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Chordates: Phylum Chordata

Chordates: Phylum Chordata. An Introduction to Vertebrate Animals . Introduction. Chordates (vertebrates) are the group of animals most familiar to us Ex: mammals, birds, amphibians, reptiles, fish Name comes from: Notochord “Back” “Cord”

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Chordates: Phylum Chordata

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  1. Chordates: Phylum Chordata An Introduction to Vertebrate Animals

  2. Introduction • Chordates (vertebrates) are the group of animals most familiar to us • Ex: mammals, birds, amphibians, reptiles, fish • Name comes from:Notochord “Back” “Cord” • Def: a skeletal rod made of body of cells enclosed by a fibrous covering, which extends, in most cases the length of the body • Primary purpose/function: to support and stiffen the body, provide muscle support • In most vertebrates the notochord is displaced by vertebrae

  3. Introduction • Five distinct/unique characteristics** to chordates: 1) Dorsal, tubular nerve cord (anterior end becomes enlarged to form brain) 2) Notochord 3) Pharyngeal slits /pouches (will become middle ear cavity, tonsils, parathyroid glands, etc.) 4) Endostyle (becomes thyroid gland) for filter feeders 5) Post-anal tail for propulsion (vestigial structure in humans; coccyx) ** Some of these characteristics appear ONLY in the embryonic (pre-birth) stages of vertebrates!!!

  4. Introduction • Chordates have many characteristics that are similar to some invertebrate animals: • Bilateral symmetry (like mollusks, arthropods) • Anterior to posterior axis , right/left halves • Coelom well developed (Tube-within-a-tube arrangement ) • Metamerism (segmentation) restricted to outer body wall, head and tail and not into coelom • Cephalization (concentrated head region)

  5. Introduction • Chordates have many characteristics that are similar to some invertebrate animals: • Endoskeleton (some mollusks, arthropods) • Paired appendages (arthropods) • Sensory organs are highly developed (mollusks, some arthropods) • Three germs layers (ectoderm, mesoderm, endoderm) • Complete digestive system

  6. Diversity • Belong to Phylum Chordata • Enormous variation • Live in all ecosystems on earth • Most adaptable phylum on earth • LARGE fossil record • According to fossil record, chordates are ~500 million years old • Approximately 60,000 different species

  7. Characteristics • Endoskeleton: • Grows as animal grows • Series of vertebrae surrounding a spinal cord • Skull is attached to anterior end of backbone (head-region) • Functions: • Protection, muscle attachment, organ attachment

  8. Characteristics • Circulation: • Closed system • Contain arteries, vessels, veins, ventral heart • Allows for rapid circulation of blood • Most have separation of oxygenated and deoxygenated blood • Can regulate body temperature(one of two ways) • 1) Endotherms – control with internal body processes (mammals, birds) • 2) Exotherms – control by outside environment (fish, amphibians, reptiles)

  9. Characteristics • Endocrine system: • All chordates have a thyroid gland • Function: to produce hormones • Nervous system: • Cephalization is present • Concentrated in anterior region • VERY highly developed • Allows for much, higher-order processes • Sensory receptors highly developed (eye, nerve endings, brain processes, etc)

  10. Classification: 3 Subphyla • Three subphyla: • 1) Urochordata • Example: sea squirt • 2) Cephalochordata • Examples: lanceletes • 3) Vertebrata • Examples: birds, mammals, reptiles, amphibians

  11. Classification • Three subphyla: • 1)Urochordata • Known as tunicates • Examples: sea squirts • 2000 species • Found in all seas (shoreline to great depths) • Most are sessile (permanent) adults, some are free living • Name tunicate comes from “tunic” • This is a tough surrounding that protects animal • May be solitary or live in colonies • Hermaphrodites (contain both sexes)

  12. Classification • Three subphyla: • 2)Cephalochordata • Examples: lanceletes • Only 25 species • Found in marine environments • Sandy bottoms of coastal regions • VERY small (5-7 cm in length) • Free living, swimmers • Separate sexes • Considered the evolutionary beginning to all other chordates

  13. Classification • Three subphyla: • 3) Vertebrata • Examples: mammals, birds, fish, amphibians, reptiles • Largest and most diverse chordate subphylum • ~57,000 species • Found in all ecosystems, environments • WIDE range of sizes • Grouped together because of the skull region (bony or cartilaginous braincase) • Tripartite brain (fore, mid and hindbrain) • Can possess both endoskeleton AND exoskeleton

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