Glossary

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M

Macrofauna
Large animals in a community within an arbitrary size range, e.g. between 2 mm and 20 mm body width, in soil invertebrates.
Macroinvertebrate
An invertebrate with a body length greater than 2 mm.
Macroparasite
A parasite which grows in its host but multiplies by producing infective stages that are released from the host to infect new hosts. They are often intercellular or live in body cavities, rather than within the host cells.
Marginal value theorem
A proposed decision-rule (derived from theoretical exploration) for a predator foraging from patches of prey which it depletes, which states that the predator should leave all patches at the same rate of prey extraction, namely the maximum average overall rate for that environment as a whole.
Marsupial mammal
A mammal in which the young are born in a very immature state and migrate to a pouch where they are suckled until relatively mature.
Masting
The production, in some years, of especially large crops of seeds by trees and shrubs.
Maturation
The process of becoming fully differentiated, fully functional and hence fully reproductive.
Maximal food chain
A sequence of species running from a basal species (plant) to another species that feeds on it and so on to a top predator (fed on by no other).
Maximum sustainable yield (MSY)
The maximum crop or yield that can be removed repeatedly from a population without driving it towards extinction.
Mean intensity of infection
The mean number of parasites per host in a population (including those hosts that are not infected).
Megafauna
The largest arbitrary size categorization of animals in a community, e.g. > 20 mm body width in soil invertebrates.
Megaherbivore
A term referring to very large terrestrial grazing animals (> 1000 kg), such as elephants, also including the many species that went extinct in the last 30 000 years or so.
Megaphyte
Plants with normally unbranched stems or trunks and bearing a crown of very large leaves. The inflorescence is commonly also massive.
Meristem
A part of a plant in which cell division is concentrated (especially the shoot apices, lateral buds and a zone near the tips of roots and rootlets).
Mesofauna
Animals in the size-range 100 mm to 2 mm body length.
Mesophyll
The internal non-vascular tissue of a leaf. In green plants it is in these cells that most chloroplasts are found and in which most photosynthesis occurs.
Metabolism
The sum of all chemical reactions occurring within a cell or an organism
Metamorphosis
Abrupt transition between life stages; for example from larval to adult form.
Metapopulation
A population perceived to exist as a series of subpopulations, linked by migration between them. However, the rate of migration is limited, such that the dynamics of the metapopulation should be seen as the sum of the dynamics of the individual subpopulations.
Microbes
Microorganisms: any microscopic organism, including bacteria, viruses, unicellular algae and protozoans, and microscopic fungi such as yeasts.
Microbivores
Animals that feed on microorganisms.
Microclimate
The climate within a very small area or in a particular, often tightly defined, habitat.
Microfauna
The smallest arbitrary size categorization of animals in a community.
Microflora
Bacteria, fungi and microscopic algae.
Microparasite
A parasite which multiplies directly within its host, usually within host cells.
Microsite
The small subset of environments within a habitat that provide the specialized resources and conditions required for a phase in the life of an organism, e.g. the cracks or crevices which provide conditions suitable for germination of the seed of a particular species.
Microtopography
Very small scale (roughly, 'organism-sized') variations in the height and roughness of the ground surface.
Migration
The movement of individuals, and commonly whole populations from one region to another.
Mimicry
The resemblance of an organism (the mimic) either to another organism or to a non-living object (the model), presumably conferring a benefit on the mimic in natural selection.
Miocene
A geological era lasting from approximately 25 to 5 million years ago.
Modular organism
One that grows by the repeated iteration of parts, e.g. the leaves, shoots and branches of a plant, the polyps of a coral or bryozoan. Modular organisms are almost always branched, though the connections between branches may separate or decay and the separated parts may in many cases then become physiologically independent, e.g. Hydra spp. and duckweeds (Lemna spp.). (See also Ramet and cf. Unitary organisms.)
Moisture gradient
A spatial gradient in the availability of water in soil.
Monoclimax theory
The concept that all successional sequences lead to a single characteristic climax in a given region.
Monocotyledons
One of the two main groups of flowering plants (see Angiosperms). Characterized normally by the presence of just a single seedling leaf (cotyledon) and commonly by floral parts arranged in threes, parallel leaf veins and the inability to form secondary tissues, e.g. wood, from cell division within the tissues.
Monoculture
A large area covered by a single species (or, for crops, a single variety) of plant; or, in experiments, plants of the same species grown alone without any other species.
Monogenean
An ectoparasitic trematode flatworm, parasitic on fish or amphibia, and having only one host in its life cycle.
Monomorphic
Occurring in only one form.
Monophagy
Where an organism consumes only a single type of food item.
Monotreme mammal
A primitive mammal belonging to one of only three genera, laying eggs but having hair and secreting milk.
Morphogenesis
The development of size, form and other structural features of organisms.
Morphology
The form and structure of an organism.
Motile organism
An organism capable of spontaneous movement.
Multiple resistance (to pesticides)
Resistance of an organism to a number of pesticides requiring different mechanisms to counteract their effects.
Mutual antagonism
Describes two species with reciprocal negative effects on each other (either interspecific competition or mutual predation).
Mutual interference
Interference amongst predators leading to a reduction in the consumption rate of individual predators which increases with predator density.
Mutualism
An interaction between the individuals of two (or more) species in which the growth, growth rate and/or population size of both are increased in a reciprocal association. (See also Facultative mutualism and Obligate mutualism.)
Mycorrhiza
A commonly mutualistic and intimate association between the roots of a plant and a fungus. (See also Ectomycorrhiza and Vesicular arbuscular mycorrhiza.)

 
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