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Simple Animals. L2 Biology. A breakdown of the animal kingdom reveals many phyla. Porifera - sponges Cnidaria – jellyfish, coral Platyhelminthes – flat worms Nematoda – round worms Annilida – segmented worms Mollusca – clams, snails, squid Echinodermata - starfish
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Simple Animals L2 Biology
A breakdown of the animal kingdom reveals many phyla • Porifera - sponges • Cnidaria – jellyfish, coral • Platyhelminthes – flat worms • Nematoda – round worms • Annilida – segmented worms • Mollusca – clams, snails, squid • Echinodermata - starfish • Arthropoda – insect, spider, crustacean • Chordata– frogs,fish, humans SIMPLE ANIMALS
Cnidaria (formerly called Coelenterata) • All have stinging cells (cnidocytes) • Two body forms: • Medusa – like a jelly fish • Polyp – like a hydra • Radial symmetry • Have tentacles
Cnidarian Cnidocyte Have you ever been stung by jellyfish?
Cnidarian Life Cycle – medusa and polyp alternate medusa polyp egg larva
Hydra Hydroid Polyp body form
Hydra Anatomy mouth tentacles testis bud Gastrovascular cavity ovary Basal disc
Coral is actually a colony of polyps, most of which are the size of a single hydra – they just make a case around them for their home.
- Platyhelminthes • Have flat bodies • Some are parasitic • Most are free-living
These are free-living flatworms Planaria
Scolex – head with hooks and suckers Tapeworms – the ultimate parasite –only highly developed system is its reproductive system - hermaphroditic
Phylum Nematoda - roundworms • Mouth – digestive tube – anus • Most free-living • Some parasitic • Look like threads in the microscope
Hookworm Enters through soles of feet Larvae in human feces Causes fatigue – may cause physical and mental retardation if children have it Trichina From undercooked pork Causes severe muscle aches when larvae migrate from intestine to muscles Some are parasitic to humans • Filaria • Causes elephantiasis • No treatment • Carried by mosquitoes
Elephantiasis • Caused by filaria – the worm blocks the lympatic vessels and the area swells with lymph. No treatment is available.
Phylum Annelida • Segmented worms • Includes earthworms and leeches • Most are free-living • Complex body with organ systems • hermaphroditic
Phylum Arthropoda • Jointed legs • Chitinous exoskeleton • Ventral nerve cord • Must molt to grow • Some undergo metamorphosis • Includes insects, crustaceans, spiders, millipedes and centipedes
Class Insecta • Six legs • May have wings • Undergo metamorphosis • Varied mouthparts • Breathe using spiracles
Class Arachnida – 8 legs, no antennae, simple eyes, chelicerae, scorpion tick Dust mites spiders
CCrustacea – two body regions = cephalothoraxmost live in water