| TERM | GROUP | DEFINITION | |
|---|---|---|---|
| NATURAL SELECTION | NP | EVOLUTION | Pronunciation: Etymology: Differential survival and reproduction due to variation in heritable traits. |
| NATURAL TAXON (NATURAL TAXA) | NP | SYSTEMATICS | Pronunciation: Etymology: A group of organisms that exists as the result of a common evolutionary history. |
| NAUPLIUS LARVA (NAULPII OR NAUPLIUS LARVAE) | NP | ANIMALS | Pronunciation: Etymology: The nauplius larva is the earliest larval form of crustaceans. It is characterized by having three pairs of legs. |
| NECK CANAL CELL | NP | PLANTS | Pronunciation: Etymology: The central row of cells in the neck of an archegonium; the ventral canal cell is the most proximal, i.e adjacent to the ovum. These cells dissolve allowing sperm to reach the ovum. |
| NEMATOCYST | N | ANIMALS, PROTISTS | Click here |
| NEOTENY | N | EVOLUTION | Pronunciation: Etymology: Neoteny is the situation in which an immature form becomes sexually mature in the developmental history. |
| NERVE CORD | N | ANIMALS | Pronunciation: Etymology: A nerve cord is a major nerve that runs the length of most bilaterian animals. They are ventral in the protostomes and usually dorsal in the deuterostomes. |
| NINE PLUS TWO (9 + 2) FLAGELLUM | NP | ANIMALS, PLANTS, PROTISTS, FUNGI | Pronunciation: Etymology: A 9(2)+2 microtubular array is the standard form of the eukaryotic flagellum. In cross section, 9 microtubular doublets circle a free pair of microtubules. |
| NITROGEN FIXATION | NP | BACTERIA | Pronunciation: Etymology: Nitrogen fixation is the ability to use energy to take nitrogen gas and reduce it to ammonium, nitrite, or nitrate. The initial step requires a nitrogenase enzyme and the energy of about 38 ATP molecules to fix one nitrogen molecule. |
| NODE | N | SYSTEMATICS | Etymology: Node come from the Latin, nodus, which means knot. Later, during the Renaissance, node began to mean a point of intersection. It is this latter derived meaning that is used in Biology. Node is a botanical term that refers to the point of branching in vascular plants. In macrophyllic plants, a node also is the point on a stem from which a leaf emerges. In cladistics, because it uses the tree metaphor, a node in a cladogram also is a branch point. |
| NODULE | N | PLANTS | Pronunciation: Etymology: Small or rounded structures on roots of plants that fix nitrogen. |
| NOTOCHORD | N | ANIMALS | Pronunciation: Etymology: A notochord is a cartilaginous rod that lies ventral to the hollow dorsal nerve cord in the chordate phyla. |
| NUCELLUS (NUCELLI) | N | PLANTS | Pronunciation: Etymology: Central part of a plant ovule; contains the embryo sac. |
| NUMERICAL TAXONOMY | NP | SYSTEMATICS | Pronunciation: nu-ME-ri-k’l taks-O-mo-mi Etymology: Numerical is derived from the Latin, numerus, which means number. Taxonomy has been defined elsewhere. Numerical Taxonomy is a method of systematics in which classification systems are constructed by similarities (mainly numerical similarities) between phenotypes. Thus, the method is called phenetics. There is no effort made to determine whether the characters are primitive or derived (apomorphic). So, they do not necessarily reflect evolutionary relationships. |
| NUT | N | PLANTS | Pronunciation: Etymology: A dry, one-seeded, indehiscent fruit with a woody pericarp. |
