My Science School

I’m a girl of 17 and I have completed Std XII. Now I have taken admission in a girls’ college. I’m nervous about dealing with my fellow students. What should I do?

After standard XII you have taken admission in a girls’ college and are nervous about how to deal with your new fellow students. You already have experience in dealing with fellow students in your previous college. Therefore put on a smile and deal lovingly and respectfully with your new friends as you did in the past. If this has helped you in the past, it will help you also in the future.

 

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I am in Std XI and I love a girl in my class. But whenever I talk to her she teases me with another girl’s name. She does not know about my feelings and I am unable to express them to her. How can I express my feelings to her?

The girl you “love” in your class teases you “with another girl’s name” when you want to talk to her. He is not taking the relationship with you seriously and is making fun of you. As you are unable to express your feelings to her, it is better for you to be a good and simple friend to her without pretending to talk too much about feelings that are not yet clear to you and are unable to express.

 

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I’m a 15-year-old girl and I’m very lonely. I don’t have a friend with whom I can share my feelings and thoughts. I want to join dance classes but my parents won’t allow it. I am a very active girl, but my parents are making my mind weak by keeping me at home. I don’t know what to do. Sometimes I think I should commit suicide. I love my parents. But they don’t understand me. I enjoy school, but at home I am very lonely.

I am sorry to read that you don’t have a friend with whom to share your feelings and thoughts. You feel that your parents are making your mind weak by keeping you at home. Unfortunately sometimes you think of committing suicide. This is a serious situation because you love your parents but judge them unable to understand you. Your parents who brought you into this world and care for you every day have your life and future in their hearts. You should enter into a respectful and loving dialogue with them, maybe with the help of a good family friend or relation. You could also share the situation with a good school teacher or counsellor who could talk to your parents. Go on loving your parents and trust them.

 

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I love a girl but she doesn’t love me. She loves someone else. But that boy has one more girlfriend in his life which this girl doesn’t know anything about. All of our friends tease us that we love each other. I think she loves me, but I have a problem. But my sister doesn’t like that girl. When I speak to her, my sister sometimes doesn’t talk to me and ignores me; she has a lot of negative attitude and sometimes gives me back answers. I love my sister very much. What should I do?

In your letter there are many negative situations: you love a girl “but she doesn’t love” you, “she loves someone else”, all your friends “tease us that we love each other”, your “sister doesn’t like that girl, when I speak to her, my sister sometimes doesn’t talk to you and ignores you”, you love your sister “very much” and do not know what to do. You cannot handle so many negative situations. At this moment of your life it is better for you to concentrate on your studies, family and good friends. A beautiful friendly relationship is better than a complicated and painful “love”.

 

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          The largest animals on land today, elephants share the same distant ancestor as the manatees and dugongs. They are famous for their huge size, their tusks and of course, their long trunks.

          The strong, flexible trunk is actually an extended nose and top lip. Though mainly used for feeding, it is also useful for bathing and for communicating with others through touch. Using its trunk, an elephant can reach down to the ground to drink or up into the trees to pull down branches.

          Elephants feed on all types of plant material including grasses, leaves, branches and fruits. They pick up food or suck up water with their trunks and put it into their mouths. They can also spray water over their backs to cool themselves off. The tusks (actually long front teeth) are used to dig for roots or peel bark from trees, and also as weapons in fights between males.

          Elephants can live for up to 60 years in the wild—almost as long as humans. Many roam the open grasslands of Africa, but others live in forests or mountainous areas. Female elephants stay in family groups led by the oldest female, while males travel alone or in small bands.

          There are two kinds of elephants: African and Asian elephants. African elephants are larger than Asian elephants, with bigger ears and a less rounded back. Asian elephants have been used by humans for thousands of years to carry heavy loads. They are still used today in the logging industry.

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          The name given to the group of mammals that includes seals and sealions is pinnipeds, which means “wing-footed”. It is a good description for these animals, clumsy on land but agile and graceful in the water.

          Seals and sealions spend most of their time in the ocean waters, but, unlike whales and dolphins, they also come out on to land to breed and suckle their young. Their four limbs have developed into flippers that propel them through the water at speed.

          Walruses also belong to the pinnipeds group. They are large, slow-swimming Arctic mammals with huge tusks.

          Seals and sealions can be divided into the eared seals, which include all sealions and the fur seals, and the true seals (all other seals). The eared seals are so called because they have small ear flaps.

          True seals have short front flippers but powerful hind flippers, which they use to propel themselves through the water. When on land they shuffle along on their bellies. Eared seals have long, strong front flippers that support their bodies when on land. In the water, they use these flippers like oars to pull themselves along.

          Seals and sealions feed on fish, squid, krill and other small sea creatures. Some also eat birds and even the young of other seals.

 

 

 

          Like cetaceans, sirenians—manatees and their relatives, the dugongs—are mammals that live in water all the time. They have large, bulky bodies and live in tropical coastal waters and rivers. Manatees and dugongs feed only on water plants.

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          Cetaceans are carnivorous mammals that live permanently in the water. The group is made up of the whales, dolphins and porpoises.

          Whales have a long, streamlined shape with no hair or fur on their bodies, so that they can swim quickly and easily. They also have a thick layer of fat called blubber to keep them warm in cold waters. Like all other mammals, whales must breathe air. Although they are able to hold their breath underwater for long periods of time, they have to come to the surface to breathe.

          Whales are the largest animals in the world. In fact, the enormous blue whale, which can measure over 30 metres long, is probably the biggest animal that has ever lived. Whales are able to grow so large because their huge weight is supported by the water. If a land animal grew to this size, its legs would collapse under the weight of its own body.

          Despite their huge size, most great whales feed on tiny creatures called zooplankton, which float through the oceans in great masses. The whales take in mouthfuls of water and filter out the zooplankton through plates of horn-like material, called baleen, in their mouths. Some will also feed on schools of tiny fish using this method.

          Other whales such as the sperm whale or the beluga have many small, peg-like teeth. These whales feed mainly on fish or squid.

          The sperm whale preys on giant squid. It is able to dive to depths of over 3000 metres and stay underwater for over an hour in search of its deep-dwelling prey.

          There is little light underwater, so most whales find their way using echolocation, in the same way as bats. They communicate with one another using clicks, squeals and moans.

          Dolphins also live in water all the time, but they are smaller than the whales. They all have teeth and feed mostly on fish or squid, which they are able to chase through the water at speed. The largest member of the dolphin family, the orca or killer whale, also feeds on sea mammals such as seals or even whales.

          Dolphins range in size from just over one metre, to the orca which can be nine metres in length. They have a backward-curving dorsal (back) fin, and many have beak-like snouts. Most dolphins live in the oceans, but a few live in large rivers.

          Like most whales, dolphins use echolocation to navigate through the water. This also helps them to find shoals of fish or squid. The few species of dolphin that live in the long rivers of India, China and South America, are almost blind and rely completely on echolocation to find their way through the muddy waters.

          Most dolphins are social animals. They often form large groups which can number several hundred. Dolphins will frequently move between groups, but some species, such as the orca, form small, stable families.

          Dolphins are intelligent, inquisitive animals. Some kinds will often swim beside boats or come up to investigate us if we enter the water. Dolphins are famous for their acrobatics, leaping and twisting up out of the water. This may be a way of taking in air quickly while swimming at top speed, signaling, or maybe just having fun.

 

        Porpoises are smaller than dolphins, and have blunt snouts. They have small, flattened teeth rather than the pointed teeth of dolphins. Porpoises usually live alone or in small groups. Most are shy animals that stay below the surface of the water as much as possible. This means that they are rarely seen by humans.

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          Rodents include mice, rats and squirrels, as well as beavers and porcupines. They are a very large group of mammals that live almost everywhere in the world, from the freezing Arctic to the hottest deserts. They are so successful because they can adapt easily to new environments, survive on many different kinds of food and breed very quickly.

          Unfortunately, rodents often come into close contact with humans, and can become pests. They eat and contaminate vast quantities of crops, stored grain and household food, and also spread diseases.

          Rodents are usually small animals, with short legs and a tail that may be either long or barely visible. They are intelligent, and have keen senses of smell and hearing. They also use their sensitive whiskers to find out about their surroundings. All rodents have a set of grinding teeth and two pairs of large, sharp front teeth for gnawing.

          Rodents feed mainly on plant material including nuts, seeds, fruits, leaves, bark and wood. Their front gnawing teeth keep growing all the time to avoid getting worn down by such a tough diet.

          Most kinds of rodents live in groups, from small families of beavers to large colonies of ground squirrels or prairie dogs. Many live underground, but others, such as tree squirrels and flying squirrels, nest in trees. Harvest mice weave tiny grass nests between tall reeds or stems. Like some monkeys, they have prehensile tails that can grasp the sterns.

          The lifespan of the smaller rodents is short, often only one or two years in the wild. However, they breed from a very early age and can have many young at once.

 

 

 

          As well as rats, mice and squirrels, the rodent group contains voles, cavies (also known as guinea pigs) and larger animals such as porcupines, capybaras and coypus.

          Porcupines of the Americas live mostly in trees, while those of Africa and Asia are ground-dwellers. However, they both possess a set of sharp spines and hollow quills. If threatened, the porcupine will run backwards into its attacker, leaving several quills embedded in its attacker’s skin.

          Capybaras, the largest rodents, and their relatives, the coypus, are very good swimmers. Coypus feed in the water, while capybaras leap in to escape from predators.

 

 

 

         The word lagomorph means “hare-shaped”. The group includes rabbits, hares and pikas. All lagomorphs have long soft fur all over their body, even on their feet. They feed mainly on grasses, but also eat leaves, bark, seeds and roots.

          Lagomorphs are prey to many animals, so they have large ears to listen for danger and eyes on either side of their head, allowing them to see a wide area around them. Rabbits dig burrows where they sleep and give birth. They are also a place to escape from predators. Some pikas also live in burrows, while others shelter in crevices between rocks. Hares and their young rest in small areas of flattened grass called forms. To escape from predators, hares use their long, strong legs which can carry them at speeds of up to 80 kilometres per hour.

          Like rodents, lagomorphs can breed very quickly and have many young at once. This means that where there are not enough predators, they can become pests.

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          The first groups of higher primates are the monkeys. All monkeys except marmosets and tamarins have well-developed fingers and toes. They have nails instead of claws, which they use to grasp things and pick up food. Most feed on fruit, leaves, insects and other small creatures. Large monkeys, such as baboons, will kill hares or young deer.

          Most monkeys live in trees although some come down to feed or travel. Baboons can walk for long distances on all fours. When in the trees, monkeys leap or swing from branch to branch. The spider monkeys and howler monkeys of Central and South America have prehensile tails. This means they can use their tails like an extra limb, to grasp on to branches and even hang, leaving their hands free to feed.

 

          All apes have long arms, no tails, and can stand and walk upright on two legs. The lesser apes, the Gibbons, live in the rainforest of Southeast Asia. They hang from the trees, moving each powerful arm in turn to swing their bodies along.

          Chimpanzees, orang-utans and gorillas are known as the great apes. Chimpanzees and gorillas usually travel along the ground on all fours. Chimpanzees feed both on the ground and in the trees, eating insects, fruit and leaves. They will also hunt and kill monkeys, pigs or deer. Gorillas feed only on ground-level vegetation.

          All the great apes make “nests” to sleep in at night. They tear and bend leafy branches to make a platform in a tree or a cushion on the hard ground. A fresh nest is usually built every night. Adults have their own nests but babies sleep with their mothers.

          Orang-utans differ from the other great apes because they spend most of their time in the trees. Their very long arms and hook-shaped hands and feet allow them to climb and swing between branches. Only very large males spend much time on the ground. Orang-utans live alone, travelling through the Southeast Asian rainforest in search of fruit to eat.

         The great apes are the closest relatives to humans. They are able to use tools, solve problems and learn quickly. They live in societies that are often similar to our own. However, like many other animals, the survival of the great apes is threatened by hunting and the destruction of the great rainforests of Africa and Asia.

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          The group of mammals known as primates is made up of lower primates (prosimians), such as lemurs and lorises, and higher primates - monkeys, apes and humans. Apart from humans, primates are found in all parts of the world except North America and Australasia.

          The lower primates have quite pointed faces, a good sense of smell and smaller brains than the higher primates, who have flat faces, better vision and larger brains.

          Most of the lower primates are tree-dwellers that leap or climb from branch to branch feeding on fruit, insects or leaves. Some will also catch small reptiles, birds or bats. They usually have long tails to help them balance on landing.

 

 

 

 

      Bush babies, lorises and tarsiers are nocturnal. Bush babies and tarsiers move quickly through the trees by running or leaping, while lorises move slowly and carefully. They will freeze and not move again for hours on end if they sense danger.

          Lemurs are the largest group of lower primates, but they are found only on the island of Madagascar off the African coast. Most lemurs have long, bushy tails and soft coats, often with striking markings. When on the ground most lemurs move on all fours, but indris and sifakas bound along on their hind legs.

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          Several kinds of mammals can glide through the air for short distances, but bats are the only mammals that can truly fly. Their wings are made of skin stretched tightly between the long fingers of their hands and their ankles.

          Bats make up almost a quarter of all species of mammals in the world today. There are two main groups of bats: one is the flying fox family and the second contains all other bat families. The flying foxes have foxlike heads, and feed mostly on plant material, including fruits, flowers, nectar and pollen. They use their large eyes and keen sense of smell to find their food.

          Most members of the second group of bats are carnivores, feeding on insects, small mammals, frogs, birds and even fish. These bats generally hunt at night, using echo-location to find their prey. They produce very high-pitched squeaking sounds through their noses or mouths, and then use their large ears to listen to the echoes that bounce back. The bats are then able to build up a picture of their surroundings so that they can fly at top speed and catch insects in flight even in pitch darkness.

          Bats usually hunt at night and rest during the day, hanging upside down in caves, hollow trees or even buildings. Some kinds of bats roost singly while others will gather together in their thousands. Many female bats will roost together in “nursery” colonies where they leave their babies clustering together for warmth while they go out to hunt.

 

          The insectivores are a group of small mammals that includes hedgehogs, moles and shrews, as well as some lesser-known animals such as tenrecs and the rare solenodons. Many insectivores are nocturnal, emerging at night to feed. They have long snouts and a very keen sense of smell which they use to find their prey. Most insectivores eat insects, worms and other tiny creatures, but some shrews are able to kill quite large prey such as frogs.

 

          Some insectivores feed and nest on the surface of the ground, while others, especially moles, live in burrows underground. Otter shrews, which belong to the tenrec family, spend much of their time in water, just like real otters. To defend themselves, hedgehogs and some tenrecs have spines while moles and shrews have foul-tasting skin.

 

 

 

 

          Larger animals such as pangolins and aardvarks are also insect-eaters. They feed from ant or termite nests, shooting their long, sticky tongues in and out to pick up many insects at once. Some pangolins can eat up to 200,000 ants in one night.

          Both aardvarks and pangolins are solitary, nocturnal animals. They use their keen sense of smell to locate good sources of food. They have strong front claws, used for breaking open insect nests, as well as for burrowing (the aardvark) or climbing trees (the pangolin). If threatened, the pangolin will curl up into a ball so that its scales shield it from harm. The aardvark will dig itself into a burrow at top speed.

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          Marsupials are mammals that do not give birth to fully developed young. Instead, the young are born at a very early stage, and then continue to develop while clinging to their mother’s body.

          When the young marsupial is born, it is tiny, blind and hairless. Its limbs are not even properly formed, but somehow it still manages to crawl through its mother’s fur to find its mothers’ nipples. Many marsupials, including kangaroos and wombats, have large pouches of skin around their nipples. A kangaroo’s pouch is deep and forward-facing, so that the young kangaroo does not fall out. Wombats are burrowing animals, so they have backward-facing pouches to stop soil getting inside. Other marsupials hardly have any pouch at all. Their young simply hang on to the nipples until they are old enough to let go.

          If a female marsupial has only one or two young, she can carry them in her pouch or, like the koala, on her back. Small marsupials, such as possums or bandicoots, which have several young at a time, must transfer them to a nest when they become too heavy to carry around.

          Most (but not all) marsupials live only in Australia. For millions of years, until the arrival of humans, Australia was isolated from the rest of the world. On the other continents, marsupials tended to lose out in competition for food with the placental mammals (those mammals that are born fully developed) and so, with the exception of the opossum family in the Americas, they died out. In Australia, they had no other mammalian rivals and so they thrived.

 

 

        Edentates are a group of mammals made up of anteaters, armadillos and sloths. The word “edentate” means “without teeth”, but only the anteaters have no teeth at all. Armadillos and sloths have a few very simple, grinding teeth.

          Sloths live in the rainforest of South America. They spend nearly all their time hanging upside down in the trees, feeding on leaves. Sloths move so slowly that they may only travel a few metres every day. In wet weather, a layer of green algae grows on their fur, which helps to camouflage them among the trees.

          Armadillos do not need camouflage they have a suit of armour to protect themselves. Made of bony plates, it covers the whole body, including the tail, head and limbs. Only the belly is soft, and some kinds of armadillo can protect even this part by curling themselves up into a ball.

          Anteaters feed on both ants and termites, which they detect using their keen sense of smell. The tongue of the giant anteater can unfurl an amazing 60.

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          When the first mammals appeared, all the continents were locked together in one large landmass. Over millions of years, they gradually drifted apart. This meant that the mammals were split up on to large “islands”, where they evolved into many different groups.

          North and South America eventually drifted back together again, and mammals from the two continents found themselves competing for food and territory with unfamiliar “relatives”. They also faced new predators. Some kinds died out altogether. The marsupials suffered in most parts of the world, but in Australasia, which was still isolated, many were able to thrive.

          Around the world, each kind of mammal adapted to its environment. Giraffes evolved a very long neck to browse from the tallest trees which other mammals could not reach. Whales and dolphins lost the fur and four legs of their ancestors and developed tails and fins to move more easily through the water.

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          Since the beginnings of life on Earth, all animal have gradually changed. Some have developed (or “lost”) legs, while others have grown horns, beaks or wings. Some kinds have died out altogether, giving way to others that are better suited to their environment. This process of change and adaptation is called evolution.

          Mammals are descended from mammal-like reptiles called pelycosaurs that lived on Earth about 300 million years ago. The first warm-blooded animals were probably the cynodonts. Small, fast-moving carnivores, the cynodonts may have had fur rather than scales. Fur is an essential feature of warm-blooded animals, as it helps them to keep their bodies at a stable temperature.

          The first true mammals evolved about 210 million years ago, when the dinosaurs dominated the Earth. In order to avoid the dinosaurs, the mammals came out only at night. Gradually, the three main groups of mammals evolved: marsupials, monotremes and placental mammals. The extinction of the dinosaurs meant that there was suddenly an absence of any large animals on land. This gave the mammals the opportunity they needed to spread rapidly and evolve into many different species.

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          Mammals are the group of animals to which humans belong. They are vertebrates (animals with a backbone) that give birth to live young and then feed them with milk. Most mammals have four limbs and a covering of hair or fur. Sea mammals, such as whales, have adapted to life in the water by losing their hair and hind limbs and forming their front limbs into flippers.

          All mammals are warm-blooded, which means that their bodies can control their own temperature. They obtain warmth from the process of burning fuel (food) inside the body, rather than from basking in the sun as the cold-blooded reptiles do. The skin and hair of the body are very important both for keeping in warmth in cold conditions and letting it escape to cool off the body in hot conditions. Most mammals also produce sweat, which cools the skin as it evaporates.

          Mammals have large brains and complex sensory and circulatory systems. They rely on their sense of smell more than any other kind of animal. Scent is used to communicate between members of the same species, to mark the borders of a territory, to find food and to detect an approaching predator.

          The most important feature which sets mammals apart from other animals is the way they care for their young after birth. All female mammals have mammary glands which produce milk after their young are born. The young feed on this milk, which gives them all the nutrition they need, until they are able to survive and feed on their own. By not having to find their own food, they can put all the energy gained from feeding into growing larger and stronger.

          During the period of suckling (feeding on milk), and also while the young learn to feed for themselves, the mother will protect them as much as possible from predators.

          Some female mammals raise their young alone while others share the task with the father or other members of a group.

          Most mammalian young, apart from the monotremes, are born live (not inside an egg). Small mammals can give birth to several young at one time, which grow and become independent quite quickly. The young of large mammals take longer to grow to full size, and need more care, so litter size (the number of young born at once) is smaller, often only one at a time.

          All mammals except the marsupials and the monotremes are born fully formed, though some, such as rabbits, are hairless, blind and helpless. They can grow further while in the safety of their burrow or den.

          In contrast, animals that live in open spaces, such as horses, cattle or deer, are able to walk and even run a few minutes after birth. If a predator appeared, they would need to run away with the rest of the herd.

          Many mammals live in social groups that can be made up of a few or many animals. Often the whole group will help to rear and protect the young. Carnivores such as lions or hyenas also hunt together, using their combined strength and skill to kill larger animals than they could tackle alone. Herbivores, such as deer or cattle, form large herds that give them some protection against predators.

          Like marsupials, monotremes give birth to under-developed young. However, monotremes young are born inside soft-shelled eggs. These hatch after a few days, and the young are suckled until they have developed fully.

          There are two kinds of monotremes: the echidna and the platypus. Both are found only in Australia and surrounding islands. Echidnas have a small pouch that holds their young after hatching. Platypuses do not have a pouch, but instead leave their young in a special burrow.

          Apart from a few types of shrew, monotremes are the only venomous mammals. Echidnas cannot use their venom but the platypus can kill a dog with poison ejected from a sharp spur on its leg.

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