Category Biology

Why do rabbits have large ears?

          Rabbit is a small furry mammal with a short tail and large pointed ears. Rabbits live in burrows in the ground. Each burrow is the home of a single family. The first fossils which can be attributed to this family came from North America. But now they are found in most parts of the world. As compared to the rest of its body the rabbit has large-sized ears.

          Rabbit is a weak and timid animal and is usually surrounded by many enemies. Therefore nature has provided it with large ears to enable it to hear even the faintest of sounds. The large area of the ear catches most of the sound waves produced in the air and passes them into the inner ear. This enables the rabbit to detect its enemies in time and to run to safety areas.

         You must have noticed that a rabbit washes its ears by repeatedly licking its forepaws and rubbing them over the surface of its ears. It does this just not to keep its ears clean, but also to take into its mouth the natural oil which covers the ear surface. This oil is important in forming Vitamin D which in turn is necessary for the growth of the healthy bones. If the rabbit is prevented from doing this, it will develop rickets.

          Wild rabbits spend most of the day underground and usually come out for food only between dusk and dawn. They also have a keen sense of smell. They have long, hind legs which give them a good speed. A rabbit can run at a speed of 65 km per hour. Rabbits feed mainly on grass but eat other vegetation also. Their fertility rate is very high. Only their extraordinary fertility has enabled them to survive inspite of their many enemies. On an average a doe (female rabbit) produces 10 to 12 young ones every year. The natural enemies of rabbits are cats, dogs, foxes, minks, weasels and wolves. Man is the biggest enemy of rabbits because he hunts them for their skin, fur and meat.

 

How do fish breathe inside water?

               We see many kinds of fishes in ponds, lakes, rivers and seas. They cannot survive outside water. Whenever somebody gets drowned in water he quickly dies of asphyxia caused by obstructed breathing. On the contrary, the fish survives only in water and dies when taken out of it. Now the question arises: how does it breathe inside water? 

               Except the lungfish, all other fishes breathe by means of their gills. They do not have lungs like human beings nor do they breathe through their noses. They have peculiar process of respiration. They take some water in their mouths for the purpose of respiration. This water flows over the gills and comes out through the openings behind the cover of gills. The oxygen in water is absorbed by the cells of the gills. Since the surface area of the gills is quite large, the amount of oxygen absorbed is also considerable. The oxygen gets mixed in the blood and is circulated throughout the whole body. That is how it purifies the blood. Carbon dioxide produced in its body is brought by the circulating blood to the gills where it gets dissolved in water and passes out. In this way, the cycle of respiration in the fishes continues.

               If the water is dirty, the fishes sometimes come up to the surface of water and take air in for breathing. However they do not use gills for this purpose. The fish is a cold-blooded creature. It is also sensitive to touch, taste, smell etc. It has different organs for these functions. Scientists have already studied more than 20,000 species of fishes.

How are bats different from birds?

           According to the available fossil records, bats are in existence on the earth for more than 60 million years. They are found everywhere in the world except the poles. There are different varieties of bats. Scientists have so far studied more than 2,000 kinds of bats. It is a peculiar creature which flies and yet not regarded as a bird. But why is it so?

          Bats come under the category of mammals. Mammals are those animals whose females give birth to the young and suckle them. Secondly, unlike birds they don’t have feathers on their bodies but have hair. Bat is the only mammal which has wings for flying and the wings measure from 15 cms to 2 mts when spread.

          Most of the bats live on insects and worms. In tropical areas they live on fruits and flowers only. There are some other kind of bats which feed on the blood of other animals and birds – they are called the vampire bats. Due to this characteristic of some bats, people fear bats in general. The teeth of vampire bats are as sharp as needles and they even attack human beings and suck their blood.

          Bat has another peculiarity – while resting it hangs itself upside down with its head facing downward and its legs holding tightly the branch of the tree. The formation of its limb is such that it cannot stand erect. Another feature of bat is that it can fly at night as they produce high-pitched sounds which bounce off nearby objects and this ‘echo’ is picked up by the bat’s large ears which conveys the presence of obstacles.

          The largest bat is the Flying fox with a body length of over 40 cm. Bats have, normally, a lifespan of 20 years.

 

How does a wall lizard get rid of its tail?

            When a wall lizard is attacked by an enemy it often flees, leaving behind some portion of its tail. The detached tail keeps wagging for some time. This confuses the enemy and the wall lizard escapes. This is how it protects itself from its enemies.

            The wall lizard can detach a portion of its tail at its will. The bones in its tail are joined together loosely, so that any portion of the tail separates easily from the main body. When the tail is separated, it does not lose much blood because the ends of the blood vessels are almost sealed. It is, therefore, possible for the wall lizard to get rid of its tail. Soon it grows a new tail.

            Scientists have studied more than 3,000 species of lizards till today. It has been found that their bodies are usually divided into three distinct parts: head, trunk and tail. Most species have four legs. Although most lizards are hatched from eggs, a few are directly born. Most lizards feed on insects; a few of the larger species are more than 3 metres long. They are quite frightening in sight. They can easily kill a fairly large animal with one blow of their long, strong tails. They are mostly found in tropical countries. A number of African species live in tropical forests where they climb trees. Some of them have flattened flaps of skin which can be stretched down between hind and fore limbs to jump from tree to tree. Lizards can run fast, and some can swim or even glide through the air.

            Crabs and lobsters are also able to get rid of their legs in a similar fashion. When a fish catches the leg of a lobster, it jerks away its leg and escapes. These are the defence mechanisms which enable some animals to survive.

 

How does a firefly glow at night?

          The glowing fireflies or glow worms at night present a wonderful spectacle. Scientists have been engaged from the very beginning to find out how and why fireflies emit light.

         The firefly is, in fact, a flying worm. Both the male and the female of this worm have wings. In some species, however, females are without wings and are known as glow worms. They are blackish and their bodies are very soft. They mainly live on the nectar of the flowers. They are found in large numbers in tropical humid areas. Light is emitted in flashes by them. The light producing organ is located in the bottom of the abdomen in the rear side and controlled by nerves. It contains two chemicals named ‘luciferin’ and ‘luciferase’. Luciferin combines with oxygen to produce light. Luciferase helps in this combination, i.e., acts like a catalyst. It is interesting to note that no heat is produced by the light emitted by them. Such a process of production of light is called ‘bio-luminescence’. Luciferin is the active luminescent material in the fireflies. The firefly can control the length and rhythm of the flashes from the abdomen.

          The light emitted by the fireflies is either yellow or orange. Today scientists can produce such lights in their laboratories. But that is done by extracting luciferin and luciferase from the fireflies only. Fireflies range from 4 to 11 mm in length.

          Now the question arises: why does the firefly produce light? The first possible reason is that both the male and the female fireflies emit light to attract each other. The second reason may be that the light so produced may frighten birds and prevent them from attacking the fireflies. Whatever may be the reason for this, everybody is enchanted to see them at night.

 

Which are the warm and cold-blooded creatures?

               On the basis of body temperatures, all the living beings have been classified into two categories: the cold-blooded and the warm-blooded. Cold-blooded creatures are those whose body temperature does not remain constant. Their body temperature changes according to the surroundings. It becomes high during the summer and low during the winter. Interestingly it changes even during the day – being less in the cool morning than in the hot moon. Frogs, tortoises, snakes, skunks, and some variety of fishes are the cold-blooded creatures. During the winter their temperature falls down to such a proportion that in order to survive they go into their holes inside the earth. If they do not do so, their blood would freeze and they would die. During winter they keep on sleeping in their holes inside the earth. This is called the ‘hibernation’ period. They do not take food during this period. Even their physical processes get slowed down. When they come up on the earth’s surface after this period, they remain very weak.

                On the other hand warm-blooded creatures are those whose body temperature remains almost constant in winter or summer. The surroundings do not affect their body temperature. Man, bat, dog, cat, cock, cow, etc., come under this category. For example, the normal body temperature of man is 98.4°F. And of some other creatures it is as follows: bat, 104°F; dog, 102°F; cow, 101°F; cat, 101.6°F; cock, 101°F. They need more energy to maintain a constant body temperature. That is why the warm-blooded creatures need to consume more food. Their physical processes continue normally all round the year. There are special organs like hypothalamus in their bodies that control the temperature and do not allow it to go beyond or below a certain level. In these animals there is a balance between the heat lost and the heat produced.