Movement of internal organs are essential for the animals because:
(i) Food and urine are moved forward by the movements of the muscles present in the digestive and urinary tracts respectively.
(ii) Movements of cardiac muscles enables the heart to receive and distribute the blood.
(iii) Inspiration and expiration involves the movements of the diaphragm, ribs, etc.
(iv) Movements of uterine wall enable the mother to give birth to a child.