a basic body plan in which the organism can be divided into similar halves by passing a plane at any angle along a central axis, characteristic of sessile and bottom-dwelling animals, as the sea anemone and starfish.
a type of structure of an organism or part of an organism in which a vertical cut through the axis in any of two or more planes produces two halves that are mirror images of each other Compare bilateral symmetry
Symmetrical arrangement of parts of an organism around a single main axis, so that the organism can be divided into similar halves by any plane that contains the main axis. The body plans of echinoderms, ctenophores, cnidarians, and many sponges and sea anemones show radial symmetry. Compare bilateral symmetry.
- Radioactive isotope
radioactive isotope n. An isotope having an unstable nucleus that decomposes spontaneously by emission of a nuclear electron or helium nucleus and radiation, thus achieving a stable nuclear composition.
noun, Physics, Chemistry. 1. a succession of elements initiated in the radioactive decay of a parent, as thorium or uranium, each of which decays into the next until a stable element, usually lead, is produced. noun 1. (physics) a series of nuclides each of which undergoes radioactive decay into the next member of the series, […]
noun 1. the radioactive by-products from the operation of a nuclear reactor or from the reprocessing of depleted nuclear fuel. noun 1. any waste material containing radionuclides Also called nuclear waste Radioactive materials that may be left after a commercial or laboratory process has been carried out. Some is “low-level” waste, such as objects that […]
- Radio alarm
noun clock radio Examples Easily switch between your favorite stations on the radio alarm with preset tuning buttons. Word Origin 1949