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Mollusks, Arthropods, and Echinoderms Ms. Cushman 7th Grade General Science November 16, 2015 Bell Ringer • What seafood have you tried or do you know about? Make a list. What are the main characteristics of mollusks? Characteristics of Mollusks • In addition to a soft body often covered by a shell, a mollusk has a thin layer of tissue called a mantle that covers its internal organs, and an organ called a foot. • Body Structure: bilateral symmetry, two opening digestive system, centralized organs • Circulatory System: Open • Obtaining Oxygen: Gills What are the three kinds of mollusks? Gastropods: Snails and Slugs • Gastropods have a single external shell or no shell at all • Obtaining food: Can be herbivores or carnivores, uses a radula (READ pg 42) • Movement: Creeps along on a broad foot creating and leaving a trail of mucus Bivalves – Oysters, Clams, Scallops, and Mussels • Bivalves are mollusks that have two shells held together by hinges and strong muscles. • Obtaining food: most are filter feeders and omnivores • Movement: They move slowly and may attach themselves to a solid surface during adulthood. • Protection: Some form pearls around sand that would otherwise be an irritant Cephalopods – Octopuses, squids, nautiluses, and cuttlefish. • A cephalopod is an ocean dwelling mollusk whose foot is adapted to form tentacles around its mouth. • Obtaining food: Carnivores, captures prey with tentacles, crushes it in a beak, and then scrapes and cuts it with a radula (Read 44-45) • Nervous system: excellent vision, large brain, can learn • Movement: swim by jet propulsion What are the main characteristics of mollusks? What are the three kinds of mollusks? Bell Ringer • Compare similarities between some sea creatures and insects. Do any look similar in appearance? Do any function similarly? What are the four major groups of arthropods and what are their characteristics? How many species of arthropods have been discovered? Characteristics of Arthropods • Arthropods are invertebrates that have an external skeleton, a segmented body, and jointed appendages • Outer Skeleton – a waxy covering called an exoskeleton that sheds as the animal grows and then is replaced by a new one. • Segmented Body – may be divided in up to three sections: head, midsection, hind section Characteristics of Arthropods • Jointed Appendages: highly specialized tools for moving, obtaining food, reproducing, and sensing the environment • Diversity – Scientists have identified more species of arthropods – over one million – than all other species of animals combined Crustaceans: Lobster, Crab, Shrimp, Crayfish • Body structure: has two or three body sections, five or more pairs of legs, and two pairs of antennae • Obtaining oxygen: most live in water and have gills • Obtaining Food: They are scavengers or predators • Life cycle: starts as swimming larva – goes through metamorphosis Arachnids • Body Structure: Two body sections, four pairs of legs, not antennae. Abdomen is the hind section for digestion and reproduction • Read pg 52-53 • Spiders • Mites • Scorpions • Ticks Centipedes and Millipedes • Body Structure: Two body sections, many pairs of legs • Centipedes - “hundred feet” one pair of legs per segment. • Millipedes – “thousand feet” two pair of legs per segment – These don’t necessarily have that exact number of feet but may be close one way or another. Which one is a millipede and which one is a centipede? How do arthropod groups differ? • Draw Figure 10 on page 49. • Draw Figure 11 on page 50. What are the four major groups of arthropods and what are their characteristics? Bell Ringer • Draw figure 17 on page 56 What are the three main characteristics of insects? Body Structure • Three body sections, uses a system of tubes to get oxygen, six legs, one pair of antennae, and usually one or two pairs of wings, most are camouflaged to avoid predators • HEAD – location of sense organs like antennae and compound eyes and simple eyes • THORAX – midsection where wings and legs are attached • ABDOMEN – houses internal organs What is one way insects are adapted to obtain particular types of food? Obtaining Food • An insect’s mouthparts are adapted for a highly specific way of getting food. – Sponge like mouthpart – Coiled tube like straw – Sharp-edged mouthparts • Look at Figure 18 on page 57 What are two types of metamorphosis that insects undergo? Life Cycle • Each insect species undergoes either complete metamorphosis or gradual metamorphosis • Complete Metamorphosis – four different stages: egg, larva (for growing and eating), pupa, and adult (beetles, butterflies, flies, and ants) • Gradual Metamorphosis – An egg hatches a nymph and it grows into an adult (grasshoppers, termites, cockroaches, and dragonflies) Complete Metamorphosis Gradual Metamorphosis Let’s Review • What are the three main characteristics of insects? • What is one way insects are adapted to obtain particular types of food? • What are two types of metamorphosis that insects undergo? Let’s Draw • Complete and Gradual Metamorphosis • Figure 19 on pages 58-59 Bell Ringer • Would the world be better off without insects? Why or why not? Why are insects important in food chains? What is a food chain? Insects and the Food Chain • PRODUCER – makes its own food (a plant) • CONSUMER – eats other organisms • DECOMPOSER - breaks down wastes and dead bodies • Insects could be CONSUMERS or DECOMPOSERS. They play a key role in the food chain. Insects as Consumers of Plants • Insects play key roles in food chains because of the many different ways that they obtain food and then become food for other animals. • Insects eat 20% of the crops grown for humans and wild plants too. Insects as Prey • The main source for trout and bass is insects • A single swallow chick can eat 200,000 insects before it leaves the nest. Insects as Decomposers • Insects breakdown decaying matter, expose soil to oxygen and nutrients, and clean up waste materials. Insects as Food for Humans (Eww) • Read page 65. • (I was going to insert a photo of a chocolate covered bug, but I just couldn’t. I just couldn’t.) What are two other ways insects interact with their environment? Pollen Carriers • Bees are pollinators and so are many beetles and flies. Without pollinators, some plants cannot reproduce. What plants need bees? Disease Carriers • Mosquitos, fleas, and ticks • Malaria, Yellow Fever • The Plague • Lyme’s Disease, Rocky Mountain Spotted Tick Fever What are some ways used to control insect pests? Controlling Pests • To try to control pests, people use chemicals, traps, and living things, including other insects. • Traps • Plants that aren’t attractive to pests • Biological Controls – predators or diseases that effect only the pest. Why are insects important in food chains? What are two other ways insects interact with their environment? What are some ways used to control insect pests? What are the main characteristics of echinoderms? Echinoderms: Sea Cucumbers, Sea Stars, Sea Urchins, Sand Dollars • Invertebrates with an internal skeleton and a system of fluid-filled tubes called a water vascular system • They all live in salt water • Body structure: Endoskeleton, body parts (usually five) are arranged like spokes on a wheel. They have radial symmetry Echinoderms: Sea Cucumbers, Sea Stars, Sea Urchins, Sand Dollars • Movement: they use tube feet to move slowly and their water vascular system to capture food. • Reproduction and Life Cycle: Eggs are fertilized in the water and grow into tiny swimming larva that eventually develop into adults. What are the major groups of echinoderms? Diversity of Echinoderms • Sea Stars Diversity of Echinoderms Brittle Stars Diversity of Echinoderms • Sea Urchins Diversity of Echinoderms • Sea Cucumbers Quizlet.com • Vocabpirate • Animals Ch 2 Study Guide