January 22, 2022


4 min read






Invertebrates such as scallops, cnidarians, and some squid are jet-propelled using water that they squirt in and out of certain body parts. Such animals are able to control their body shape and movement by using muscles to change the shape of the fluid-filled compartments. All animals other than sponges have nerves that are used to transport signals to control the movements all over their body. Simple invertebrates have very small nerve cords throughout their body. Such type of animals has no head or brain. Insects, crustaceans, and some other invertebrates have a hard outer exoskeleton. This prevents them from predators and blows and keeps them from drying out.  Some invertebrates (except cephalopods) have a small nervous system composed of many small brains (ganglia). On the other hand, there is one animal that lacks a brain or any kind of nervous tissue: the sponge.

Locomotion and movements are two significant terms you are likely to encounter on the subject of the motion. They come from the same assumption, but there is a prominent difference between locomotion and movement.

What is Locomotion?

Locomotion refers to the movement of any living thing from one place to another. To move from one place to another, humans or any organism runs, walks, crawls, swims, or fly using various body parts (legs, feet, fins and tails, wings, and body parts). Humans, although, also use different ways of transportations such as buses, trains, cars, boats or aircraft to move from one place to another.

What is Movement?

Movement is related to any kind of motion. It can take place at any level i.e. atomic, cellular, or within an organ. In addition, movement is of two types, (1) voluntary (2) involuntary. Voluntary movement is under our control, clapping of the hands is an example of voluntary movement, while involuntary movement doesn’t produce due to our will but also takes place on its own. Heartbeat is an example of a movement that is involuntary.

Locomotion in spiders:

   Spiders show a remarkable movement by using their body fluid pressure or hydrostatic pressure from their blood to move. They generally use their hydrostatic pressure to extend their legs and muscles to flex their legs. Many spiders use silk and natural wind in special locomotion called ballooning.

Ballooning in spiders: Very lightweight spiders, generally young spiders can use their silk to fly or ‘balloon’ on a jet stream of air. Pilots have observed spiders flying 10,000 feet off the ground. They first crawl up to a high place and then let out their silk in an updraft of warm air until the drag force is enough to them. Once they are in the air, they are able to control the duration of ballooning by spreading their legs to increase the drag of the air, contributing to a slower fall or bringing their legs in contributing to faster fall.  In order to control the dragging force of air, they can reel up their ballooning silk. The reason is that the spiders can disperse to a new area. This ballooning character of the spider makes it one of the highest altitude flyers among the animal world, even without wings.


Locomotion in Earthworm                      


Earthworms have a combination or group of bristles on every segment of their body that move in and out to grip surfaces as they stretch and contract their muscles to push them forward or backward. During the movement, the earthworms, first, expand or extend their body keeping the rear portion fixed to the ground. After this, they fix the front end and release the rear end of their body. Then they shorten their body pulls the rear end forward. This makes, them move in a forward direction by a small distance.


Locomotion in snail                        


A snail peoples by changing or deforming layers of muscles beneath it through muscular contractions in its foot muscle. This special type of locomotion allows the snail to traverse approximately any obstacle.

Generally, a snail creates a wave-like motion along its foot, stretching and contracting its muscle which pushes its body against the surface moving in a forward direction.

Locomotion in Cockroach           


The way of locomotion in cockroach is swiftly walking but it also takes to flight by its wings. In walking the legs are used on one side, the forelegs pull the body forward and hind legs push it in the same direction. The middle leg of the opposite side acts as a prop. In the meantime, the remaining three legs start to move together and the process is repeated. 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 weight and drive it through the air. During locomotion the first pair of legs is directed forward, (as mentioned before) they determine the course of the insect during walking or running. In locomotion on land, the six legs are used as two tripods.


Locomotion in starfish             


Starfish moves with the help of tube feet. The tube feet are present on both sides of the 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 the starfish also help in swimming.

Locomotion in jellyfish                                                          

The body of the jellyfish shows radial symmetry and is divided into three main parts, the umbrella, the oral arms around the mouth, and the stinging tentacles. They have an internal cavity, in which the process of digestion takes place. Jellyfish has an umbrella-like body called a 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.





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