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The following is a list of the classes in each phylum of the kingdom Animalia.There are 107 classes of animals in 33 phyla in this list. However, different sources give different numbers of classes and phyla.
Cilia are formed through the process of ciliogenesis. An early step is docking of the basal body to the growing ciliary membrane, after which the transition zone forms. The building blocks of the ciliary axoneme, such as tubulins, are added at the ciliary tips through a process that depends partly on intraflagellar transport (IFT).
The mechanisms by which such non-membrane bounded organelles form and retain their spatial integrity have been likened to liquid-liquid phase separation. [ 15 ] The second, more restrictive definition of organelle includes only those cell compartments that contain deoxyribonucleic acid (DNA), having originated from formerly autonomous ...
The timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth.Dates in this article are consensus estimates based on scientific evidence, mainly fossils.
A polyp is an animal of very simple structure, [1] a living fossil that has not changed significantly for about half a billion years (per generally accepted dating of Cambrian sedimentary rock). [citation needed] The external form of the polyp varies greatly in different cases.
Schizocoely (adjective forms: schizocoelous or schizocoelic) is a process by which some animal embryos develop.The schizocoely mechanism occurs when secondary body cavities are formed by splitting a solid mass of mesodermal embryonic tissue.
The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolved to lose their tails (e.g. frogs and hominid primates), the coccyx is the homologous vestigial of the tail.
Scutes on a crocodile. Reptile skin is covered with scutes or scales which, along with many other characteristics, distinguish reptiles from animals of other classes. They are made of alpha and beta-keratin and are formed from the epidermis (contrary to fish, in which the scales are formed from the dermis).