Unit 10: Invertebrates II

13-1: Mollusks13-2: Annelids

13-3: Arthropods13-4: Echinoderms

º Soft-bodiedº Bilateral symmetryº Organsº Usually one or two shells with a

fluid filled cavity

13-1: Mollusks

º Body 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

º Classification– grouped based on presence or

absence of shell– then grouped on shell type and foot

type–Most common groups:

1. Gastropods2. Bivalves3. Cephalopods

º Gastropods–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

º Bivalves– hinged, two-part shell– includes• Clams• Oysters• Scallops• Mussels

º Cephalopods–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

º Importance of Mollusks– Food – Shells• jewelry• shelter for other animals

Cephalopod Bivalve

Gastropod

13-2: Annelids

º Soft-bodiedº Tube shapedº Bilateral symmetryº Mouth & anusº Setae– hair-like bristles on the outside of the body

º Earthworms– 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 O2 and CO2 through skin

– small brain– nerve cord connects all segments• respond to light, temperature, moisture

– hermaphrodites• produce sperm and egg

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

º Leeches– no setae– parasites• feed on blood

– suckers used to attach to animal host

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

13-3: Arthropods

º means “jointed foot”º segmented bodiesº bilateral symmetry

º mouth and anusº nervous systemº separate sexes (males & females)– sexual reproduction

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

º Insects– 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» egg larva

pupa adult

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

º Arachnids– 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

º Centipedes & Millipedes– long bodies–many segments– lots of legs

º Crustaceans– one or two pairs of antennae–mandibles for crushing food– crabs, crayfish, shrimp, barnacles pill

bugs, water fleas

º Importance of Arthropods– food for other organisms– agriculture (pollinators)

– some are pests• insecticides

13-4: Echinoderms

º Means “spiny skin”º Hard endoskeletonº Radial symmetryº Mouth & stomachº Nerve ring

º Water-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

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

º Brittle stars– like sea stars, but have slender arms that

are very fragile– used for defense– use arms to move instead of tube feet

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

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

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