Chordata
The Chordates are animals that derive from the phylum Chordata. The phylum Chordata includes three subphyla: Tunicata; Cephalochordata (vertebrates), and the Craniata. Common characteristics of the Chordata include having, for some period of their life cycles, a notochord, a hollowdorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. The phylum Hemichordata has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum.
The muscular system of the Chordates is a quite simple one. Most chordates have an internal skeleton against which muscles work. Also, most have a postanal tail that extends beyond the anus. This tail, in some (like humans), t may only appear in embryos. Lancelets (shown above) have segmented muscles and their dorsal hollow nerve cord has periodic branches. The endoskeleton and muscles form an organ system (the musculoskeletal system) that allows rapid and efficient movement.
Some of the organisms that exist in this phylum are fish, amphibians, and reptiles. For the most part, all three of the sub -categories contain a notochord, post-anal tail, and a hollowdorsal nerve cord.
The muscular system of the Chordates is a quite simple one. Most chordates have an internal skeleton against which muscles work. Also, most have a postanal tail that extends beyond the anus. This tail, in some (like humans), t may only appear in embryos. Lancelets (shown above) have segmented muscles and their dorsal hollow nerve cord has periodic branches. The endoskeleton and muscles form an organ system (the musculoskeletal system) that allows rapid and efficient movement.
Some of the organisms that exist in this phylum are fish, amphibians, and reptiles. For the most part, all three of the sub -categories contain a notochord, post-anal tail, and a hollowdorsal nerve cord.