- TENTACLES and STING CELLS
Jellyfish, Sea Anemones, Corals (marine),
Hydra (freshwater)
ECHINODERMS > 5 starfish > 8 sea urchin
- tough SPINY SKIN
- RADIALLY SYMMETRICAL, with
5 radiating strips of TUBE FEET
- MARINE
Starfish & Sea Urchins
FLATWORMS (Some free-living,some parasites).
> 1 tapeworm > 2 liver fluke > 3 planarian > 10 flatworm
- dorso-ventrally flattened body !
Flukes, tapeworms, freshwater flatworms
NEMATODES (Roundworms, Eelworms, Threadworms, etc.) > 6 > 7
- THREADLIKE BODY - ROUND in cross-section - many PARASITES and DEBRIS FEEDERS.
What is the advantage to a simple organism of being A) radially symmetrical, and B) flattened?
>A) can react to stimuli/ take food from any direction
>B) no part of the body is far from the outside, so oxygen and food can diffuse easily
ANNELIDS > 12 earthworm > 15 leech > 22 ragworm
- ELONGATED BODY, divided into similar SEGMENTS, with bristles
- earthworms, Tubifex, etc.
- ragworms, lugworms, tubeworms, etc.
- leeches
MOLLUSCS > 13 scallop > 14 ramshorn snail > 25 cuttlefish
(use numbers again below)
- SOFT BODY, usually protected by CHALKY SHELL (greatly reduced in some cases)
- MUSCULAR "FOOT"
- Some are filter feeders.
GASTROPODS - SINGLE SHELL, may be coiled (snails, slugs,limpets) > 14 ramshorn snail
BIVALVES - TWO SHELLS (cockles, mussels, oysters, etc.) > 13 scallop
CEPHALOPODS - TENTACLES, very advanced (cuttlefish, squid, octopus) > 25 cuttlefish
ARTHROPODS ("jointed limbs")
- EXTERNAL SKELETON : hard cuticle
- outnumber rest of animal kingdom!
ARACHNIDS - 8 LEGS (spiders, scorpions,mites & ticks) > 19 spider > 23 scorpion
CENTIPEDES & MILLIPEDES - MANY LEGS > 22 centipede > 18 millipede
CRUSTACEANS - CHALKY cuticle (crabs, lobsters, shrimps, Daphnia, barnacles, woodlice)
> 17 Daphnia ("water flea") > 20 lobster
INSECTS - 6 LEGS (butterflies, moths, dragonflies, locusts, crickets, termites, bugs, beetles, ants, wasps, flies, etc.)
> 16 ant > 21 beetle
What are the advantages and disadvantages of a chalky outer layer (either shell or exoskeleton)?
> advantages: protection, against predators, water currents etc
> disadvantages: heavy (when out of water), must be in neutral/alkaline environment