What is locomotion in Protoctista and invertebrates and vertebrates?There are varieties of organisms which have evolved different modes of locomotion. Let’s discuss in detail locomotion in Protoctista and invertebrates are as under;
LOCOMOTION IN PROTOCTISTA AND INVERTEBRATES
LOCOMOTION IN EUGLENA
Euglena moves with the help of flagellum. As the flagellum is whipped backward the organism moves forward. However, when flagellum moves’ forward the Euglena does not backwad. Locomotary flagellum is at its anterior end of the body and pulls the organism forward. Waves of activity are generated by itself, and they pass in a spiral fashion from the base of the flagellum to its tip. They increase amplitude and velocity. The activity of the flagellum caused the body of Euglena to rotate forward about its axis.
Euglena is able to change its direction by the active contractile myonemes which lie along the length of its body. When they contract the shape of the body is changed as well as its direction. First body becomes short and wider at the anterior end then in the middle and later at the posterior end. This characteristic movement is called Euglenoid movement.
LOCOMOTION IN PARAMECIUM
Paramecium moves with the help of cilia. This is called ciliary movement. All the cilia do not move simultaneously but a bunch of cilia move in a progressive wave-like manner at a time. The wave starts at the anterior end and progresses in the backward. Cilia are short, fine thread-like extensions of the cell membrane. The length of cilia ranges. from many microns to many hundred microns and the diameter varies from 0.1 to 0.5u.
Internal structure of cilia: A cilium consists of nine peripheral double fibrils giving an appearance of the 8-shaped figure and two central smaller fibrils. All these fibrils run longitudinally through the cilium. These are covered with the extensions of the membrane.
Mechanism of movement: The exact mechanism of movement of cilia is not known. However, in 1955 Bradford suggested that movement of cilia is due to simultaneous contraction or sliding of double fibrils in two groups one after the other.
i) Effective stroke: Five out of nine (5/9) double fibrils contract or slide simultaneously, cilia bend o/ shorten. It is called an effective stroke.
ii) Recovery stroke: The four out of nine double fibril contract and cilia become straight. It is called Recovery stroke.
As a result of bending and recovery stroke, the paramecium swims against water.
Energy for the movement; The energy for the movement provided from the ATP. The enzyme present in the cilia breaks up ATP to release energy.
Coordination in ciliary action: The action of the cilia is coordinated and all the cilia beat together in a sequence to propel’ the animal ‘in one direction.
LOCOMOTION IN AMOEBA
In Amoeba, the movement takes place by means of Pseudopodia. The Pseudopodia are finger-like projections thrown in the direction of movement. After the formation of Pseudopodia, the organism attaches with the substratum and pull the body in the forward direction. The exact mechanism of formation of Pseudopodia is still debatable.
LOCOMOTION IN JELLY FISH
Jellyfish has an umbrella – like body called bell. First of all, water enters the bell then the bell contracts, the water is forced out like a jet and the animal moves forward. This movement is known as jet propulsion.
LOCOMOTION IN EARTHWORM
Earthworm shows accordion- like movement, in which setae and muscles both are involved. First of all earth worm becomes long and thin. The setae present on the lower side of anterior end come out, anchor and hold this end firmly. The longitudinal muscles now contract and circular muscles relax and body shortens thus pulling this portion forward. Then the setae of the posterior, end come out and fix the animal on the ground. Now circular muscles contract, longitudinal muscles relax and body again becomes thin and long. In this way, earthworm moves from one lace to the other.
LOCOMOTION IN COCKROACH
The mode of locomotion in a cockroach is swift walking but it also takes to flight by its wings.
Walking: In walking the legs are used. On one side the foreleg pull the body forwards and hind leg push it in the same direction. The middle leg of the opposite side acts as a prop (support). In the mean time, the remaining three legs begin to move together and the process is repeated.
Flight: Out of the two pairs, the posterior pair of wings brings about the flight. These beat in the air in such a manner that they support the body and drive it through the air.
LOCOMOTION IN SNAIL AND MUSSELS
Snails and mussels are mollusks, which crawl or move very slowly by “foot”.
LOCOMOTION IN STAR FISH
Starfish moves with the help of tube feet. The tube feet are present on both sides of a radial canal that extends up to the tip of the arm. The tube feet extend when water is pumped into them then they fix themselves by the suction cup with some object. Later on, they shorten and pull the body in this direction. In this way starfish moves in any direction. Arms of starfish also help in swimming.
LOCOMOTION IN VERTEBRATES
In vertebrates, skeletal muscles and skeleton help in locomotion.
Swimming in Fishes
Swimming in water presents very different problems from walking on land like a man or flying in the air like a bird. The adaptations for moving efficiently through the water are:
i) Stream-lined body: The body of most of the fishes is streamlined, being tapered at both ends. This means that water. flows readily over the body surface and drag is reduced to a minimum. Apart from the fins, no other structures project from the body of fish and it seems that faster the fish, the more perfect is the stream lined.
Mucus or oil glands: The dermal denticles of cartilaginous fish the scales of bony fish are moist by slimy exudation from mucus or oil glands and this also considerably reduces friction between fish and water.
Fins: The Dorsal and ventral, unpaired fins help to stabilize the fish. The paired pectoral and pelvic fins are used for steering and balancing the animals. The caudal or tail fin, along with, paired fins provide forward movement of fish through water.
Swim bladder: Buoyancy in the water is maintained by a specialized structure in bony fish called swim bladder.
LOCOMOTION IN AMPHIBIAN
The. general build of a body is essentially fish like in amphibians. Such forms have two means of locomotion.
i) Wriggling: They wriggle along the belly on the ground, with the help of segmentally arranged muscles as it “swims on land” with ‘legs hardly touching the ground when moving deliberately.
A few raises up its body on the legs which then propel it along as a muscular system has become specialized for the peculiar swimming and jumping methods of locomotion; by means of extensor thrusts of both kind limbs, acting together. Frogs and toads, also walk and hop on land due to strong hind limbs.
LOCOMOTION IN REPTILES
They move better than amphibians due to the evolution of skeleton. The reptiles use the method of walking and running. The general form of the reptilian skeleton is based on one inherited from ancient amphibians. The reptiles show striking adaptations for locomotion.
Active flight: When little or no support can be gained from upward air currents, the same effect can be achieved by flapping the wings and is called active flight. As the bird moves through the air, the air flows move quickly over the curved upper surface than over the lower surface. This reduces the air pressure on the top of the wing, compared with air pressure on the below the wing. There is, therefore, a net upward pressure on the wing this gives bird lift.
LOCOMOTION IN MAMMALS
The most efficient way of supporting the body is seen in mammals. The limbs of the mammals have undergone further modifications to produce the following modes of locomotion.
In this mode of locomotion, the mammals used to walk on their soles with palm, wrist, and digits all lending to rest more or less on the ground, such as monkeys, apes, man and bear etc.
Some mammals tend to walk on their ‘digits only. They run faster than plantigrade animals. In these mammals, the first digit usually reduces or completely lost such as rabbit, rodents etc.
These mammals walk on the tips of toes modified into hoof such as deer, goat. It is the swiftest type of locomotion.