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The result is cell movement through the fluid medium. Furthermore, the direction of movement is determined by chemotaxis. When chemoattraction occurs in a particular area of the cell membrane, actin polymerization can begin and move the cell in that direction. [9] An excellent example of an organism that utilizes pseudopods is Naegleria fowleri ...
The three modern orders are Anura (the frogs), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians). [15] It has been suggested that salamanders arose separately from a temnospondyl-like ancestor, and even that caecilians are the sister group of the advanced reptiliomorph amphibians, and thus of amniotes. [16]
Crayfish can move backward much faster than they can move forward. Gait analysis is the study of gait in humans and other animals. This may involve videoing subjects with markers on particular anatomical landmarks and measuring the forces of their footfall using floor transducers ( strain gauges ).
[3] Other terms sometimes used to refer to the water vascular system are "ambulacral system" [4] [5] [6] and "aquiferous system". In the past, "aquiferous system" was also used to refer to many unrelated invertebrate structures, [7] [8] but today, it is restricted to water channels in sponges [9] and the hydrostatic skeleton of some mollusks ...
Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians (frogs/toads, salamanders/newts and caecilians) — by the development of three extraembryonic membranes (amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage), thicker and keratinized ...
Similar to Eusthenopteron, the radials do not articulate with the radius on the distal end. [3] Acanthostega also has a 1:2 ratio of humerus to radius and ulna, a feature seen in all tetrapods higher than Acanthostega on the phylogeny. [3] Unlike Panderichthys, Acanthostega hind limbs are at least the size of its fore limbs, if not larger. [3]
Of the three orders of amphibians, Anura (frogs and toads) and Urodela (salamanders) have representative species with webbed feet. Frogs that live in aquatic environments, like the common frog (Rana temporaria), have webbed feet. Salamanders in arboreal and cave environments also have webbed feet, but in most species, this morphological change ...
The three domains are coloured, with bacteria blue, archaea green and eukaryotes red. More recently, evidence for common descent has come from the study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids. [59]