Invertebrates(Sponges, Cnidarians,Worms, Mollusks, Arthropods, Echinoderms)

I. Sponges A. Phylum Poriferaa. asymmetricb. filter feeders – take in tiny

particles of food from water

1. pores - openings where water enters

2. choanocyteschoanocytes – cells with a flagella that move water through sponge3. osculumosculum – a

large opening where water and wastes exit

c. spicules – form simple skeleton

d. Internal fertilizatione. many other organisms

can live inside sponge (mutualism)

 

spicules

Body of a Sponge

Cnidarians

II. Cnidarians A. Phylum Cnidaria ex: jellyfish, hydra,

coralsa. radial symmetryb. carnivoresc. nematocystsnematocysts - poison filled stinging cells that paralyze or kill preyd. gastrovascular cavity – for digestion; single openinge. transport materials by diffusion

Cnidarians are carnivorous animals that have stinging tentacles arranged around their mouths. Stinging cells called cnidocytes are used to capture and paralyze prey.

f. nerve net – many nerve cells that detect stimuli

g. hydrostatic skeleton – layer of muscles that allow movement

h. external reproduction – separate sexes

i. many other organisms live on corals (mutualism)

 

B. Two Stages of Life Cycle

a. Polyps mouth points upward with arm-like tentacles surrounding it; sessile

b. Medusa motile, bell shaped body with the mouth on the bottom & tentacles hanging around it

III. FlatwormsA. Phylum Platyhelminthes

ex: tapeworms, flukesa. bilateral

symmetryb. simplest

wormc. very flat (<

3mm thick)

d. no coelom – body cavity not from mesoderm

e. pharynx – muscular tube near mouth; important in digestion

f. diffusion – respiration, excretion, and circulation

g. carnivoresh. some are parasitesi. flame cells – remove

excess water and wastes from body

j. ganglia – groups of nerve cellsk. eyespoteyespot – detects changes in lightl. hermaphrodite – has both male and

female reproductive partsm. sexual and asexual reproduction

IV. Roundworms A. Phylum Nematoda ex: hookworms

a. have a pseudocoelom – body cavity between endoderm & mesoderm layers

Roundworms such as hookworms are unsegmented worms that have a pseudocoelom and a digestive system with a mouth and an anus.

b. 2 openings (mouth and anus)

c. predatorsd. diffusione. ganglia – nervous

systemf. muscles &

hydrostatic skeleton

g. sexual reproduction (male and females)

h. parasites 1. ascaris – intestine

parasite2. hookworms –

consume blood and enter through foot

Filarial worms cause elephantiasis

V. Segmented Worms A. Phylum Annelida ex: earthworm,

leechesa. septa –

body segmentsb. true coelom

– body cavity formed from mesoderm

c. digestion1. pharynx2. cropcrop – stores

food3. gizzardgizzard – grinds food

d. closed circulatory system

e. respiration through gills

f. nephridia – excretiong. brain and nerve cordsh. hydrostatic skeletoni. ClitelumClitelum – thick ring

where eggs and sperm are released into

j. leeches – parasites that suck blood

k. Earthworms important to soil ecology (mix soil, wastes provide nutrients for plants); important to food chain

FRIEND!

~ They are decomposers

~ Indicate healthy soil

~ Mix soil

~ Provide channels for root growth