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Initially this phylum was considered to be a member of the deuterostomes, [2] but because of recent transcriptome analyses, it was concluded that phylum Xenacoelomorpha is the sister group to the Nephrozoa, which includes both the protostomes and the deuterostomes, which makes the phylum the basalmost bilaterian clade.
Other gastropods develop external asymmetry, such as Glaucus atlanticus that develops asymmetrical cerata as they mature. Histioteuthis is a genus of squid , commonly known as the cock-eyed squid, because in all species the right eye is normal-sized, round, blue and sunken; whereas the left eye is at least twice the diameter of the right eye ...
This results in the activation of different developmental pathways on each side, and subsequent asymmetry. [37] [38] Schematic diagram of signalling pathways on the left and right side of a chick embryo, ultimately leading to the development of asymmetry. Much of the investigation of the genetic basis of symmetry breaking has been done on chick ...
Intra-phylum vs. inter-phylum phylotypic period [ edit ] The phylotypic period is defined as a period of maximal similarity between species within a phylum, but a recent study compared the phylotypic period across different phyla to examine whether the same conserved periods during development have been maintained across deeper phylogenetic ...
Proarticulata is a proposed phylum of extinct, near-bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately [ 1 ] [ 2 ] The name comes from the Greek προ ( pro- ) = "before" and Articulata , i.e. prior to animals with true segmentation such as annelids and arthropods .
Stratification for breast cancer risk on a mammogram is based on a reporting system known as Breast Imaging-Reporting and Data System , developed by the American College of Radiology in 1993. It has five general categories of findings: mass, asymmetry, architectural distortion, calcifications, and associated features.
One is that breast density can make it more difficult to spot a cancer on a mammogram, because dense breast tissue – the glandular elements and connective tissue supporting elements – looks ...
Definition of Phylum based on body plan – High level taxonomic rank for organisms sharing a similar body plan; Ediacaran biota – Life of the Ediacaran period; Macroevolution – Evolution on a scale at or above the level of species; Precambrian body plans – Structure and development of early multicellular organisms