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Protostome and deuterostome embryos differ in several other ways. Secondary body cavities ( coeloms ) generally form by schizocoely , where the coelom forms out of a solid mass of embryonic tissue splitting away from the rest, instead of by enterocoelic pouching , where the coelom would otherwise form out of in-folded gut walls.
In humans (a deuterostome), the development proceeds differently. The buccopharyngeal membrane is created in the foregut and is perforated during the fourth week of human development, creating the primitive mouth, whereas the cloacal membrane is created in the hindgut and is perforated during the eighth week of human development, creating the ...
[21] [22] That implies that the protostome and deuterostome lineages split long before Kimberella appeared, and hence well before the start of the Cambrian 20] i.e. during the earlier part of the Ediacaran Period (circa 635-539 Mya, around the end of global Marinoan glaciation in the late Neoproterozoic). It has been proposed that the ancestral ...
Ecdysozoa (/ ˌ ɛ k d ɪ s oʊ ˈ z oʊ ə /) is a group of protostome animals, [8] including Arthropoda (insects, chelicerata (including arachnids), crustaceans, and myriapods), Nematoda, and several smaller phyla.
Nematoida is a clade of pseudocoelomate free living or parasitic animals.It consists of phyla Nematoda and Nematomorpha. [3] [4] The two groups share a number of features in common; the presence of a cloaca in both sexes, aflagellate sperm, and a cuticle made of collagen.
A cell can only be indeterminate (also called regulative) if it has a complete set of undisturbed animal/vegetal cytoarchitectural features. It is characteristic of deuterostomes—when the original cell in a deuterostome embryo divides, the two resulting cells can be separated, and each one can individually develop into a whole organism.
Lophotrochozoa (/ l ə ˌ f ɒ t r oʊ k oʊ ˈ z oʊ ə /, "crest/wheel animals") is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. [2] [3] The clade includes animals like annelids, molluscs, bryozoans, and brachiopods. [4]
The nematodes (/ ˈ n ɛ m ə t oʊ d z / NEM-ə-tohdz or NEEM-; Ancient Greek: Νηματώδη; Latin: Nematoda), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic.