Variety of Locomotion
A number of animals are sendentary, remaining attached to some substratum. These animals may move parts of their body but this does not result in the movement of the animal from one place to another place. Conversely most animals make slow or swift movements from one place to another. This may include crawling, creeping, leaping, walking, swimming or flying. These organelles may be temporary formations like pseudopodia in Amoeba or may be permanent differentiations of the cell such as cilia and flagella. The metazoans are, though, characterized by the development of specialized contractile tissue called muscles for this aim. The motile machinery required for movement in metazoans may have simple or specialized organs of locomotion and operates mainly based on the contraction and relaxation of related muscles. Though the locomotor machinery appears to be quite different in protozoans' on the one hand and metazoans on the other, the basic components involved are identical. They involve fibrous threads which are polymerisation products to large protein molecules. These threads contain contractile properties. When these are related with skeletal structures, these bring about movement. We are here concerned along with how muscles bring about locomotion in animals.