Category Biology

          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.

 

          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. 

          Amongst the thousand kinds of insects, there are some who bite us and are our great enemies. When they bite us, they inject germs of many dangerous diseases into our body. Do you know which insects are our enemies?

          Dangerous among the insects which spread various diseases through bites are mosquitoes, tse tse flies, lice, rat fleas, bed bugs etc. When these insects bite any sick person, and suck the blood, the germs of the disease pass into the bodies of the insects. When these insects bite a healthy person, they pass on to him the germs of that disease along with the saliva through a needle-shaped hollow organ. These germs infect the healthy person and make him sick. 

Continue reading “Why insect bites are dangerous?”

          Mammals are vertebrates or animals with back bones. They have large brains and a keen awareness of their surroundings. They are warm-blooded and have their skin covered with hair. The young are born alive except for egg laying platypus and sping anteater and suckle milk from the milk glands of female. You will be surprised to know that many animals which are otherwise very different from one another come under this category. For example the cow, seal and bat have nothing in common, yet they come under the category of the mammals. Man is a mammal too.

          Many of the mammals are very peculiar. Some of these live on the land, some on trees while some others inside the earth. There are some which live in water also.

          Some of them are carnivorous while others are herbivorous. Some mammals are both carnivorous and herbivorous.

          Monkey, gorilla, chimpanzee, baboon, etc. are the mammals with resembling features. Cow, pig, camel, horse, rhinoceros, elephant, rabbit, rat, squirrel etc., are some other mammals. Most of the time they live on the ground. The dugong, dolphin, whale etc., are mammals which live in water. Amongst the flying mammals are the bat and colugo. The kangaroo is a peculiar mammal that has a pouch on its belly for keeping its young ones.

          Platypus is another peculiar mammal which does not give birth to its young but lays eggs. Generally it is found in Australia. Pangolin does not have teeth. It lives on ants. The wolf, lion, cheetah, bear, cat, seal – all are mammals. There are about 4000 distinct species of mammals. It is not possible to describe all of them. Only important ones have been described here.

          The web made by a spider is a fascinating thing, but spider itself is more amazing in many other respects. It is a peculiar creature found in all seasons and at all places – air, water, land and also inside the earth. Its size varies from that of a small dot to 20 cms. There are some spiders which can live without water for a year. A giant spider called tarantula feeds on birds and can live for as long as 15 years. In February 1985, Charles J. Seiderman of New York City captured a female bird-eating spider near Paramaribo, Surinam, which weighed a record peak of 122.2 grams. Generally most of the spiders live only for one year. The spider has 8 legs and 8 eyes. Its body has only two parts – head and trunk. 

          The silk that spiders fabricate for making their webs is produced in certain abdominal glands. A liquid in the form of fine thread comes out from a small hole at the top of its abdomen, which solidifies after coming in contact with air. These threads are of various types. Some of them are sticky while some others are dry and soft. The sticky thread helps the spider in catching its prey. As soon as a fly or a small insect touches or falls on the web it gets entrapped in it. Now the question arises: why doesn’t the spider itself get caught in its web?

          It is interesting to note that the spider itself does not get trapped in it because it has a kind of oil on its legs. In fact, when the spider moves across the web, it uses the dry-soft threads and is careful to avoid touching the sticky threads with its legs. Even if it did, the oily secretions on its feet would prevent it from sticking and it moves along those threads easily. In England and Wales there are more than 2,000,000 spiders in every acre of meadow land. It has been estimated that in one year the spiders in the country eat a weight of insects that exceeds the total weight of the human population of England and Wales.

           The spiders make many kinds of webs. Some of these are wheel-shaped while some are shaped like a funnel. The sticky threads which are meant for trapping the prey are separately located.