of the nucleus of a sperm cell with the nucleus of an egg cell, producing a zygote
Filament
The stalk that supports the anther in a flower
Fitness
The ability of an organism to grow to maturity and produce fertile offspring
Fixed-Action Pattern
A behavior that continues to completion even if the stimulus is removed
Flagellum
A tail-like structure that facilitates cellular movement
Fluid-Mosaic Model
The model of cell membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids
Fossil
A preserved remnant or impression of an organism that lived in the past
Fossil fuel
Hydrocarbon fuels consisting of the partially decomposed remains of organisms that lived millions of years ago
Founder Effect
Random change in the gene pool that occurs in a small colony of a population
Frameshift Mutation
A mutation that results in a shift of the reading frame of the coding portion of a gene resulting from addition or deletion of nucleotides
Follicle-Stimulating Hormone (FSH)
Follicle-stimulating hormone; secreted by the anterior pituitary, stimulates development of the follicle
Gamete
A haploid egg or sperm cell; gametes unite during sexual reproduction to produce a diploid zygote
Gametophyte
The multicellular haploid form in plants undergoing alternation of generations; mitotically produces haploid gametes that unite and grow into the sporophyte generation
Ganglion
A cluster of nerve cell bodies
Gastrula
The embryonic stage resulting from gastrulation in animal development, commonly made up of three layers of cells: ectoderm, endoderm, and mesoderm
Gene
A segment of DNA that codes for a specific protein
Gene Amplification
An increase in the number of copies of a specific gene in an organism, leading to the increased production of a corresponding protein
Gene Flow
The gain or loss of alleles from a population by the movement of individuals into or out of the population
Gene Linkage
The presence of genes on the same chromosome, which makes those genes more likely to be passed to offspring together
Gene Pool
All the genes in a population at one time
Genetic Drift
Changes in the gene pool of a small population due to chance
Genotype
The genetic composition of an organism with respect to a specific trait
Genus
The taxonomic category of classification consisting of related species
Germination
Growth of a plant from a seed
Gibberellins
A class of plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and help to stimulate fruit development
Gibbs Free Energy
The energy difference between the reactants and products in a chemical reaction
Gizzard
A digestive organ used for mechanical digestion
Glomerulus
A ball of capillaries surrounded by Bowman's capsule in the nephron and serving as the site of filtration in the vertebrate kidney
Glucagon
A hormone secreted by the pancreas that raises blood glucose levels
Gluconeogenesis
The conversion of non-carbohydrates to glucose
Glycerol
One of the components of a fat, the others usually being fatty acids
Glycogen
The glucose storage polysaccharide found in the liver and muscle of animals
Glycolysis
The chemical breakdown of one molecule of glucose into two molecules of pyruvate; in the cytoplasm
Golgi Apparatus
An organelle in eukaryotic cells that modifies, stores, and routes proteins for secretion
Gradualism
The theory that evolution is a product of slow, steady changes
Granum
A stack of hollow disks formed of thylakoid membranes in a chloroplast
Gravitropism
Plant growth with (positive) or against (negative) gravity
Greenhouse Effect
The heating of the planet caused by absorption and emission of heat by greenhouse gases, such as carbon dioxide and methane
Growth Hormone
A hormone produced in the pituitary gland that stimulates growth and cell division
Gymnosperms
Plants that have seeds and vascular tissue, but no flowers
Habituation
The loss of sensitivity to non-harmful stimuli
Haploid
Containing only one set of chromosomes
Helicase
The enzyme that separates the two strands of the DNA double helix during replication
Helper T-cell
A type of T cell that is required by some B cells to help them make antibodies or that helps other T cells respond to antigens or secrete lymphokines or interleukins
Hemoglobin
An iron-containing protein in red blood cells that reversibly binds oxygen
Hemophilia
A hereditary disorder in which the blood fails to clot normally
Herbivore
An animal that eats only plants or algae
Heterotroph
Organism requiring an organic form of carbon as a carbon source
Heterozygous
Having two different alleles for a given trait
Histamine
A substance released by injured cells that causes blood vessels to dilate and become leaky
Homeostasis
The ability of an organism or cell to maintain internal equilibrium by adjusting its physiological processes
Homologous Chromosomes
Chromosomes that possess genes for the same traits at corresponding locations
Homologous Structures
Structures in different species with different functions that have similar structures because of common ancestry
Homozygous
Having two identical alleles for a given trait
Hormone
A chemical formed in specialized cells in all multicellular organisms that travel in body fluids and coordinate the various parts of the organism by interacting with target cells
Hybrid
An organism produced by mating of two organisms of different species; usually sterile
Hydrogen Bond
A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule
Hydrolysis
A chemical process that splits molecules by the addition of water
Hydrostatic Skeleton
A skeletal system composed of fluid held under pressure in a closed body compartment; the main skeleton of most cnidarians, flatworms, nematodes, and annelids
Hypertonic
Having a higher solute concentration
Hyphae
Filaments that collectively make up the body of a fungus
Hypothalamus
An endocrine gland in the brain that functions in maintaining homeostasis and coordinating the endocrine and nervous systems
Hypotonic
Having a lower solute concentration
Immigration
Migration into a population
Imprinting
A type of learned behavior with a significant innate component, acquired during a limited critical period
Incomplete Dominance
A type of inheritance in which heterozygotes have a phenotype that is intermediate between those of the parents
Independent Assortment
A general rule in inheritance that inheritance of alleles for one trait is independent of inheritance of alleles for another trait
Insecta
An incredibly diverse class of arthropods with six legs and wings
Insulin
A hormone secreted by the pancreas that lowers blood glucose levels
Interneuron
A nerve cell within the central nervous system that forms synapses with sensory and motor neurons and integrates sensory input and motor output
Interphase
The period in the cell cycle when the cell is not dividing
Interstitial Fluid
The fluid filling the spaces between cells in multicellular animals
Intron
A noncoding sequence of DNA within a coding region in eukaryotic genes
Ionic Bond
A chemical bond resulting from the attraction between oppositely charged ions
Ionization
The formation of ions
Iris
The colored part of the eye that, by changing size, regulates the amount of light entering the pupil
Jointed Appendages
A defining characteristic of arthropods that allows for more specialized and more versatile body parts
Karyotype
A picture of the complete set of chromosomes for a particular organism
Kingdom
The taxonomic category of classification consisting of related phyla
Lactic Acid
The product of fermentation in human muscle cells
Lamarck, J.B.
A 19th century scientist who theorized that modifications an organism acquires during its lifetime can be passed along to its offspring
Larynx
An organ in the neck involved in sound production
Leaching
The removal of minerals from a solid by dissolving them in a liquid
Legume
A mutualistic association a plant and a nitrogen-fixing bacterium
Lens
The portion of the eye that focuses light onto the retina
Leukocyte
A white blood cell; involved in the immune response
Luteinizing Hormone (LH)
A hormone secreted by the anterior pituitary that stimulates ovulation
Lichen
An symbiotic association of a fungus and a photosynthetic alga
Ligament
A type of fibrous connective tissue that joins bones together at joints
Liver
An organ that synthesizes bile, stores glycogen, and detoxifes alcohol
Logistic Growth
A pattern of growth of a population characterized by exponential growth followed by a plateau
Loop of Henle
The portion of the nephron that descends from the renal cortex to the renal medulla, and then ascends back to the renal cortex
Lymph
Interstitial fluid that is returned to the bloodstream through lymphatic vessels
Lymphocyte
A type of white blood cell; a T-cell or a B-cell
Lyse
To undergo the dissolution or destruction of the cell by disruption of the cell membrane
Lysogenic Cycle
The integration of viral DNA into a bacterial genome; the viral DNA remains in the host genome until external stimulus triggers the lytic cycle
Lysosome
A membrane-enclosed sac found in the cytoplasm of eukaryotic cells that functions in digestion
Lytic Cycle
Viral DNA in an infected bacterium directs the production of new viral particles, which are then released when the cell lyses
Macrophage
A cell that engulfs bacteria, dead cells and other debris by phagocytosis
Malphigian Tubules
A unique excretory organ of insects that removes nitrogenous wastes from the blood and empties into the digestive tract
Mammalia
The class of chordates who carry out internal gestation, and have hair and mammary glands
Mammary Glands
Milk-secreting glands characteristic of mammals
Medulla Oblongata
The part of the vertebrate brain that controls autonomic, homeostatic functions
Memory B-Cell
A long-lived lymphocyte formed during the primary immune response that remains in a lymph node until activated by exposure to the same antigen that triggered its formation
Meristem
Plant tissue that is responsible for growth of the plant
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 tissue of a leaf that is specialized for photosynthesis
Metamorphosis
The transformation of an animal larva into a sexually mature adult
Metaphase
The stage of mitosis or meiosis in which the chromosomes line up along the metaphase plate
Micropyle
A minute opening in the ovule of a seed plant through which the pollen tube usually enters
Mimicry
One species mimics a characteristic of another species to deter predators
Mitochondrion
An organelle in eukaryotic cells that serves as the site of aerobic cellular respiration
Mollusca
The animal phylum composed of snails, oysters, squids, etc...; distinctive structures include the mantle, foot, and gill
Monera
The kingdom of unicellular prokaryotes called bacteria
Monhybrid Cross
A cross of two individuals heterozygous for the same trait; results in a 3:1 phenotypic ratio
Morula
The stage of embryonic development in animals produced by the rapid cell division of the zygote with virtually no growth
mRNA
Messenger RNA; the type of ribonucleic acid that conveys genetic information to the ribosomes
Mutagen
A chemical or physical agent that interacts with DNA and causes a mutation
Mutualism
A type of symbiosis in which both species benefit
Mycorrhizzae
Mutualistic associations of plant roots and fungi
Myelin
A fatty material that forms an insulating coat around a neuron
Myosin
A type of protein filament that interacts with actin filaments to cause muscle contraction
NAD
A coenzyme that conveys electrons during the reactions of cellular respiration; the reduced form is NADH
NADP
The electron carrier of the light reactions of photosynthesis; the reduced form is NAPDH
Natural Selection
The success or failure of groups within populations based on how well suited they are to their environment
Nematoda
The phylum of roundworms found in aquatic habitats, wet soil, moist tissues of plants, and body fluids of animals
Nephridia
A tubular excretory organ in many invertebrates, such as mollusks and annelids
Nephron
The functional unit of the kidney
Neuromuscular Junction
The junction of an efferent nerve fiber and the muscle fiber plasma membrane
Neurotransmitter
A chemical messenger released from a nerve cell that stimulates another cell
Nitrifying Bacteria
Soil bacteria that convert ammonium into nitrates and nitrites
Nitrogen-Fixing Bacteria
Bacteria that convert atmospheric nitrogen into ammonia
Nodes of Ranvier
The small gaps in the myelin sheath along the axon of a neuron; contain a high concentration of voltage-gated ion channels
Nondisjunction
An accident of meiosis or mitosis in which both members of a pair of homologous chromosomes or both sister chromatids fail to move apart properly
Norepinephrine
A hormone secreted by the adrenal medulla that causes vasoconstriction and increases in heart rate, blood pressure, and blood sugar; also known as noradrenaline
Notochord
A longitudinal, flexible rod formed from mesoderm and located between the gut and the nerve cord in all chordate embryos
Nucleic Acid
The polymer of nucleotide monomers that serves as the genetic material of all organisms
Nucleolus
The region of the nucleus where ribosomes are made
Nucleotide
The monomer of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group
Nucleus
The DNA-containing organelle of a eukaryotic cell
Olfactory
Relating to the sense of smell
Omnivore
A heterotrophic animal that consumes both animal and plant material
Oocyte
A cell from which an egg or ovum develops by meiosis; a female gametocyte
Oogenesis
The process in the ovary that results in the production of female gametes
Order
The taxonomic category of classification consisting of related families
Organic Matter
Matter composed of carbon and hydrogen
Osmosis
The diffusion of water across a selectively permeable membrane
Ovary
In animals, the female gonad, which produces egg cells and reproductive hormones; in flowering plants, the portion of a flower in which the egg-containing ovules develop
Oviduct
The tube that conveys egg cells away from an ovary; also called a fallopian tube
Ovule
A structure that develops in the plant ovary and contains the female gametophyte
Oxidation
Loss of electrons
Oxidative Phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain
Oxytocin
A hormone produced in the hypothalamus that stimulates contractions during labor
Ozone Layer
A layer of O3 in the upper atmosphere that protects life on earth from the harmful ultraviolet rays in sunlight
Palisade Cells
Closely packed mesophyll cells in plant leaves
Pancreas
An organ that produces digestive enzymes, as well as insulin and glucagon
Parasitism
A type of symbiosis in which one species benefits at the expense of the other
Parenchyma
A relatively unspecialized plant cell type that functions in metabolism, photosynthesis, food storage, and respiration and may develop into more differentiated cell types
Parthenogenesis
A form of reproduction in which an unfertilized egg develops into a new individual
Passive Immunity
Temporary immunity obtained by acquiring antibodies without a primary immune response
Pathogen
A disease-causing organism, virus, or particle
Pyruvate Dehydrogenase Complex (PDC)
A complex of enzymes that convert pyruvate to acetyl CoA
Pepsin
A digestive enzyme that breaks down proteins
Peptide
A molecule composed of amino acids
Peptide Bond
The covalent bond between two amino acids
Peristalsis
Rhythmic waves of contraction of smooth muscle that push food along the digestive tract
Phage
A virus that infects bacteria
Phagocytosis
A type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm
Pharynx
An area in the vertebrate throat where air and food passages cross
Phenotype
An expressed trait of an organism
Pheromone
A volatile chemical signal that functions in communication between animals
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
Phospholipid Bilayer
A membrane consisting of two layers of phospholipids
Phosphorylation
The addition of a phosphate group to a molecule
Photon
The smallest allowable quantity of light energy
Photoperiodism
A physiological response to day length, such as flowering in plants
Photosynthesis
The conversion of light energy to chemical energy that is stored in sugar compounds; occurs in plants, algae, and certain protists
Phototropism
The bending of a plant towards light
Phylum
The taxonomic category of classification consisting of related classes
Pinocytosis
A type of endocytosis whereby a cell indiscriminately takes in liquid from the outside environment
Pistil
The female portion of a flower
Pith
The core of the central vascular cylinder of monocot roots, consisting of parenchyma cells; tissue interior to vascular bundles in dicot stems
Pituitary
An endocrine gland at the base of the hypothalamus that secretes hormones produced by the hypothalamus as well as those produced in the pituitary gland
Placenta
A temporary organ in female placental mammals during pregnancy that mediates exchange of materials between the mother and the developing fetus
Plasma
The liquid component of blood
Plasma B-Cell
An antibody-secreting lymphocyte
Plasmid
A small ring of DNA that carries accessory genes separate from those of a bacterial chromosome
Plasmodesmata
Pores connecting adjacent plant cells
Plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment
Platelets
Small blood cells lacking nuclei that are important in blood clotting
Platyhelminthes
The animal phylum composed of bilaterally symmetric flatworms
Pleiotropy
The ability of a single gene to have multiple effects
Point Mutation
A mutation in which one base is substituted for another
Polymerase Chain Reaction (PCR)
A laboratory technique that creates millions of copies of a piece of DNA
Polypeptide
A chain of amino acids linked together by peptide bonds
Polyploidy
The possession more than two complete chromosome sets
Population
A group of interacting individuals belonging to one species and living in the same geographic area
Porifera
The phylum of filter-feeding animals commonly called sponges
Prairie
North American grasslands with frequent wildfires and long periods of drought
Precipitation
The removal of dissolved pathogens from solution by antibodies in the blood
Primary Structure
The sequence of amino acids in a polypeptide
Primary Succession
The establishment of a biological community in an area virtually barren of life
Producer
An autotroph; an organism that sustains itself without eating or decomposing other organisms
Progesterone
A steroid hormone secreted by the corpus luteum of the ovary and by the placenta, which maintains the uterine lining during pregnancy
Prolactin
A hormone secreted by the anterior pituitary that stimulates mammary gland growth and milk synthesis in mammals
Prophase
The stage of mitosis in which the nuclear envelope dissolves, chromatin condenses, the nucleolus disappears, and the spindle fibers form
Protista
The kingdom that contains the unicellular eukaryotes and closely related multicellular organisms called protists
Protostome
A member of one of two distinct evolutionary lines of coelomates, consisting of the annelids, mollusks, and arthropods
Pseudopod
A cellular extension of amoeboid cells used in moving and feeding
Parathyroid Hormone (PTH)
The hormone secreted by the parathyroid glands that raises the blood calcium level
Pulmonary
Referring to the lungs
Punctuated Equilibrium
The theory that most species don't evolve much for most of their evolutionary history, with short periods of rapid speciation interspersed
Pupil
The opening in the eye that allows light to pass through
Quaternary Structure
The interaction of separate polypeptides to form a protein
Radioactive Dating
A method of determining the age of fossils and rocks using half-lives of radioactive isotopes
Recessive
The allele that is not expressed in the phenotype of a heterozygous individual
Redox Reaction
A chemical reaction involving the transfer of one or more electrons from one reactant to the other
Reduction
Gain of electrons
Reflex Arc
The route followed by nerve impulses to produce a reflex act, from the periphery through the afferent nerve to the nervous system, and then through the efferent nerve to the effector organ
Reptilia
The vertebrate class of reptiles, characterized by scales and an amniotic egg; represented by lizards, snakes, turtles and crocodiles
Respirometer
A device that measures the rate of respiration in a system by measuring the rate of exchange of oxygen and carbon dioxide
Restriction Enzyme
An enzyme that cuts DNA in predictable places, often leaving an overhang, or "sticky end"
Retina
The sheet of photoreceptors that coats the back of the eye
Reverse Transcriptase
An enzyme encoded by some RNA viruses that uses RNA as a template for DNA synthesis
Ribosome
A cell organelle constructed in the nucleolus that functions as the site of protein synthesis in the cytoplasm
RNA Polymerase
An enzyme that catalyzes the synthesis of RNA from a DNA template
rRNA
Ribosomal RNA; the type of ribonucleic acid that, together with proteins, makes up ribosomes
SA (sinoatrial) Node
The pacemaker of the heart, located in the wall of the right atrium
Saccharide
A class of molecules composed of varying numbers of simple sugars covalently bonded together
Saliva
A fluid produced by the salivary glands in the mouth containing water, mucus, and digestive enzymes
Sarcomere
The functional unit of skeletal muscle, consisting of actin and myelin filaments
Savanna
A tropical grassland biome with scattered individual trees, large herbivores, and three distinct seasons based primarily on rainfall; maintained by occasional fires and drought
Sclerenchyma
A rigid, supportive plant cell type possessing thick secondary walls strengthened by lignin at maturity
Secondary Structure
The shapes of small portions of a polypeptide
Secondary Succession
The establishment of a biological community in an area where the existing community has been destroyed, but the soil remains intact
Secretin
A hormone produced in the duodenum (in the crypts of Lieberkuhn) that regulates the release of bicarbonate into the duodenum
Segregation
A general rule in inheritance that gametes receive only one of the parent's two alleles for a gene
Semicircular Canal
Fluid-filled channels in the inner ear that detect changes in the head's rate of rotation or angular movement
Seminiferous Tubules
Highly coiled tubes in the testes in which sperm are produced
Sepal
The set of leaves in angiosperms that encloses and protects the flower bud before it opens
Serial Dilution
The dilution of a substance at several different concentrations
Sessile
Unable to move about; usually permanently attached to a solid substrate of some kind, such as a rock
Setae
Hair-like structures on the ventral side of an annelid which are used for grip
Sex-Influenced
An autosomal trait that is influenced by sex; e.g. baldness
Sex-Linked
A trait located on a chromosome involved in the determination of sex; e.g. color-blindness
Sieve-Tube cells
Living cells without nuclei that conduct phloem in plants
Society
A population distinguished by division of labor
Solute
A substance that is dissolved in a solution
Solvent
The dissolving agent of a solution
Somatic Nervous System
The branch of the motor division of the vertebrate peripheral nervous system composed of motor neurons that carry signals to skeletal muscles
Speciation
The development of a new species from another species
Species
A group whose members have the ability to interbreed and produce fertile offspring
Spectrometry
Analysis of light with respect to its wavelength and intensity
Spermatogenesis
The formation of sperm cells
Sphincter
A ringlike valve in a muscular tube, such as a digestive tract
Spleen
An organ that removes old red blood cells and antibody-coated cells from the circulation
Spongy Cells
Loosely packed mesophyll cells in plant leaves
Sporophyte
The multicellular diploid form in plants undergoing alternation of generations that results from a union of gametes and meiotically produces haploid spores that grow into the gametophyte generation
Stabilizing Selection
Natural selection that favors the middle ground between two extremes of a trait
Stamen
The male portion of a flower
Starch
The energy storage polysaccharide found in plants
Steroid
A type of lipid derived from cholesterol composed of four fused carbon rings
Stigma
The part of the flower that receives pollen for fertilization
Stomata
Pores surrounded by guard cells in the epidermis of leaves and stems that allow gas exchange between the external environment and the interior of the plant
Stop Codon
Codon that signals ribosomes to terminate protein synthesis
Stroma
The fluid of the chloroplast surrounding the thylakoid membrane
Style
The tube that supports the stigma and conveys pollen towards the ovary in a flower
Substrate
The substance on which an enzyme acts
Sulfur Dioxide
A gas produced in many industrial process that mixes with water vapor to form sulfuric acid, a main component of acid rain
Sympatric
A mode of speciation that produces a reproductively isolated subpopulation in the midst of its parent population
Synapse
The synaptic terminal of an axon, the surface of the cell it stimulates, and the space between them (the synaptic cleft)
Synapsis
The pairing of and exchange of material between replicated homologous chromosomes during prophase I of meiosis; also known as crossing over
Synthesis
Formation of a compound from simpler compounds or elements
Taiga
The forest biome characterized by considerable snow, harsh winters, short summers, and evergreen trees
Taproot
The main root of a dicot plant, usually stouter than the lateral roots and growing straight downward from the stem
Taxis
A movement toward or away from a stimulus
Telophase
The stage of mitosis in which two distinct nuclear envelopes appear, chromosomes become chromatin, nucleoli appear, and the spindle fibers disappear
Tendon
A type of fibrous connective tissue that attaches muscle to bone
Tertiary Structure
The shape of an entire polypeptide
Test Cross
A cross carried out between an individual with the dominant phenotype and an individual with the recessive phenotype in order to determine the genotype of the dominant individual
Testosterone
The male steroid hormone, produced in the testes, that stimulates the development of secondary sexual characteristics
Thigmotropism
Plant growth towards contact
Thylakoid
The disk-shaped membranous sacs inside the chloroplast; contain chlorophyll and the enzymes of the light reactions of photosynthesis
Thyroid
An endocrine gland in the neck that secretes thyroxine and calcitonin
Thyroxine
A hormone secreted by the thyroid gland that stimulates metabolism in virtually all body tissues
Tight Junction
The area of two cells where they join together to prevent the passage of fluid between them
Trachea
A cartilage-lined tube that conveys air to and from the lungs
Tracheid Cells
Water-conducting and supportive elements of xylem
Tracheophyte
A vascular plant that has a conducting system of xylem and phloem
Transformation
The phenomenon in which external genetic material is taken in by a cell
Translocation
The movement of mRNA through the ribosome during translation; also, a mutation in which part of a chromosome moves to a non-homologous chromosome
Transpiration
The loss of water vapor from the stomata of a plant
Triploid
Containing three sets of chromosomes
Trisomy
The presence of three, instead of the normal two, homologous chromosomes in an organism
tRNA
Transfer RNA; the type of ribonucleic acid that conveys amino acids to the ribosomes
Trophic Level
The division of species in an ecosystem on the basis of their main nutritional source
Tropical Rainforest
The biome located near the equator where rainfall is abundant; harbors more species of plants and animals than all other terrestrial biomes combined
Thyroid-Stimulating Hormone (TSH)
A hormone produced in the pituitary gland that regulates the function of the thyroid gland
Tundra
A treeless area that has little rainfall and permanently frozen subsoil (permafrost) thus supporting only low-growing vegetation
Turgor
The firmed state of a walled cell as a result of the entry of water from a hypotonic environment
Tympanic Membrane
A thin membrane that vibrates in response to sound energy and transmits the resulting mechanical vibrations to the structures of the middle ear
Urea
A soluble form of nitrogenous waste excreted by mammals and most adult amphibians
Ureter
A duct that conveys urine from the kidney to the urinary bladder
Urethra
A duct that conveys urine from the urinary bladder to the outside and, in males, also conveys semen out of the body during ejaculation
Uric Acid
An insoluble nitrogenous waste excreted by insects, lizards, and birds
Urinary Bladder
A pouch where urine is stored prior to elimination
Urine
Concentrated filtrate produced by the kidneys, stored in the urinary bladder, and excreted via the urethra
Uterus
The organ in which the development of young occurs in mammals
Vaccine
A harmless variant or derivative of a pathogen used to stimulate a host organism's immune system to mount a long-term defense against the pathogen
Vagina
The part of the female reproductive system between the uterus and the outside opening that acts as the birth canal in mammals
Vas Deferens
The tube that conveys sperm from the epididymis to the urethra
Vascular System
A system formed by xylem and phloem of a plant, serving as a transport system for water and nutrients
Vein
A large vessel that carries blood towards the heart
Vena Cava
The two veins (superior and inferior) that convey deoxygenated blood to the heart
Venule
A vessel that carries blood from capillaries to veins
Vestigial Structure
A structure that is of little or no use to the organism
Villi
Fingerlike projections into the lumen of the small intestine containing cells specialized for absorbing nutrients
Vitamin
An organic nutrient that an organism requires in very small quantities that generally functions as a coenzyme
Water Vascular System
In echinoderms, a radially arranged system of water-filled canals that provide movement and circulate water, facilitating gas exchange and waste disposal
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
Zygote
The diploid cell that results from the union of a sperm cell nucleus and an egg cell nucleus
Zymogen
A protein that is an inactive precursor of an enzyme
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