Nonvertebrate Chordates, Fishes, and Amphibians

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Nonvertebrate Chordates, Fishes, and Amphibians

• Unit VI
• Chapter 30

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The Chordates

• A chordate is an animal that has, for at least
  some stage of its life, a dorsal, hollow nerve
  cord a notochord pharyngeal pouches and a tail
  that extends beyond the anus
• Dorsal hollow nerve cord runs along the back
  part of the body with nerves that branch and
  connect to organs
• Notochord long supporting rod that runs through
  the body just below the nerve cord
• Pharyngeal pouches found in the pharynx region
  may develop into gills
• Post anal tail contains bone and muscle and is
  used in swimming by aquatic species

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Chordate Characteristics
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Most Chordates are Vertebrates
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Nonvertebrate Chordates

• The two groups of nonvertebrate chordates are
  tunicates and lancelets
• Both are soft-bodied marine organisms

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Tunicates

• Tunicates are filter feeders that exhibit all of
  the chordate characteristics as larva but not as
  adults

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Lancelets

• Lancelets are small, fishlike creatures that
  thrive on the sandy ocean floor
• An adult lancelet has a head region that contains
  a mouth

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Fishes

• Fishes are aquatic vertebrates that are
  characterized by paired fins, scales, and gills

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The Rise of Modern Fishes

• While most early jawed fishes disappeared, they
  left behind two major groups that continued to
  evolve and still survive today
• Cartilaginous fishes (sharks rays)
• Boney fishes (modern fishes)

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Fish Anatomy
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Form Function in Fishes

• Adaptations to aquatic life include various modes
  of feeding, specialized structures for gas
  exchange, and paired fins for locomotion

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Fish Feeding

• Fish can be herbivores, carnivores, parasites,
  filter feeders, and detritus feeders.
• The diagram below highlights some internal organs
  important during the fishs digestion

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Fish Respiration

• Most fishes exchange gases using gills located on
  either side of the pharynx
• Oxygen-rich water is pulled in through the mouth
  and over the gill filaments
• Oxygen-poor water is pushed out through the
  openings in the sides of the pharynx
• Some fishes, including the lungfish, have a
  lung-like adaptation that allows them to survive
  in oxygen poor water

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Fish Circulation

• Fishes have closed circulatory systems with well
  developed heart that pumps blood around the body
  in a single loop
• From the heart to the gills
• From the gills to the rest of the body
• Back to the heart

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Fish Circulatory System
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Fish Excretion

• Fishes rid themselves of nitrogenous wastes in
  the form of ammonia
• Kidneys help fishes control the amount of water
  in their bodies

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Fish Response

• Fishes have well-developed nervous systems
  organized around a brain which has several parts
• Olfactory bulb sense of smell
• Cerebrum voluntary activities of body
• Optic lobe eye function
• Cerebellum coordinates body movement
• Medulla oblongata controls internal organ
  functions
• Spinal cord
• Most fishes can detect gentle currents and
  vibrations in the water with a sensitive receptor
  called the lateral line system

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Fish Movement

• The streamlined body shapes of most fishes help
  to reduce the amount of drag (friction) as they
  move through the water
• Fins assist in movement
• Many bony fishes have an internal, gas-filled
  organ called a swim bladder that adjusts their
  buoyancy
• Because their body tissues are more dense than
  water, sinking would be an issue without the swim
  bladder

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Fish Reproduction

• Fishes whose eggs hatch outside the mothers body
  are oviparous
• As the embryos develop, they obtain food from the
  yolk in the egg
• Fishes whose eggs stay inside the mothers body
  are ovoviviparous
• Egg yolk is used for nourishment
• Fishes whose embryos stay in the mothers body
  and get nourishment from the mother are
  viviparous
• These fishes are born alive

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Groups of Fishes

• All living fishes can be classified into three
  groups
• Jawless fishes (class Agnatha) have no true
  teeth or jaws
• Lampreys and hagfishes
• Cartilaginous fishes (class Chondrichthyes)
  skeletons are built entirely of cartilage, not
  bone
• Sharks, rays, skates
• Bony fishes (class Osteichthyes) skeletons are
  made of hard, calcified bone
• Most other fishes

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Amphibians

• An amphibian is a vertebrate that, with some
  exceptions, lives in water as a larva and on land
  as an adult, breathes with lungs as an adult, has
  moist skin that contains mucus glands, and lacks
  scales and claws
• Amphibian adaptations for life on land include
• Limb bones become stronger
• Lungs and breathing tubes
• Sternum to protect internal organs

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Amphibian Feeding

• Tadpoles are filter feeders whereas adult
  amphibians are carnivorous
• Many have long, sticky tongues used to capture
  insects
• Digestion involves food traveling from the mouth
  down the esophagus into the stomach
• From the stomach into the small intestine
• From the small intestine to the large intestine
• From the large intestine into the cloaca (the
  pathway for waste to leave the body

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Frog Digestive System
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Amphibian Respiration Circulation

• In larval amphibians, gas exchange occurs through
  the skin and gills
• Lungs replace gills in adult amphibians but
  some gases continue to diffuse through the skin
• In adult amphibians, the circulatory system forms
  a double loop
• 1st loop carries oxygen-poor blood from the heart
  to the lungs and skin and takes oxygen-rich blood
  from the lungs and skin back to the heart
• The 2nd loop transports oxygen-rich blood from
  the heart to the rest of the body and oxygen-poor
  blood from the body back to the heart

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Frog Circulatory System Heart

• The amphibian heart has 3 chambers
• Left atrium, right atrium, and ventricle

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Amphibian Excretion Reproduction

• Amphibians have kidneys that filter wastes from
  the blood
• Amphibian eggs must be kept moist to avoid drying
  out
• External fertilization
• Eggs are abandoned after the frogs lay them
• Offspring metamorphosize from tadpoles into frogs

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Amphibian Movement

• Amphibian larvae move like fishes
• Adult salamanders have legs that stick out
  sideways walking involves moving the body into
  an S-shaped curve
• Frogs and toads have well-developed hind limbs
  that enable them to jump
• Tree frogs have disks on their toes that serve as
  suction cups for climbing

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Amphibian Response

• The brain of an amphibian is very similar to that
  of a fish
• They have well developed nervous systems
• They hear through tympanic membranes (eardrums)
  located on each side of the head

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Groups of Amphibians

• Salamanders
• Frogs Toads
• Caecilians

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Amphibian Concept Map