15D – Other Invertebrates

Page 468 – 473

Phylum Mollusca2nd largest animal phylum3 Classes

Class BivalviaClass GastropodaClass Cephalopoda

Phylum MolluscaOctopus, oysters, snails, slugs, squid, clamsAll Mollusca have the following:

Mantle: protects the organs (insides); helps it breathe

Shell: hard outer covering; protects the bodyVisceral Hump: holds the heart, stomach, and

excretory organs (where it pees and poops)Foot: allows it to moveRadula: organ with small teeth that grabs food

and pulls the food into the mouthBabies are called trochophore

Phylum Mollusca

Class BivalviaOysters, clams, mussels, and scallopsThis class has a shell with two halvesCalled “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 Bivalvia

Class GastropodaCalled Stomach-footed mollusks because they

have their foot under their visceral humpSnails, slugs, nudibranchesUsually move by crawlingUsually 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 Gastropoda

Class CephalopodaOctopus and squid – the foot is divided into

arms with suckers that are used to catch foodCalled head-footed mollusks because their

foot is under their headThey live in the ocean and swim

Class Cephalopoda

Phylum EchinodermataSea urchins, starfish, sand dollars, sea

cucumbers, brittle stars, basket stars, sea lilies, and feather stars

Live in the oceanThey have an endoskeleton called ossiclesThey have radial symmetryThey 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

Phylum Echinodermata

Class AsteroidaStarfishTube 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 Asteroida

Class EnchinoideaSea Urchins and Sand DollarsThey have spines that protect themThey are scavengers: they will eat anything

Class Enchinoidea

Class HolothuroideaSea CucumbersThey are slow-moving and eat whatever they

can trapWhen they are attacked, they throw out their

internal organs and run away, then regenerate (make) new organs

Class Holothuroidea

Class OphiuroideaBrittle Stars and Basket StarsBrittle stars throw away their arms when

they are attacked, then regenerate their armsBasket Stars eat at night – they raise their

arms to make a basket shape to trap small animals and eat them

Class Ophiuroidea

Class CrinoideaSea Lilies and Feather StarsSea lilies are sessile (don’t move)Feather stars are able to crawl slowly

Class Crinoidea