Broader definitions of chemicals or chemical substances can be found, for example: the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including â (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature.
The major groups of worms include various species of flatworm, annelid, ribbon worm, spiny-headed worm, and aschelminth. Worms typically have an elongated, tubelike body, usually rather cylindrical, flattened, or leaflike in shape and often without appendages.
manipulate in the laboratory. Despite obvious physical differences, model organisms and humans share many key biochemical and physiological functions that have been conserved (preserved) during evolution. The nematode worm C. elegans is one of sev-eral organisms commonly studied by biological researchers today. C. elegans is a microscopic roundworm. Although some roundworms are para-sitic, C. elegans is a free-living worm that feeds on soil bacteria. These worms grow