Glossary

TermDefinition
Absorbancea measure of the amount of light absorbed by a sample in a colorimeter
Acute Toxicitywhen chemicals cause an adverse reaction in a short period of time
Agara gelatinous substance extracted from seaweed and used to grow different types of cell cultures in science labs
Antibiotica medicine used to inhibit the growth of or to kill microorganisms
Asexual Reproductiona mode of reproduction via mitosis, where the daughter cells are genetically identical to the single parental cell
Bioaccumulationoccurs in an organism when the rate of intake of a substance is greater than the rate of at which it’s used or excreted
Biofilma dense community of cells living within a sticky matrix that the cells themselves produce
Bioinformaticsuse of computer technology to store and analyze biological data, particularly in the field of genetics
Buffera solution that prevents rapid changes in pH
Cannibalismthe act of eating members of your own species
Chelexa chemical used in DNA extraction that breaks up cells and inhibits damage to the DNA in the cells. It binds metal ions that are needed by DNA-degrading enzymes.
Chemotaxisa change in direction of movement in response to chemicals in an organism’s environment
Chronic toxicitywhen chemicals accumulate in an organism and cause damage months or years after the initial exposure
Cilia“hair-like structures” found on the outside of some eukaryotic organisms; cilia are used primarily for motion and food consumption in Tetrahymena
Ciliatesa group of protozoans that have cilia
Clonesa group of identical cells that are derived from the same parent cell by asexual reproduction
Colony (bacterial)a visible accumulation of bacteria on an agar plate, formed when the descendants of a single original bacterial cell pile up in a layer made of millions of bacteria
Colorimetera device that shines a beam of light from an LED through a sample and detects the amount of light that gets through
Contractile Vacuolesstructures that remove excess water and salts from the cytoplasm in protists
Controla portion of the experiment in which the variable being tested ISN’T changed. It allows the scientist to compare the results when the variable IS changed (the experiment). For example, if you wanted to know whether fertilizer makes a plant grow taller the control would be a plant grown with just water and the experiment would be a plant grown with water and fertilizer.
Dependent Variablethe variable that is measured in the experiment
DNA (deoxyribonucleic acid)a molecule that makes up the genes of an organism. It encodes the genetic instructions for how that organism will function.
DNA Polymerasethe enzyme that puts nucleotides together to make a DNA molecule
Enzymea substance that acts as a catalyst to speed up a specific reaction (most enzymes are proteins)
Eukaroytean organism that has a membrane-bound nucleus and organelles
Evolutiona change in the inherited characteristics of biological populations over multiple generations
Exocytosisthe process of producing something inside a cell and releasing it for use outside the cell (exo = outside, cyto = cell)
Flagelluma lash or whip-like appendage found on some prokaryotic and eukaryotic cells; used in movement and in some eukaryotes, may act as a sensory organelle, detecting changes in environment
Food Vacuolesbubble-like sacs created when a cell ingests material from its environment. The material is digested inside the vacuole and the cell absorbs nutrients needed to carry out basic life functions. Indigestible material is released back into the environment when a vacuole fuses to the cell membrane for excretion.
Growth Ratethe rate at which cells reproduce
Hydrophilicattracted to water (hydro = water, philia= loving)
Hydrophobicrepelled by water (hydro = water, phobos = to fear)
Hypertonichaving a higher concentration of solutes. The cytoplasm of a cell is hypertonic to distilled water.
Hypothesisa proposed explanation for a phenomenon that can be tested
Hypotonichaving a lower concentration of solutes. Distilled water is hypotonic to a cell.
Independent Variablethe variable that you change or manipulate in an experiment
Index of Biotic Integritya scientific tool used to evaluate the quality of the water in a pond or stream by looking at the types of invertebrates that live in it
Indicator Speciesa species whose absence, presence or abundance reflects a specific environmental condition; can be used an as early warning system to assess the overall status of an ecosystem
Isotonichaving an equal concentration of solutes outside and inside the cell
LD50 (lethal dose, 50%)the dose that kills 50% of a population of test animals (often rats) to whom the chemical has been given; usually measured in “mg/kg”
Macroinvertebratesinvertebrates large enough to see with little or no magnification
Macronucleus (MAC)the “working nucleus” that is usually larger, contains many copies of the cell’s DNA and directs synthesis of all necessary proteins
Macrostomelarger, cannibalistic form of Tetrahymena vorax
Meiosisa type of nuclear division in sexual reproduction where the number of sets of chromosomes in the cell is reduced to half the original number (diploid to haploid); the daughter cells are genetically different from the parent cells
Microcosm“mini-world”, a small, limited version of a larger, more complicated system; it allows scientists to control variables and look at interactions between some members of the larger system
Microevolutionchanges in allele frequencies in a population over a relatively short period of time. The term “macroevolution” refers to changes in species that have occurred over long (geologic) periods of time
Microliterone-millionth of a liter, the symbol is µL
Micronucleus (MIC)smaller nucleus, has a single copy of the genetic information; used for sexual reproduction in Tetrahymena
Micropipettea tool used to measure small volumes of liquid in science labs; measurements are in µL (microliters)
Microstomesmall-mouthed version of Tetrahymena vorax
Microtubulestiny tubes that make-up cilia; they are made of a protein called tubulin
Milliliterone-thousandth of a liter, the symbol is mL
Mitosisa form of nuclear division in which a cell replicates its chromosomes and provides a copy of each to the daughter cells; the daughter cells are genetically identical to the parent cells
Model Organismone that is used in science to study how it works. The information learned is often used to compare similar organisms or similar structures in other organisms; rats are common model organisms used in science to understand human biology
Morphologyshape and structure of an organism
Motilitythe ability to move
Mucocyststructure just under the cell membrane of Tetrahymena that stores a protein called mucus
Mutationpermanent change to an organism’s DNA
Natural Selectionthe process whereby organisms better adapted to their environment tend to survive and produce more offspring than other members of the population
Neffa mixture of protein and yeast extract with added sugar and iron chloride; a solution of Neff is used to grow Tetrahymena in a lab environment
Nichethe specific type of habitat an organism inhabits and its role or function in an ecosystem
Nonpathogenican organism that does not cause disease
Nucleotidesthe A, C, G and T building blocks of DNA
Oral Groovethe mouth-like opening in a ciliate where food particles are collected and transported through the organism’s gullet into food vacuoles for digestion
Osmoregulatorsorganisms that spend energy to maintain water balance with an environment that has a water and salt concentration that’s different from their cytoplasm; Tetrahymena is an osmoregulator
Osmosisrefers to the movement of water across a membrane
PCR (Polymerase Chain Reaction)a laboratory technique used to make many copies of DNA from living organisms
Pelletthe dense collection of particles at the bottom of a tube caused by spinning a sample of culture in a centrifuge
Phagocytosisthe process of engulfing a particle for the purpose of obtaining food
Predatoran organism that preys on and consumes another organism; Ex. Tetrahymena are predators of bacteria
Primersa short piece of nucleic acid that serves as a starting point for DNA synthesis
Protozoananimal-like organisms in Kingdom Protista that are single-celled and microscopic; these include ciliates, amoebae, flagellates and sporozoans
Pseudomonas fluorescensa rod-shaped, flagellated bacteria that lives in water films in the soil and in association with plant roots; it does not cause disease in healthy people and is used frequently in lab activities
RNA (ribonucleic acid)a large molecule whose main function is to transfer information coded in a cell’s DNA to the ribosomes, where the information is used to make proteins
Selectively Permeable Membranea membrane in that allows some substances to pass through while other substances are blocked
Serial Dilutiona stepwise dilution of a substance where the dilution factor is known at each step
Sexual Reproductiona mode of reproduction involving meiosis, where the daughter cells are genetically different from the parental cells
Solutea substance dissolved in a solvent; in cells, the solvent is water
Spread Platea technique used to distribute diluted bacterial cells across a large area of an agar plate so you can see individual colonies; a small volume of liquid culture is transferred to the plate and then spread to cover the entire plate
Standard Curvea graph of the relationship between two variables based on many actual measurements. For example, it could be a graph of the relationship between the concentration of a solute and the amount of light a solution absorbs. Once graphed, the concentration of an unknown solution can be determined by measuring the solution’s absorbance and finding that point on the curve
Stock Culturea culture that is used to grow more cultures. It may also be a back-up sample in case your working cultures become contaminated.
Stomatina mixture composed of hypoxanthine and uracil, which are metabolic products of the breakdown of nucleic acids; it is secreted by prey organisms and triggers the change from normal to “cannibal” in Tetrahymena vorax
Streak Platea technique used to distribute an originally dense sample of bacterial culture across an agar plate; sterile loops are used to streak bacteria into uncontaminated areas of the plate, diluting the total number with each successive streak so that individual colonies can grow
Tetrahymenasingle-celled protist, only about 50μm, that lives in fresh water environments and consumes mostly bacteria that decompose dead animal or plant matter
Traitsinherited characteristics of an organism that are the product of genes, like height or flower color
Trisan isotonic mixture of salts without any carbon source or amino acids, used to starve Tetrahymena
Turbiditycloudiness of a solution
Working Culturelarger volume of cells prepared for the whole class to use in experiments
μl (microliter)symbol for microliter