My Science School

               Scientists say that in the ancient past, there were no reptiles upon the land. As was the case with life in general, the earliest reptiles lived in the sea. The scarcity of food forced them to come over to land. More than 250 million years ago, they journeyed to the shore in search of food. On the land, there were forests of ferns and other vegetation then.

               The presence of vegetation helped the proliferation of plant-eating insects and the early reptiles moved to the land in search of these insects. The competition for life in the sea may also have forced them to make the shore their home. These reptiles developed legs for walking around, lungs for breathing air and scales for protection. Gradually they evolved into reptiles fully adapted for life on land.

               How do we know about these facts when no one was actually present to watch the evolution of reptiles then? We examine fossils, the remnants of prehistoric animals and plants and come to conclusions. Scientists argue about the order in which separate adaptations such as the legs and the lungs appeared. However, they all agree that the most important adaptation was with regard to laying eggs.

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            Who will not have chills down the spine when they meet with a reptile all of a sudden? Their appearance, movement and venom make them dangerous and at times nightmarish. However, they are like any other animal with some astonishing characteristics.

            Reptiles have a backbone like us but they crawl or swim along, as they do not have legs or feet. Like fish, they have scales, breathe air and lay eggs with shells. They are cold-blooded; and therefore, they depend on outside sources for body heat. Although sixteen orders of reptiles have lived on the face of the earth so far, only four orders survive today.

            Among the reptiles that exist today, the largest group is the Squamata. These reptiles comprise lizards and snakes. There are 5700 living species in the Squamata group. On the other hand, there are only 200 species of turtles and 23 species of crocodilians. The smallest of the four groups has only a single species – the tuatara. The tuataras live on a group of remote islands off the New Zealand coast. Do you know the only continent in the world that does not house reptiles? Antarctica!

            Various life forms need appropriate environments for their survival. Forests and mountain ranges often provide conductive environments for organisms to thrive. The Western Ghats, besides aiding the balance of climate in the southern part of India, also sustains a wide range of biodiversity.

            The Western Ghats, a 1600 kilometre long mountain range, runs from north to south, along the western edge of the Deccan Plateau. This mountain range is home to a large number of animals that are not found anywhere else. The region is also termed as one of the ‘hottest biodiversity hotspots’ in the world and 170 different amphibian species are found here.

            In the recent past, a dozen or so frogs, new to science, were discovered in the forests of the Western Ghats. The frogs were discovered in the hill ranges of the Southern Western Ghats after several expeditions spanning the last few years. Six are bush frogs, one is a canopy bush frog, and two species are associated with bamboo reeds.

            Frogs all over the world are facing high risk of extinction due to climate change, pollution, and habitat destruction. The new discovery points to the hidden biodiversity wealth of the Western Ghats, and this calls for intense research and conservation efforts in the region.

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            We breathe through our nostrils. The air goes into our lungs, from which oxygen is carried to our blood. This is how the respiratory system of mammals functions. However, amphibians have a different system. As amphibians live on both land and water, their respiratory system must allow them to take in oxygen not only from the air but also from water.

            When amphibians stay in the water, they breathe through their skin, but once they come on land, they breathe with their lungs, and through the membranes in their mouth. Even when the lungs are used, amphibians obtain oxygen through their skin. For this to happen, the skin must remain moist at all times. When an amphibian is in the larval stage, it uses gills for breathing much like fish. These gills later develop into lungs, as the amphibian undergoes the changes that transform it into an adult.

            To sum up, amphibians can get oxygen into their bodies in three different ways. The first way is by using their lungs, which are similar to ours. The second way is through their skin, and the third is by using gills. Another curious matter is amphibians do not breathe constantly as humans do. Instead, they just breathe occasionally when their body needs more oxygen.

            Scientists say that life started in water. It is beyond imagination how life will survive without water. Although amphibians can live both in water and on land, they cannot exist on land alone. For them, water is essential for survival.

            Water keeps their skin moist and they get the oxygen they need from the water as they absorb oxygen through their skin. Water is vital for their reproduction too. The eggs of amphibians do not have a hard shell; and therefore, they need water to keep them from drying out and to protect them from the rays of the Sun.

            Some species of amphibians are aquatic and spend their entire lifetime in water.

Others, such as frogs, spend the beginning of their lives in water as larvae and undergo a change called metamorphosis to move on to land.

            Since water is so important for them, amphibians like frogs seek out damp shady places to live in. others try to prevent water loss by burrowing underground. Although it might seem strange, in spite of being so dependent on water, amphibians rarely drink it.

            In the course of the evolution of life on Earth, various curious animals have come into being and many species have ceased to exist. Interestingly, the ancestors of most animals that we see today were huge. Some of the earliest amphibians were huge.

            Amphibians must have first appeared on Earth around 360 million years ago. For tens of millions of years, they were the dominant land animals on Earth. Some of these ancient creatures measured up to 4.5 metres long. They terrorized smaller animals with their size. Amphibians evolved from fishes that had fins that looked like legs. These fish may have crawled on to the land to escape their enemies. They were probably attracted by the good supply of food on land as well.

            Gradually, these first amphibians developed lungs for breathing, and their fins developed into limbs for crawling. Over hundreds of millions of years, many different amphibians evolved and disappeared, leaving the familiar salamanders and frogs of today.

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            There is a huge variety of animals found in the class of Amphibia. Amphibians are classified into three main orders, each having its own species. The first order is Anura. Anura means “absence of tails”. Frogs and toads belong to this order, which is also known as Salientia.

           The second order is the Gymnophiona, which is also known as Apoda. A little known species that belong to this order is Caecilians. About 50 species of amphibians belong to this order. They are mostly found in tropical forests and freshwater sediments. They are aquatic in nature and are found in Africa and South Asia and America. Gymnophiona species resemble large worms and lack limbs.

             The third order is Caudate, which is also called as Urodela. The Species that belong to this order are salamanders and newts. About 500 species belong to this order. The term Caudate means ‘tail’. The species in this category have tails and four limbs. Around 90 per cent of known amphibians are frogs.

            If a fish is taken out of water, its natural habitat, it will not live long. A fish does not have the ability to absorb oxygen from the air like us or any other land animal. However, a frog, although generally found in water, will not be harmed even if stays out of water for many hours. Some animals can live both in water and on land. Such animals are known as amphibians.

            The word ‘amphibian’ means double life. Amphibians are animals that are called by this name because they need both land and water during their life cycle. They start life in the water, and live on the land as adults. Amphibians are vertebrates; and therefore, they have a backbone. They are also cold-blooded. A cold-blooded animal is an animal that cannot regulate its own body heat. So, an amphibian depends on its surroundings for warmth and its body temperature varies according to the surroundings.

            Amphibians have no hair, feathers or surface scales. The reason is that they can breathe through their skin, although some amphibians have lungs as well. Frogs and toads are some of the most common amphibians and therefore, all of us have seen an amphibian at some time or the other.

           We all know that the giraffe is the tallest animal in the world. Some males reach 5.4 metres in height and weigh up to 907 kilogrammes.

            Everything about this curious animal is long. Its neck alone is over 1.8 metres long and weighs 272 kilogrammes. The legs of a giraffe are also around 1.8 metres long. If none of that length was enough for these spotted giants, they have yet another tool to reach up to tall tree branches, their tongue. Giraffes’ tongues are 45 centimetres long – long enough to reach around the thorns of the acacia trees whose leaves are their favourite food. This lanky animal has a long heart too. Its heart is 60 centimetres long and weighs about 11 kilogrammes! Its lungs can hold 55 litres of air! Therefore, it is no wonder that they are considered giants among animals.

            A giraffe needs a lot of food since it is so big. This mammal eats up to 34 kilogrammes of food per day. When they do get thirsty, giraffes have to spread their legs and bend deep down, to drink from a lake or stream!

            Both male and female giraffes have two distinct, hair-covered horns. Male giraffes use their horns to fight playfully with one another. As male giraffes age, calcium deposits form on their skulls and other horn-like bumps develop. The pattern on a giraffe’s coat is good camouflage. Many have been fooled into mistaking a giraffe for an old dead tree!

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               Some animals love spending time in the water. They feel more secure and more powerful when they are in water. The hippopotamus is one such animal that makes the river its home.

               The animal, which is also known as the hippo, is found only in Africa. A hippo is smaller than the rhino, but is still very big; an adult weighs around three and a half tonnes. It has four toes on each foot, with each toe ending in a hoof like nail.

               Hippopotamuses enjoy spending time in water. That is why the Greeks named the animal a ‘river horse’. They spend up to 16 hours a day submerged in water. This keeps their massive bodies cool. Hippos are good swimmers, and can hold their breath underwater for up to five minutes. They are often large enough to simply walk or stand on the lake floor. Their eyes and nostrils are located high on their heads, which allows them to see and breathe while their bodies remain underwater.

              Hippos have huge mouths. We are often misled to believe that the animal is yawning when it opens its mouth wide. In fact, hippo is preparing to fight and its wicked-looking tusks can inflict terrible wounds on its enemy.

               At sunset, hippopotamuses leave the water, and travel up to 10 kilometres overland in a night to graze. They consume around 35 kilograms of grass. If they are threatened on land, they will rush back to the water.

               The rhino is a strange, wild animal due to its peculiar horn on its nose and thick skin. The rhino is probably the largest land animal after the elephant. Rhinos are very heavy, and the white rhino of Africa weighs around four tonnes!

               The skin of all rhinos is hairless, except for a brush of bristles at the tip of the tail. The skin is also very thick and this allows rhinos to rush through thorny thickets without hurting themselves. Rhinos generally have poor eye-sight, but their sense of smell is very keen.

               The word ‘rhino’ is short for rhinoceros, which means ‘horned nose’. Unfortunately, the primary cause of the rhino’s extinction is its horn. These animals are being hunted and slaughtered so that their horns can be made into dagger handles or crushed to make certain medicines. In fact, rhinos are being killed at such an alarming rate that in a matter of 20 or 30 years, there may be no rhinos left at all!

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                  The wild is a place of uncertainties and dangers. Animals use various ways to escape from their enemies. While some use their speed and power to escape predators, others have natural camouflaging techniques.

                  A zebra’s stripes are believed to be for camouflage-the patterns confuse the enemy, and make it difficult for predators to identify a single animal from a running herd. These stripes are unique to individual zebras, as no two zebras have identical stripes on their body. Due to their uniqueness, stripes may also help zebras recognize one another.

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            Among the animals that Man has domesticated, the horse is probably the most powerful animal. Horses have been our friends for thousands of years in our travels, wars and industries; there is a variety of horses among both wild and domesticated species. Today, however, there are very few wild horses left. In fact, the only wild horse is the Przewalski’s horse.

            Zebras are large, fast-running mammals that live on the African plains. They are social animals that spend time in herds. They graze primarily on grass. Zebras have horse-like bodies, but their manes comprise of short, erect hairs. Their tails are tufted at the tip and their coats are striped. In fact, no animal has a more distinctive coat than the zebra.

                Do you know that each zebra’s stripes are as unique as our fingerprints? No two zebra coats are exactly alike.

             There is so much diversity among mammals. Various factors relating to their environment, climate and availability of resources have resulted in the development of distinct species despite the apparent similarity in the appearance of these animals. Among camels, Bactrian camels and Dromedary camels are such animals.

           Dromedary camels have only one hump on their back. They are very common in Africa and the Middle East. Bactrian camels, on the other hand, are native to the Gobi Desert in Mongolia, and have two humps.

          Bactrian camels differ from dromedary camels in other ways too. A bactrian camel grows a thick coat of hair in each winter. This coat of hair is temporary and falls off every spring. This is to deal with the extreme variation of temperature in the Gobi desert, where summer heat often goes up to 100 degrees Fahrenheit, and winter months can see significant amounts of snow. The dromedary camel, on the other hand, has uniform length of hair all year round.

          Yet another difference is that Dromedary camels are not found in the wild while a few wild Bactrian camels still exist in the Gobi Desert. Finally, Bactrian camels are much more mild-mannered than the hot-tempered dromedary camels.

              In the olden days, when science was not as developed as it is today, the ancient man made intercontinental travels by ships. He stored the necessary goods for consumption on his big ships. Just as ships cross vast distances over water, carrying men and goods from one shore to another, camels travelled over scorching deserts, carrying loads from one place to another. Any other animal would die of heat and thirst, but the camel is able to survive because it has abilities that suit desert conditions.

              Camels can go for days without drinking water. They can also drink from waterholes that are too bitter or saline for other animals. Camels drink 100 litres of water within 10 minutes and then live without drinking for 3 or 4 days.

              These mammals eat almost anything, regardless of how tough or how thorny it is. A camel has leathery mouth, tongue and tooth enamel, enabling it to eat thorny desert plants. A camel’s hump is not used to store water as is commonly believed. Rather, it stores fat. If food is hard to find, the fat in the hump provides energy for the animal. If a camel is starving, its hump shrinks!

              The camel’s fur allows excess body temperature to radiate out and protects them from cold nights. Camels have enough tear glands and double rows of long, curled eyelashes to protect their eyes from blowing sand. They can close their noses by contracting muscles during sand storms. Their broad, padded toes are insulated to avoid the sand’s heat. The strong, flexible webs of their toes prevent them from sinking into the sand.

              Now you will certainly agree that camels are amazing mammals.

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