Excellent: Subphylum vertebrata characteristics
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| Subphylum vertebrata characteristics | 4 hours ago · Phylum Chordata Characteristics & Classification The Chordates. admin Send an email September 19, 0 1, 3 minutes read. Phylum Chordata is an important phylum. Its name is derived from the notochord. Endoskeleton is the chief basic character of the Chordata phylum. This endoskeleton is an important factor in the development and. 2 days ago · The phylogenetic position of amphioxus, together with its relatively simple and evolutionarily conserved morphology and genome structure, has led to its use as a model for studies. 6 days ago · The phylum Chordata includes a wide range of organisms, as it is comprised of all vertebrates, which are organisms with a backbone, and many invertebrates; organisms that don’t have a backbone. There are three subphyla to Chordata: Cepahlochordata, Urochordata, and Vertebrata. |
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Stephanie Bertrand, Hector Escriva; Evolutionary crossroads in developmental biology: amphioxus. Development 15 November ; 22 : — The phylogenetic position of amphioxus, together with its relatively simple and evolutionarily conserved morphology and genome structure, has led to its use as a model for studies of vertebrate evolution.
In particular, the recent development subphylum vertebrata characteristics usbphylum approaches, as well as access to the complete amphioxus genome sequence, has provided the community with tools with which to study the invertebrate-chordate to vertebrate transition. Here, we present this animal model, discussing its life cycle, the model species studied and the experimental techniques that it is amenable to.
We also summarize the major findings made using amphioxus that have informed us about the evolution of vertebrate traits. Amphioxus also called lancelets or cephalochordates form one of the three chordate subphyla, along with urochordates see Glossary, Box 1 and vertebrates Schubert et al.
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They form a small group comprising about 35 species Poss and Boschung, The number of genera within the cephalochordate subphylum has long been debated, but recent molecular phylogenetic studies show that cephalochordates are divided into three genera Kon et al. Described for the first time in Pallas,lancelets were classified as molluscs and were called Limax lanceolatus. Later, inthey were renamed as Branchiostoma lubricus Costa, and classified as animals subphylum vertebrata characteristics related to vertebrates. The first to use the name Amphioxus was William Yarrell, who named them Amphioxus lanceolatus and for the first time described their notochord see Glossary, Box 1the defining morphological trait of chordates Yarrell, After these initial studies, and until the beginning of the 20th century, amphioxus was considered to be a vertebrate.
A consensus was then reached whereby amphioxus were considered to be the closest living relatives of vertebrates, with urochordates representing the most basally divergent chordate lineage. These evolutionary subphylum vertebrata characteristics were based on morphological characteristics and on some molecular studies of rRNA genes Winchell et al.
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However, inbased on large molecular data set analyses, it was established that cephalochordates represent the most basally divergent lineage of subphylum vertebrata characteristics, being the sister group of urochordates and vertebrates Bourlat et al. The adult anatomy of amphioxus is vertebrate-like, but simpler. Amphioxus possess typical chordate characters, such as a dorsal hollow neural tube and notochord, a ventral gut and a perforated pharynx with gill slits, segmented axial muscles and gonads, a post-anal tail, a pronephric kidney, and homologues of the thyroid gland and adenohypophysis the endostyle and pre-oral pit, respectively Fig. However, they lack typical vertebrate-specific structures, such as paired sensory organs image-forming eyes or earspaired appendages, neural crest cells and placodes see Glossary, Box 1 Schubert et al.
This simplicity can also be expanded to the amphioxus genome structure. Indeed, two rounds of whole-genome duplication occurred specifically in the vertebrate lineage. Thin external processes around the amphioxus mouth, which function as the first filter during feeding by eliminating unwanted large or noxious particulates. When an existing gene, subphylum vertebrata characteristics or structure is recruited for a new function during evolution.
General characteristics
Gill bars. The cartilaginous structures on each side of the pharynx localized between the gill slits in amphioxus.
Holoblastic segmentation. Cleavage of whole embryo or zygote that can be equal, resulting in sister cells of subphylum vertebrata characteristics sizes, or unequal, giving rise to sister cells of different sizes. Different amphioxus species show different holoblastic segmentation. An elongated skeletal structure present in all chordate embryos found dorsal to the gut and ventral to the nerve cord.]
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