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Invertebrates 2 There are more than 100,000 species of mollusks Most live in the ocean, but some can live in freshwater, some even on land No matter what their shape or size, they all have the same basic body plan Mollusks are soft bodied invertebrates with a muscular foot and a mantle Phylum Mollusks Soft body ◦ Covered with a skinlike tissue called a mantle In many mollusks, the mantle produces a hard shell Contain organs organized into systems ◦ Most organs in located in one area of their body called a visceral mass Muscular foot ◦ Used for movement Characteristics of Mollusks You can tell that snails are very different from clams… And that both are different than an octopus… They are all examples of mollusks! ◦ They just belong to different classes within the mollusk phylum Diversity of Mollusks Mollusks that glide along on a foot underneath their bodies are called gastropods ◦ Ex. Snails, slugs Most have one coiled shell, but not all ◦ Limpets have flattened cone shaped shells ◦ Slugs and nudibranches have no shell at all Gastropods Most eat plants and algae, some eat other invertebrates As an adaptation for getting their food, gastropods have a tongue-like organ covered with rows of teeth called a radula ◦ Gastropods move their radula back and forth to scrape off and scoop up food Gastropods Eating Gastropods that live in water have respiratory organs called gills ◦ As water flows over the gills, oxygen is extracted Gastropods living on land have evolved a cavity inside their bodies that serves as a simple lung Gastropods Breathing The octopus and squid are the major members of a second class of mollusks called cephalopods In cephalopods, the foot is divided into tentacles Cephalopods Mollusks with two shells hinged together make up a third class called the bivalves ◦ Ex. Clams, oysters, mussels, and scallops Have no head Move very little, some remain attached to one place Muscular foot ◦ Shaped and used differently than a gastropod foot Normally hidden inside the two shells Move by hooking the foot in sand then pulling themselves along Bivalves Bivalves use gills to get oxygen ◦ They have a large surface area and a rich supply of blood ◦ Oxygen from the water passing over the gills circulates into the blood ◦ Carbon dioxide, which is a waste product of animals, is moved from the blood back into the water In some kinds of bivalves, water flows over the gills when the shells are open In clams, the water enters through a muscular tube called a siphon ◦ After it flows over the gills, it leaves through another siphon Bivalves Breathing Bivalves are filter feeders Cilia move water across the gills Tiny food particles, such as plankton, are trapped by mucus on the gills Cilia then push the food into the animal’s mouth Bivalves Eating Arthropod means “joint foot” The largest of all animal phyla About 85% of all animals are arthropods!! More than a million different species Some are so tiny you can barely see them Some can grow to more than 4m across Phylum Arthropoda Jointed appendages Segmented body ◦ Head Has appendages used for sensing and feeding ◦ Thorax Holds legs for movement ◦ Abdomen Contains most organs Exoskeleton Characteristics of Arthropods Arthropods are the only invertebrates with jointed appendages ◦ Appendages are parts that extend from the body ◦ Used for movement, defense, feeding, sensing, and even reproduction ◦ A single arthropod may have a great variety of appendages, each adapted for a particular use Jointed Appendages Arthropods’ bodies are covered by an outer support structure called an exoskeleton ◦ Similar to a suit of armor worn by a medieval knight ◦ Waterproof and helps prevent the loss of body fluids ◦ Provides support for the body ◦ Hard for protection but more flexible around the joints Liquid secreted that hardens quickly to form the exoskeleton Some are thin and flexible Others are very thick and rigid Exoskeleton The arthropod’s exoskeleton doesn’t grow with its body When the body gets too big for its exoskeleton, it goes through a process called molting Molting Just before an arthropod molts, it makes a new, thin, flexible exoskeleton under the old one The old exoskeleton splits along the top surface and the animal crawls out The arthropod swallows as much water and air as it can to make itself as large as possible and waits until the new armor has hardened ◦ Very vulnerable and nearly defenseless as it is waiting Molting Process Spiders, ticks, scorpions, and mites are all arachnids Two main body regions ◦ Cephalothorax: head and thorax fused together Four pairs of legs attached ◦ Abdomen ◦ In ticks and mites, the cephalothorax and abdomen are also fused together Arachnids Spiders produce a liquid form of silk in glands and spin the silk into thread with spinnerets ◦ When the liquid silk is exposed to air, it becomes strong and solid ◦ Make different kinds of silk for catching prey, making sacs for eggs, and anchoring webs Not all spiders spin webs, but all produce silk Spider Silk Spiders usually eat insects They catch them in their web Once trapped, the spider will inject a poison into the insect that paralyzes it Next the spider injects its digestive enzymes into the insect and sucks out its insides that have become liquefied Catching Prey Oxygen goes into the spider’s blood through book lungs Book lungs are made up of sheets of tissue like the pages of a book ◦ It gives them a large surface area for gas exchange Spider Breathing Although the word centipede means “100 legs” in Latin, most centipedes have about 30 legs ◦ Each body segment has one pair of legs ◦ Predators that eat insects, snails, slugs, & worms ◦ Have poison claws, antennas, mandibles, and the ability to move very quickly Millipedes are slow moving and eat plants and decaying organic material ◦ More segments than centipedes, but still 2 legs per segment Centipedes and Millipedes Crayfish, barnacles, crabs, shrimps, lobsters, water fleas, pill bugs, and sow bugs are all crustaceans Crustaceans Have mandibles, which are jaw-like appendages used for chewing and crushing food Have 2 pairs of antennas that are used for balance and sensing ◦ Other arthropods have one pair but no others have two pairs Have eyes that have multiple lenses called compound eyes ◦ Very sensitive to light and movement ◦ Don’t produce a single image like human eyes Characteristics of Crustaceans Crayfish are typical crustaceans Large claws attached to their thorax to grab food, protect itself, and walk Behind the claws are four pairs of walking legs Like all crustaceans, crayfish have appendages on their abdomen ◦ For swimming Crayfish Most crustaceans move around freely, but barnacles remain attached to one place Many barnacles produce hard, volcano shaped shelters ◦ Inside this shelter is a crustacean with jointed appendages Appendages used to paddle food into the barnacle’s mouth when it is under water Barnacles Another class of arthropods are the insects More species of insects than any form of life combined Insects Ability to adapt to many different habitats ◦ From high mountains to dry deserts to rivers and wetlands to your backyard Ability to fly ◦ Helps insects find food, escape predators, locate mates, and reach new places to live Flexible adaptability ◦ In the process of evolution, insect body parts have been modified for different ways of living ◦ Changes in mouthparts allow different species ability to eat different food Insect Advantages Three pairs of legs Only arthropods that have wings ◦ Most but not all have them Three body regions ◦ Head, thorax, abdomen Insects have tiny openings called spiracles in its thorax and abdomen for air to enter and flow through tubes called trachea ◦ Oxygen diffuses from these tiny tubes into the body cells Body Structure of Insects All insects reproduce sexually ◦ In most species the eggs are fertilized inside the female’s body by a male’s sperm ◦ Many insects lay their eggs on a food source so the young can begin to eat right after they hatch Most insects don’t look exactly like their parents when they hatch from their eggs ◦ As they grow, they undergo a process called metamorphosis ◦ During metamorphosis, a young organism changes its appearance to become an adult Insect Reproduction Some insects, such as grasshoppers, go through an incomplete metamorphosis This is a series of molts in which the insect changes from an egg to a nymph to an adult ◦ A nymph looks like a little adult, but it has no wings and is not yet able to reproduce Incomplete Metamorphosis Most insects go through complete metamorphosis, which involves a more complete change of appearance ◦ Bees, wasps, flies, beetles, butterflies, and moths all go through it They change from eggs to larvae to pupae to adults ◦ In the larvae stage, the insect usually looks like a worm ◦ During the pupa stage, the insect does not eat or move around In many species the pupa is surrounded by a cocoon The insect is changing rapidly, forming adult structures ◦ When metamorphosis is complete, an adult insect emerges Complete Metamorphosis Most insects live on their own, but some species live together in colonies They are called social insects Social insects include termites, most ants, bees and some wasps The members of the colony have specialized functions and a system of communication that allows them to work together smoothly Social Insects Honeybees are a common example of social insects ◦ Some bees go out of the hive to collect flower nectar ◦ Some turn sheets of wax into the combs for honey to be stored ◦ Queen bees lay eggs ◦ Some (nurse bees) care for and feed the young larva Honeybees What the larva are fed determines their development ◦ Larva fed honey and pollen develop into worker bees (always female) or into males called drones The worker bees egg-laying structures become modified as a stinger ◦ Larva fed “royal jelly” develop into queen bees that have both egg-laying structures and stingers Queen bees are only produced when the hive starts to become overcrowded The first larva that becomes a queen bee leaves the hive to find the first drone to mate with and becomes the new queen of the hive ◦ The worker bees kill all the other developing queen bees ◦ The old queen takes half the worker bees and start a new community Determining Roles The male drones are produced when the queen lays an unfertilized egg Drones do almost nothing in the colony Only one drone mates with the queen Toward the end of the summer, the worker bees either kill or chase all of the drones out of the hive ◦ They are no longer needed for the survival of the community Drones How does oxygen reach an insect’s body cells? What is a social insect? Give an example and explain why social behavior helps the group survive. What determines whether a female larva will become a worker bee or a queen bee? What is the difference between a larva and a nymph? How is each different from an adult insect? Choose an insect that you are familiar with. Write a paragraph describing its body structure. Draw a picture and label its body parts. Homework Head Thorax ◦ ◦ ◦ ◦ 3 simple eyes, 2 compound eyes Upper and lower lips 2 jaws that bite sideways instead of up and down Pair of antennae that have tiny sensory hairs for smell and touch ◦ 3 pairs of jointed legs First 4 used for walking, last 2 used for jumping ◦ 2 pairs of wings Abdomen ◦ Spiracles on each side for breathing ◦ Tympanum (eardrums) on each side ◦ Females have an egg-laying device called an ovipositor on the end of their abdomen that they can dig a hole to lay their eggs in Grasshopper External Anatomy Brain is in the upper part of the head ◦ Connected with and receives messages from the eyes Two nerve cords pass around the esophagus and join together underneath to form another brain-like structure (ganglion) Ventral nerve cord ◦ Runs along the ventral side of the body to the tail end Grasshopper Nervous System Crop: food stored here Gizzard: food ground up Stomach: digestive juices secreted where the food is digested Intestines: digested food is absorbed into the blood stream Rectum: undigested food is sent here where water is reabsorbed into the blood stream Anus: unused materials are eliminated here Grasshopper Digestive System Spiracles: breathing pores on outside of abdomen Spiracles open into air tubes called trachea that branch to all parts of the body ◦ Trachea is lined with a constant film of moisture Some are connected to large air sacs in the thorax and abdomen ◦ Muscles cause the body to contract and expand with pumps air in and out of the air sacs Body cells absorb oxygen directly from the air tubes Grasshopper Respiratory System Males have testes that produce sperm Females ◦ Have ovaries that produce eggs ◦ Have ovipositor (egg-laying equipment) that allows for digging a hole to lay fertilized eggs into Grasshopper Reproductive System
