ENCYCLOPEDIA BRITANNICA:
Gamete
Sex,
or reproductive, cell containing only one set of dissimilar chromosomes, or
half of the genetic material necessary to form a complete organism (i.e.,
haploid). During fertilization, male and female gametes fuse, producing a
diploid (i.e., containing paired chromosomes) zygote. Gametes may be identical
in form (isogamy), as in the black mold (Rhizopus), or there may be more than
one morphological type (heterogamy), as with many green algae of the genus
Chlamydomonas. Gametes of animals, some algae and fungi, and all higher plants
exhibit an advanced form of heterogamy called oogamy. In oogamy, one of the
gametes is small and motile (the sperm), and the other is large and nonmotile
(the egg).