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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.
The notochord is the defining feature (synapomorphy) of chordates, and was present throughout life in many of the earliest chordates. Although the stomochord of hemichordates was once thought to be homologous or from a common lineal origin, it is now viewed as analogous, convergent , or from a different lineal origin. [ 22 ]
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a spine or backbone), which evolved from the notochord.It is a paraphyletic grouping including all animals excluding the chordate subphylum Vertebrata, i.e. vertebrates.
Tunicates are the only chordates that have lost their myomeric segmentation, with the possible exception of the seriation of the gill slits. [8] [9] However, doliolids still display segmentation of the muscle bands. [10] Some tunicates live as solitary individuals, but others replicate by budding and become colonies, [11] each unit being known ...
Phylum Kinetoplastida – Flagellated protists belonging to the phylum Euglenozoa; Alveolata phyla – Superphylum of protists; Phylum Ciliophora – Taxon of protozoans with hair-like organelles called cilia; Phylum Apicomplexa – Phylum of parasitic alveolates; Phylum Dinoflagellata – Aquatic, unicellular protists with two flagella
The cells of most archaeplastidans have walls, commonly but not always made of cellulose. [citation needed] The Archaeplastida vary widely in the degree of their cell organization, from isolated cells to filaments to colonies to multi-celled organisms. The earliest were unicellular, and many groups remain so today.
The main deuterostome phyla are the Ambulacraria and the Chordata. [147] Ambulacraria are exclusively marine and include acorn worms, starfish, sea urchins, and sea cucumbers. [148] The chordates are dominated by the vertebrates (animals with backbones), [149] which consist of fishes, amphibians, reptiles, birds, and mammals. [150] [151] [152]
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).