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Locomotion And Movement In Plants And Animals


Both plants and animals respond to external stimuli. They react to these factors by showing a series of movements. The stimulus is sent from one part of the body, the ‘receiving zone’, to another part of body, the ‘reaction zone’.

The resultant reaction in the movement of plants is different from that of animals. For example, in plants, it involves only the movement within the body or often movement of organs of the body such as flower and roots. The entire plant body does not move.

In animals, the entire body moves from one place to another. This movement of the whole organism from one place to another is called locomotion.

Movement and locomotion are indispensable for all the vital activities of animals. This phenomenon is observed in all the animal forms, ranging from the acellular protozoans to the multicellular and complex animals such as humans.

Movement in Plants


Plants, unlike animals, do not move from one place to another and respond to any external stimuli. Instead, they exhibit behaviours such as growing in a particular direction or opening and closing their leaves. There are two kinds of movements in plants, namely nastic movements and tropic movements (tropism).

Nastic Movements
 These movements are response to stimuli coming from all directions.

  • For example, in tulip and crocus, change in temperature acts as the stimulus for the flowers to open and close. When the temperature rises they open, and when it drops they close.
  • Closing of the carnivorous venus fly-trap leaf when it captures a prey and folding of the Mimosa leaf when it is disturbed are also nastic movements. Folding of leaf of Mimosa is referred to as seismonasty movement.
  • Tropic Movements The response of an organism in the direction of a stimulus or away from it is called tropic movement or tropism. Tropic movements are of various types, in response to different stimuli.
  • When a young green plant receives light from only one direction, the stem grows towards the light source. Thus, the stem is said to be positively phototropic because the stem tip grows in the direction of light.
  • Geotropism is the tropic response of organisms to gravity. When a growing portion of the plant is placed horizontally, the stem tip grows away from the pull of gravity, while the root tip grows towards it. Thus, the stem is said to be negatively geotropic, while the root is positively geotropic.
  • The growth of roots towards soil moisture is called hydrotropism.
  • Thigmotropism is a growth in response to touch, e.g. tendrils on contact with a solid object, such as a twig, response curvature in that direction producing coiling around the object.

Locomotion or Movement in Animals

  • Animals exhibit three basic types of movements, namely amoeboid, ciliary and muscular.
  • Amoeba, an active unicellular animal, presses its cytoplasm against the cell membrane and produces a number of finger-like projections called pseudopodia. This type of locomotion is called amoeboid movement.
  • Euglena, which is pear-shaped or spindle-shaped, swims by means of a flagellum. The flagellum is held straight in front and the tip is rotated. This pulls the body of the organism forward through the water.
  • Paramecium moves with the help of tiny hair-like projections from the cell membrane called cilia. Cilia are arranged in rows and they lash through the water like tiny oars.
  • Multicellular organisms like Hydra have a strange looping or somersaulting motion. Hydra bends over, attaches its tentacles to the surface, swings the base over its mouth and attaches itself on the surface again. After loosening the tentacles, it repeats the process.
  • An earthworm uses its body muscles and setae to grip the ground so that the body can move forward by regular contractions and expansions of the muscles.
  • Insects such as grasshoppers and locusts have six-jointed legs and wings. The last pair is longer, stouter and more powerful to help them to hop.
  • Fishes use their fins against water to swim. Side fins help them steer. The fin at the back provides them balance.
  • Birds are the most common flying animals. They use their wings to fly and their two legs to walk or jump when they are not flying.

Locomotion in Humans


Movements in humans are performed by two types of independent systems, namely muscular system and skeletal system. Movements of internal organs are controlled by muscular system whereas locomotion and movement of most external body parts are brought about by coordination of both the systems.

Muscular System
In humans, the muscles are of three types, namely skeletal, smooth and cardiac muscles.

  • Skeletal muscles are made up of myofibrils, which consist of sarcomeres. Skeletal muscles are attached to the bones by tendons and help in the movement of the parts of the skeleton. These muscles are under the control of conscious mind and are called voluntary muscles. Anisotropic band of skeletal muscle fibre refers to its dark band.
  • Skeletal muscles show transverse strips and hence are called striated muscles.
  • Cardiac muscles are also striated and under involuntary control.
  • Contraction of muscles results from the sliding of the actin and myosin filaments into each other.
  • Calcium and magnesium ions are necessary in the chemical events of muscle contraction.

Skeletal System The skeletal system, i.e. bones and joints, working interdependently with the skeletal muscle system, provides basic functions that are essential for life.

 The study of bones is called osteology. Bone cells are called osteoblasts. The total number of bones in adult human is 206. Axial skeleton in man is made up of 80 bones and appendicular skeleton is made up of 126 bones.

  • Skull of man is made up of 22 bones.
  • Foramen magnum is found on posterior side of the skull.
  • Seven cervical vertebrae are present in the neck.
  • The femur is the longest, largest and strongest bone.
  • Ribs which form the lateral walls of thoracic cage are of 12 pairs. The first 7 pairs of ribs reach the sternum directly and are called true ribs. The 8th, 9th and 10th pair of ribs which are attached to the sternum indirectly are called false ribs and 11th and 12th pair of ribs fall short of the sternum and are called floating ribs.
  • The primary function of pectoral girdle is to provide an attachment point for the numerous muscles that allow the shoulder and elbow joints to move.
  • The pelvic girdle is formed of two innominate bones or coxal bones. Each coxal bone has three separate parts, namely iliumischium and pubis. Two halves of pelvic girdle is joined by pubic symphysis.
  • Ear ossicles have three small bones, namely incus, malleus and stapes. Stapes is the smallest bone in mammals.
  • Cartilage is a soft tissue which is found between the bones or at the end of two bones. It acts as a shock absorber and reduces friction in the joints as the bones move upon one another or rub against each other.
  • Ligament is a short band of tough fibrous connective tissue. It connects one bone to another.
  • Tendon is a fibrous connective tissue that connects muscle to bone.
  • Joints: Bones articulate with each other at joints. Muscular contractions move the bones at the joints.
  • At fixed or fibrous joints, the articulating bones are firmly held together by a white fibrous tissue so that the bones are not allowed to move at such joints.
  • At slightly movable or cartilaginous joints, the opposing surfaces of the articulating bones are joined by white fibrocartilage, allowing a limited movement at the joint.
  • At freely movable or synovial joints, a slippery synovial fluid occurs in the space between the articulating surfaces of bones. Its lubricating action permits considerable movements at such joints. The synovial joints are classified into ball and socket joints, hinge joints, pivot joints, gliding joints and ellipsoid joints according to the movements they permit.
  • Arthritis and osteoporosis are the widespread diseases related to bones, affecting mainly the elderly person.

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