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Invertebrates What is an animal? An animal is... • • • • Multicellular. Eukaryotic. Heterotrophic. An organism whose cells lack cell walls. 95% of all animal species are grouped in an informal category: invertebrates. • This group is defined by describing a characteristic that its members do not have - a backbone! • They range in size from microscopic dust mites to the giant squid. When we want to compare invertebrates, we talk about how they are structured and how they carry out essential functions: • • • • • • • Feeding Respiration Circulation Excretion Response Movement and reproduction. There are eight phyla of invertebrates that we will be briefly be discussing. Or they be asymmetrical and have no equal divisions, like Our first group of invertebrates the SPONGES . 3. Sponges are “filter feeders ’. Water enters through pores, bringing food in with it. Collar cells have flagella, which move to help bring water in. 6. Sponges may reproduce either asexually by budding.. Characteristics of Sponges • Habitat - most found in warm, salty water • Movement - sessile (scientists originally thought they were plants because they didn’t move) • Symmetry - asymmetrical, some radial • Method of feeding - filter feeders • Special structures – Pores - bring water into body – Collar cells - move water along with flagella – Spicules - small needlelike structures between cells that give body structure – Spongin - skeleton of fibrous material • Reproduction – asexually by forming buds – Regeneration – Sexually by forming sperm and eggs (hermaphrodites) Characteristics of Cnidarians • Latin for stinging cells – Examples include corals, sea anemones, jellyfish, hydras • Habitat - most in salt water, some hydras in fresh water – Hydras, corals are colonial Cnidarians have two different body types: 1. Polyp - vase-shaped and attached 2. Medusa - bell -shaped and free-swimming Jellyfish (illustration) Copyright (c) Grolier Interactive Inc. • Movement - some sessile, some freeswimming • Symmetry - radial • Method of feeding - Most capture food • Special structures – Polyp - shaped like vase (hydra) – Medusa - bell-shaped, free swimming (jellyfish) – Tentacles - armlike structure around mouth – Stinging cells with harpoon like thread and poison, used to capture food Hydra (coelenterates) Copyright (c) Science Photo Library • Reproduction - asexual and sexual – Polyp • produce buds • Or can produce eggs or sperm – Medusa • Form eggs and sperm, develop larvae • Larvae grow into polyps, new medusae bud off Flatworms and Roundworms Tapeworm Copyright (c) Grolier Interactive Inc. What is a worm? • A worm is an invertebrate with a soft body and bilateral symmetry. • There are flatworms, roundworms and worms with segments. • Segmented worms are not part of this phyla. Flatworms • They belong to the phylum Platyhelminthes. • This phylum includes planarians and tapeworms. Characteristics of Flatworms • Habitat - salt water (some fresh water) • Movement – Free-living ones such as planarians move by secreting a mucous track and then using their cilia to move through the mucous. – Parasitic ones like tapeworms use hooks and suckers to attach themselves to the intestines of a host organism. • Symmetry - Bilateral • Method of Feeding – Planarians feed on small organisms and dead bodies; have a mouth, pharynx, and digestive tract – Tapeworms feed by absorbing food already digested by the host. No mouth or digestive system • Special structures – Planarians - triangular shaped head, two eye spots – Tapeworms - have hooks and suckers • Grow new segments behind the head • Reproduction – Planarians • reproduce asexually by dividing in two • Can regenerate • Can produce eggs or sperm and can exchange sperm with one another, then lay eggs – Tapeworms • Each body segment makes eggs and sperm, fertilizes itself, breaks off; eggs hatch in another host Characteristics of Roundworms • Belong to phylum Nematoda • 500,000 species, including heartworm • Habitat - soil, animals, plants, fresh and salt water • Movement - Muscles contract against fluid • Symmetry - bilateral • Method of Feeding – Digestive system with mouth and anus • Special structures – Body is tube within a tube, with fluid in between – Three well developed tissue layers • Reproduction – Male and female worms reproduce sexually Harmful Roundworms • Hookworms - acquired by walking barefoot over dirt; eventually move to intestines • Ascaris - acquired by eating contaminated food or water; eventually move to intestines causing severe illness damaging lungs, intestines and brain • Trichinella -acquired by eating undercooked pork that has been contaminated, eventually causing fever, vomiting, pain and stiffness • Heartworm - harmful to dogs; acquired by dog through bite of infected mosquito, move to heart and damage heart Characteristics of Mollusks • Mollusks are soft bodied invertebrates that usually have shells. • There are three classes of mollusks gastropods, bivalves and cephalopods. • Habitat - land, fresh water or salt water • Movement – Slugs and snails contract their foot muscles and slide along a layer of mucus they have secreted – Mussels and oysters cement themselves to a surface – Scallops close shells quickly to move – Octopus and squid move by jet propulsion • Symmetry - bilateral • Method of Feeding – Snails, slugs conches and other gastropods obtain food by scraping and tearing – Clams are filter feeders – Octopus and squid kill and eat other animals • Special structures – -Mantle - a thin layer of tissue that secretes the shell or protects the body – Gills - organs that exchange oxygen and carbon dioxide with the water – Visceral mass - area of mollusk that contains body organs – Muscular foot - used for movement – Open circulatory system - blood bathes organs rather than being contained in veins and arteries • Reproduction - most have separate sexes – A male octopus uses one of its tentacles to transfer sperm from its mantle cavity to the mantle cavity of the female. Then the female lays fertilized eggs and guards them until they hatch Gastropods • Largest class of mollusks • Includes snails, slugs, abalones, whelks, sea slugs and conches • Also called univalves • Except for slugs, have single shell, pair of tentacles and eyes at the tips • Have radula, a tongue-like organ with rows of teeth used to scrape Slug Copyright (c) Grolier Interactive Inc. Snail anatomy Copyright (c) Grolier Interactive Inc. Bivalves • Have two-part shell joined by a hinge • Include clams, oyster and scallops • Use a muscle to open and close shell Clam Copyright (c) Grolier Interactive Inc. Cephalopod • Also called head-footed • Include squid, octopus and chambered nautilus • Large developed head with foot divided into many tentacles (8 in octopus, 10 in squid, 94 in nautilus) with suckers for capturing prey • Well-developed nervous system,and enlarged eyes • Also have closed circulatory system • All live in oceans • Bodies are adapted for swimming • Some think the coloration of octopuses is a form of communication Nautilus (mollusk) Copyright (c) Grolier Interactive Inc. Squid Copyright (c) Grolier Interactive Inc. Octopus Copyright (c) Fred Winner/Jacana, Photo Researchers Characteristics of Annelids (Segmented Worms) • Habitat - fresh water, salt water and moist soil • Movement - Use bristle-like structures called setae on the outside of each segment • Symmetry - bilateral • Method of feeding – Earthworms eat soil. Soil passes through digestive system including crop, gizzard and intestine. Undigested soil and waste leave worm through anus. • Special structures – Earthworms • have blood vessels and five hearts with a closed circulatory system • have nerves that respond to light, temperature and moisture • have a small brain • exchange oxygen and carbon dioxide through skin Worm Copyright (c) Grolier Interactive Inc. • Leeches – Have no setae – Have two suckers which are used to attach to an animal – Feed on blood of ducks, fish and humans; suck out two to ten times its weight in blood – Produce an anesthetic • Leeches – Prior to 1900s doctors used leeches to drain blood from sick people – Today leeches are used to keep blood flowing to reattached body parts. – Leech saliva contains anticlotting chemical that may be used with heart patients • Marine worms – Include species that float, burrow, build structures, walk on the bottom or produce their own light – Have setae that occur in bundles – Have fleshy outgrowths on their segments called parapodia which help in feeding and movement • Scientists infer that mollusks and segmented worms share a common ancestor because – both have bodies with space for organs – both have a similar larva stage • Reproduction – hermaphrodites – must reproduce with another worm Characteristics of Arthropods • This is the largest phylum of animals. This phylum includes insects, shrimps, spiders and centipedes. • Name means jointed foot, which describes the jointed appendages (structures that grow from the body) • Bodies are segmented; this suggested a common ancestor with segmented worms • Three body parts - head, thorax and abdomen • Also have body cavity, digestive system with mouth and anus, nervous system, larger brain than annelids • Also have exoskeleton – External covering that supports, covers and protects the body – Made of protein and chitin – Is shed and replace by molting • Arthropod is vulnerable during this time Insects • 700000 classified species • Body plan – Head - includes pair of antennae, eyes and mouth • Simple eyes detect light and dark • Compound eyes can detect colors and movement • Antennae use touch and smell – Thorax - 3 pairs of jointed legs and possibly 1 2 pairs of wings – Abdomen - 11 segments and no wings or legs Butterflyanatomy Copyright (c) Grolier Interactive Inc. Grasshopper Copyright (c) Grolier Interactive Inc. • Open circulatory system • Blood does not carry oxygen • Spiracles , openings on abdomen and thorax bring in air and give out waste gas • Reproduce sexually; females lay thousands of eggs • Go through series of changes called metamorphosis – Complete -four stages • Egg, larva, pupa and adult – Incomplete -three stages • Egg, nymph and adult • Short life span • Small size allows them to live in a wide range of environments Butterflylife cycle Copyright (c) Grolier Interactive Inc. Other arthropods • Arachnids - spider – – – – Two body regions Four pairs of legs No antennae Have poison glands, stingers or fangs to kill prey – Appendages near mouth hold food • Centipedes and millipedes – Long bodies, many segments • Crustaceans – – – – One or two antennae Jaws called mandibles used for crushing food Most live in water Five pairs of legs • First pair are claws – Appendages on the abdomen are called swimmerets • Help with movement and reproduction – Can regenerate lost parts Crayfish Copyright (c) TomMcHugh, Photo Researchers Characteristics of Echinoderms • Spiny-skinned invertebrates that live on the ocean bottom • Feed on dead organisms and help recycle materials • Most have radial symmetry • Move by means of a water-vascular system – Network of water-filled canals – Thousands of tube feed connected – Tube feet act like suction cups • Feed by using tube feet to open the shells of mollusks • Importance – Invertebrate group closely resembles the chordates – Viewed as advanced because the embryo develops the same way that the embryos of chordates do There are several classes of echinoderms • • • • Sea stars Brittle stars Sea urchins and sand dollars Sea cucumbers Starfish(illustration) Copyright (c) Grolier Interactive Inc. • Sea stars – Five or more arms – To feed - opens shell with feet, turns its stomach inside out, surrounds the soft body of the mollusk – Reproduce sexually – Can regenerate Starfishregeneration Copyright (c) Grolier Interactive Inc. Brittle star (illustration) Copyright (c) Grolier Interactive Inc. Sea urchin Copyright (c) Grolier Interactive Inc. • Brittle stars – Move quickly and break off arms as a defense – Can quickly regenerate • Sea urchins and sand dollars – Have skeletons made of calcium carbonate plates – Covered with spines • Sea cucumbers – Soft bodied with leathery covering – Tentacles around mouth – When threatened may expel internal organs