Oogamy on:
[Wikipedia]
[Google]
[Amazon]
Oogamy is an extreme form of anisogamy where the gametes differ in both size and form.
In oogamy the large female
Oogamy is an extreme form of anisogamy where the gametes differ in both size and form.
In oogamy the large female gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...
(also known as ovum) is immobile, while the small male
Male (Mars symbol, symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization.
A male organism cannot sexual reproduction, repro ...
gamete (also known as sperm) is mobile. Oogamy is a common form of anisogamy, with almost all animals and land plants being oogamous.
Occurrence
Oogamy is found in most species that reproduce sexually, all higher species being oogamous. Oogamy is found in all land plants, and in some red algae, brown algae andgreen algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...
. Oogamy is favored in plants because only one gamete has to travel through harsh environments outside the plant. Oogamy is also present in oomycetes.
Almost all animals are oogamous. There are exceptions, such as the opiliones
The Opiliones (formerly Phalangida) are an order of arachnids colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs. , over 6,650 species of harvestmen have been discovered worldwide, although the total number of ext ...
that have immobile sperm.
Etymology
The term oogamy was first used in the year 1888.Evolution
It is generally accepted thatisogamy
Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or ...
is the ancestral state and that oogamy evolves from isogamy through anisogamy. However, transitions do exist between anisogamy and oogamy.
When oogamy has evolved, males and females typically differ in many aspects. According to David B. Dusenbery internal fertilization probably originated from oogamy. But one study in 2014 on Colemanosphaera said that oogamy in '' Volvox'' may have evolved before the transition from external to internal fertilization.
In streptophytes, oogamy likely first occurred before the split between algae and land plants.
See also
*Gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...
* Anisogamy
* Isogamy
Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or ...
References
{{Eggs Reproductive system Germ cells