The Living Organisms and their Surroundings

Category : UPSC

 The Living Organisms and their Surroundings


1.           Habitat and Adaptation


  • Camels have long legs which help to keep their bodies away from the heat of the sand.They excrete small amount of urine, their dung is dry and they do not sweat. Since camels lose very little water from their bodies, they can live for many days without water.
  • There are so many kinds of fish, but they all have something common about their shape. All the ones have the streamlined shape. This shape helps them move inside water. Fish have slippery scales on their bodies. These scales protect the fish and also help in easy movement through water. Fish have flat fins and tails that help them to change directions and keep their body balance in water. Gills present in the fish help them to use oxygen dissolved in water.
  • The presence of specific features or certain habits, which enable a plant or an animal to live in its surroundings, is called adaptation.
  • The surroundings where organisms live is called a habitat.
  • The living things such as plants and animals, in a habitat, are its biotic components. Various non-living things such as rocks, soil, air and water in the habitat constitute its abiotic components. Sunlight and heat also form abiotic components of the habitat.
  • Desert animals like rats and snakes, which do not have the long legs that the camel has. To stay away from the intense heat during the day, they stay in burrows deep in the sand. These animals come out only during the night, when it is cooler.
  • Desert plants lose very little water through transpiration. The leaves in desert plants are absent very small, or they are present in the shape of spines. This helps in reducing loss of waier from the leaves through transpiration e.g. The leaf-like structure in a cactus is, in fact, its stem.
  • Photosynthesis in these plants is usually carried out by the stems. The stem is also covered with a thick waxy layer, which helps to retain water. Most desert plants have roots that go very deep into the soil for absorbing water.
  • In a mountain region trees are normally cone shaped and have sloping branches. The leaves of some of these trees are needle-like. This helps the rainwater and snow to slide off easily.
  • Animals living in the mountain regions are also adapted to the conditions there. They have thick skin or fur to protect them from cold. For example, yaks have long hair to keep them warm. Snow leopard has thick fur on its body including feet and toes. This protects its feet from the cold when it walks on the snow.
  • The mountain goat has strong hooves for running up the rocky slopes of the mountains.
  • A lion lives in a forest or a grassland and is a strong animal that can hunt and kill animals like deer. It is light brown in colour. Lions have long claws in their front legs that can be withdrawn inside the toes.
  • A deer is another animals that lives in forests and grasslands. It has strong teeth for chewing hard plant stems of the forest. A deer needs to know about the presence of predators (animals like lion that make it their prey) in order to run away from them and not become their prey. It has long ears to hear movements of predators. The eyes on the side of its head allow it to look in all directions for danger. The speed of the deer helps them to run away from the predators.
  • Squids and Octopus do not have this streamlined shape. They stay deeper in the ocean, near the seabed and catch and prey that moves towards them. However, when they move in water they make their body shapes streamlined. These animals have gills to help them use oxygen dissolved in water.
  • There are some sea animals like dolphins and whales that do not have gills. They breathe in air through nostrils or blowholes that are located on the upper parts of their heads. This allows them to breathe in air when they swim near the surface of water. They can stay inside the water for a long time without breathing. They come out to the surface from time to time, to breathe in air.
  • Aquatic plants, roots are much reduced in size and their main function is to hold the plant in place. The stems of these plants are long hollow and light. The stems grow up to the surface of water while the leaves and flowers, float on the surface of the water.
  • Frogs usually have ponds as their habitat. Frogs can stay both inside the pond water as well as move on land. They have strong back legs that help them in leaping and catching their prey. They have webbed feet which help them swim in water.



2.           Living Organism and Nutrition


  • In sunlight, plants use carbon dioxide of air to produce their own food and give out oxygen. Plants produce their food only during the daytime whereas respiration in them takes place day and night. The amount of oxygen released in the process of food preparation by plants is much more than the oxygen they use in respiration,
  • Bees and humming-birds suck the nectar of plants.
  • Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested.
  • Cows, buffaloes and other grass-eating animals chewing continuously even when they are not eating. Actually, they quickly swallow the grass and store it in a part of the stomach called rumen. Here the food gets partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination and these animals are called ruminants.
  • The grass is rich in cellulose, a type of carbohydrate. Many animals, including humans, cannot digest cellulose.
  • Ruminants have a large sac-like structure called Caecum between the small intestine and large intestine.
  • The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.
  • Amoeba is a microscopic single-celled organism found in pond water. Amoeba has a cell membrane, a rounded, dense nucleus and many small bubble-like vacuoles in its cytoplasm. Amoeba constantly changes its shape and position. It pushes out one, or more finger-like projections, called pseudopodia or false feet for movement and capture of food.
  • Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole.
  • Digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed.


3.           Soil


  • Polythene bags and plastics pollute the soil. They also kill the organisms living in the soil.
  • The rotting dead matter in the soil is called humus.
  • The mixture of rock particles and humus is called the soil.
  • The soil is classified on the basis of the proportion of particles of various sizes. If soil contains greater proportion of big particles it is called sandy soil. If the proportion of fine particles is relatively higher, then it is called clayey soil. If the amount of large and fine particles is about the same, then the soil is called loamy.
  • Sand particles are quite large. They cannot fit closely together, so there are large spaces between them. These spaces are filled with air. We say that the sand is well aerated. Water can drain quickly through the spaces between the sand particles. So, sandy soils tend to be light, well aerated and rather dry.
  • Clay particles, being much smaller, pack tightly together, leaving little space for air. Unlike sandy soil, water can be held in the tiny gaps between the particles of clay. So clay soils have little air. But they are heavy as they hold more water than the sandy soils.
  • The best topsoil for growing plants is loam. Loamy soil is a mixture of sand, clay and another type of soil particle known as silt.
  • The organic manure is considered better than fertilisers. This is because :
  • it enhances the water holding capacity of the soil.
  • it makes the soil porous due to which exchange of gases becomes easy.
  • it increases the number of friendly microbes.
  • it improves the texture of the soil.
  • All living beings need water to live. Water is important for proper growth and development of flowers, fruits and seeds of plants. Water is absorbed by the plant roots. Along with water, minerals and fertilisers are also absorbed.
  • Plants contain nearly 90 per cent water. Water is essential because germination of seeds does not take place under dry conditions. Nutrients dissolved in water get transported to each part of the plant. Water also protects the crop from both frost and hot air currents. To maintain the moisture of the soil for healthy crop growth, fields have to be watered regularly.
  • Sprinkler System: This system is more useful on the uneven land where sufficient water is not available. The perpendicular pipes, having rotating nozzles on top, are joined to the main pipeline at regular intervals. When water is allowed to flow through the main pipe under pressure with the help of a pump, it escapes from the rotating nozzles. It gets sprinkled on the crop as if it is raining. Sprinkler is very useful for sandy soil.
  • Drip system: In this system, the water falls drop by drop just at the position of the roots. So it is called drip system. It is the best technique for watering fruit plants, gardens and trees. The system provides water to plants drop by drop. Water is not wasted at all. It is a boon in regions where availability of water is poor.


4.           Gait of Animals


  • Earthworm
  • The body of an earthworm is made up of many rings joined end to end. An earthworm does not have bones. It has muscles which help to extend and shorten the body.
  • During movement the earthworm first extends the front part of the body, keeping the rear portion fixed to the ground. Then it fixes the front end and releases the rear end. It then shortens the body and pulls the rear end forward. This makes it move forward by a small distance.
  • Repeating such muscle expansions and contractions, the earthworm can move through soil. Its body secretes a slimy substance to help the movement.
  • The earthworm, actually, eats its way through the soil. Its body then throws away the undigested part of the material that it eats. This activity of an earthworm makes the soil more useful for plants.


  • Snail
  • The rounded structure it carries on its back is called the shell and it is the outer skeleton of the snail, but is not made of bones.
  • The shell is a single unit and does not help in moving from place to place. It has to be dragged along.
  • A thick structure and the head of the snail may come out of an opening in the shell. The thick structure is its foot, made of strong muscles.


  • Cockroaches
  • Cockroaches walk and climb as well as fly in the air. They have three pairs of legs. These help in walking. The body is covered with a hard outer skeleton. This outer skeleton is made of different units joined together and that permits movement.
  • There are two pairs of wings attached to the breast. The cockroaches have distinct muscles - those near the legs move the legs for walking. The breast muscles move the wings when the cockroach files.
  • Birds
  • Birds fly in the air and walk on the ground. Some birds like ducks and swans also swim in water. The birds can fly because their bodies are well suited for flying. Their bones are hollow and light.
  • The bones of the hind limbs are typical for walking and perching. The bony parts of the forelimbs are modified as wings. The shoulder bones are strong. The breastbones are modified to hold muscles of flight which are used to move the wings up and down.


  • Fish
  • The head and tail of the fish are smaller than the middle portion of the body – the body tapers at both ends. This body shape is called streamlined.
  • The shape is such that water can flow around it easily and allow the fish to move in water. The skeleton of the fish is covered with strong muscles. During swimming, muscles make the front part of the body curve to one side and the tail part swings towards the opposite side.
  • The fish forms a curve. Then, quickly, the body and tail curve to the other side. This makes a jerk and pushes the body forward. A series of such jerks make the fish swim ahead. This is helped by the fins of the tail.
  • Fish also have other fins on their body which mainly help to keep the balance of the body and to keep direction, while swimming.


  • Snake
  • Snake have a long backbone. They have many thin muscles. They are connected to each other even though they are far from one another. Muscles also interconnect the backbone, ribs and skin.
  • The snake's body curves into many loops. Each loop of the snake gives it a forward push by pressing against the ground. Since its long body makes many loops and each loop gives it this push, the snake moves forward very fast and not in a straightline.


5.           Wastewater Treatment Plant (WWTP)


  • Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical and biological matter that contaminates the wastewater.
  • Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed.
  • Water then goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.
  • The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water.
  • The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.
  • Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water. After several hours, the suspended microbes settle at the bottom of the tank as activated sludge. The water is then removed from the top.
  • The activated sludge is about 97 per cent water. The water is removed by sand drying beds or machines. Dried sludge is used as manure, returning organic matter and nutrients to the soil.
  • The treated water has a very low level of organic material and suspended matter. It is discharged into a sea, a river or into the ground. Nature cleans it up further. Sometimes it may be necessary to disinfect water with chemicals like chlorine and ozone before releasing it into the distribution system.


6.           Important Facts


  • Sometimes the voice of some of the boys in your class cracks. At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes. The growing voice box in boys can be seen as a protruding part of the throat called Adam's apple. In girls, the larynx is hardly visible from the outside because of its small size.
  • Generally, girls have a high pitched voice, whereas boys have a deep voice. In adolescent boys, sometimes, the muscles of the growing voice box go out of control and the voice becomes hoarse. This state may remain for a few days or weeks after which the voice becomes normal.
  • An adult human excretes, on an average in 24 hours, 1 to \[1.5\]litres of urine per day. Urine contains 95 per cent water, 2.5 per cent uria and 2.5 per cent other waste material.
  • Bacteria have lived on the earth for much longer than human beings. They are such hardy organisms that they can live under extreme conditions. They have been found living in boiling mudpots and extremly cold icy waters. They have been found in lakes of caustic soda and in pools of concentrated sulphuric acid. They can survive at depths of several kilometres. They probably can survive in space, too. A kind of bacterium was recovered from a camera which stood on the moon for two years. There is probably no environment in which bacteria cannot survive.
  • On 22 March, 2005, the General Assembly of the United Nations proclaimed the period \[2005-2015\]as the International Decade for action on "Water for life".
  • Enzymes generally function in a narrow range of temperature and pH. Each enzyme shows its highest activity at a particular temperature and pH called the optimum temperature and optimum pH. Activity declines both below and above the optimum value. Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.




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