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Daily Opener

Daily Opener. Echinoderm means “spiny skin.” Using this information name 3 animals you think belong to Phylum Echinodermata. 28.4 Echinoderms. Phylum Echinodermata. Essential Questions. What are the distinguishing features of echinoderms?

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Daily Opener

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  1. Daily Opener • Echinoderm means “spiny skin.” • Using this information name 3 animals you think belong to Phylum Echinodermata.

  2. 28.4Echinoderms Phylum Echinodermata

  3. Essential Questions • What are the distinguishing features of echinoderms? • What functions are carried out by the vascular system of echinoderms? • What are the different classes of echinoderms?

  4. Echinoderms: An Introduction • Echinoderms are marine animals that are often found attached to rocks. • Echinoderm means ‘spiny skin’ and includes sea stars, brittle stars, featherstars, sea urchins, sand dollars, and sea cucumbers. • Echinoderms are characterized by a water vascular system with tube feet and radial symmetry.

  5. Echinoderms: An Introduction • They have an internal skeleton made of calcium carbonate • Adults have five-part radial symmetry • Larvae are bilaterally symmetrical • They are deuterostomes which means that the blastopore develops into anus

  6. Vocabulary • Endoskeleton - internal skeleton; made of calcium carbonate in echinoderms • Water vascular system - system of internal tubes that carry out essential functions like respiration, circulation and movement • Madreporite - sieve-like structure that connects to the water vascular system and opens to the outside • Tube foot - suction cup-like structure attached to the radial canals used to walk and open shells

  7. Form and Function • A unique feature of echinoderms is a system of internal tubes called a water vascular system. • Filled with fluid and carries many essential functions such as respiration, circulation, and movement. • Opens to the outside through a sieve-like structure called a madreporite (MAD-ruh-pawr-yt) • In sea stars the madreporite connects to a ring canal that forms a circle around the animals mouth. • From the ring canal, five radial canals extend along body segments.

  8. Response • Most species have a nerve ring surrounding the mouth and radial nerves that connect to the nerve ring to the body sections. • Most echinoderms have scattered sensory cells that detect light, gravity, and chemicals released by prey.

  9. Importance of Tube Feet • Attached to each radial canal are hundreds of tube feet. • A tube foot has suckers on the end that allows it to function like a suction cup. • Muscles pull the center of the sucker upward, forming a cup shape. • This action creates suction on the surface that the foot is attached to, allowing the animal to “walk” and even to pull open shelled prey such as clams.

  10. How Echinoderms Move • When echinoderms move, they force water into the podia, which causes them to expand. • Echinoderms also have muscles attached to the podia, which they can use to retract the podia. • This system of expansion by forcing water into the podia and then contraction by muscle allows echinoderms to move.

  11. Respiration, Circulation, Excretion • Other than the water vascular system, echinoderms have very few adaptations to carry out these functions. • The tube feet have thin-walled tissues that provide the surface for respiration. • Some species have outgrowths called skin gills that provide gas exchange. • Circulation of food, oxygen, and wastes takes place throughout the water vascular system. • Excretion of solid wastes are released as feces through the anus. • Ammonia based waste products are excreted through skin gills.

  12. Reproduction • Echinoderms reproduce by external fertilization. • Sea species are separate in most star species. • Sperm are produced in testes and eggs are produced in ovaries. • Gametes are shed into open water, where fertilization takes place. • Larvae have bilateral symmetry, swim for some time and end up on the ocean floor where they develop into adults with radial symmetry.

  13. Groups of Echinoderms

  14. Starfish or Sea Star Eyespot Endoskeleton plates Anus Stomach Digestive glands Ring canal Madreporite Radial canal Reproductive glands Tube foot Sucker

  15. Sea Stars (Starfish) • Sea stars fall under the class Stelleroidea. There are two main subclasses of sea stars: Asteroidea and Ophiuroidea. • Asteroids are the true sea stars and sun stars. • Ophiuroidsare composed of brittle stars and basket stars.

  16. Sea Stars (Starfish) • The main difference between asteroids and ophiuroids is the way that the rays, or arms, attach to the body. • In ophiuroids, the arms are not joined to each other and the body and arms are clearly separated, but in the asteroids the arms are joined to each other and the boundary between arms and the central disc is blurred.

  17. Sea Stars (Starfish) • Sea stars eat many things including clams, mussels, barnacles, coral, sea urchins and even other sea stars. • Some sea stars have a remarkable way of eating shells. They pry the shell open just slightly with their powerful arms and then they insert their stomach into the shell. When they are finished, there is nothing but an empty shell left.

  18. Sea Urchins and Sand Dollars • Sea urchins and sand dollars are echinoids from the class Echinoidea. • Spines radiating outwards protect them from predators. The spines are connected to the skeleton by a ball joint and muscle, which can swivel towards a predator. • Echinoids are herbivores, grazing on algae on rocks and the sea floor. • They have five bands of tube feet, which they use to move around and cling to rocks. A Sea Urchin with Spines

  19. Sea Cucumbers • Sea cucumbers belong to the class Holothuroidea. • They get their name because some sea cucumbers look like vegetable cucumbers. • Sea cucumbers have five rows of tube feet along their sides and tentacles around their mouths. • The tentacles filter seawater or sand for plankton and other organic matter. A Sea Cucumber A Filter Feeder

  20. Regeneration • Sea Stars and Sea cucumbers have a special characteristic: they can regenerate (re-grow) lost body parts. If you cut an arm off of a starfish, it will be able to regenerate that arm. Sometimes, even the separated arm can become a whole new sea star. This makes sea stars very hardy and can even cause some problems. • For example, the crown-of-thorns starfish damages coral reefs, but because of its regenerative properties, it is very hard to kill. • Sea cucumbers have the amazing ability to eviscerate (expel) their internal organs, when attacked. The predator is often satisfied with this easy meal and moves on. The sea cucumber then regenerates the expelled organs.

  21. Compare/Contrast Table Section 28-4 Comparing Groups and Major Characteristics of Echinoderms Feeding Shape Movement Sea urchins and sand dollars Detritivores Disc- or globe-shaped, no arms Burrow in sandy ocean bottom or wedge in rock crevices using moveable spines attached to endoskeleton Seastars Sea lilies andfeather stars Brittlestars Sea cucumbers Characteristic Detritivores Star-shaped, arms Move rapidly along ocean floor using arms Detritivores Cucumber-shaped, no arms Move slowly along ocean floor using muscular body wall to crawl Most carnivores Star-shaped, arms Creep slowly along ocean floor using arms Herbivores Stalk with feathery arms Cannot move; attached to ocean bottom

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