12'2 Sponges and Cnidarians

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12.2 Sponges and Cnidarians
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Importance of Sponges

• Sponges are important to many organisms as a food
  source or home.
• Human use 17 species of sponges
• Most bath sponges are not real sponges but are
  still available.
• Chemicals gathered from sponges can be used fight
  disease causing bacteria and viruses.

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Origins of sponges

• Sponges appeared on earth 600 MYA.
• Scientists think they evolved on a separate
  branch than the other animals.

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Characteristics of sponges

• Most sponges live in warm shallow salt water.
• Salt water sponges are brightly colored but those
  of freshwater are very dull.
• Most are asymmetrical, and sessile.
• At one time they were classified as plants
  because they didnt move.

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Body structure

• The body of a sponge is a tube that is closed at
  one end.
• Sponges are not complex they have no tissues,
  organs or organ systems.
• Collar cells are the specialized cells that move
  water through the sponge to help it feed.

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Body Structure

• Spongin is the part of the psonge used for
  washing.
• Spicules are the skeletons of sponges.

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Obtaining food and oxygen

• Sponges get food and oxygen by filtering the
  water.

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Reproduction

• Sponges are hermaphrodites - they produce both
  sperm and egg cells.
• Sperm are released into the water until they are
  brought in another sponge where they fertilize
  the egg cell.
• The zygote becomes a larva that swims to a new
  location.

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Cnidarians

• Include anemone, jellyfish, and corals.
• cnidarians have two body forms polyp and medusa.
• Polyps are sessile vase shaped with tentacles at
  the top.
• Medusa are bell shaped free swimming

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Body structure

• Cnidarians have radial symmetry and one body
  opening.
• Each cell gets its own oxygen and rid of wastes.
• Have a very basic nervous system.
• Have tentacles surrounding the mouth with
  stinging cells to stun food.

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Reproduction

• Some cnidarians have a two stage reproductive
  cycle with sexual and asexual stages.
• The medusa stage reproduces sexually releasing
  sperm and egg to make polyps.
• The polyp form reproduces asexually by budding to
  produce the medusa form.

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Origins

• Oldest fossils 600 MYA
• Medusa body form probably came first.
• Coral fossils are the most common to find because
  of their shells.

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Importance of corals

• Coral reefs are the most productive ecosystems of
  the ocean.
• Beaches and shorelines are protected from large
  waves.
• Chemicals gathered from corals are being tested
  as medicines.