Invertebrates

Chapter 28

Sponges (Phylum Porifera) Body is made of pores that water enters

through. Has a large opening where water leaves. Sponges are sessile (cannot move) The lining of the internal cavity is made of collar cells that act as sieves to trap plankton and other food

Sponges (Phylum Porifera) Sponges have a skeleton made of spicules. A spicule is made of silica or calcium carbonate. Can reproduce both sexually or asexually. Asexual – pieces of sponges can regenerate Sexual – (most are hermaphrodites) Sperm cells

from one sponge enter another through pores.

Cnidarians

Body forms:1. Medusa – free-floating, and umbrella-shaped2. Polyp – tube like and attached to something There are tentacles around the opening of the

gastrovascular cavity. They have stinging cells with a barbed harpoon

used for defense and to spear their prey

Cnidarians Examples:1. Hydras2. Jellyfish – sting prey with tentacles (some

have toxins)3. Sea anemones – polyp form, feed on fish,

reproduce asexually4. Corals – live in reefs, tough skeleton of

calcium carbonate

Phylum Platyhelminthes (Flatworms) Can be parasitic Include:1. Marine flatworms2. Tapeworms – parasitic, attach to host’s intestines.

Grow producing proglottids (rectangular body sections)

3. Parasitic flukes – have suckers to attach to host

Phylum Nematoda (Roundwoms) Have a body cavity called pseudocoelom (fluid

moved within this cavity) One way digestive system Some are parasites you find in dogs, others

are free living hunters Human parasites include:1. Ascaris lumbricoides2. Trichinella spiralis3. Necator

Phylum Molluska Includes:1. Snails2. Slugs3. Oysters4. Clams5. Scallops6. Octopuses7. Squids Found in marine, freshwater and terrestrial

habitats

Phylum Molluska Characteristics:1. Bilateral symmetry2. Foot – used for movement Mantle – forms the outer layer of

the body3. Most have one or two shells4. Radula – tongue-like organ

found in the mouth

Phylum Molluska Most species have male and female

individuals. Some, though, are hermaphrodites (some

species of slugs and snails) Oysters and sea slugs can change from one

sex to the other and back again

Phylum Molluska Gastropods1. Snails and sea slugs2. Most have a single shell and a pair of

tentacles on their head with eyes at the tip3. Can secrete mucus from their foot to glide

along4. Can be herbivores or predators

Phylum Molluska Bivalves1. Most marine, some freshwater2. Clams, oysters, scallops, mussels3. Two-part hinged shell4. Some use jet propulsion to move quickly5. Most are filter feeders

Phylum Molluska Cephalopods1. Squid, octopuses, cuttlefish and nautiluses2. Body is made of a large head attached to

tentacles3. Tentacles have suction cups or hooks to

catch prey4. Most intelligent invertebrate5. Some have color vision6. Move via jet propulsion7. Marine predators, feeding on fish, mollusks,

crustaceans and worms

Phylum Annelida (Segmented worms) Marine worms, earthworms, leaches Have a primitive brain in an anterior

segement Have specialized organ systems Bristles called setae on each segment

Phylum Arthropoda Named after their jointed appendages. Includes: insects, spiders, scorpions,

crustaceans Segmented Exoskeleton (the crunch you hear when you

squish them)

Phylum Arthropoda

Arachnids1. Spiders, scorpions, ticks, mites2. Most are carnivores, inject their prey with

enzymes to dissolve tissue

Phylum Arthropoda Insects1. Ants, mosquitoes, flies, bees, crickets2. Largest group of organisms3. Head, thorax, abdomen

Phylum Arthropoda Crustaceans1. Crabs, lobsters, crayfish, shrimp, barnacles,

water fleas and pill bugs2. Major food source for humans3. Barnacles are sessile as adults and they

have hard plates used for protection. They are also hermaphrodites but typically don’t fertilize their own eggs

Phylum Echinodermata Spiny invertebrates that live on the ocean

floor Sea stars, brittle stars, sea urchins, sea

cucumbers Endoskeleton make of calcium Radial symmetry Water-vascular system – tubes filled with

water connected to hallow tube feet

Phylum Echinodermata Sea stars – carnivores Brittle stars – thin, branched arms for

movement Sea lilies and feather stars – very old, mouth

located on the upper surface

Phylum Echinodermata Sea urchins and Sand dollars – spines for

protection, sometimes venom Sea cucumbers – soft, no arms. Some are

hermaphrodites. They trap food in the water with tentacles

Sea daisies – no arms

Invertebrate Chordate Skeleton is completely internal. A rod called the notochord develops along the

back of the embryo Pharyngeal pouches – later develop into gills

in aquatic animals

Invertebrate Chordates Tunicates – adults are sessile, hermaphrodites Lancelets – found in shallow ocean water.

Draw water through their mouth with cilia