Encyclopedia of Biology

funnel-shaped opening, collects body fluids and
nitrogenous compounds and discharges at the other
end, the nephridiopore. Also reabsorbs fatty acids,
water, and amino acids back into circulation.

metaphase A development stage in mitosis or meio-
sis. Characterized by chromosomes aligning along the
equatorial plane of the cell.
See alsoMEIOSIS;MITOSIS.

metapopulation Groups of local species populations
where each group occupies separate habitat patches
that often are connected by corridors allowing migra-
tion between them.

metastable SeeSTABLE.

metastasis The spread of cancer cells from one part

of the body to another.

See alsoCANCER.

Metazoa The kingdom that includes all multicellular

organisms. It includes vertebrates and invertebrates.

methane mono-oxygenase AMETALLOENZYMEthat

converts methane and dioxygen to methanol using

NADHas coSUBSTRATE. Two types are known, one con-

taining a dinuclear oxo-bridged iron center; the other is

a copper protein.

See alsoNUCLEARITY.

methanogens Strictly ANAEROBIC ARCHAEAthat are

able to use a variety of SUBSTRATES(e.g., dihydrogen,

methanogens 219

1.

Prophase

2.

Metaphase

Mitosis 2. Metaphase

3.

Anaphase

4.

Telophase

centromere

microtubules

centrioles

chromosomes

The phase of mitosis, or cell division, when the chromosomes align along the center of the cell. Because metaphase chromosomes are
highly condensed, scientists use these chromosomes for gene mapping and identifying chromosomal aberrations.(Courtesy of Darryl
Leja, NHGRI, National Institutes of Health)