Bilateria
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A Bilateria is an ParaHoxozoa that includes animals with bilateral symmetry and three germ layers.
- Example(s):
- Counter-Example(s):
- See: Radial Symmetry, Triploblasty, Coelomata, Ediacaran, Holocene, Science (Journal), Berthold Hatschek, Proarticulata, Extinction, Xenacoelomorpha, Nephrozoa, Ikaria Wariootia, Deuterostomia, Chordata.
References
2023
- (Wikipedia, 2023) ⇒ https://en.wikipedia.org/wiki/Bilateria Retrieved:2023-6-10.
- Bilateria is a group of animals, called bilaterians, with bilateral symmetry as an embryo (i.e. having a left and a right side that are mirror images of each other). This also means they have a head and a tail (anterior–posterior axis), as well as a belly and a back (ventral–dorsal axis).[1] Nearly all are bilaterally symmetrical as adults as well; the most notable exception is the echinoderms, which achieve secondary pentaradial symmetry as adults, but are bilaterally symmetrical during embryonic development.
Most animals are bilaterians, excluding sponges, ctenophores, placozoans and cnidarians. For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm, and ectoderm. Except for a few phyla (i.e. flatworms and gnathostomulids), bilaterians have complete digestive tracts with a separate mouth and anus. Some bilaterians lack body cavities (acoelomates, i.e. Platyhelminthes, Gastrotricha and Gnathostomulida), while others display primary body cavities (deriving from the blastocoel, as pseudocoeloms) or secondary cavities (that appear de novo, for example the coelom).
- Bilateria is a group of animals, called bilaterians, with bilateral symmetry as an embryo (i.e. having a left and a right side that are mirror images of each other). This also means they have a head and a tail (anterior–posterior axis), as well as a belly and a back (ventral–dorsal axis).[1] Nearly all are bilaterally symmetrical as adults as well; the most notable exception is the echinoderms, which achieve secondary pentaradial symmetry as adults, but are bilaterally symmetrical during embryonic development.
- ↑ Brusca, Richard C. (2016). "Introduction to the Bilateria and the Phylum Xenacoelomorpha: Triploblasty and Bilateral Symmetry Provide New Avenues for Animal Radiation" (PDF). Invertebrates. Sinauer Associates. pp. 345–372. ISBN 978-1-60535-375-3.