My Science School

            The outermost part of Earth is where we live. Our home, school, play-grounds and all of human civilization is built up on this layer of earth. Lithosphere is one of the non-living parts of the environment.

            Lithosphere represents the solid, outer portion of the earth. It includes the brittle upper portion of the mantle and the crust and the outer most layers of the earth’s structure. Lithosphere is connected to the atmosphere above and asthenosphere, another part of the upper mantle, below.

            The cool brittle lithosphere is just one of four great spheres that shape the environment of the earth. The other spheres are the biosphere, the hydrosphere and the atmosphere. These spheres are instrumental in regulating various climatic conditions on our planet. They interact with each other to influence diverse elements such as ocean salinity, biodiversity and landscape.

            The lithosphere also interacts with the atmosphere and influences temperature difference. For example, tall mountains play a significant role in the temperatures of the valley.

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                We know that there is no single climate across the globe. When there is monsoon in India, there is heat and drought elsewhere in the world. In the case of our planet, it has faced prolonged periods of climates, which persisted for very long time.

                Several types of climates can be found on Earth. The difference in climates depends on the distance of a particular region from the equator, altitude, moisture, wind-pattern, soil, vegetation, pollution etc. Thus, there are many forces that control and change the climate. The climates will gradually alter when these factors undergo change.

                The extended climatic changes also depend on the different ages Earth has gone through over the period. For example, Ice Age was a period of prolonged extreme cold climatic condition. It was an age marked by vast snow and ice sheets all the year round. The earth has experienced many Ice Ages. The most recent Ice Age occurred in the Pleistocene period. However, it was thousands of years ago.  

                Besides closeness of the earth to the sun, volcanic eruptions and certain other natural phenomena can also cause changes in the earth's climate.

            There may have been times when you had to cancel a journey due to heavy rain; or your parents warned you of excessive heat and forbade you from playing outdoors. Have you ever wondered how to describe such changes, often sudden and unpredicted such as a rain, in the atmosphere? Is it a change in climate, or in weather?

            Earth is able to support a wide variety of living beings because of its diverse regional climates. These climates range from extreme cold at the poles to tropical heat at the Equator. Regional climate is often considered as the average weather in a place over more than 3 years. A region's climate, therefore, is often described as sunny, windy, dry, or humid.

          However, these events can also describe the weather in a certain place, but while the weather can change in just a few hours, climate changes over a longer span of time.

            Earth's global climate is an average of regional climates. The global climate has either cooled or warmed for longer periods throughout history. Nowadays, however, we are experiencing unusually rapid warming of our planet.

 

                      Our atmosphere is the protective covering over the earth. Although there are no perceivable layers or distinguishable boundary marks, the atmosphere can be divided into layers for the sake of comprehension. The atmosphere comprises of five layers: the troposphere, the stratosphere, the mesosphere, thermosphere and the exosphere.

                    Animals and plants live in the troposphere. This is because this layer is rich in oxygen, which is an indispensable element for the survival of life. The troposphere be-gins at the surface of the earth and extends to between 7 km at the poles and 17 km at the equator. The tropopause is the boundary between the troposphere and stratosphere.

                        The next layer is called stratosphere and it extends from the tropopause to about 51 km upwards. The stratopause, which is the boundary between the stratosphere and mesosphere, typically is at 50 to 55 km. The mesosphere extends from the stratopause to 80-85 km. It is in this layer where most meteors burn up upon entering the atmosphere.

                        The top of the thermosphere is the bottom of the exosphere, called the exobase. The height of exosphere varies with solar activity and ranges from about 250 to 800 km. The outermost layer of Earth's atmosphere is called exosphere.

              In the biting cold of a winter morning, we would prefer to lie curled up, wrapping ourselves in the comfort of a thick blanket. If necessity compels us to get out of our home, we would wear a pullover to warm ourselves. The pullover and blanket help us keep the chill at bay. While Man has invented clothing to adapt to the change of seasons and climate, our earth has a natural blanket called atmosphere.

              Atmosphere protects our planet from harmful ultraviolet rays of the sun. It acts like a blanket around the earth. It not only protects our planet from the sun but also provides the conditions necessary for the sustenance of life on Earth. Life exists on Earth because of atmosphere.

              Dry air in the atmosphere consists of 78 per cent nitrogen, 21 per cent oxygen, 1 per cent argon and other inert gases, such as carbon dioxide. Other than these gases, there are many other gases in the atmosphere too. The ozone layer of the earth's atmosphere plays an important role in preventing the ultraviolet (UV) radiation from reaching the planet's surface.

            There is a variety of water bodies on earth. They differ from each other in terms of the amount of water they hold, the salinity of water and variety of ecosystems they contain.

            We call a body of water a lake when it is inland and is not part of an ocean, lakes are larger and deeper than a pond and are fed by a river, Natural lakes on Earth are generally found in mountainous area, rift zone and areas with ongoing or recent glaciations. Other lakes are found in basins, which have no connection to seas, or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them. Lake Superior is the longest fresh water lake in the world. It is 560 km long with a surface area of 82,100 sq. km. On the other hand, a pond is a body of water that does not flow anywhere. Ponds are either natural or man-made, and are usually smaller than a lake. Ponds and lakes are distinguished from streams by the speed of their currents.

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            Civilizations world over have developed on the banks of great rivers. Our nation derives its name from a river! Rivers have been not only the backbones of civilizations, but also home to many ecosystems.

          Rivers are large natural streams of water flowing into an ocean, a lake or any larger body of water. Unlike oceans, rivers, lakes and waterfalls are freshwater ecosystems. Water within a river is generally collected from precipitation through surface runoff, groundwater recharge, springs, and the release of stored water in natural ice and snow-packs such as glaciers.

            There are several other names to denote smaller rivers, such as stream, creek and brook. Most small rivers and ponds appear only in monsoons, as rain is their main source of water. Therefore, they dry up in summers. Such rivers are called non-perennial rivers. On the other hand, big rivers that contain water throughout the year are called perennial rivers.  

            Streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity. The study of streams and waterways in general is known as Surface Hydrology.

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            The deep blue seas have fascinated Man for thousands of years. While Man has conquered even the highest mountain peaks on land, he has not been successful in exploring the oceans fully. Oceans are a very different world!

            Water covers about two-thirds of the earth's surface. Oceans are the largest ecosystems existing on Earth. Atlantic Ocean, Pacific Ocean, Arctic Ocean, Indian Ocean and Southern Ocean are the five great oceans of the earth. The Pacific and Atlantic may be further subdivided by the equator into northerly and southerly portions.

            Smaller regions of the oceans are known as seas, gulfs and bays. There are also salt lakes, which are smaller bodies of landlocked saltwater. Most of these lakes are not interconnected with the larger oceans. Two notable examples of salt lakes are the Aral Sea and the Great Salt Lake.

            The ocean bed is not plain. There are huge mountains, trenches, ridges and volcanoes under the water. Such diverse landscape underwater makes many different habitats possible.

            Life exists in various forms in oceans. However, the oceans do not contain a large variety of species. Just 20 percent of the species existing on Earth live in the oceans.

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              Have you observed the carcass of an animal or a bird decomposing and disintegrating into the soil? If you observe closely, you could find small maggots or worms that eat up the dead body. When animals or plants die, they slowly become part of the soil thanks to the presence of decomposers.

             Decomposers play a crucial role in the process of recycling. They eat away the dead remains of the plants and the animals. They have the capability of breaking down organic matter and converting them into simpler substances. This means that these substances go through a cyclical life by being integrated into organisms and are used repeatedly.

              Nowadays, people are encouraged to use biodegradable materials. Materials that can be broken down into simpler substances naturally are called biodegradable materials. However, human activities have hindered the process of natural recycling.

              Materials such as tin, plastic and glass are non-biodegradable. These materials cannot be broken down naturally; and therefore, they can remain in the environment for hundreds or thousands of years. They can pose a threat to life and are possible health hazards.

             Governments, these days, are urging people to replace non-biodegradable products with biodegradable products.

            If every living thing is comfortably placed in nature and allowed to grow and multiply at leisure, the earth would soon become inadequate for life! Therefore, the equilibrium of life on earth should be kept in check. Food chains play that vital role in our environment.

            Every living thing, at one or other time, is consumed by another. The process of who eats whom is called food chain. It is basically, a series of living beings linked together because each one is the food for another. The position each species occupies within a food chain is called a feeding level. Thus, plants come to the first as they represent the lowest level. The final consumer comes at the last level. Thus a pyramid is formed in the biosphere.

            For example, grasshoppers eat plants; meanwhile, grasshoppers become prey to frogs. Snakes consume frogs. However, snakes are eaten by peacocks, which is the final consumer in the pyramid. When the final consumer at the top of the pyramid dies and disintegrates, its substances are taken up as nourishment by plants. Thus this chain or cycle continues. If any of the links is lost or damaged it affects the whole chain. All living beings are inter-connected and inter-dependent; and therefore, all living things are part of this chain.

            Have you ever wondered whether we would run out of oxygen at some point in time if all living things used it for their existence? However, we know that trees and plants release oxygen to the atmosphere. Life in biosphere is cyclical. The elements that sustain life travel from one form of life to another making each of them dependent upon the other. The most important cycles in the biosphere are nitrogen cycle, oxygen cycle, carbon cycle and water cycle.

            Nitrogen is required in all living beings to produce proteins. Nitrifying bacteria present in certain plants carry out the process of nitrogen fixation. Denitrifying bacteria decompose the dead remains and waste products of plants and animals and release nitrogen back into the atmosphere.

            Living things take in oxygen from the air as it helps the release of energy from the food they consume. The process of photosynthesis that occurs in the leaves of green plants releases oxygen. Additionally, green plants play an important role in carbon cycle. They consume carbon dioxide to produce food. When animals consume these plants, they get some part of carbon. Carbon dioxide is released back to the H atmosphere when the animals exhale. Carbon is returned to nature when the animals die.

            In the case of water cycle, water changes into vapour and rises up in the atmosphere. When it cools down, it condenses into water droplets which combine together to constitute clouds. When clouds become heavy with water droplets they fall back on Earth in the form of rain or snow.

            These cycles are vital for the existence and sustenance of life on Earth.

            If you observe a pond or a river, you would be amazed to see the variety of living things there. You would find not only fishes, but also plants, frogs, insects, birds and many more creatures! They all live there quietly and interdependently.

            An ecosystem is the coexistence of different life forms in a given geographical area. Various species of creature from a community at such locations. The communities with its surroundings such as soil, temperature, vegetation etc. from an ecosystem.

            Individual animals fight for resources in an ecosystem, because there is a limit to resources available for a biological community. Different species interact with each other in the ecosystem for their survival, food, shelter etc.

            This interaction, however, may be in the form of relationships like that of the prey and the hunter. It may be one of mutual benefit or symbiotic. Symbiotic living means interdependence and a friendly relationship with nature and living beings.

            Life in an ecosystem is cyclical in nature as living organisms depend on each other. The continuity of the fragile ecosystem depends on the interrelationship between various physical and biological factors.

            In the entire universe known to him, Man is yet to find another planet like Earth where there is life. Our planet, therefore, is unique because it holds a system that contains life in its diverse manifestations. This diversity is so enormous that our attempt to study it seriously has just begun!

            You may have heard the saying that nature is the greatest teacher. Man tries to know more about nature systematically and scientifically. Ecology is the science that studies the behaviour of plants and animals, and in Particular, environmental conditions. Ecology addresses the full scale of life, from tiny bacteria to processes that spay entire planet.

            Ecology comes from the Greek word ‘Oikos’. The word means a place to live in. Ernest Haeckel, a renowned German biologist, used the term for the first time. However, his idea of ecology was forgotten until about 1900 when biologists began to take serious interest in it. Ancient Greek philosophers such as Hippocrates and Aristotle were the first thinkers who discussed ecology in their studies on natural history.

            Ecology has many practical applications today. Modern ecology became a much more rigorous science only in the late 19th century.

            When Man goes into space, he needs protective gear because he is out of his environment. We live comfortably in the biosphere where life thrives.

            Biosphere comes from the Greek word 'bios', which means life. We humans live in the biosphere. Biosphere is a layer that extends slightly above and slightly below the surface of the earth. This space covers the earth's entire surface.

            Biosphere is, in fact, the living part of our home planet and it comprises a number of ecosystems. It also includes the atmosphere. The atmosphere acts just like a blanket over the earth as it protects our planet from harmful rays of the sun.

            Millions of different ecosystems are present in the biosphere and they are contained within many geographical areas known as biomes. The ecologists divide the biosphere into smaller units such as ecosystems, habitats and niches. This division makes its study easier because each of these units can be studied individually in detail.

            Biosphere consists of some 35,000 species of living creatures including human beings.

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            We tend to take our life for granted and think that the survival of living beings on earth depend; exclusively on the availability of fresh air, food and drinking water. However, our life depends on so many other factors too. The environment around us preserves life as a mother's womb protects the child within!

            Environment is formed by whatever surroundings we live in. In the case of Earth, all the physical surroundings present on our planet are called environment. In other words, environment is the setting in which human life, as well as countless other life forms, comfortably exists.

            The environment includes both living and non-living things. The part of the environment where life exists is called the biosphere. All the living beings including human beings and plants are part of the biosphere.

            The non-living part of the environment has three main parts: the atmosphere, the hydrosphere, and the lithosphere. The atmosphere is the air, which comprises of various gases such as oxygen, nitrogen, and carbon. Hydrosphere, as the name suggests, consists of water bodies. All oceans and other bodies of water on earth such as rivers and lakes make up the hydrosphere. The lithosphere denotes the outer layer of Earth.

            Our existence and survival depends entirely on atmosphere. All animals, plants, and other living beings rely on the non-living aspects of the environment to survive.

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