organelles, chromosomes, as well as the cell itself.
Microtubules also form the spindle fibers of mitosis.
microvillus Very small hairlike or fingerlike projec-
tion from the surface of some types of epithelial cells,
particular those in the small intestine, where they serve
to increase surface area.
middle lamella The gel-like pectin layer between
adjacent plant cell walls that binds or cements the plant
cells together; in woody tissues, lignin replaces pectin.
mimicry The ability of an individual to look or share
similar traits of an individual of a different species to
protect it from predation. It can be in the form of pro-
tective coloration, imitation of characteristics, or
deception. Two forms of mimicry are common. BATE-
SIAN MIMICRYis where the mimic, which is palatable to
a predator, resembles an unpalatable species; and MÜL-
LERIAN MIMICRY is where two or more unpalatable
species have a reduced predation rate due to their simi-
larity, so that predators avoid them to a greater degree
than they would individually. The viceroy butterfly,
which mimics the monarch, is an example of Batesian
mimicry, while the queen butterfly (Danaus gilippus),
which is a poisonous butterfly, mimics the poisonous
monarch and is an example of Müllerian mimicry.mineral A naturally occurring homogeneous solid,
inorganically formed, with a definite chemical composi-
tion, usually crystalline in form, and an ordered atomic
arrangement, e.g., quartz.mineralocorticoid Any of the group of C21 (21 car-
bon) corticosteroids, principally aldosterone, that are
predominantly involved in the regulation of electrolyte
and water balance through their effect on ion transportmineralocorticoid 221Caterpillar of Papilio troilusfrom Albany pine bush. It is a mimic of South American tree snakes that migratory birds have learned to
avoid. Illustrates Batesian mimicry and protective coloration.(Courtesy of Tim McCabe)