Invertebrate animals
Invertebrates have no internal skeleton (backbone). Protozoa have a body of a single cell with digestive and contractile vacuoles, and divide to multiply: amoeba, euglena (green, photosynthesises and swims with a flagellum) and paramecium. Coelenterates (hydra, sea anemone, jellyfish) have a body of two layers – ectoderm and endoderm – and catch prey and defend themselves with stinging cells; they regenerate well. Flatworms (white planarian, liver fluke, bovine tapeworm) have flat bodies with no body cavity; many are parasites. Roundworms (ascaris, guinea worm, root-knot nematode) are round in cross-section, covered with a cuticle, and have a body cavity. Annelids (earthworm, nereis, leech) have a body divided into rings and a circulatory system; the earthworm loosens soil. Molluscs (snail or slug, bivalve, octopus) mostly have a shell; the bivalve cleans water. Arthropods have jointed bodies and legs and an outer skeleton of chitin: crustaceans (crayfish), arachnids (spider, 8 legs) and insects (ladybird, 6 legs). The ladybird’s bright colour is a warning colour, and it helps by eating aphids.
Make “Who is who?” cards for the seven phyla: the animal’s name on one side (for example leech), its phylum and main feature on the other. Quiz each other in pairs. Safety: outdoors do not pick up insects and spiders with bare hands, as they may sting or bite; do not touch jellyfish and other sea animals; use a spade for digging only with adults; to avoid parasitic worms, wash fruit and vegetables and wash your hands with soap.