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.
Flatworms are the simplest of the worm groups. There are about 20,000 species in this group. They are found many places and can be free living or parasitic. A parasite lives off of another living thing called a host and can be harmful. One of the best known flatworms is the tapeworm.