Movement

Abstract

Movement can occur at the cellular level as cytoplasmic streaming or as the passage of food vacuoles around a cell (cyclosis). Movements of organs could include contractions of the heart or a limb, whereas movement of a whole body is called locomotion. Locomotion is much more common in animals than in plants where only the simplest move their whole bodies e.g. by flagella in some algae. This is presumably the result of differences in nutrition, requiring most animals to seek their food, whereas most plants photosynthesise and do so more effectively stationary. Motility also provides access to new habitats for animals or to a mate for sexual reproduction. At the cellular level movement by gametes, usually just the male, is essential for fertilisation. Plants have evolved more passive methods of spreading by spores and seeds, which avoid overcrowding, but, except in the higher plants, a swimming male gamete is still involved in fertilisation.