## m-p

### m

- mammal n. Phylum Chordata, Class Mammalia. Animals characterized by body hair and mammary glands that produce milk to nourish their young.
- mantle n. In molluscs, a tissue that covers the gut organs and secretes the animal's hard shell.
- medusa n. (plural: medusae) One of two main body forms in the life cycle of certain cnidarians, typically dome shaped and free-swimming. Compare to polyp.
- metabolism n. The set of biochemical processes which cells use to release energy from complex molecules as well as to build complex molecules.
- metamorphosis n. The dramatic change of structure and lifestyle a larva undergoes when it becomes an adult.
- millipede n. arthropods with many segments, each segment having two pairs of legs. Millipedes are often have long bodies and they are detritivores.
- mite n. A very small arthropod in the class Arachnida.
- mitra n. Phylum Mollusca, Class Gastropoda. A shelled mollusc with a thick shell typically bullet shaped and vaguely resembling a bishop's headdress, or mitre; most commonly found in the Indo-Pacific region.
- mollusc n. Any soft-bodied invertebrate of the phylum Mollusca, usually wholly or partly enclosed in a calcium-carbonate shell secreted by a soft mantle covering the body, and often possessing a single foot and a radula.
- molting v. or adj. In arthropods, the periodic process by which the exoskeleton is discarded and replaced by a new, larger one that allows the animal to grow. (This term can also be applied to birds when they lose their feathers.)
- moon jelly polyp n. The polyp phase of the moon jelly life cycle that asexually buds off the ephyra stage. See ephyra.
- moon snail n. Phylum Mollusca, Order Gastropoda. A predatory marine snail with an impressively large foot that it uses to plough through soft bottoms in search of prey
- multicellular organism n. An organism composed of many cells, which are to varying degrees integrated and independent.
- muricanthus n. Phylum Mollusc, Order Gastropoda. A type of mollusc with an impressively robust and sculpted shell, found in the Indo-Pacific.
- muscle n. A tissue composed of contractile cells that contain proteins -- actin and myosin -- and is capable of exerting forces by shortening and causing movement among animals.
- mutation n. A change in the DNA of genes that creates genetic diversity.

### n

- nautiloid n. Phylum Mollusca, Class Cephalopoda, Order Nautiloid Marine shelled animals related to the modern pearly Nautilus, the design of which has persisted for 500 million years
- nematocyst n. A capsule containing a harpoon-like structure used by cnidarians -- jellyfish, coral, and sea anemones -- for protection, capturing prey, and anchorage.
- nerve n. A specialized cell able to transmit information in the form of electrical signals and found only in animals.
- nerve chord n. In chordate animals, a long, hollow tubular tract of neural tissue located above the notochord that develops into the spinal cord and the brain.
- nerve ring n. In echinoderms, a bundle of nerve cells encircling the mouth and connecting to radial nerves. It functions to relay the sensory and motor signals throughout the body.
- nervous system n. An organized group of cells specialized for the conduction of an electrochemical signal from a receptor through a network to the site at which the response occurs.
- neural crest cells n. A band of cells that migrate to various parts of the embryo and form pigment cells in the skin, the bones of the skull, the teeth, the adrenal glands and parts of the nervous system.
- new caledonia n. French overseas territory in the southwestern Pacific Ocean, about 900 miles (1,500 kilometres) east of Australia.
- notochord n. A flexible rod supporting the bodies of chordate embryos and some adults, but typically replaced in the adult by a bony vertebral column and persisting only as soft disks between each separate vertebra.

### o

- opabinia n. A Cambrian Explosion animal, dating back 520 to 512 million years ago, with five eyes and a long nozzle, perhaps with arthropod affinities.

### p

- paleontology n. The scientific study of fossils.
- parasite n. An organism that lives in or on another species and gets its food from the tissues or fluids of its host.
- penis-fencing v. A form of reproduction wherein certain tropical flatworms vie for the opportunity to stab each other with their penises in order to inject sperm into their mate. Each individual has the power to be both male and female (i.e., they are hermaphroditic).
- pharynx n. A part of the gut in animals located between the mouth and the esophagus.
- physiology n. The study of the functioning of living organisms, animal or plant, and the functioning of their tissues or cells.
- pikaia n. Phylum Chordata. A Cambrian Explosion fossil dating back 520 to 512 million years ago, that bears a striking resemblance to today's Amphioxus, or lancelet.
- planarian n. Phylum Platyhelminthes, Class Turbellaria. A group of widely distributed, mostly free-living flatworms with a gut with three branches.
- plankton n. Organisms that drift in mid-water in ponds, lakes, or the sea; generally moved more by water currents than by their own swimming.
- platelet n. A small blood cell important in blood clotting.
- pollination n. the process in plants of transferring pollen from the male structure in a flower to the female structure so fertilization can occur to produce the next generation.
- praya n. Phylum Cnidaria, Order Siphonophora. A type of cnidarian known as a siphonophore that contains both medusa and polyp forms.
- pycnopodia n. Phylum Echinodermata, Class Asteroidea. A large predatory sea star found on the northwest coast of the United States that possesses over 20 arms and is capable of reaching sizes as large as a manhole cover.