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A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
Tunicates (subphylum Tunicata) are a group of filter-feeding marine invertebrates. [1] As chordates , they have been proposed to be the closest relatives of vertebrates . [ 2 ] Tunicates are divided into three classes: the sessile Ascidiacea , and the free-swimming Thaliacea and Appendicularia . [ 1 ]
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata (/ ˌ tj uː n ɪ ˈ k eɪ t ə / TEW-nih-KAY-tə).This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates).
This article contains a list of all of the classes and orders that are located in the Phylum Chordata. The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not. Animals in Olfactores are characterized as having a more advanced olfactory system than animals not in it.
The tracheal system branches into progressively smaller tubes, here supplying the crop of the cockroach. Scale bar, 2.0 mm. One type of invertebrate respiratory system is the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues. [22]
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization ), usually near organs for special senses such as vision , hearing and olfaction .
Also like vertebrates, the muscles are arranged in blocks called myomeres. [ 50 ] Unlike vertebrates, the dorsal nerve cord is not protected by bone but by a simpler notochord made up of a cylinder of cells that are closely packed in collagen fibers to form a toughened rod.
The heads of vertebrates are complex structures, with distinct sense organs for sight, olfaction, and hearing, [12] and a large, multi-lobed brain protected by a skull of bone or cartilage. [13] Cephalochordates like the lancelet ( Amphioxus ), a small fishlike animal with very little cephalization, are closely related to vertebrates but do not ...