BIOL10005 Study Guide - Symmetry In Biology, Triploblasty, Coelom
11 Nov 2013
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No symmetry, organs, systems, mouth or gut. Diploblastic (no mesoderm), but with mesoglea (gelatinous layer) at centre acoelomate. Have cnidocytes (stinging cells) which contain nematocysts (stinging filament) on their tentacles. Examples: hydra (polyp) with mouth surrounded by tentacles, jellyfish (medusa), corals and anemones (polyps) are colonial. Protostome (mouth developed first) have a gut. Example: tapeworms (parasites, made up of reproductive units, not segments as such) Triploblastic (have mesoderm) and coelomate (have a coelom) allows for girth. Examples: marine worms (mostly sexual), earth worms (hermaphrodites, sexual), leeches (feed on blood, sexual -> hypodermic impregnation) Chitinous exoskeleton protection, muscle support, prevents desiccation) Moult (shedding of exoskeleton) common to nematodes as well. Jointed appendages: chelicerata (scorpions, spiders, myriapoda (centipedes, millipedes, crustacea (mostly marine, biramous appendages limbs split into 2 or are branched, 2 pairs of antennae) Insects (mostly terrestrial, wings for flight, uniramous appendages limbs unbranched, head, thorax and abdomen) Chitinous exoskeleton protection, muscle support, prevents desiccation.
