The original Animal Kingdom proposed by Linnaeus included the protozoans, sponges, jelly fishes, worms, crabs, insects, spiders, snails, starfishes, sharks, bony fishes, frogs, lizards, birds and mammals. In general, animals exhibit the following distinguishing characters.
* The animal body generally exhibits a definite symmetry, form and shape.
* Animals have the capacity to move from place to place in search of their necessities.
* Growth in animals is determined and occurs proportionately in all parts of the body.
* Animals are generally heterotrophic, obtaining their food from plants and other animals.
* Animals have the property of irritability - the capacity to respond to a stimulus.
* The cells, which form an animal's body do not have a cell wall. Plastids and vacuoles are generally absent and centrioles & lysosomes are present.
* Animal cells cannot synthesize all the necessary amino acids, vitamins and coenzymes and as such will have to obtain them from external sources.
* Reserve food is glycogen.
Classification of Kingdom Animal