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 In the adults, the notochord has been replaced by the bony, rigid vertebral column.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. Which group of invertebrates is most closely related to vertebrates? Larvae of many species develop into very different adults, a process called metamorphosis. Can develop resistance to insecticides- demonstrates how quickly they adapt to a changing environment.
Short generations and many offspring increase the chance that random mutations will produce a few resistant individuals Arthropods are segmented animals with jointed appendages and an exoskeleton Chelicerates Include horseshoe crabs and arachnids, such as spiders, scorpions, mites, and ticks Millipedes and Centipedes. Find out More. Perspectives in Environmental Science The basics Environmental issues are particularly difficult to solve because often the solutions require sacrifice….
Inline Feedbacks. As you proceed through this section, you can use the phylogenetic listing following this introduction to keep track of arthropod groups. These intriguing and largely harmless creatures are among the most visible and approachable of all Sonoran Desert animals.
Keep an eye out on your next desert walk, and you may see an arthropod or two that you have previously encountered in the pages of this book. Alcock, John. NY: W. Norton, Conniff, Richard. NY: Henry Holt, Friederici, Peter. Werner, Floyd G. Tucson: Fisher Books, In essence, phylogenies are family trees.
Since most of the branching in the arthropod family tree took place before humans came into existence, the tree structure is deduced from the study of fossils, and the examination of molecular, developmental, anatomical, and behavioral characteristics of contemporary species.
Many characters important in determining relationships between species are not observable in the field. The informal notes in this phylogeny are intended to help readers develop a feel for arthropod classification by using visual characteristics alone.
Animals with an exoskeleton, a segmented body, and jointed legs. The earliest arthropods probably had one pair of appendages per body segment, but there have been many divergences from the ancestral arrangement. Segments may be fused or grouped into body regions and appendages may be exaggerated, modified, or lost.
Members of this subphylum have two major body divisions, the cephalothorax the head and mid section combined and the abdomen. The first pair of appendages on the cephalothorax is modified into jaw-like structures. Chelicerates have simple eyes resembling unfaceted beads. All species in this category lack antennae and wings. The arachnid cephalothorax appears to be unsegmented. In some orders, the abdomen is clearly segmented scorpions ; in others most spiders no segments are apparent.
Arachnids have four pairs of legs; however, some arachnid mouthparts such as scorpion claws have evolved into structures that could be mistaken for limbs. Almost all arachnids are terrestrial.
Members of this group have two pairs of antennae and branched biramous appendages. Five pairs of appendages are associated with the head, including a pair of jointed mandibles. Many species have compound eyes, which are made up of simple eyes grouped together to form faceted spheres.
Most species are marine. This class contains some of the most familiar crustaceans. Members have eight trunk segments and six abdominal segments. All abdominal segments bear appendages. Only a few species belonging to this group are found in the Southwest.
Species in this subphylum are distinguished from ones in subphylum Crustacea by having a single pair of antennae, unbranched uniramous appendages, and mandibles that are usually unjointed. These animals have a long, flattened body with numerous segments. One pair of legs arises per trunk segment and 15 or more pairs of legs are present.
Members of this class have long, cylindrical bodies. Every other body segment is fused to the one ahead of it, so the animals appear to have two pairs of legs per body segment. Insects have three distinct body regions: the head, thorax, and abdomen. Three pairs of legs, and often two pairs of wings, arise from the thorax. Many insects have well developed compound eyes. You can unsubscribe at any time by clicking the link in the footer of our emails.
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Learn more about Mailchimp's privacy practices here. Visit Teachers - Bring Your Class! Become a Member! Adopt a friend! Green Initiatives. Gift a Virtual Program! Share your photos! A Vertebrate Looks at Arthropods Barbara Terkanian At close range even a familiar arthropod like a grasshopper may seem appallingly strange. Kingdom: Animalia Phylum: Arthropoda Animals with jointed external skeletons, such as lobsters, spiders, centipedes, and insects Phylum: Chordata Animals with dorsal nerve cords vertebrates and others.
The Design of Arthropod and Vertebrate Skeletons Both arthropods and vertebrates have articulated skeletons. More than a Million Arthropod Species Arthropods are the most diverse of all animals, comprising over 85 percent of all living animal species. Similar, Different, and Interesting Remarkable parallels and contrasts can be developed when arthropods and vertebrates are compared.
Additional Readings Alcock, John. Evans, Arthur V. An Inordinate Fondness for Beetles. Imes, Rick. The Practical Entomologist. New York: Fireside, Smith, Robert L. Venomous Animals of Arizona. Tucson: University of Arizona, Kingdom Animalia Phylum Arthropoda Animals with an exoskeleton, a segmented body, and jointed legs.
Subphylum Chelicerata Members of this subphylum have two major body divisions, the cephalothorax the head and mid section combined and the abdomen. Class Arachnida The arachnid cephalothorax appears to be unsegmented.
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