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.
Chital prefer to be near water and will drink in mornings and evenings in hot weather. Predators of the chital include wolves, tigers, Asiatic lions (in Gir Forest only), leopards, Indian rock pythons, dholes, Indian pariah dogs, and mugger crocodiles. Red foxes and golden jackals also sometimes prey on chital fawns.hital prefer to be near water and will drink in mornings and evenings in hot weather. Predators of the chital include wolves, tigers, Asiatic lions (in Gir Forest only), leopards, Indian rock pythons, dholes, Indian pariah dogs, and mugger crocodiles. Red foxes and golden jackals also sometimes prey on chital fawns.