14'2 FISH

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14.2 FISH
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Fish Characteristics

• Largest group of vertebrates
• All fish are ectotherms
• Live in all types of aquatic environments.
• Fins and their streamlined shape allows most fish
  to move quickly through the water.
• Most produce a slime layer to reduce friction in
  the water.

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Characteristics Cont.

• Most have scales that are hard thin plates that
  cover the skin, overlap like shingles.
• Have fins that are attached to the skeleton and
  are used for propulsion, steering and balance.

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Body Systems

• Most fish have a lateral line which is a shallow
  canal that is filled sensory organs.
• The lateral line lets fish sense motion and
  electrical signals
• Fish have a two chambered heart, used blood (CO2)
  mixes with fresh blood (O2).

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Gas Exchange

• Most fish have gills, located on both sides of
  the head.
• The feathery parts of gills contain many blood
  vessels diffusion makes CO2 and O2 move out and
  into the blood.

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Feeding adaptations

• Fish have many different adaptations in how they
  obtain food.
• Filter feeders strain the water as it passes
  through their gills.
• Parrot fish have beaks to break coral.

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Reproduction

• All fish reproduce sexually
• Reproduction is controlled by hormones that are
  affected by environmental factors.
• In most fish the female releases large amounts of
  eggs which are fertilized externally.
• Some fish have internal fertilization.

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Jawless Fish

• Jawless fish have round toothed mouths.
• Have tube-like bodies no scales and slimy skin.
• Have a flexible cartilage skeleton
• Lamprey are parasites and hagfish are scavengers.

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Cartilaginous fish

• Have skeletons made of cartilage like jawless
  fish.
• Do have movable jaws with well developed teeth.
• Have tiny scales that make their skin rough.
• Shark reproduction is slow and shark numbers are
  falling.

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Bony fish

• About 95 of all fish are bony fish.
• Have a bony flap covering the gills.

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Swim Bladder

• Is an air filled sac that allow fish to change
  their density.
• If their density is greater than water they sink.
• In most fish gasses like oxygen and nitrogen move
  from the blood to the sac.

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Lobe finned fish

• Have lobe like fleshy fins.
• Were thought to have been extinct for 70 million
  years.
• Are important in studying the evolution of early
  amphibians.

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Lung fish

• A lung fish has one lung and gills.
• The lung allows the fish to breath air when water
  evaporates or there is not enough air in water.
• Can bury in the mud and cover them selves in
  mucus until water returns.

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Ray Finned Fish

• The fins of most fish are made of bones that are
  covered with skin.
• Body shapes are adapted to specific life styles.

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Importance of origin of fish

• Fish are important to humans as food, control
  pests, and pets.
• Thought to have involved from soft bodied filter
  feeders.
• Bony fish probably evolved from the jawless fish
  410MYA