Mollusks are soft-bodied invertebrates that usually have one or two shells. They have a mantle that covers their organs and secretes shell material. Mollusks are classified based on their shells and feet into gastropods like snails, bivalves like clams, or cephalopods like squid. Arthropods are the largest animal group with over 1 million species. They have jointed appendages and segmented bodies with an exoskeleton. Examples include insects, spiders, and crustaceans. Echinoderms have a hard endoskeleton and radial symmetry, examples are sea stars and sea urchins.

1. Higher Animals Chapter 13

2. Mollusks Mollusks are soft-bodied, invertebrates, that have bilateral symmetry, and usually one or two shells. Mostly they live in water but some live on land. Snails, clams, and squid are examples. All mollusks have a mantle, or a thin tissue layer, that covers all of its organs. The mantle contains gills, which exchange CO2 for the oxygen in the water. The mantle also secretes the shell of the mollusk, which protects the animal. As the mollusk grows more shell material is produced. Mollusks have open circulatory systems which means that blood is pumped into open spaces that surround organs.

3. Mollusk classification First we classify them by seeing if they have shells. The ones that do have shells are then classified by the type of foot that they have. Gastropods- Largest group, and include snails, and conches. These mollusks have a single shell and a radula, which is a tongue like organ used to obtain food. They move contracting their muscular foot, that secretes mucus to allow them to slide in a particular direction.

5. Bivalves These mollusks have a hinged two part shell, and are clams, muscles, and oysters. They open and close these shells by using muscles near the hinge. These shells can be used for both protection from predators and can also be used to help in movement of the mollusk through the water. H.W.- pg 368 ques. 1-4

6. Cephalopod These are the most complex of the mollusks. Squids, octopi belong to this group. These are predators and feed on fish and other marine organisms. They have well developed nervous systems with a large eye and closed circulatory systems. Blood does not pool up and surround the organs here, it is pumped into the organ by tiny vessels. Cephalopods are great swimmers and can propel themselves by filling up a hollow body cavity and squeezing it out to shoot them in a certain direction.

7. Segmented Worms or Annelids These worms have tube shaped bodies and are divided into many segments. Each segment contains setae, or a brisstle like structure that aids them in moving around in the ground. They have bilateral symmetry, a body cavity that holds organs, and 2 body openings, a mouth and an anus. Ex: earthworms, leaches

8. Body structure They have a front end and a rear end, and over 100 body segments. Each segment has 4 pairs of setae. They have a set of muscles that runs the length of the body and a set that circles the body. When they move soil enters its mouth and moves to the worms crop, which is like a stomach that is used for storage. From the crop the food will move to the gizzard where the food is ground up. From here the food is pushed through the intestine where nutrients are absorbed, and eventually passes through the anus.

9. Circulation and Nerves Annelids have a closed circulatory system with two blood vessels along the top of the body and one below the body. They join at the front end of the worm at a heart like structure called aortic arches. They get oxygen by absorbing it from the air into their skin. They have a small brain that has a nerve chord that connects the brain to nerves in each segment of the worm. They are hermaphrodites but reproduce sexually. H.W. pg 373 ques. 1-4

11. Arthropods This is the largest group of animal, and has over a million species. They have jointed appendages. These include legs, antennae, claws, and pinchers. They have bilateral symmetry, segmented bodies, an exoskeleton, and digestive and nervous systems. Their exoskeleton cannot grow with them so they go through a shedding process called molting. When this occurs the arthropod is very unprotected.

12. Insects Insects are part of the arthropod group. Their bodies are composed of three regions, a head, a abdomen, and a thorax. The head- has a pair of antenna, eyes and a mouth. The antennae are used for touch and smell, and the eyes can be simple or compound, meaning they have many lenses. Thorax- These segment contains three pairs of legs, and sometimes, 1 or 2 pairs of wings. Insects are the only invertebrate that can fly.

13. Insects Abdomen- This sections contains the reproductive structures, and an open circulatory system. The open circulatory system carries digested food to cells and removes waste. Insects do not have blood to carry oxygen, but they have spiracles, or openings in the thorax and abdomen which oxygen passes through and waste gases leave.

14. Insects They obtain food by eating plants, the blood of animals, nectar, decaying materials, wood, and clothing materials. Depending on the type of diet that an insect has, they will have different mouth pieces. Grasshoppers have large mandibles (jaws) that allow for chewing grass. And bees will have siphons that they use to lap up honey.

16. Arachnids Spiders, scorpions, mites, fleas, and ticks are arachnids. They have 2 body regions, a cephalothorax, and an abdomen. They have 4 pairs of legs and no antennae. They kill their prey using fangs or stingers that are connected to poison glands.

17. Centipedes & Millipedes They have long bodies with many segments, exoskeletons, jointed legs, antennae, and simple eyes. They make nests for their eggs and stay with them until they hatch. Centipedes hunt their hunt their prey which included snails ,slugs, and worms. Millipedes feed on plants and decaying material found under damp plant material.

18. Crustacean Crabs, lobster, shrimp are examples of these. These live in water and have 1 or 2 pairs of antennae and mandibles that are used to crush food. Mostly they live in water, but some live on land, like pill bugs. They have 5 pairs of legs, one of which is a set of claws. All of these legs have the ability to regenerate. H.W. pg 382 ques. 1-4

19. Echinoderms Echinoderms have a hard endoskeleton that is covered by a thin, bumpy or spiney epidermis. Ex: Sea star They have a mouth stomach and intestines and also radial symmetry, which allows them to sense food and prey all around them. They have no brain or head, but do have a nerve ring that surrounds the mouth.

20. Echinoderms They have a water-vascular system, a network of water-filled canals with thousands of tube feet connected to it. Tube feet are small suction cupped feet that allows the animal to move. A sea star is an echinoderm that has at least 5 arms arranged around a central point. They have thousands of tube feet on them.

22. Echinoderms Sea Urchins & sea dollars and disk or globe shaped animals that are covered in spines. They do not have arms but they do have spines for protection. H.W. 394 ques. 1-15