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15D – Other Invertebrates. Page 468 – 473. Phylum Mollusca. 2 nd largest animal phylum 3 Classes Class Bivalvia Class Gastropoda Class Cephalopoda. Phylum Mollusca. Octopus, oysters, snails, slugs, squid, clams All Mollusca have the following:
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15D – Other Invertebrates Page 468 – 473
Phylum Mollusca • 2nd largest animal phylum • 3 Classes • Class Bivalvia • Class Gastropoda • Class Cephalopoda
Phylum Mollusca • Octopus, oysters, snails, slugs, squid, clams • All Mollusca have the following: • Mantle: protects the organs (insides); helps it breathe • Shell: hard outer covering; protects the body • Visceral Hump: holds the heart, stomach, and excretory organs (where it pees and poops) • Foot: allows it to move • Radula: organ with small teeth that grabs food and pulls the food into the mouth • Babies are called trochophore
Class Bivalvia • Oysters, clams, mussels, and scallops • This class has a shell with two halves • Called “filter feeders” because they pull in water and eat the smaller animals out of the water • Water is pulled in and pushed back out by siphons – these work like straws • Gills allow Class Bivalvia to breathe • These are usually sessile (don’t move) with 2 external (outside the animal) shells
Class Gastropoda • Called Stomach-footed mollusks because they have their foot under their visceral hump • Snails, slugs, nudibranches • Usually move by crawling • Usually have one external shell (not slugs) • Usually have a mantle cavity: a space between the shell and the body that acts as a lung
Class Cephalopoda • Octopus and squid – the foot is divided into arms with suckers that are used to catch food • Called head-footed mollusks because their foot is under their head • They live in the ocean and swim
Phylum Echinodermata • Sea urchins, starfish, sand dollars, sea cucumbers, brittle stars, basket stars, sea lilies, and feather stars • Live in the ocean • They have an endoskeleton called ossicles • They have radial symmetry • They have a water-vascular system: they pull water into themselves in order to change water pressure around them and work the suction cups on their arms
Class Asteroida • Starfish • Tube feet are the suction cups inside of the rays (arms) that help the starfish grab food and move • They regenerate (if you cut a part off, it will grow back)
Class Enchinoidea • Sea Urchins and Sand Dollars • They have spines that protect them • They are scavengers: they will eat anything
Class Holothuroidea • Sea Cucumbers • They are slow-moving and eat whatever they can trap • When they are attacked, they throw out their internal organs and run away, then regenerate (make) new organs
Class Ophiuroidea • Brittle Stars and Basket Stars • Brittle stars throw away their arms when they are attacked, then regenerate their arms • Basket Stars eat at night – they raise their arms to make a basket shape to trap small animals and eat them
Class Crinoidea • Sea Lilies and Feather Stars • Sea lilies are sessile (don’t move) • Feather stars are able to crawl slowly
