| TERM | GROUP | DEFINITION | |
|---|---|---|---|
| RACEME | N | PLANTS | Pronunciation: Etymology: An indeterminant inflorescence with pedicullate flowers. |
| RADULA (RADULAE OR RADULAS) | N | ANIMALS | Pronunciation: Etymology: The radula is a rasping tongue-like structure in the mouths of various mollusks. |
| RANK | N | PLANTS | Pronunciation: Etymology: Vertical row of lateral organs. For example, grasses are 2-ranked. That is, as seen from the end of the stem, the leaves seem to emerge from two sides of the stem. |
| RAPHE | N | PROTISTS | Pronunciation: Etymology: A raphe is a slit in the frustule of some of the pennate diatoms. Those cells with a raphe are mobile. |
| RECEPTACLE | N | PLANTS | Pronunciation: Etymology: The end of the stem which bears the flower parts. |
| RECURRENT FLAGELLUM (RECURRENT FLAGELLUM) | NP | PLANTS, PROTISTS | Pronunciation: Etymology: Recurrent flagella bend to the posterior end of the cell. Typically, they are identified as recurrent when anteriorly-directed flagella are present. |
| RESERVOIR | N | PROTISTS | Pronunciation: Etymology: See flagellar pocket. |
| RETICULOPODIUM (RETICULAPODIA) | N | PROTISTS | Pronunciation: Etymology: Reticulopods are pseudopods that form a branched, web or net-like structure. |
| REVERSAL | N | SYSTEMATICS | Pronunciation: re-VER-s’l Etymology: Reverse comes from the Latin, revertere, which means turn back. Reversal is a noun which means the condition of being reversed. In an evolutionary sense, a reversal occurs when, as one progresses up the cladogram, a character state changes from state a to b and then back to a. Reversals should be avoided whenever possible during the construction of a cladogram. |
| RHABDITE | N | ANIMALS | Pronunciation: Etymology: Rhabdites are certain epidermal secretion droplets that have a defined layered ultrastructure in certain Platyhelminthes. |
| RHIZOID | ADJ OR N | PLANTS, PROTISTS, FUNGI | Pronunciation: Etymology: Thread-like growths, simple or branched, which serve for absorption and anchorage. |
| RHIZOMATOUS | ADJ | PLANTS | Pronunciation: Etymology: Plants having rhizomes (horizontal stems, often underground or on the surface of the ground, bearing scale-like leaves). |
| RHIZOME | N | PLANTS | Pronunciation: Etymology: A rhizome is a creeping underground stem from which erect stem axes may emerge. |
| RHIZOPLAST | N | PLANTS, PROTISTS | Pronunciation: Etymology: A rhizoplast is a striated root system that extends from the basal body tinto the cell, usually to the nuclear envelope. |
| RHOPTERY | N | PROTISTS | Pronunciation: Etymology: An rhoptery is part of the apical complex in the apicomplexa. It is a variously shaped body that likely is involved in secretions from the cell that enable its entry into a host cell. |
| RHYNCHOCOEL | N | ANIMALS | Pronunciation: Etymology: A rhynchocoel is a fluid-filled body cavity (coelom? pseudocoelom?) into which the nemertene evertible proboscis retracts. |
| RIBBON-LIKE FLAGELLUM (RIBBON-LIKE FLAGELLA) | N | PROTISTS | Pronunciation: Etymology: The ribbon-like flagellum is a tinsel (with flagellar hairs) flagellum and is flattened. Although it occurs in several groups of microbial eukaryotes, it is characteristic of dinoflagellates where it lies in the cingulum. |
| RIBOSOME | N | ANIMALS, PLANTS, PROTISTS, FUNGI | Pronunciation: Etymology: A ribosome is an organelle made of RNA which functions in the assembly of proteins. |
| RNA POLYMERASE | NP | ANIMALS, PLANTS, PROTISTS, FUNGI, BACTERIA | Pronunciation: Etymology: RNA Polymerase comes in several functional forms. RNA Polymerase I is an enzyme that functions in the ribosome is an organelle made of RNA which functions in the assembly of proteins. |
| ROD | N | BACTERIA | Pronunciation: Etymology: A rod is an elongate cell form such that it has distinct ends (called poles). |
| ROOT | N | PLANTS | Pronunciation: Etymology: A root is a plant axis without nodes and internodes, and it has a vascular stele that is different from that of the stem axis. |
| ROSTELLUM (ROSTELLA) | N | ANIMALS | Pronunciation: Etymology: A rostellum is a prominent rounded apex on the scolex of some tapeworms. It also is a beak-like tubular mouth part in some sucking insects. |
| RUMPOSOME | N | FUNGI | Pronunciation: Etymology: Structure composed of interconnecting tubules at the posterior end of the zoospore. |
