June 20, 2018
Locomotion is important to all organisms for various purposes like to find food, to mate, to escape from predators, for survival purpose, etc. and altogether, they influence in locomotive organ evolution process in animals. Locomotive organs are different in nature from one species to other. Muscles play important role in movement of the animals. In higher animals along with muscles, bones also associate for the movement. Animal movements can differentiate as walk, run, swim, fly, crawl and jump. Bacterial movement can classify as flagellar, spirochaetal and gliding movement. Single cell organisms also show crawling like movement often called amoeboidal movement as well as they show cillary movement, flagellar movement. Nature of movement is different in plants in which roots, branches, leaves move in response to environmental abiotic factors but overall the plant is non-movable. Here we discuss the different types of locomotion or movement and their mechanisms briefly.
Locomotion can defined as an ability to move from one place to another. The organs which helps for the locomotion is called as locomotive organs. Ex: limbs, flagella, cilia, etc.
Locomotion in single cell organisms
Prokaryotic and eukaryotic single cell organism do movement for their survival, growth and reproduction.
Bacteria are single cell prokaryotic organisms. They show three different types of movements. They are
- Flagellar movement
- Spirochaetal movement and
- Gliding movement.
Mechanism of these movements are partially understood.
Bacteria can move in liquids with help of flagellum. Depends on number of flagella, arrangement over cell surface, bacteria were named differently like monotrichous, lophotrichou,amphitrichous and peritrichous. According to the arrangement they are classified into different classes and those bacteria are motile.
Flagellum is a lash-like cell surface appendages and it consists of protein flagellin. It generally divided into 3 portions and they are basal body, hook and filament. Basal body areimplanted in cell wall. Basal body of the flagellum has M (motor) ring, S(stator) ring and C ring. M and s ring together bind with peptidoglycan layer of the bacteria whereas c ring present in the cytoplasmic region. Basal body is connected with the filament by hook. Flagellum can rotate either clockwise or anticlockwise. Further basal body has around 40 proteins including ‘mot’ proteins and ‘fli’ proteins which are essential in the active movement through proton pumping mechanism. Ex. for flageller bacteria Vibrio, Spirillum, Salmonella,Klebsiella, etc..
Spirochetes are Class V bacteria. The movement of Spirochetes is called as spirochetal movement. Spirochetes are long right handed helically shaped bacteria. Axial fibrils and periplasmic flagellum, present in the periplasmic region of the bacteria, overlapped together and run one sub-polar end to other of the Spirochetes. The mechanism of Spirochetal movement is not clear, however the proposed anticlockwise rotation of the flagellum can lead the bacterial movement. Classical example for this type movement is Treponemapallidum.
Group of gliding bacteria show non flagellum based gliding movement. Fimbriae like appendages (pili), present at polar region, involve in the gliding movement with the help of motor system A and S along chemosensory system ‘Frz’. Here coordinated movement of two different motor system, known as S and A system, response for the motility of bacteria.But their mode of action is unclear. Ex. Myxococcus, cyanobacterium, Oscillatoria.
But other hypotheses like generation of contractile waves or surface tension or pushing by secreted slime was also proposed as possible mechanisms of gliding
Eukaryotic single cell movement
Both single cell life forms as well as multicellular life forms are exist in eukaryotes. According to the life form they adopt their own mode of locomotion.
Protozoan are single cell eukaryotes. Theyare following different type of locomotion according their life form. Amoeba is a single cell protozoa. It can migrate with the help of pseudopodia and this movement is called as amoeboid movement. Most of the time amoeba move to get the food. Various hypotheses regarding the amoeba movement: front contraction hypothesis, tail contraction hypothesis, ectoplasmic contraction theory, cytoplasmic streaming, sol-gel theory, etc., Here we discuss the simple ameboidal locomotive sol-gel theory.
The simple mechanism of amoeba movement as follows
- Swelling of the plasmagel results pseudopodia in response of semipermeable membrane turgidity.
- Movement of plasmasol towards the pseudopodia with simultaneous contraction of plasmagel
- Gelation of plasmosol results enlargement of pseudopodia
- Adhesion to the food particle.
Most of non-flagellated cells often follow the amoeboid movement. Ex. Macrophages
Euglena is another single cell eukaryotic organism. Euglena contains flagella as well as pellicular structure. Euglena can move by waving the flagella. Pellicular structure of the euglena also help them to move. Adjacent pellicular strips move very quickly thus by changing own shape euglena can move without the help of flagella.
Paramesium (ciliary) movement
Paramesium is one more single cell eukaryotic organism which show cilia movement. Dense hair like cilia is present on entire outer surface of the euglena. In a coordinated manner, cilia move one after one all over the body result the paramecium movement.
Movements in animal cells
Animals, insects, birds, reptiles and fishes are multicellular eukaryotes. They migrate in three different modes. They are amoeboid movement, ciliary movement and muscular movement.
Amoeboid movement: In animal cell migration is possible by cytoplasm streaming which followed by the formation of pseudopodia. In animal cells, microfilament involvement is observed in amoeboid movement.
Ciliary movements: Cilia is the short form of the flagella present in ciliated epithelium. Coordinated movements of cilia helping those cells to migrate. The function of cilia almost similar to flagellum.
Muscular movement: In higher organisms, muscles based movement is very common. Coordinated function of muscles, skeletal and neural systems results the muscle movement.
Locomotion in lower animals
In lower animals skeletal system is underdeveloped or absent. In such condition they have to use muscles or specialized locomotive organs for the locomotion. Ex. Earthworms, snails, snake, fishes, etc.
Locomotion in Earthworm
Long tube like structured earthworm moves underground by means of waves of muscular contraction. During muscular contraction body segments are alternatively shorten and lengthen. A special type S-shaped setae ring present in all segments of the earthwork except first, last and clitellum which help to anchor the surrounding soil. Mucus lubrication secretion make easier of their movement in soil.
Locomotion in Snake
Snakes also use muscles for their locomotion. Four types of locomotion were identified in snakes. They are lateral undulation, rectilinear movement, concertina movement and sidewinding. In common lateral undulation mode, wave like muscle reflexion from head to tail results the locomotion.
Locomotion in Sea-anemone
Bilateral sea-anemone moves by radial operation of radial pedal. Sea-anemone creeps in the direction of plane of symmetry
Locomotion in fishes
Fishes swim by using their specialized locomotive organ fins. While moving the fins, the generated thrust help to move to the fish. With the help of multiple fins fishes can control the direction of movement.
Locomotion in cockroach
Cockroaches have wings as well as legs. Primarily they use the legs for the locomotion and as well as they can use the wings too for the locomotion.
Locomotion in Higher animals:
Large number of animals use limbs for their movement in which muscles are attached
endoskeleton or exoskeleton. In vertebrates endoskeleton muscle system is present in which muscles are attached external portion of the bones. But in arthropods exoskeleton muscle system is present in which muscles are attached inside of the skeleton system.
In birds, limbs are developed into wings as well as legs. Such differentiation is absent in vertebrates
Most of the insects use limb system for their movement but they follow different mode of locomotion according to their systems.
Movements in plants
Plants also show movements like phototrophism, gravitrophism.
In response to light, plant grow towards the light. This phenomenon is called as phototropism. Whereas signalling molecules have their own roles in this process. Auxin is one them. It triggers shoot growth. Stems show positive phototropism and roots show negative phototropism.
The growth in response to gravity is called as geotrophism. Roots show positive geotrophism and stems show negative trophism. Here again auxin plays an important role in geotrophism.
Plant movement against contact stimuli is called as thigmotropism. Climbing plants such as vines are the examples of thigmotropism. When the plant touches some surface, the cell which contacts the surface secrete the auxin to the untouched neighbour cell and induce them to grow long. This results bending around the object.