Key Terms

biological carbon pump

process by which inorganic carbon is fixed by photosynthetic species that then die and fall to the sea floor where they cannot be reached by saprobes and their carbon dioxide consumption cannot be returned to the atmosphere

bioluminescence

generation and emission of light by an organism, as in dinoflagellates

contractile vacuole

vesicle that fills with water (as it enters the cell by osmosis) and then contracts to squeeze water from the cell; an osmoregulatory vesicle

cytoplasmic streaming

movement of cytoplasm into an extended pseudopod such that the entire cell is transported to the site of the pseudopod

endosymbiosis

engulfment of one cell within another such that the engulfed cell survives, and both cells benefit; the process responsible for the evolution of mitochondria and chloroplasts in eukaryotes

endosymbiotic theory

theory that states that eukaryotes may have been a product of one cell engulfing another, one living within another, and evolving over time until the separate cells were no longer recognizable as such

hydrogenosome

organelle carried by parabasalids (Excavata) that functions anaerobically and outputs hydrogen gas as a byproduct; likely evolved from mitochondria

kinetoplast

mass of DNA carried within the single, oversized mitochondrion, characteristic of kinetoplastids (phylum: Euglenozoa)

mitosome

nonfunctional organelle carried in the cells of diplomonads (Excavata) that likely evolved from a mitochondrion

mixotroph

organism that can obtain nutrition by autotrophic or heterotrophic means, usually facultatively

pellicle

outer cell covering composed of interlocking protein strips that function like a flexible coat of armor, preventing cells from being torn or pierced without compromising their range of motion

phagolysosome

cellular body formed by the union of a phagosome containing the ingested particle with a lysosome that contains hydrolytic enzymes

plankton

diverse group of mostly microscopic organisms that drift in marine and freshwater systems and serve as a food source for larger aquatic organisms

plastid

one of a group of related organelles in plant cells that are involved in the storage of starches, fats, proteins, and pigments

raphe

slit in the silica shell of diatoms through which the protist secretes a stream of mucopolysaccharides for locomotion and attachment to substrates

test

porous shell of a foram that is built from various organic materials and typically hardened with calcium carbonate