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Mollusks and Echinoderms. What is a mollusk?. Mollusks are invertebrates with soft bodies that are often protected by a hard shell (oysters, clams, snails). Some lack the shell All mollusks have a thin layer of tissue that covers their internal organs called the mantle. Found everywhere.
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What is a mollusk? • Mollusks are invertebrates with soft bodies that are often protected by a hard shell (oysters, clams, snails). • Some lack the shell • All mollusks have a thin layer of tissue that covers their internal organs called the mantle. • Found everywhere.
Other Structure • Mollusks have bilateral symmetry. • Internal organs include kidneys: What are they used for? • Many mollusks also have a structure called the radula: a flexible ribbon of teeth. This structure is used to scrape food off of objects.
Mollusks have been around for millions of years. We know this because their hard shells form very nice fossils. Also form Limestone. What are fossils? History
Limestone • Biological sedimentary rock—formed from shells of organisms (mollusks) over many years. • Different names of limestone based on how rock is formed, its appearance or composition. • Limestone is rock by definition that contains at least 50% calcium carbonate.
Types of Limestone Coquina: A poorly-cemented limestone that is composed mainly of broken shell debris. It often forms on beaches where wave action segregates shell fragments of similar size.
Other types of limestone Chalk: A soft limestone with a very fine texture that is usually white or light gray in color. It is formed mainly from the calcareous shell remains of microscopic marine organisms such as foraminifers or the calcareous remains from numerous types of marine algae.
Limestone rock Tufa: A limestone produced by precipitation of calcium-laden waters at a hot spring, lake shore or other location.
Coral reef forming limestone from calcium carbonate skeletons
Limestone- Forming Environment Nasa satellite image 100mi wide
Stomach Foot • The largest group of mollusks are the snails and their relatives (gastropods). • Get their name from the fact their stomach and foot are in the same area.
Live everywhere from the ocean to treetops. Can be herbivores, scavengers and carnivores (cone shell). Many snails have a tight fitting trap door on their shell that they can close off if threatened. Slugs have the same features as snails except one. Continue
Two Shelled Mollusks • Have two shells held together by a hinge and muscle. • Lack radula • Are filter feeders - use their gills to catch food as they breathe. • Food sticks to mucus on the gills; then cilia take it to the stomach.
Bivalves • Bivalves have three layers in their shell. The inside layer has a pearly appearance. • As adults typically stay in one place. • Clams and scallops however can actively move if startled • Clams use their foot if startled to bury themselves. • Scallops can clap their shells to leap away.
Bivalves Sea Scallop Giant Clam
Clams Greater European Peaclam Asian Clam
How are Pearls Formed? • Pearls are formed when a sand grain or parasitic worm gets caught in a bivalve. The mantle becomes irritated and produces the pearly layer over the irritation. This just makes it bigger and more irritating. It keeps putting on layer after layer forming a pearl.
Pearls Natural pearls vary in size and shape. Their shape depends on the piece being coated. These are rare and very expensive. Cultured pearls are formed when the shells are opened and different shape beads are inserted.
Head Foots • Cephalopods means “head-footed”. • Foot is adapted as tentacles around the mouth. • Some members of this group are the octopus, cuttlefish, and squid. • Most advanced of all invertebrates.
Octopus • Found only in the ocean where they move by jet propulsion. • Communicate by changing the color and patterns of their skin. • Use their tentacles and suckers to capture food. • Excellent vision and nervous system. • They have even been found to remember things they have learned in captivity.
Why does this use a bright coloring? Blue-ringed octopus. One of the most toxic animals.
Squid Giant Pacific Squid
Spiny Skinned animals • Have radial symmetry (?) • Invertebrates that live in the ocean. • Have an endoskeleton that is made up of calcium plates: Where would we find an endoskeleton? • Symmetry is based on fives • Also have a water vascular system
Sea Stars or Starfish Dissected starfish. Notice the radial canals which are part of the water-vascular system.
Sand dollars Arrowhead Flat Round
Sea Biscut Pancake
Parts of the tubes can contract and squeeze the water into tube feet. This allows the feet to grip the surface underneath the organism, allowing it to move. They also use these tube feet to pull open the shells of mollusks Water vascular system
Water-Vascular System Tube feet
