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The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus) [41] but this is a great deal smaller than the largest amphibian that ever existed—the extinct 9 m (30 ft) Prionosuchus, a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil. [42]
Anatomy of a wood frog tadpole (Lithobates sylvaticus) As a frog tadpole matures it gradually develops its limbs, with the back legs growing first and the front legs second. The tail is absorbed into the body using apoptosis. Lungs develop around the time as the legs start growing, and tadpoles at this stage will often swim to the surface and ...
The chromosome number n = 9 is the basic number in many species of Marchantiales. In some species of Marchantiales, plants with various ploidy levels (having 18 or 27 chromosomes) were reported, but this is rare in nature. [14] 11 Thale cress (Arabidopsis thaliana) 10 12 Swamp wallaby (Wallabia bicolor) 10/11: 11 for male, 10 for female [15] 13
Female Branchiura do not carry eggs in external ovisacs but attach them in rows to rocks and other objects. [ 33 ] : 788 Most leptostracans and krill carry the eggs between their thoracic limbs; some copepods carry their eggs in special thin-walled sacs, while others have them attached together in long, tangled strings.
Fish, amphibians, and reptiles make use of various forms of gynogenesis and hybridogenesis (an incomplete form of parthenogenesis). [50] The first all-female (unisexual) reproduction in vertebrates was described in the fish Poecilia formosa in 1932. [ 51 ]
The key innovation in amniotes over amphibians is the amnion, which enables the eggs to retain their aqueous contents on land, rather than needing to stay in water. (Some amniotes later evolved internal fertilization, although many aquatic species outside the tetrapod tree had evolved such before the tetrapods appeared, e.g. Materpiscis.)
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While the early amniotes resembled their amphibian ancestors in many respects, a key difference was the lack of an otic notch at the back margin of the skull roof. In their ancestors, this notch held a spiracle , an unnecessary structure in an animal without an aquatic larval stage. [ 25 ]