Different forms of anisogamy: A) anisogamy of motile cells, B) oogamy (egg cell and sperm cell), C) anisogamy of non-motile cells (egg cell and spermatia)
'Anisogamy' (also called '
heterogamy') refers to a form of
sexual reproduction involving
gametes of different sizes. The smaller gamete is considered to be male (
sperm cell) whereas the larger gamete is regarded as female (
egg cell).
There are several types of anisogamy. Both gametes may be
flagellated and thus motile. Conversely, neither of the gametes may be flagellated. This situation occurs for example in some algae and plants. In the
red alga ''Polysiphonia'', large non-motile egg cells are fertilized by small, non-motile
spermatia. In
flowering plants, the gametes are non-motile cells within
gametophytes.
The form of heterogamy that occurs in
animals is '
oogamy'. In oogamy, a large, non-motile egg cell (
ovum) is fertilized by a small, motile sperm cell (
spermatozoon). The large egg cell is optimized for longevity, whereas the small sperm cell is optimized for motility and speed. The size and resources of the egg cell allow for the production of
pheromones, which attract the swimming sperm cells.
See also
★
Gamete
★
Isogamy
العربية
中国
Français
Deutsch
Ελληνική
हिन्दी
Italiano
日本語
Português
Русский
Español
