In some groups, some of these traits are present only during embryonic development. In addition to containing vertebrate classes, the phylum Chordata contains two clades of invertebrates: Urochordata tunicates and Cephalochordata lancelets. However, even though they are invertebrates, they share characteristics with other chordates that places them in this phylum. For example, tunicate larvae have both a notochord and a nerve cord which are lost in adulthood.
Most tunicates live on the ocean floor and are suspension feeders. Cephalochordates, or lancelets, have a notochord and a nerve cord but no brain or specialist sensory organs and a very simple circulatory system. Lancelets are suspension feeders that feed on phytoplankton and other microorganisms. The phylum Chordata contains all of the animals that have a rod-like structure used to give them support. In most cases this is the spine or backbone. Within Chordata there are five classes of animals: fish, amphibians, reptiles, birds, and mammals.
Three dividing factors separate these classes:. Learning Objectives Name the features that distinguish the members of the phylum chordata. Key Points The phylum chordata is named for the notochord, a longitudinal, flexible rod between the digestive tube and the nerve cord; in vertebrates, this is the spinal column. The chordates are also characterized by a dorsal nerve cord, which splits into the brain and spinal cord. Chordata contains two clades of invertebrates: Urochordata tunicates and Cephalochordata lancelets , both of which are suspension feeders.
All chordates have a post-anal tail. A post-anal tail is an extension of the body that runs past the anal opening. In some species, like humans, this feature is only present during the embryonic stage.
The chordata phylum is divided into three groups or subphylums : lancelets, tunicats, and vertebrates. Cephalochordata lancelets. Vertebrata vertebrates. Home Wild Files N. Chordata - Vertebrates, Tunicates, Lancelets At some point, all of the organisms in this phylum have a structure called a notochord.
Vertebrata is named for the vertebral column, which is a feature of almost all members of this clade. The name Craniata organisms with a cranium is considered to be synonymous with Vertebrata. Figure Which of the following statements about common features of chordates is true?
Which of the following is not contained in phylum Chordata? Hagfish, lampreys, sharks, and tuna are all chordates that can also be classified into which group? The characteristic features of the phylum Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. What is the structural advantage of the notochord in the human embryo? Be sure to compare the notochord with the corresponding structure in adults. In the adults, the notochord has been replaced by the bony, rigid vertebral column.
This loss of flexibility restricts the movement of adult humans, and would make it unlikely that the embryo would fit within the small space it is allotted inside the uterus. Skip to content Vertebrates. Learning Objectives By the end of this section, you will be able to do the following: Describe the distinguishing characteristics of chordates Identify the derived characters of craniates that sets them apart from other chordates Describe the developmental fate of the notochord in vertebrates.
Deuterostome phylogeny. All chordates are deuterostomes possessing a notochord at some stage of their life cycle. Visual Connection. Chordate features. In chordates, four common features appear at some point during development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. The endostyle is embedded in the floor of the pharynx. Link to Learning. Chordates and the Evolution of Vertebrates Two clades of chordates are invertebrates: Cephalochordata and Urochordata.
Cephalochordate anatomy. In the lancelet and other cephalochordates, the notochord extends into the head region. Adult lancelets retain all five key characteristics of chordates: a notochord, a dorsal hollow nerve cord, pharyngeal slits, an endostyle, and a post-anal tail.
Urochordata The 1, species of Urochordata are also known as tunicates Figure. Urochordate anatomy. These colonial tunicates feed on phytoplankton. Salps are sequential hermaphrodites, with younger female colonies fertilized by older male colonies. Subphylum Vertebrata Craniata A cranium is a bony, cartilaginous, or fibrous structure surrounding the brain, jaw, and facial bones Figure.
A craniate skull. The subphylum Craniata or Vertebrata , including this placoderm fish Dunkleosteus sp. A vertebrate skeleton. Vertebrata are characterized by the presence of a backbone, such as the one that runs through the middle of this fish. All vertebrates are in the Craniata clade and have a cranium. Visual Connection Questions Figure Which of the following statements about common features of chordates is true? The dorsal hollow nerve cord is part of the chordate central nervous system.
In vertebrate fishes, the pharyngeal slits become the gills. Humans are not chordates because humans do not have a tail. Vertebrates do not have a notochord at any point in their development; instead, they have a vertebral column. Figure A. Review Questions Which of the following is not contained in phylum Chordata? Cephalochordata Echinodermata Urochordata Vertebrata.
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