Evolution is the process by which this occurs and it is spread out over many generations. Thus, the short minimal definition of biological evolution is, Evolution is a process that results in heritable changes in a population spread over many generations. This is a good working scientific definition of evolution; one that can be used to distinguish between evolution and similar changes that are not evolution.
Bone, cartilage, or dentine is used in the Ostracoderm fish and turtles. Chitin forms the exoskeleton in arthropods including insects, arachnids such as spiders, crustaceans such as crabs and lobsters (see arthropod exoskeleton), and in some fungi and bacteria. Calcium carbonates constitute the shells of molluscs (see Mollusc shell), brachiopods, and some tube-building polychaete worms.
What is the function of chitin? Chitin is a polysaccharide (polymer of sugar [saccharide],  monomers) that is found in the exoskeletons of arthropods (insects,  crabs, lobsters, shrimp), mollusks, and in t â¦ he   beaks of cephalopods (squid and octopus).It is also found in the  cell walls of fungi.hat is the function of chitin? Chitin is a polysaccharide (polymer of sugar [saccharide],  monomers) that is found in the exoskeletons of arthropods (insects,  crabs, lobsters, shrimp), mollusks, and in t â¦ he   beaks of cephalopods (squid and octopus).