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migration
micronutrient substance which an organism must obtain from its environment
to maintain health, though necessary only in minute amounts, either vitamins or trace elements. ~trace elements.
microorganisms (syn. microbes) organisms of very diverse groups including viruses, prions, viroids, Bacteria, Fungi, algae and Protozoa. The first three groups are all
acellular and incapable of independent existence. The study of microorganisms is called microbiology.
micropaleontology the study of microfossils. The rapid evolutionary changes of
microscopic organisms make micropaleontology an important biostratigraphical tool (~biostratigraphy), while the specific tolerances of microorganisms can be used for paleo-environmental interpretations. Once the relations have been established between the distributions of species and environmental parameters such as temperature, salinity, and water depth, this
relationship can be used to reconstruct the geologic history, e.g., the history
of the oceans by studying distributions of marine microfossils in the sediment (~facies). A major advantage of micropaleontology is that only small
quantities of sediment are needed: often thousands of microfossils can be
found in 1 g of sediment.
microphytobenthos small (usually unicellular) algae living on the (shallow) sea
floor. Particularly abundant on tidal flats. ~benthos.
microplankton small-sized (between 20 and 200 11m) planktonic organisms.
~plankton.
microtektite small glassy object, usually droplet-shaped and less than 1 mm in
diameter, found in some deep-sea sediments, and obviously strongly related
to tektites.
mid-ocean ridge a broad, bilaterally symmetrical, elongate submarine ridge with
sloping sides, 1 to 3 km in elevation, about 1500 km in width, and over 60 000
km in length. Mid-ocean ridges are formed at divergent plate boundaries and
are not necessarily located in the middle of oceans. The new oceanic floor
accreted there by volcanic activity sinks as each side moves laterally away
and cools, which gives the ridge its form. Examples: Mid-Atlantic Ridge, East
Pacific Rise, and Carlsberg Ridge. ~plate tectonics.
migration periodical movement of organisms between alternative habitats, e.g.,
the area of reproduction and one or more areas of nonreproductive life, or
between areas of foraging and areas used for other activities. Migrations
occur at predictable times; in most cases they anticipate unfavorable conditions and are triggered by stimuli timed by biological clocks. Organisms capa-
migration
micronutrient substance which an organism must obtain from its environment
to maintain health, though necessary only in minute amounts, either vitamins or trace elements. ~trace elements.
microorganisms (syn. microbes) organisms of very diverse groups including viruses, prions, viroids, Bacteria, Fungi, algae and Protozoa. The first three groups are all
acellular and incapable of independent existence. The study of microorganisms is called microbiology.
micropaleontology the study of microfossils. The rapid evolutionary changes of
microscopic organisms make micropaleontology an important biostratigraphical tool (~biostratigraphy), while the specific tolerances of microorganisms can be used for paleo-environmental interpretations. Once the relations have been established between the distributions of species and environmental parameters such as temperature, salinity, and water depth, this
relationship can be used to reconstruct the geologic history, e.g., the history
of the oceans by studying distributions of marine microfossils in the sediment (~facies). A major advantage of micropaleontology is that only small
quantities of sediment are needed: often thousands of microfossils can be
found in 1 g of sediment.
microphytobenthos small (usually unicellular) algae living on the (shallow) sea
floor. Particularly abundant on tidal flats. ~benthos.
microplankton small-sized (between 20 and 200 11m) planktonic organisms.
~plankton.
microtektite small glassy object, usually droplet-shaped and less than 1 mm in
diameter, found in some deep-sea sediments, and obviously strongly related
to tektites.
mid-ocean ridge a broad, bilaterally symmetrical, elongate submarine ridge with
sloping sides, 1 to 3 km in elevation, about 1500 km in width, and over 60 000
km in length. Mid-ocean ridges are formed at divergent plate boundaries and
are not necessarily located in the middle of oceans. The new oceanic floor
accreted there by volcanic activity sinks as each side moves laterally away
and cools, which gives the ridge its form. Examples: Mid-Atlantic Ridge, East
Pacific Rise, and Carlsberg Ridge. ~plate tectonics.
migration periodical movement of organisms between alternative habitats, e.g.,
the area of reproduction and one or more areas of nonreproductive life, or
between areas of foraging and areas used for other activities. Migrations
occur at predictable times; in most cases they anticipate unfavorable conditions and are triggered by stimuli timed by biological clocks. Organisms capa-