BIOL10005 Study Guide - Symmetry In Biology, Arthropod Leg, Triploblasty
Document Summary
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.