Unit 10: Invertebrates II 13-1: Mollusks 13-2: Annelids 13-3: Arthropods 13-4: Echinoderms

ºSoft-bodied ºBilateral symmetry ºOrgans ºUsually one or two shells with a fluid filled cavity 13-1: Mollusks

ºBody Structure – Mantle thin layer of tissue that covers the body organs secretes shell protects body if organism lacks a shell Mantle

– Mantle cavity space between mantle and body contains gills – organs used for respiration

– Circulatory System open blood is pumped into open areas and surrounds the organs

– Head has a mouth sensory organs some have tentacles foot—very muscular, used for movement MOUTH SENSORY ORGANS FOOT

ºClassification – grouped based on presence or absence of shell – then grouped on shell type and foot type – Most common groups: 1. Gastropods 2. Bivalves 3. Cephalopods

ºGastropods – means “stomach foot” – usually have one shell—except slugs – most have tentacles with eyes at tips

– have a radula tongue-like organ with rows of teeth works like a file used to scrape and tear food – foot glands secrete mucus

– Includes Snails Slugs Conchs Abalones Whelks

ºBivalves – hinged, two-part shell – includes Clams Oysters Scallops Mussels

ºCephalopods – means “head foot” – most complex mollusks – well-developed head – tentacles with strong suction cups – closed-circulatory system (vessels)

– move using jet propulsion – some use camouflage – Includes Squids Octopi Nautilus

ºImportance of Mollusks – Food – Shells jewelry shelter for other animals

Cephalopod Bivalve Gastropod

13-2: Annelids ºSoft-bodied ºTube shaped ºBilateral symmetry ºMouth & anus ºSetae – hair-like bristles on the outside of the body

ºEarthworms – front and back end – segmented bodies – eat soil crop: organ used to store soil gizzard: organ that grinds soil intestine: absorbs nutrients anus: exits the body — wastes are called castings; help to fertilize soil

– closed circulatory system two blood vessels with 5 hearts – no lungs or gills exchange O 2 and CO 2 through skin

– small brain – nerve cord connects all segments respond to light, temperature, moisture – hermaphrodites produce sperm and egg

ºMarine Worms – called polychaetes – means “many bristles” – setae come in bundles sessile or free-swimming

ºLeeches – no setae – parasites feed on blood – suckers used to attach to animal host

ºImportance of Annelids – aerate soil – medicinal uses (leeches) – food for other organisms

13-3: Arthropods ºmeans “jointed foot” ºsegmented bodies ºbilateral symmetry

ºmouth and anus ºnervous system ºseparate sexes (males & females) – sexual reproduction

ºExoskeleton – hard outer covering – some have a waxy coating – has to be shed as organism grows process is called molting

ºInsects – largest group of animals – three body regions — Includes ants, beetles, butterflies, flies, grasshoppers, etc.

– Head two antennae eyes mouth – Thorax three pairs of legs – six legs total wings, if present – Abdomen reproductive organs spiracles – openings through which air enters/exits

– Metamorphosis series of body changes as insects become adults 2 types – Incomplete » smaller versions of parents, just get bigger » eggs nymph adult

– Complete » completely different looks » egglarvapupaadult

– Obtaining Food insects eat a variety of things mouth parts are adapted for types of foods they eat

ºArachnids – spiders, scorpions, mites, ticks – two body regions cephalothorax abdomen

– four pairs of legs eight legs total no antennae Legs

– Scorpions sharp, poison filled stinger also have pincers – Spiders inject prey with enzymes – Mites & Ticks usually parasites carry diseases

ºCentipedes & Millipedes – long bodies – many segments – lots of legs

ºCrustaceans – one or two pairs of antennae – mandibles for crushing food – crabs, crayfish, shrimp, barnacles pill bugs, water fleas

ºImportance of Arthropods – food for other organisms – agriculture (pollinators) – some are pests insecticides

13-4: Echinoderms ºMeans “spiny skin” ºHard endoskeleton ºRadial symmetry ºMouth & stomach ºNerve ring

ºWater-vascular system – system of water-filled canals with tube feet tube feet: hollow tubes with a suction cup – used for movement, capture food, release wastes, and breathing

ºSea Stars – at least 5 arms arranged in a circle – reproduce sexually by releasing sperm & eggs – reproduce asexually by regeneration

ºBrittle stars – like sea stars, but have slender arms that are very fragile – used for defense – use arms to move instead of tube feet

ºSea urchins & Sand dollars – disk or globe shaped – covered with spines

ºSea Cucumbers – soft-bodied with a leathery covering – tentacles around mouth – expel internal organs

ºImportance of Echinoderms – feed on dead organisms – some used in medicine – control other animal populations