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Rh factor Refers to the presence or absence of the Rh antigen on red blood cells.
ribosomal A site Site that holds the tRNA carrying the next amino acid to be added to the chain.
Ribosomal E site Site where discharged tRNAs leave the ribosome.
ribosomal P site Site that holds tRNA carrying the growing polypeptide chain.
ribosomal RNA (rRNA) RNA molecules that construct ribosomal subunits.
ribosomes Complex particles that facilitate the orderly linking of amino acids into polypeptide chains.
ribozymes . RNA molecules that function as enzymes
RNA interference Blocking gene expression by means of an miRNA silencing complex.
RNA polymerase Enzyme that links together the growing chain of ribonucleotides during transcription.
RNA processing The modification of mRNA before it leaves the nucleus that is unique to eukaryotes.
RNA splicing Process by which the introns are removed from RNA transcripts and the remaining exons are joined together.
rough ER A network of interconnected membranous sacs in a eukaryotic cell's cytoplasm; covered with ribosomes that make membrane proteins and secretory proteins.
rubisco The most abundant protein on earth. Performs Carbon Fixation in the Calvin Cycle.
S phase The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.
salicylic acid A plant hormone that may be partially responsible for activating systemic acquired resistance to pathogens.
scaffolding proteins A type of large relay protein to which several other relay proteins are simultaneously attached to increase the efficiency of signal transduction.
Schwann cells Type of glia in the PNS, Supporting cells of the peripheral nervous system responsible for the formation of myelin.
second law of thermodynamics Every energy transfer or transformation increases the entropy of the universe.
second messengers Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion.
secondary consumer Carnivore that eats herbivores.
secondary immune response Immune response after the body has already been exposed to a specific antigen. Response is faster, of greater magnitude, and more prolonged.
secondary production Amount of chemical energy in consumers' food that is converted to new biomass.
secondary structure . Either an alpha helix or beta pleated sheet
secondary succession Succession when an existing community has been cleared, but soil left intact.
seed coat A tough outer covering of a seed, formed from the outer coat of an ovule.
selective permeability A property of a plasma membrane that allows some substances to cross more easily than others.
self-incompatibility The ability of a seed plant to reject its own pollen and sometimes the pollen of closely related individuals.
semelparity Big-bang reproduction.
semiconservative model Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.
sensitive period A limited phase in an animal's development that is the only time when certain behaviors can be learned.
sensory neurons Neurons that carry incoming information from the sense receptors to the central nervous system.
sepal A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens.
serial endosymbiosis Sequence of endosymbiotic events that led to an ancestral eukaryote.
serotonin A neurotransmitter that affects hunger,sleep, arousal, and mood.
sex chromosomes X and Y chromosomes.
sex linked genes Genes located on the sex chromosomes.
sexual dimorphism Differences between the sexes in secondary sexual characteristics.
sexual recombination Crossing over and shuffling of genes during meiosis.
sexual reproduction When two parents give unique combination of genes to offspring.
sexual selection Natural selection for mating success.
shared derived character Evolutionary novelty unique to that clade.
shared primitive character Trait shared beyond the taxon.
short-day plant A plant that flowers only when the light period is shorter than a critical length. Usually fall or winter.
sickle-cell disease Genetic disorder in which red blood cells have abnormal hemoglobin molecules and take on an abnormal shape.
sign stimulus External sensory stimulus that triggers a fixed action pattern.
signal A behavior that causes change in another's behavior.
signal peptide A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell.
signal transduction A series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell.
signal transduction pathway The process by which a signal on a cell's surface is converted into a specific cellular response.
signal-recognition particle A protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome.
simple epithelium Single layer of cells.
simple fruit A fruit derived from a single carpel or several fused carpels.
single-strand binding protein (SSB) Binds to and stabilizes single-stranded DNA until it can be used as a template.
siRNAs (small interfering RNAs) RNAs of similar size and functions as miRNAs that inhibit gene expression.
sister chromatids Identical copies of a chromosome; full sets of these are created during the S subphase of interphase.
skeletal muscle Muscle that is striated, multinucleated.
smooth ER Synthesis of lipids, phospholipids and steroid sex hormones-help detoxify drugs and poisons (liver cells).
smooth muscle Muscle that is not striated, is single nucleated.
social learning Learning through observing others.
solute Something dissolved in a solution.
solute potential This measurement has a maximum value of 0; it decreases as the concentration of a solute increases.
solvent Dissolving agent of a solution.
somatic cell Any of the cells of a plant or animal except the reproductive cells.
Southern blotting A hybridization technique that enables researchers to determine the presence of certain nucleotide sequences in a sample of DNA.
spatial learning The modification of behavior based on experience with the spatial structure of the environment.
speciation Origin of new species and the source of biological diversity.
species diversity Variety of different kinds of organisms that make up a community.
species richness Total number of different species.
species transplant Movement of a species to areas where it was previously absent.
species-area curve The larger the geographic area, the greater the number of species.
specific epithet Second part of scientific name.
spirilla Spiral bacteria.
splicosome Different particles that recognize splice sites are compiled in a large assembly. A complex of RNA and protein subunits. Removes introns from a transcribed pre-RNA segments.
spores Produced by meiosis. Grow into haploid organisms by mitosis.
sporophyte Diploid, or spore-producing, phase of an organism. Makes haploid spores by meiosis.
squamous epithelium Cells that look like floor tiles.
stabilizing selection Shift that favors the mean.
stamen The pollen-producing reproductive organ of a flower, consisting of an anther and a filament.
standard metabolic rate (SMR) The metabolic rate of a resting, fasting, nonstressed ectotherm.
starch Storage polysaccharide of plants.
stem cell Unspecialized cell that can both reproduce itself indefinitely and differentiate into specialized cells of one or more types.
steroids Made of four rings of carbon.
sticky end A single-stranded end of a double-stranded DNA restriction fragment.
stigma The sticky part of a flower's carpel, which receives pollen grain.
stomata Microscopic pores in the leaf which lets CO2 in and O2 out. Also where water is lost.
stratified epithelium Multiples tiers of cells.
stroma Fluid inside the chloroplast where the Calvin Cycle happens.
stroma The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
stromatolites Oldest known fossils formed from many layers of bacteria and sediment.
structural isomers Differ in arrangement of atoms.
style The stalk of a flower's carpel, with the ovary at the base and the stigma at the top.
substrate-level phosphorylation When an enzyme transfers a phosphate group from a substrate molecule.
survivorship curves Graph of the proportion of a cohort still alive at each age.
sympathetic division The part of the autonomic nervous system that arouses the body to deal with perceived threats.
sympatric speciation Speciation without a divided population.
synapse The junction between two neurons or between a neuron and a muscle.
synapsis Homologous chromosomes pair up, aligned gene by gene.
synaptic cleft The narrow gap that separates the presynaptic neuron from the postsynaptic cell.
synaptic terminal A bulb at the end of an axon in which neurotransmitter molecules are stored and released.
synaptic vesicles Membrane-bounded compartments in which synthesized neurotransmitters are kept.
synthesis To put together.
systematics Analytical approach to understanding the diversity and relationships of present and past organisms.
systemic acquired resistance (SAR) A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.
T cell receptor Antigen receptors on a T cell. Unlike antibodies, T cell receptors are never produced in a secreted form.
T lymphocytes (T cells) Lymphocyte that matures in the thymus and acts directly against antigens in cell-mediated immune responses.
TATA box A promoter DNA sequence crucial in forming the transcription initiation complex.
taxis Automatic, oriented movement toward or away from some stimuli.
taxonomy A classification of organisms into groups based on similarities.
Tay-Sachs disease A human genetic disease caused by a recessive allele that leads to the accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth.
telomerase An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.
telomeres Repeated DNA sequences at the ends of eukaryotic chromosomes.
temperate phage A phage that is capable of reproducing by either the lytic or lysogenic cycle.
template strand The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript.
temporal isolation When two species breed at different times of day, season, or years.
tendons Attach muscles to bones.
terminator In prokaryotes, a special sequence of nucleotides in DNA that marks the end of a gene.
territoriality Defense of a space against encroachment by other individuals.
tertiary consumer Carnivore that eats carnivores.
tertiary structure Results from interactions between side chains.
testcross The result of breeding a recessive homozygote with an organism of dominant phenotype but unknown genotype.
tetrad A pair of chromosomes form tetrads made up of four chromatids.
thalamus Major input center for sensory information going to the cerebrum and the main output center for motor information leaving the cerebrum.
The Law of Segregation Two alleles separate during gamete formation and end up in different gametes because they are on on homologous chromosomes.
the three-domain system Domains Bacteria, Archae, and Eukarya.
therapeutic cloning The cloning of human cells by nuclear transplantation for therapeutic purposes, such as the generation of embryonic stem cells to treat disease.
thermal energy Kinetic energy associated with the random movement of molecules or atoms.
thermophiles Archaea that thrive in very hot environments, such as volcanic springs.
thermoregulation Process of maintaining an internal temperature within a tolerable range.
thoracic cavity cavity housing lungs and heart
threatened species Species that is likely to become endangered.
threshold potential The minimum membrane potential that must be reached in order for an action potential to be generated.
thylakoid Flattened membranes in the chloroplast where the light reactions take place.
thylakoids Membranous structures within a chloroplast that serve as the site for light harvesting in photosynthesis.
thymus Gland in the thoracic cavity above the heart where T lymphocytes mature.
tissues Groups of cells with a common structure and function.
tonicity The ability of a solution to cause a cell to gain or lose water; depends partly on concentration of nonpenetrating solutes relative to inside of cell.
top-down model I nfluence moves from top trophic levels to bottom.
topoisomerase Enzyme that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
torpor Physiological state in which activity is low and metabolism decreases.
totipotent Cells that are able to develop into any type of cell found in the body.
totipotent Stem cells with the potential to differentiate into any type of cell.
trait Each variant of a character.
Created by: ssteuter