Class 11 Movement and Locomotion
Movement is one of the most important characteristics of living organisms. Nonliving objects do not move. If nonliving objects show movement, that is always due to some external force. For example, the cart is moved by the horse and the fan revolves around the energy of electric current. The movement of a nonliving object is, therefore induced (due to an external force) while the movement of living things is autonomic (self-sustained). Study of movement is called kinesiology (G. Kinein = to move, Logos = study). The movement of living systems are thus autonomic or active, that is affected by the organisms themselves without external influences. On the other hand, the movement of nonliving systems are induced or passive i.e. made to occur by external forces. Movement of animals is two main types muscular and not muscular.
(1) Muscular movement: Muscular movement are found in the majority of animals brought about by sliding of myofilaments. The muscular movement further divides into two kinds: Locomotion and movement of body parts.
· Locomotion (locus = place + move = to move): Locomotion is the movement of an animal as a whole from one place to another.
· Types of locomotion: Locomotion takes several forms such as walking (man), creeping (earthworm, lizard), hopping (frog, rabbit), running (dog, horse), flying (insects, birds) and swimming (fish, whale). Locomotion distinguishes most animals from plants. The word ‘most’ has been used with animals because all animals do not have the power of locomotion. Sponges, many coelenterates (Obelia) and tunicates (Herdmania) are sedentary, i.e., they live fixed to the substratum throughout life. However, even they show the considerable movement of their body parts, and their larvae are capable of locomotion (swimming) to bring about dispersal. Animals have suitable adaptations for their specific mode of locomotion. Adaptations for running, hopping, swimming and flying are respectively called cursorial, saltatorial, natatorial, and volant adaptations. Morphogenetic movement, i.e., the streaming of cells in the early embryo to form tissues or organs, may be considered a form of locomotion.
· Movements of body parts: Movement of the body parts help the animals in several respects.
· Movement of external parts: Many annelids have several pairs of flat parapodia, arthropods have 3 to many pairs of jointed legs, molluscs have an unpaired foot, echinoderms have numerous paired tube-feet, vertebrates have fins in fishes or limbs in all others.
· Movements of internal parts: Visceral movements make many vital activities possible :
o Heartbeats circulate blood in the blood vessels.
o Peristalsis of alimentary canal propels food through it. Segmenting and pendular movements of gut help mix digestive juices with food.
o Movements of diaphragm assist the chest in the flow of air through the respiratory tract.
o Peristalsis propels secretions and wastes through the ducts.
o Movements of genital tract effect egg laying and delivery of the baby.
o Visceral movements are also responsible for sound production, defaecation and micturition.
(2) Non-Muscular movement: Besides locomotion and movements of body parts, some of the cells of multicellular animals move like unicellular organisms.
· Ciliary movement: The cilia present in the trachea, vasa efferentia and oviducts propel by their movements dust particles, sperms and eggs respectively. The cilia of flame cells of flatworms push excretory materials.
· Flagellar movement: The flagella of choanocytes (collar cells) of the sponges maintain a regular current of water in the body. The flagella of certain cells of gastrodermis of hydra help in the circulation of food. Sperms move by flagellar movements.
· Pseudopodial movement: Leucocytes and macrophages move by pseudopodial movement.
· Cytoplasmic streaming movement: Streaming movement of the cytoplasm is called cyclosis. It is observed in most of the cells.
Movement & Locomotion of an animal includes two systems.
(a) Skeletal system
(b) Muscular system
· Skeletal system: Body of animals is supported by the skeleton. That branch of science which deals with bones and cartilage is called Osteology. Bones are made up of a protein called ostein and cartilage are made of a protein called chondrin. Hence study of bones is called osteology and study of cartilage is called chondrology. Whereas skeleton of vertebrates develops most often underneath the surface forming a living or growing endoskeleton. Three types of skeletons develop in vertebrates :
(i) Epidermal horny exoskeleton: These include hard and horny of keratinized derivatives of the epidermal layer of skin, such as claws, reptilian scales, bird feathers and mammalian hairs, horns, nails and hoofs, etc. All living amphibians lack an exoskeleton.
(ii) Dermal bony skeleton: Dermal bony skeleton is derived from the dermis of the skin. It includes bony scales and plates or scutes (osteoderms), fin rays and antlers of fishes, reptiles and mammals. In fishes, dermal scales become exposed due to wearing out of epidermis and form an exoskeleton.
(iii) Endoskeleton: The greater part of vertebrate skeleton lies more deeply, forming the endoskeleton. It develops from mesenchyme. Endoskeleton is formed by bones in vertebrates. Skeleton in different animals are as follows –
· Protozoa – No skeleton.
· Porifera – Calcarius spicules + silicious spicules + spongin fibre.
o Spicules in Porifera represent endoskeleton.
· Coelenterata – Calcareous corals.
· Helminth – No skeleton, cuticle present.
· Annelida – No skeleton, cuticle present.
o In earthworm and Ascaris is hydrostatic skeleton is found that is fluid is filled in coelom and form the turgid skeleton.
· Arthropoda – Chitinous exoskeleton.
o Chitin is modified cuticle.
· Mollusca – Calcarius shell.
· Echinodermata – Calcareous plates are present.
· Vertebrates: In vertebrates, the dermal skeleton is formed by bones. Bone is the connective tissue with intercellular spaces filled with ossein matrix composed of calcium salts 2/3 and calcium oxalate) and organic matter 1/3. In the ossein, osteocyte cells are found and the outer surface of the bone is covered by periosteum. The innermost region is full of bone marrow having various types of cells. In mammals, the bone is full of Haversian canals. The bones are of three types :
o Cartilage bones: The bones which are formed by the ossification of preexisting cartilage are called cartilage bones or replacing bones.
o The membrane or dermal bones: The bones which are formed by independent ossification in connective tissue are called dermal, membrane or investing bones.
o Sesmoid bone: Ossification takes place on Ligament and Tendons.