Definitions in Biology, ecology, and zoology

Definitions A - B , C, D - E, F, G, H, I-L, M - N , O-P, Q - S , T-Z

Macroclimate	the climate of the major geographical regions
Macroevolution	Evolutionary change on a grand scale, encompassing the origin of novel designs, evolutionary trends, adaptive radiation, and mass extinction.
Macroscopic	something visible to the naked eye or visible through a hand lens
Madreporite	The sieve-like structure that is the intake for the water vascular system of echinoderms
Maggot	the grub-like larval stage of some insects, e.g. flies
Malacology	the study of molluscs
Malacostraca	a class in the Crustacea containing the crabs, shrimps, lobsters and woodlice
Mallophaga	the chewing/biting lice
Malpighian/Malphigian tubes	Excretory organs of insects that empty into the digestive tract, remove nitrogenous wastes from the blood, and function in osmoregulation.
Mandibles	the first or uppermost part of the jaw, often used when describing insects
Mandibulates	Animals with jaw-like appendages, e.g. many insects and crustaceans.
Mantis shrimp	Squilla mantis
Mantle	lateral skirt-like fold of the molluscan body wall, usually having a spacious cavity beneath it.
Mantle cavity	In molluscs, a cavity between the mantle and the rest of the body. The cavity is filled with water in aquatic molluscs, and often contains the gills.
Mantoidea	The sub-order containing the mantises, praying mantis, etc.
Mask	The specialised mouthparts of dragonfly and damselfly nymphs. The mask is a modified lower lip with moveable and jointed "Jaws". The whole thing can be shot out at great speed to capture prey.
Maxillae/maxilla	the second or lower part of the jaw, often used in describing insects.
Mechanoreceptors	Sensory receptors that detect physical deformities in the body associated with pressure, touch, stretch, motion and sound.
Medusa	the free-living, sexual, jelly-fish-like stage of certain cnidarians
Melanism	the opposite of albinism. An undue development of colouring making the animal appear darker then normal. This is quite common in certain bumblebees.
Mesoglea	The jelly-like substance between the two layers of the body wall in Cnidaria and Porifera.
Mesothorax	the middle segment of an insect's thorax which bears the middle pair of legs and the front wings.
Metabolism	the totality of an organism's chemical processes, consisting of catabolic and anabolic pathways.
Metameric	a body largely comprising of a series of segments, as in the annelids
Metamorphosis	an abrupt change in body form from one larval stage to another, or from larva to adult, as seen in some insects.
Metanephridium	A type of excretory tube in Annelida that has internal openings called nephrostomes which collect body fluids, and external openings called nephridophores.
Metathorax	the second segment of an insect's thorax which bears the third pair of legs and the hind wings
Microclimate	The highly localised climate of a strictly limited habitat, e.g. inside a flower.
Microevolution	a change in the gene pool of a population over a succession of generations
Migration	A journey to a different region, following a well-defined route. Most animals that migrate do so according to seasonal changes to benefit from good breeding, feeding or overwintering conditions.
Mimicry	A form of camouflage in which an animal resembles another animal or inanimate object. It is common in insects, e.g. some harmless flies mimic stinging bees or wasps, and stick insects resemble twigs.
Mitochondria	Organelles found in eukaryotic cells. The contain the enzymes responsible for aerobic respiration.
Mollusca	the phylum containing the slugs, snails, octopus, and other shell-fish
Monerans/Bacteria	Are the simplest fully-independent living things. They are prokaryotes, i.e. they lack the specialised structures found in eukaryotes. Energy is obtained from sunlight, organic and inorganic sources.
Morphospecies	species defined by their anatomical features
Morphs	two or more distinct forms of individuals in a population
Mortality	death
Moult	shedding of exoskeleton in order to increase size
Mullerian mimicry	mutual mimicry by two or more unpalatable species
Multipoint stability	the tendency of a population to regain stability at a different level.
Muscle cells	Contract and relax to move the different parts of the animal's body.
Mutation	a rare change in the DNA of genes that ultimately creates genetic diversity
Mutualism	Symbiosis that benefits the members of both of the participating species.
Myrmecology	The study of ants.
Nacre	The innermost, lustrous layer of a mollusc shell, secreted by the mantle, mother-of-pearl.
Natality	births
Natural selection	The differential success in reproduction of different phenotypes resulting from the interaction of organisms with their environment
Nautiloid	A free-swimming marine animal in the phylum Mollusca. It has a coiled, chambered cell.
Nematocyst	the stinging cell of cnidarians
Nematodes	Unsegmented round worms, usually small, often parasitical.
Nephridium	a excretory tube in earthworms
Neurons	Nerve cells which receive and transmit stimuli.
Neurotoxin	A substance that deactivates nerves or that disrupts the way nerves work. Some insects can produce neurotoxins and they are commonly found in many insecticides.
Niche	the limits for all important environmental features, within which individuals of a species can survive, grow and reproduce.
Nocturnal	Active at night
Notochord	A reinforcing rod that runs the length of the body. It is found in chordates.
Nucleus	The central body in a eukaryotic cell. It contains the genetic information on chromosomes.
Nuptial flight	the mating flight of insects, especially social insects, where it involves the queen mating with males.
Nymph	the immature stage of certain insects in which there is some similarity to the adult form