Part II: Invertebrates Diversity of Life Part II: Invertebrates

What is an animal? Celltissueorganorgan systemorganism Major functions: obtain food and oxygen, keep internal conditions stable, move and reproduce Vertebrates (have backbone) and invertebrates(do not have backbone – 97%) Symmetry: Balanced arrangements of parts -Bilateral, radial, none

Sponges Live in water (oceans, lakes, rivers) No symmetry, no tissues or organs Gets food by filtering the water that flows over it Reproduce by budding or sexual reproduction (sperm released into water and fertilize eggs from another sponge)

Cnidarians Ex: Jellyfish, corals and sea anemones Use stinging cells to capture food and defend themselves 2 Body structures: either polyp or medusa Both have radial symmetry, central hollow cavity and stinging cells Some just one body type, others go through stages of both Obtain food by first stinging then using tentacles Food goes to central cavity, digests and undigested food expelled out the mouth

Worms Invertebrates with long, narrow bodies Bilateral symmetry, head and tail end Have tissues, organs and body systems Simplest organisms with a brain (detect objects, food, mates, responses to environment with sense organs) Reproduce sexually (contain both sex organs, exchange sperm) and asexually (breaking into pieces)

Types of worms Flatworms: flat and soft as jelly. Most are parasites (lives inside or on another organism -host), some are free-living (Ex: Tapeworm) Roundworms: Live in any moist environment, cylindrical bodies, have digestive system that is open at both ends (food travels 1 direction) Segmented worms: Bodies made up of many linked sections (ex: earthworm), closed circulatory system (blood vessels). Quicker blood flow

Mollusks Ex: Clams, oysters, scallops, snails, squid Invertebrates with soft bodies often protected by hard outer shell Has a thin layer of tissue called a mantle that covers its internal organs, and has an organ called a foot. Open circulatory systems Water mollusks have gills for oxygen Gastropods, Bivalves and cephalopods

Types of mollusks Gatropods: (snails, slugs) single external shell or no shell. Move with foot that secretes mucous. Bivalve: (oysters, clams ) 2 shells held together by hinges and strong muscles. Uses foot to move. (Pearls form to cover unwanted grain of sand that gets stuck in shell) Cephalapods: (octopus) ocean dwelling mollusk whose foot is adapted to form tentacles around its mouth. CLOSED circulatory system (only mollusks to have this)

Arthropods Invertebrates that have external skeleton, segmented body, and jointed attachments called appendages Exoskeleton (waxy, waterproof covering):keep them from drying out, and protection First animals to live on land Molts when it needs to get a new exoskeleton (b/c growing)

Types of Arthropods Crustaceans: 2-3 body sections, 5+ pairs of legs, 2 pairs of antennae (crayfish) Arachnids: 2 body sections, 4 pairs of legs, no antennae (spiders, scorpians) Centipedes and Millipedes: 2 body sections and many pairs of legs Insects: 3 body sections(head, thorax, abdomen), 6 legs, 1 pair antennae, 1-2 pairs of wings

Echinoderms Invertebrates with an internal skeleton (endoskeleton) and a system of fluid-filled tubes called a water vascular system. Move using water vascular system squeezing water into sticky tube feet Sea stars, sea urchins, sea cucumbers