Search results
Results from the WOW.Com Content Network
Anisogamy is the form of sexual reproduction that involves the union or fusion of two gametes which differ in size and/or form. [12] The smaller gamete is considered to be male (a sperm cell), whereas the larger gamete is regarded as female (typically an egg cell, if non-motile).
Oogamy is a common form of anisogamy, with almost all animals and land plants being oogamous. Oogamy is found in most sexually reproducing species, including all vertebrates, land plants, and some algae. The ancestral state of sexual reproduction is believed to be isogamy, with oogamy evolving through anisogamy.
It is generally accepted that isogamy is an ancestral state for anisogamy [1] [9]. Isogamous reproduction evolved independently in several lineages of plants and animals into anisogamy (species with gametes of male and female types) and subsequently into oogamy (species in which the female gamete is much larger than the male and has no ability ...
Anisogamy appears to have evolved multiple times from isogamy; for example female Volvocales (a type of green algae) evolved from the plus mating type. [40]: 222 Although sexual evolution emerged at least 1.2 billion years ago, the lack of anisogamous fossil records make it hard to pinpoint when females evolved. [42]
Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. [6] [7] Sexual reproduction also occurs in some unicellular eukaryotes. [2] [8] Sexual reproduction does not occur in prokaryotes, unicellular organisms without cell nuclei, such as bacteria and archaea.
Anisogamy is a form of sexual reproduction which involves the fusion of two unequally-sized gametes. In many animals, there are two sexes: the male, in which the gamete is small, motile, usually plentiful, and less energetically expensive, and the female, in which the gamete is larger, more energetically expensive, made at a lower rate, and ...
Members of this phylum also exhibit a form of sexual reproduction known as anisogamy. [4] Anisogamy is the fusion of two sexual gametes that differ in morphology, usually size. [5] In Allomyces, the thallus (body) is attached by rhizoids, and has an erect trunk on which reproductive organs are formed at the end of branches.
Sexual dimorphism was also described in the gene level and shown to extend from the sex chromosomes. Overall, about 6500 genes have been found to have sex-differential expression in at least one tissue. Many of these genes are not directly associated with reproduction, but rather linked to more general biological features.