Category Science

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.

Can animals identify different colours?

          We know that animals can see things like us. But can they distinguish between different colours like human beings? To find an answer to this question, scientists have conducted a number of experiments on many animals like cats, dogs, apes, bees, etc.

          It has been found that dogs cannot distinguish between different colours. Some dogs were given eatables of different colours. The variation in colours had no effect on them. This has proved that dogs cannot identify different colours. Some experiments of this type were also conducted on cats. Even they were found to be colour-blind.

          Besides man, ape is the only mammal which can differentiate between different colours. All other mammals are colouring blind.

          The honey bee is also endowed with this unique property of colour discrimination. 

          However, it cannot identify the red colour. It appears black to it. It is on the basis of identification of colours that these bees are attracted towards the flowers of different colours from which they collect honey. The honey bee is capable of seeing the ultraviolet rays which even human beings cannot see.

          To test their power of colour vision, they were shown two cards – blue and red. A little syrup was placed on the blue card, whereas the red card was without it. The honey bees gathered on the blue card. Now the blue card, without any syrup on it, was kept at a different place. The bees reached there also. This proved that they can distinguish between different colours.

          Even birds can differentiate between different colours. The colours of the male birds are more attractive than those of the females. Thus the females are attracted towards them because of their colours. It has been observed that birds can identify all the colours of the rainbow.

          Generally animals have no need to distinguish between colours because most of them hunt by night and do not depend on colour. However, they have a greater power of smell and as such their colour blindness does not handicap them.

 

Why lion is called the king of the beasts?

          Lion is the largest and most powerful of the wild cats. It is regarded as the symbol of power and strength in all the countries of the world. We often hear strong people being referred to as ‘lion-hearted’. Also, the figure of the lion, as a symbol of strength, is engraved on many shields awarded to players. Even some flags carry the picture of a lion. The ancient Egyptians believed lion to be a sacred animal.

          It is generally believed that lion is the most powerful animal in the jungle. It is called the ‘King of the beasts’, because it attacks so swiftly that the victim does not get any time to defend itself. It attacks animals bigger than itself like giraffe and wild buffaloes from behind and then tears them apart with the help of its powerful paws and teeth. They often hunt as a team.

          Lions were found in many parts of Europe some 2000 years ago, but gradually they were wiped off. Now they are found only in the jungles of Africa and north-west India. A few, not more than 200 live in India’s Gir forest.

          Lion is a carnivorous animal which kills wild animals and lives on their flesh. It is a member of the cat family. The average length of an adult lion is about 3 metres and its weight varies from 180 to 225 kgs.

          The female species is smaller in size and does not have mane. Lioness generally hunts and kills the prey. Its cubs hop and jump like kittens. The roar of a male lion is a territorial proclamation. Unlike the cat it cannot climb the trees.

          Lions live in family groups called ‘prides’ of 4 to 30 in the forest. It rests during the day and kills at night. It does not attack elephants and hippopotamus. The main animals of its prey are zebra, deer, bear, jackal etc. If it is not disturbed it does not attack anybody. But on being teased or attacked, it turns extremely ferocious. Some lions which get the taste of human flesh become man-eaters and start living in the nearby jungles around villages. Whenever they get an opportunity, they kill man, sheep, goats etc. A lioness, after a gestation period of 110 days, gives birth to one to six spotted cubs.

          Lion can be domesticated and we can see them in the circus performing tricks. Lions have a potential lifespan of 20 to 30 years. 

Why is the colour of leaves green?

          The new leaves of any plant appear pink but after some time they turn green. Do you know what the reason behind it is?

          We know that the colour of any substance depends upon its property of absorption and reflection of the different colours of light. The leaves of the plant appear coloured due to the presence of some specific substances in them. For example, the presence of chlorophyll makes them appear green while the presence of carotenes makes them yellow.

          When many substances are present in one leaf, it shows the colour of the mixture. The leaves which contain both chlorophyll and carotene appear yellowish green.

          New leaves of some plants contain a red substance called anthocyanin, which gives the pink or red colour to the tender leaves. With the passage of time, chlorophyll and carotene are formed in these leaves, which ultimately turn them green.

          The structure of chlorophyll molecules is such that when the sunlight (mixture of seven colours) falls on them, they reflect the green colour and absorb the rest. This reflected green colour reaches our eyes and gives the green appearance to the leaves.

          Plants synthesize their food with the help of chlorophyll in the presence of the sunlight. This process is called ‘photosynthesis’. Plants without chlorophyll like fungi cannot make their own food. They depend on other living beings. Such plants are called parasites.

          In this way, we see that chlorophyll is a very important substance for plants which gives them the green colour.