Amoeboid~having no definite shape to the cell or able to change shape Amphiesma~the outer covering of a dinoflagellate, consisting of several membrane layers Aperture~a small opening, for example the opening in the test of a foram Bacteriophage~a virus which infects and destroys a bacterial host Capsid~the protein shell of a free virus particle Cell~the fundamental structural unit of all life Cell cycle~the complete sequence of steps which must be performed by a cell in order to replicate itself Cell membrane~the outer membrane of a cell, which separates it from the environment Cell wall~a rigid structure deposited outside the cell membrane Chloroplast~a plastid found in algal and green plant cells Chromosome~a linear piece of eukaryotic DNA, often bound by specialized proteins known as histones Colonial~a condition in which many unicellular organisms live together in a somewhat coordinated group Contractile vacuole~a specialized vacuole with associated channels designed to collect excess water in the cell Cytoplasm~the contents of a cell, including the plasma membrane,but not including the nucleus Cytoskeleton~an integrated system of molecules within eukaryotic cells which provides them with shape, internal spatial organization and motility Dikaryotic~having two different and distinct nuclei per cell Diploid~having two different sets of chromosomes in the same nucleus of each cell Double membrane~a two-layered membrane which surrounds the organelle Endoplasmic reticulum~a network of membranes in eukaryotic cells which helps in control of protein synthesis and cellular organization Eukaryote~an organism whose cells have cytoskeletons for support and their DNA contained in a nucleus Eyespot~a light-sensitive organelle found in many groups of protists, and in some metazoans Filament~a long chain of proteins, such as found in hair, muscle, or in flagella Fission~a division of single-celled organisms, especially prokaryotes, in which mitosis does not occur Flagellum~a hair-like structure attached to a cell, used for locomotion in many protists and prokaryotes Frustule~the mineral skeleton of a diatom or other unicellular organism Golgi apparatus~a Eukaryotic organelle which packages cell products, such as enzymes and hormones Haploid~a single set of chromosomes in the nucleus of each cell Haptonema~a peg-like structure unique to the Prymnesiophyta Lorica~a vase-shaped or cup-shaped outer covering Lysosome~a eukaryotic organelle which carries digestive enzymes Mastigoneme~a small hair-like filament found on the hairy flagellum of the Chromista Membrane~ a semi-fluid structure which bounds all cells, and partitions the interior of eukaryotic cells Mesokaryotic~a nuclear condition unique to the dinoflagellates in which the chromosomes remain permanently condensed Microtubules~a type of filament in eukaryotic cells composed of units of the protein tubulin Mitochondrion~a complex organelle found in most eukaryotes Mitosis~the process of nuclear division in eukaryotes MTOC~the bundles of protein tubes which may be found at the base of a eukaryotic flagellum Multicellular~any organism which is composed of many cells is termed multicellular Nanometre~a unit of measure, one millionth of a meter Nuclear membrane~the double membrane which surrounds the eukaryotic nucleus Nucleoid~the region in prokaryotes where the DNA is concentrated Nucleus~the membrane-bound organelle which contains the DNA in the form of chromosomes Organelle~a membrane-bound structure in a eukaryotic cell that carries out different cellular functions Plasma membrane~the outer membrane of a cell, sometimes called the cell membrane Plasmid~the circular loop of DNA in prokaryotes Plastid~any of several pigmented cytoplasmic organelles found in plant cells and other organisms Prokaryotic~bacteria and archaea Prokaryotic cells having no internal membranes or cytoskeleton Protoplasm~all the contents of a cell, including the nucleus Pseudopodia~the fingerlike extensions from an amoeboid cell Repeat sequences~the length of a nucleotide sequence that is repeated in a tandem cluster Reticulopodia~the long thread-like pseudopodia that branch apart and rejoin, forming a fine network Test~a hard shell produced by some unicellular protists, may be made of calcium carbonate, silica, or sand grains Theca~any stiff outer covering of a unicellular protist, and usually made up of interlocking plates Transduction~the viral transfer of DNA to new host Trichocyst~the organelle in ciliates and dinoflagellates which releases long filamentous proteins when the cell is disturbed Ultrastructure~the detailed structure of a specimen, such as a cell, tissue, or organ, that can be observed only by electron microscopy Undulipodium~a eukaryotic flagellum Vacuole~the membrane-bound fluid-filled space within a cell