Glossary
neritic zone near the shore neural related to nerve cells or the nervous system neurologist doctor who treats brain disorders neuron nerve cell neurotransmitters molecules released by one neuron to stimulate or inhibit another neuron or cell niche the habitat supplying the right environment for a particular species nm nanometer; one-billionth of a meter nocturnal characterized by activity at night, or related to the night nondisjunction failure of separation of homologous chromosomes during meiosis nuclear envelope double membrane surrounding the cell nucleus nucleated having a nucleus nucleotide the building block of RNA or DNA nucleus membrane-bound portion of cell containing the chromosomes obligate required or necessary, especially referring to a metabolic process or mode of nutrition octomer composed of eight parts oligosaccharide chain of several sugar molecules oncogene gene that causes cancer oocyte unfertilized egg opportunistic caused by a microorganism that is usually harmless but which causes infection in an immunosuppressed person organelle membrane-bound cell compartment organic composed of carbon, or derived from living organisms; also, a type of agriculture stressing soil fertility and avoidance of synthetic pesticides and fertilizers osmosis passage of water through a membrane in response to concentration differences osseous related to bone outcross fertilization between two different plants ovipary production of eggs that hatch outside the body ovovivipary production of eggs that hatch within the female’s body ovule multicellular structure that develops into a seed after fertilization oxidation reaction characterized by loss of electrons, or reaction with oxygen 247