My Science School

               Our Earth is a sanctuary of biodiversity and there are creatures with the strangest characteristics. One such animal is the tuatara.

               The tuatara is a strange reptile. It looks like a lizard; however, it is not a lizard. It is not a snake or turtle or crocodilian either. These creatures have remained beyond evolution as well. Tuataras have remained unchanged over millions of years. The tuataras in the age of the dinosaurs were the same as the tuataras of today. The tuatara is slow by nature. They grow slowly. Male tuataras grow to a length of 60 centimetres, but females are slightly shorter. The female tuatara lays 10 to 10 eggs in a shallow burrow. The eggs take long 15 months to hatch. This is the longest time for any reptile. Tuataras can live for over 120 years.

               Although snakes frighten us in several ways, it generally does not do so by flying! Snakes do not usually fly, because they do not have wings. However, if you ever go to Southeast Asia, you might see a snake flying over your head! If snakes do not have wings, how do they manage to fly?

               These snakes, in fact, are not really flying like a bird. They are merely gliding from one tree to another. A flying snake launches itself at high speed from a perch on a tree, raises its limbs, and flattens its body to form a kind of parachute. A flying snake cannot take an upward flight. They glide only downwards. It may even swish and contort itself in flight so that it can control where it lands.

               Flying snakes can hunt their prey in the air too, crushing small animals with their powerful jaws. A flying snake can glide as much as 24 metres in the air!

               There is a group of is islands 965 kilometres off the coast of Ecuador in South America. They were discovered in 1535, and are called Galapagos Islands. The islands were famous for the huge tortoises that lived there. The name of the islands derives from these reptiles. ‘Galapago’ in Spanish means saddle, and refer to the tortoise shell. It is believed that long, long ago these giant turtles must have arrived in the island from South America, on pieces of driftwood.

               Galapagos tortoises are the largest tortoises in the world. One of the most amazing facts about the Galapagos Giant Tortoise is that they keep growing for 30 to 40 years, reaching almost 1.5 metres. They also weigh about 227 kilogrammes. They are also the longest living of all vertebrates – that is, animals with backbones. Do you know these animals outlive humans? The oldest on record lived for 152 years!

               Throughout the 19th century, giant tortoises were valued by sailors as food supply. Thousands of these tortoises were killed and the species died out. The last surviving tortoise called Lone-some George died in 2012 at the Galapagos national park in Ecuador.

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            Some reptiles are excellent hunters. Crocodiles and alligators, in particular, are very clever at stalking, capturing and killing their prey. The gharial crocodile, which has a long narrow snout, eats mostly fish, and it captures its prey by a rapid sideways snap of its tooth-lined jaw. Alligators and crocodiles with broader snouts also eat fish, but their diets vary according to  their age.

            The young reptiles feed mainly on insects, spiders, crabs and small frogs. They will circle their prey with their bodies and with a sudden sideways movement of their jaws, trap them and eat them.

            Adult crocodiles and alligators eat small mammals, birds, turtles and other reptiles. They will approach their prey stealthily with their bodies submerged under water and only their eyes and tip of their snout above the water. When they are near the prey, they submerge themselves completely. With the help of their powerful tails, they reach up to the prey and capture them. Their vice-like, tooth-lined jaws snap shut with an enormous force and kills the smaller prey immediately. Larger animals are dragged underwater, drowned and then killed and eaten, sometimes over the span of several days.

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               We all have seen dragons in movies. These huge and fearsome animals can fly and spit fire. Have such animals ever existed in the past? Scientists say that, if we forget the fire-spitting part, these animals resembled a flying reptile that lived a long time ago!

               The Archaeopteryx was a part reptile and part bird that lived 150 million years ago. This animal is a wonderful example of an in-between creature, which is neither a bird nor a reptile fully. Several fossils of this reptile-bird have been found in fine-grained stone. The skeleton look like that of a dinosaur but it shows the presence of feathers. Feathers are the most important feature of birds and they have evolved from the scales of reptiles. The archaeopteryx had a toothed jaw, a long tail and a weak breastbone. Unlike the bones of birds, all the bones of birds, all the bones of the archaeopteryx were solid.

               Do you know there is an uncanny connection between the cuckoo and the crocodile? The feathers of the archaeopteryx tell us that the crocodile, in fact, is related to the cuckoo.

What do we know about the archaeopteryx?

               The first bird to inhabit the Earth is believed to be the archaeopteryx (meaning ‘ancient wing’). It was a cat-sized bird, with several reptilian features. It had a beak containing sharp teeth, claws on its wings, and a long tail with bones in the middle. They had wings, feathers and a furcula. The furcula, or wish bone in birds, is a forked bone that joins the right and left shoulder joints. Not much is known about this bird’s direct ancestors or descendants.

                We are all scared of snakes. Have you ever wondered how these animals move about without legs? Snakes have descended from lizards. In fact, they evolved from lizards millions of years ago. Scientists are still not certain regarding the group of lizards from which snakes evolved. We depend on fossils to study evolution and sometimes a snake does not make a good fossil. They leave only pieces of backbone and the odd skull in poor conditions.

                The most primitive living snakes lived underground by digging holes in the earth. Therefore, some scientists believe that snakes come from burrowing lizards, which had much reduced limbs. Others, on the other hand, think that snakes evolved in the sea.

                Many scientists hold the view that lizards descend from a super family of non-burrowing lizards known as platynota. The Gila monster, beaded lizard and a poisonous lizard called Lanthanotus belong to this super family. Members of this family do have some features in common with the snakes. The backbone and the tongue of these lizards and the snakes are similar in shape. The two halves of the lower jaw are not firmly joined.

                Therefore, lizards belonging to the super family platynota are regarded as the ‘great grandfathers’ of snakes.

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               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.