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A few species exhibit pseudogamous parthogenesis, meaning that mating is necessary to stimulate reproduction, even though no male genetic material passes to the offspring. [37] Earthworm mating occurs on the surface, most often at night. Earthworms are hermaphrodites; that is, they have both male and female sexual organs. The sexual organs are ...
The European nightcrawler (Dendrobaena hortensis) is a medium-small earthworm averaging about 1.5 g when fully grown. Generally blueish, pink-grey in color with a banded or striped appearance, the tips of their tails are often cream or pale yellow. When the species has not been feeding, it is pale pink. The species is usually found in deep ...
Earthworm head. Lumbricus terrestris is relatively large, pinkish to reddish-brown in colour, generally 110–200 millimetres (4.3–7.9 in) in length and about 7–10 millimetres (0.28–0.39 in) in diameter. It has around 120–170 segments, often 135–150. The body is cylindrical in the cross section, except for the broad, flattened ...
Triclads reproduce sexually and asexually, and different species may be able to reproduce by one or both modes. [5] Planarians are hermaphrodites. In sexual reproduction, the mating generally involves mutual insemination. Thus, one of their gametes will combine with the gamete of another planarian.
The mammalian female reproductive system contains three main divisions: the vagina and uterus, which act as the receptacle for the sperm, the ovaries, which produce the female's ova, and the vulva, which mainly consists of the labia and clitoris. The vagina, uterus and ovaries are always internal while the vulva is external.
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.
Insect reproductive system. Most insects reproduce oviparously, i.e. by laying eggs. The eggs are produced by the female in a pair of ovaries. Sperm, produced by the male in one testicle or more commonly two, is transmitted to the female during mating by means of external genitalia. The sperm is stored within the female in one or more spermathecae.
Female and male sexual behaviour differ in many species. Often, males are more active in initiating mating, and bear the more conspicuous sexual ornamentation like antlers and colourful plumage. This is a result of anisogamy, where sperm are smaller and much less costly (energetically) to produce than eggs.