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Chordates

Chordates. Biology 112. Characteristics of Phylum Chordata. A chordate is an animal with the following four features: A hollow nerve cord that runs along the back of the body A notochord is a support rod that runs just below the nerve cord

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Chordates

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  1. Chordates Biology 112

  2. Characteristics of Phylum Chordata • A chordate is an animal with the following four features: • A hollow nerve cord that runs along the back of the body • A notochord is a support rod that runs just below the nerve cord • Pharyngeal pouches are paired structures in the throat • A tail that extends beyond the anus

  3. Characteristics of Chordates

  4. Generally speaking… • Most chordates are vertebrates • Most have a backbone made up of vertebrae • The backbone replaces the notochord and supports and protects the spinal cord • It also gives muscles a place to attach

  5. Chordates that do not have backbones • Tunicates • Ocean-living filter feeders • Have no notochord or tail • As larva, they possess all the characteristics of chordates • Lancelets • Small, fish-like animals • Adults possess all four characteristics • Have a definite head region

  6. Tunicates – comparison of larva to adult

  7. Lancelet - adult

  8. Fishes • Aquatic vertebrates • Most have paired fins, scales and gills • Jaws and paired fins marked an evolutionary turning point for fish • Jaws improved defense and expanded food choices • Paired fins improved controlled movement • In order to survive in water, special adaptations include: • Various modes of feeding • Specialized structures for gas exchange • Paired fins for locomotion

  9. Fish - feeding • May be herbivores, carnivores, parasites, filter feeders, or detritus feeders • One fish may feed in many different ways, depending on the food available

  10. Fish - respiration • Most fish breathe with gills • Gills have many tiny blood vessels that provide a large surface area for gas exchange • Fish pull water into their mouths • Water moves over the gills and out of the body through openings in the sides of the pharnyx

  11. Fish - circulation • Fish have a closed circulation system • It pumps blood in a loop from its heart to gills to the body and then back to the heart • The heart consists of two chambers: an atrium and a ventricle

  12. Fish - excretion • Most fish get rid of wastes as ammonia • Some diffuse wastes through the gills into the water • Others remove wastes from the blood through the kidneys • Kidneys help control the amount of water in their bodies

  13. Fish – nervous system • Well developed with a brain housing several parts • Cerebrum responsible for smell • Cerebellum coordinates movement • Medullaoblongata controls internal organs • A lateral line system senses currents and vibrations in the water

  14. Fish - movement • Most move by contracting muscles on either side of the backbone • Fins pull the fish forward and help it steer • Many have a gas-filled organ called a swim bladder that prevents its from sinking

  15. Fish - reproduction • Eggs may be fertilized internally or externally • Oviparous fish • Lay eggs • Eggs develop and hatch outside the mother’s body • Ovoviviparous fish • Develop eggs inside the mother • Egg provides food to the young while inside mother • Young are born alive • Viviparous fish • Mother provides food to the young while inside mother • Young are born alive

  16. Classification of Fish • Jawless fish • Lampreys and hagfish • Bodies are supported by a notochord • Do not have true teeth or jaws • Parasites and scavengers • Cartilaginous fish • Sharks, rays and skates • Have a skeleton made of cartilage • Most have tooth-like scales covering their bodies • Bony fish • Skeletons made of bone • Most are ray-finned fishes • Fins have thin, bony spines that are joined by a thin layer of skin

  17. Amphibians • Vertebrates that live mostly in aquatic environments as a larva and on land as an adult • As adults, breath with lungs, have moist skin that contains mucous glands and lack scales and claws • In order for amphibians to adapt to living on land, from an evolutionary standpoint: • Bones became stronger • Lungs and breathing tubes developed • The breastbone (sternum) developed a bony shield to support organs

  18. Amphibian Characteristics • As larvae, they are filter feeders or herbivores; adults are carnivores • Gas exchange occurs through skin and gills(larvae) and lungs (adults) • Adults have three heart chambers; circulation is a double loop system • Kidneys remove wastes from blood • Eggs are laid in water and then the male fertilizes them • Eggs hatch into larvae, called tadpoles • They have good vision and can sense sound vibrations

  19. Classification of Amphibians • Salamanders • Long bodies, four legs and long tails • Frogs and Toads • Do not have tails and can jump • Frogs live close to water, toads live in moist wooded areas • Caecilians • Do not have legs • Live in water or burrow in moist soil

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