The Animal Kingdom Chapter 2: Mollusks, Arthropods and Echinoderms

Phylum Mollusca: Snails, Clams, Squid Characteristics: All have soft bodies and bilateral symmetry. The Latin word, “mollis” means “soft”. Most secret hard, calcium carbonate shells to protect themselves.

Although they don’t look much alike at first, a snail, a clam, and a squid have the same basic body structures.

Basic body pattern of most mollusks: 1. Head: containing the mouth 2. Muscular foot: for crawling, digging, or swimming. 3. Mantle: a thin layer of tissue that surrounds the main body organs. The mantle secretes the shell. 4. Gills: used to breath oxygen from water.

Classes of mollusks include: Gastropoda (stomach-foot) —snails, slugs, and sea slugs. *One shell (univalve) *Live in the water or on land *Make beautiful sea shells

Attack of the Cone Snail 2:41 *Use a flexible ribbon of tiny teeth called a radula to get food. *Some are herbivores *Some are carnivores Mouth Attack of the Cone Snail 2:41 Radula Snail Zombies 1:53 Radula Teeth

Bivalvia (two-shells)-- clams, oysters, scallops and mussels. *Filter feeders—most are omnivores *Economically important as food *Used in production of pearls.

A razor clam digs into the mud by changing the shape of its foot. - Mollusks A razor clam digs into the mud by changing the shape of its foot. Giant Clam Video 1:45

3. Cephalopoda (head-foot) —octopus, squid, cuttlefish, and chambered nautilus. *Muscular foot is divided into tentacles for swimming. *Complex and intelligent. *Range in size from 1-60 feet. *Carnivores *Crawl or swim by jet propulsion

Octopus regeneration 2:03 *Not all cephalopods have a shell Octopus—no shell Squid—internal shell Octopus regeneration 2:03 Octopus flexibility Chambered Nautilus external shell Squid video 3:38

Phylum Arthropoda: Jointed Legs Characteristics: Largest group of animals with over 1 million species known. That number may be as high as 10 million.

Exoskeleton made of chitin Exoskeleton made of chitin. Must be shed from time to time in a process called molting. Segmented bodies All have jointed appendages (legs, antenna, pinchers and claws) Open circulatory system Bilateral symmetry One-way digestive tract

Five classes: Arachnida, Crustacea, Chilopoda, Diplopoda, Insecta

Crustaceans: crabs, lobsters, crayfish, shrimp and pill bugs. *Most have two body regions: cephalothorax and abdomen. *Five pairs of appendages including large pinchers on most. *Most have two pair of antenna

Fiddler crab Pill Bug Crayfish

2. Arachnids: spiders, scorpions, mites and ticks. *Most have two body regions: abdomen cephalothorax. *simple eyes *poison glands, fangs or stingers *four pair of legs

Spiders are found everywhere Spiders are found everywhere. They spin webs using spinnerets in their abdomen.

Scorpions are found in tropical areas and hunt insects and spiders.

Ticks are external parasites that feed on the blood of a host Ticks are external parasites that feed on the blood of a host. Some transmit Lyme Disease and Rocky Mountain Spotted Fever. Mites are usually found in dust and are mostly harmless.

3. Chilopoda: centipedes *Long, flat bodies with one pair of legs per body segment. *Carnivores: eat snails, slugs and worms and can bite humans.

4. Diplopoda: millipedes Long, rounded bodies with two pairs of legs per body segment. Plant eaters: will not bite humans

5. Insects: largest group of arthropods Three body segments: head, thorax and abdomen. Three pairs of legs attached to the thorax. One pair of antenna. Some have one or two pairs of wings; some have no wings. Large, compound eyes; some also have simple eyes. Open circulatory system.

Wings Antenna Thorax Head Abdomen Compound Eyes 3 Pair of Legs

All insects undergo metamorphosis *This is a process in which an animal’s body undergoes dramatic changes in its life cycle. *Two types of metamorphosis: Complete and Gradual

-Stages of Complete Metamorphosis: *Egg, Larva, Pupa, Adult (Beetles, bees, butterflies, flies and ants use complete metamorphosis)

- Insects Life Cycle An insect with complete metamorphosis has four different stages: egg, larva, pupa, and adult.

Stages of Gradual Metamorphosis: *Egg, Nymph, Adult (Grasshoppers, termites, cockroaches and dragonflies use gradual metamorphosis)

- Insects An insect with gradual metamorphosis has no distinct larval stage. An egg hatches into a stage called a nymph, which usually looks like the adult insect without wings.

Phylum Echinodermata: Seastars 6,000 species of spiny-skinned animals All have radial symmetry. “Echinoderm” means “spiny-skin”. Have an internal skeleton made of spines that extend out through the body.

All live in the ocean. Move using a water-vascular system and tube feet. Most can regenerate lost body parts and can occasionally reproduce this way.

Characteristics of Echinoderms Echinoderms, such as this sea star, have a water vascular system that helps them move and catch food. Tube Feet Stomach Madreporite Water Vascular System

Examples of echinoderms: 1. Sea stars and brittle stars: have 5 or more arms lined with tube feet. Feed on clams by inserting their stomach into the clam and digesting it inside the shell.

2. Sea urchins and sand dollars: do not have arms 2. Sea urchins and sand dollars: do not have arms. Covered with movable spines used for defense and movement.

3. Sea cucumbers: leathery skin with no spines 3. Sea cucumbers: leathery skin with no spines. Spits out its internal organs to confuse predators.