biology-dictionary_11-06-2009

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Metamorphosis
The resurgence of development in an animal larva that transforms it into a sexually mature
adult.
Metanephridium
In annelid worms, a type of excretory tubule with internal openings called nephrostomes
that collect body fluids and external openings called nephridiopores.
Metaphase
The second stage of mitosis. During metaphase, all the cell's duplicated chromosomes are
lined up at an imaginary plane equidistant between the poles of the mitotic spindle.
Metaphase plate
An imaginary plane perpendicular to the spindle fibers of a dividing cell, along which
chromosomes align during metaphase.
Metapopulation
A subdivided population of a single species.
Metastasis
The spread of cancer cells beyond their original site.
MHC
Abbreviation of major histocompatibility complex.
Microbe
A microscopic organism.
Microevolution
A change in the gene pool of a population over a succession of generations.
Microfilaments
A solid rod of actin protein in the cytoplasm of almost all eukaryotic cells, making up part of
the cytoskeleton and acting alone or with myosin to cause cell contraction.
Microglia
Any of the small neuroglial cells of the central nervous system having long processes anssd
amoeboid and phagocytic activity at sites of neural damage or inflammation.
Micronutrient
An inorganic nutrient required in only minute amounts for plant growth, such as iron,
chlorine, copper, manganese, zinc, molybdenum, and boron.

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