Essential Functions of Life (Animals): Aquatic, Migration & Human Beings

See a butterfly, an elephant, a banyan tree and a rose plant. These living things are different from one another, yet they all perform some common activities. All of these common activities like breathing, moving, feeling, feeding, reproducing etc. should suit to their environment.

The large animal Kingdom consists of different types of animals. They have different behaviors, habits and body features. They perform these essential functions to stay alive. On the basis of their body features and habits, animals can be divided into two groups : vertebrates and invertebrates. Vertebrates are animals that have a skeleton made up of bones, e.g. mammals, birds, fish, reptiles and amphibians. Invertebrates do not have a skeleton made up bones, e.g. worms, snakes etc. The majority of animals are invertebrate. Vertebrates make up less than 3% of the world’s animals.

Different living beings perform these activities in different ways. For example, plants move in a particular way though fixed at their roots. Animals move in a variety of ways. Fish swim, frogs hop, birds and some insects fly and humans walk or run.

Let us observe these activities of life in more details :

(1) Respiration (breathing) in animals

Living beings inhale and exhale air. This process is called respiration. Different living beings have different respiratory organs which absorb oxygen from air and give out carbon di oxide.

Oxygen burns/breaks down the absorbed food to release energy for life activities. This burning is a slow process and there is a step-by-step breakdown of food. In this way, it is different from burning of fuels. Land animals breathe-in oxygen from the air while fish and other aquatic animals take oxygen from water.

Organs of Breathing : Microbes or microscopic animals like amoeba and paramecium breathe through their body surface. Insects breathe through air holes or spiracles on their body surface. The blood of insects does not have the oxygen carries called haemoglobin.

That is why their blood is not red in colour. How is then oxygen carried to various parts of an insect’s body. The spiracles lead to air tubes which form a fine network that reaches every tissue of the body. Air enters the body through this network. The body tissues take in oxygen and give out carbon dioxide which is pumped out of the body.

A fish breathes through its gills. So do prawns, crabs, oysters and tadpoles. Gills are special organs which are richly supplied with blood vessels. An exchange of gases takes place when water flows through the gills. The gills absorb oxygen from water and release carbon dioxide from the blood.

Birds, reptiles and mammals breathe through lungs. The lungs are richly supplied with blood vessels. When the air reaches the lungs, an exchange of gases takes place between the air and the blood. Oxygen from the air passes into the blood and carbon dioxide from the blood passes into the air. Then the lungs contract and air containing carbon-di oxide comes out through the nose.

Whales and dolphins are mammals. Therefore, they also breathe through lungs even though they live in water.
Frogs have special body features that enable them to live them in water as well as on land.

A frog is an amphibian. A. baby frog breathes through its gills. An adult frog breathes through its lungs on land and through its moist skin under water.

(2) Movement in animals

All animals move from one place to another in search of food, shelter or mate. This movement is called locomotion. The organs that help in this movement, are called locomotory organs. Different variety of animals have different types of locomotory organs. Large animals use their legs to move or run.

Organs of movement: Most mammals have four limbs. The two in the front are called fore limbs and the two at the back are called hind-limbs. Some animals use all the four limbs to move while others use only the hind-limbs. Man is the most famous animal which walks on two legs.

Aquatic animals

Fish have fins for swimming. A boat-shaped body and fins help a fish to push water aside and tail to balance. The two paired fins are used to move forward. The unpaired fin maintains balance and the tail fin helps to change direction.

Turtles have four paddle like limbs to push water and to swim. Penguins use their two forelimbs as flippers to push water and to swim. Frogs have webbed feet to swim. But when on land, they jump with the help of their long hind-legs.

Insects : Six-legged creatures-insects usually use their legs for movement. Insects like ants and cockroaches crawl on their legs. A grasshopper uses its long hind-legs for hopping. Swimming insects like water boatmen use their legs as ores while swimming. Some insects have one or two pairs of wings and can fly.

Human beings

In comparison to the limbs of other animals, the limbs of human beings are highly developed. They use only one pair of limbs (lower limbs) to support their body. Unlike other animals, man has an erect position or posture. He walks, stands and run with only one pair of limbs called legs. He has an advantage of this. For example, when he is in danger, he can use his legs to run and escape and his upper limbs or arm for attack or defence.

Man hands are adapted to hold objects. The arrangement of the thumb opposite the finger enables him to hold tools and do many kinds of work. So, it is true that man is the most developed among all animals.

Migration in Animals

Some animals move for distances at certain times of the year. This mass movement of animals from one place to another, is called migration. Animals migrate due to unfavourable weather conditions, shortage of food and to reach their breeding places. Some birds from other countries like Siberian cranes, storks and mallard ducks visit India every winter.

Migration of birds Migratory fish like eels spend their lives in river to lay their eggs. They travel to the sea. When the eggs hatch, parent eels die and the young ones travel back to the river from where the parents had gone.
Locusts are harmful migratory animals. Swarms of locusts settle on standing crops and destroy them. Many kinds of butterflies like monarch butterflies migrate from Canada to Mexico.

Migration is most common in birds. The European stork travels from Europe to Africa every winter. When spring comes, it returns to Europe to the same nest. The Arctic tern travels a distance of nearly 1,70,000 km between the Arctic and the Antarctic, twice a year. Migrating animals very cleverly decide where to go. Some animals use sea currents for help. The reindeers find their direction with the help of the sun’s rays. Birds follow the coast line. Scientists use various new techniques to study migration among animals. Rings and tiny transmitters are fixed on animals to track their movement patterns. We should take special care of migratory birds which visit our land.

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