Study life

 WHAT HAPPENS IT DOES NOT RAIN FOR LONG PERIOD Sometimes so happens that does not rain in region for a year or more. This leads shortage of water that region causing everywhere. environment drought. So, can say that if does not rain in region for long time causes drought sookha). Drought is period without rains leading to severe shortage of water in the region. happens follows. The soil in the fields is normally moist because it has water in it. The soil continues to lose water by rporation and transpiration. The water lost by soil is usually made up by rains. If, however, it does not rain at all (or the rainfall is very low) for a long period, the o of water from the soil is not made up and hence the soil becomes dry (see Figure 14). Due to lack of rains, the water level in the lakes and ponds also goes down and some of them may even dry up completely. In the absence of rains, no water seeps into the ground and hence the level of groundwater in wells, etc., falls drastically. Due to

 WHAT IF IT RAINS HEAVILY Every place in the world gets rains sometime or the other. The time, duration and amount of rainfall varies from place to place. For example, in some parts of the world, it rains throughout the year whereas in other parts it rains only for a few days in a year. In our country, most of the rainfall occurs in the monsoon season (rainy season). Rains are always welcome. Rains give us many advantages. For example: (1) Rains bring relief by cooling the environment after hot summer days. (ii) The sowing of many crops depends on the arrival of rains during monsoon. (iii) Rains provide water in the rivers and dams of hydroelectric power plants. (fo) Rains fill the lakes and ponds which act as sources of water. Rains are also responsible for the groundwater which gets stored under the surface of earth. When it rains heavily for a long time, we get excess rainfall resulting in too much water all around. The excessive rainfall due to heavy rains leads to many problems. S

 Carbon dioxide Carbon dioxide is a colourless and odourless gas. It has a slightly sour taste. Carbon dioxide is moderately soluble in water. Carbon dioxide gas neither burns nor supports burning. Carbon dioxide extinguishes a burning fire. Plants and animals consume oxygen from air for respiration and produce carbon dioxide. Plant and animal matter burns by consuming oxygen from air and produces mainly carbon dioxide and a few other gases. If some material is burning in a closed room, we feel suffocated. This is due to the accumulation of excess of carbon dioxide (and some carbon monoxide) in the air of the room which is produced by the burning material. Air contains only about 0.03 per cent of carbon dioxide gas. Though the amount of carbon dioxide in air is comparatively small but it is a very important component of air. The carbon dioxide gas present in air is important to green plants. Green plants need carbon dioxide gas to make food. In sunlight, green plants use carbon dioxid

 Waste materials (or rubbish) especially household wastes, are called garbage. It is called 'kole in W Hi Every household produces a lot of garbage (or wastes) daily which is collected in dustbins ps offices and schools also produce garbage or rubbish everyday What does the garbage (or rubbish) This will become clear from the following discussion. We peel off many fruits and vegetables before eating or cooking them. Sometimes cooked food also cunased in our homes and it is called left over food. The leaves of potted plants also keep on falling day in our homes. The peels of fruits and vegetables, left-over cooked food and fallen leaves of ted plants are thrown away as garbage. Every household buys a large number of packaged products such as door (atta), rice, pulses, biscuits, chocolates, milk and oil, etc, which are packed in plastic bags. ardboard cartons, paper wrappers, plastic containers, tirs and many other kinds of packing materials All the packing materials are useless and

  A large area of land covered mainly with trees and plants is called alaust And a large area of grass covered land used for grazing is called grassland There are few trees or places for animals to hide gland habitats. Due to this speal is important for the animals which live in grassland habitats (so they can nits away from their enemies) For most common purposes, however, the wrous forest and and are used in the same sense. The forest (or grassland) is a habitat Many animals such as lon som elephants deer, en live in forest habitats. There are many features of a lion, a deck, other animals and plant which help them to survive in the forest habitat. The adaptations in lion and deer to the forest habitat are described below. Adaptation of lion The lion is a camivorous animal which eats only the meat (or flesh) of oder animals. The lion lives in a forest habitat The adapted to the forest habitat in the following ways: 1.The lion is a strong, fast and agile animal which can hunt and kill

 The leaf is a thin, broad, flat and green part of a plant which is attached to the stem (or branch). plural of leaf is leaves. A plant has a large number of leaves. Leaves of different plants have differe shapes and sizes, but all of them have the same basic structure. A leaf consists mainly of two parts: lamina and petiole (see Figure 8). Lamina is commonly ke o as leaf blade and petiole is commonly known as leaf stalk. The broad, green part of the leaf is called lan th The thin stalk with which leaf is attached to the stem (or branch) is called 'petiole. There is a mid tr (main vein) in the centre of lamina (or leaf blade). A large number of veins spread out from the mid Rib to all the parts of the leaf. The mid-rib and veins consist of bundles of tiny tubes some of which carry water (and dissolved minerals) into the leaf, and others carry away the food from the leaf. There are minute pores on the surface of a leaf (which are called stomata). Stomata are so small that we cannot

  Birds Sparrow, crow, pigeon, parrot, eagle, hen, duck, swan, ove and peacock, are all birds. Birds walk on the ground and igh also fly in air. Some birds (like duck and swan) also swim in my water. Birds walk on the ground by using their hind limbs (see Figure 18). Those birds which swim in water do so by raig pushing against water with their hind limbs which have d trio webbed feet. The webbed feet help the bird in swimming in water. The birds can fly because their bodies are adapted (or modified) for this purpose. The main adaptations which have been made in the bodies of birds by nature to enable them to fly are the following: Their forelimbs are modified to form wings for flying.  Their flight feathers provide a large flat surface which is light but strong. Their bones are hollow and light. Their bodies are streamlined and extremely light. They have powerful flight muscles. Their breastbone is extended (as keel) for the attachment of large flight muscles (which move the wings up

 NITROGEN Nitrogen is a colourless, tasteless and odourless gas. Nitrogen gas is slightly soluble in water. Nitrogen gas is not essential for breathing (or respiration). Nitrogen gas neither burns itself nor supports the process of burning. That is, nitrogen does not support combustion. Nitrogen is a very unreactive gas. In this respect, nitrogen is just the opposite of oxygen (which is a very reactive gas. Nitrogen gas present in air is important for living things. All the living things need nitrogen com pounds for their growth. The plants use nitrogen gas of the air to make proteins. These proteins are used by the plants for their own growth as well as for the growth of human beings and other animals. Thus, nitrogen is needed by plants to make protein. Oxygen:- Oxygen is a colourless, tasteless and odourless gas. Oxygen gas is slightly soluble in water. Oxygen gas is essential for breathing (or respiration). We can live for several days without food and water but we will die very qui

  RAINWATER HARVESTING One way of increasing the availability of water to overcome its shortage is rainwater harvesting The activity of collecting rainwater directly and store it in big tanks for later use, or making the rainwater percolate into ground more efficiently to recharge the groundwater, is called rainwater harvesting. Thus there are two main techniques of rainwater harvesting: (1) Collection and storage of rainwater in tanks for future use when there is scarcity of water, and (i) To make rainwater percolate into the ground more efficiently by constructing percolation pits and recharge wells so as to recharge (or replenish) groundwater. The groundwater which we take out for our use by digging wells, tube wells and installing hand pumps, comes from the rainwater which seeps into the ground naturally. Now, when too much water is drawn through wells and tube-wells for use in homes, agriculture and industry, the water level in the wells and tube-wells goes down drastically. Some

 Rib Cage If we take a deep breath, hold it for a while and move our hand on the chest, we will find a number of bones in the chest region. These chest bones are called ribs. Ribs are the curved bones in our chest (see Figure 4). Ribs exist in pairs. There are 12 pairs of ribs in the chest of our body. We know that there is a long backbone at the back of our body. There is also a small bone called breast bone in the chest region, in front of our body (see Figure 4). One end of all the ribs is joined to the backbone and their other end is joined to the breast bone. In this way, all the rib bones, -Eye soo a part of backbone, and the breast bone, join to form a 'bony cage" or box-like structure'. The hollow, bony structure formed by the ribs is called 'rib cage' (see Figure 4). Some of the important internal organs of our body such as heart, lungs and liver lie inside the strong, bony rib cage. The rib cage protects the delicate internal organs like heart, lungs and

 Cartilage Most of the skeleton consists of hard bones. However, at some places in the skeleton there is a material ich is not as hard as bones and which can be bent. It is called cartilage. So, we can now say that though most of the skeleton is made of bones but it has some cartilage too Cartilage is a firm but flexible material d at some places in the skeleton Cartilage is much softer than bone. Cartilage can be bent without haking. In fact, cartilage is a kind of softer and elastic bone Cartilage is present in the following places in our body : Cartilage Cartilage is present in the pinnae of ears (upper part of ears) Cartilage is found at the end of nose. Cartilage is found on the end of bones where they meet one another at a joint Cartilage is also present (as cartilage discs) between the vertebrae of backbone. The upper part of our ear is called pinna and the lower part aled ear lobe. If we press the pinna of our ear and the ear lobe been our fingers, turn by turn, we will find th

 The food which we eat during the whole day is called our diet. A diet consists of many food items made from cereals (like wheat and rice), pulses, fruits, vegetables, meat, fish, eggs and milk, etc., which supply all the nutrients to the body. The diet which contains adequate amounts of all the nutrients such as carbohydrates, fats, proteins, vitamins and minerals (sufficient for the normal growth and development of the body), is called a balanced diet. A balanced diet also contains sufficient amount of water and roughage. Some food items are rich in carbohydrates, some are rich in fats, while others may contain more of proteins, vitamins and minerals. No single food item can provide us all the essential nutrients in adequate amounts. So, in order to make a balanced diet, we should include a number of different food items in our daily meals which, taken together, provide us all the nutrients in adequate amounts. We should also drink sufficient water and eat roughage-containing foods.

 FATS Like carbohydrates, fats also provide energy to our body. In fact, fats provide us twice as much energy as that provided by the same amount of carbohydrates. For example, a little butter (which is a fat) provides us much more energy than a large slice of bread (which is a carbohydrate). Butter, ghee, groundnut oil, mustard oil, sunflower oil and coconut oil are the common fats used by us in everyday life. Fats are the richest source of energy but they are more expensive than carbohydrates. Since both, fats as well as carbohydrates provide energy, therefore, the foods containing fats and carbohydrates are called 'energy giving foods'. Fats are supplied to our body by many foods such as: Butter, Ghee, Milk, Cheese (Paneer), Oil (Groundnut oil, Mustard oil, Sunflower oil and Coconut oil, etc.), Egg yolk (yellow of an egg), Meat, Groundnut, Cashew, and Soybean. Please note that fats and oils are similar substances, the only difference being that fats are solids at room temper

 Human Brain  Is reflex action the only function of the spinal cord? Obviously not since we know that we are thinking beings. Spinal cord is made up of nerves which supply Information to think about. Thinking involves more complex mechanisms and neural connections. These are concentrated in the brain, which is the main coordinating centre of the body. The brain and spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it.We also think about our actions, Writing, talking, moving a chair. clapping at the end of a programme are examples of voluntary actions which are based on deciding what to do next. So, the brain also has to send messages to muscles. This is the second way in which the nervous system communicates with the muscles. The communication between the central nervous system and the other parts of the body is facditated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal ne

 Excretion in Human Beings The excretory system of human beings includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are located in the abdomen, one on either side of the backbone, Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra. How is urine produced? The purpose of making urine is to filter out waste products from the blood. Just as CO, is removed from the blood in the lungs. nitrogenous waste such as urea or uric acid are removed from blood in the kidneys. It is then no surprise that the basic filtration unit in the kidneys. like in the lungs, is a cluster of very thin-walled blood capillaries. Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called Bowman's capsule that collects the filtrate.Each kidney has large numbers of these filtration units called nephrons packed close together. 7. Some substances in th

 Transportation in Plants We have discussed earlier how plants take in simple compounds such CO, and photosynthesise energy stored in their chlorophyll-containing organs, amely leaves. The other kinds of raw materials needed for building plant bodies will also have to be taken up separately. For plants the soil is the nearest and nichest source of raw materials like nitrogen phosphorus and other minerals. The absorption of these substances therefore occurs through the part in contact with the sot, namely roots If the distances between sell-contacting organs and chlorophyll- containing ongans are small, energy and raw materials can easily diffuse to all parts of the plant body. But if these distances become large because of changes in plant body design, diffusion processes will not be sufficient to provide raw material in leaves and energy in roots A proper system of transportation is therefore essential in such situations. Energy needs differ between different body designs Plants do no

 Our pump-the heart.  The heart is a muscular organ which isas big as our fist Because both oxygen and carbon dicocide have to be transported by the blood, the heart has diferent chambers to prevent the Vogen rich blood from mixing with the Bloed containing carbon dioxide. The carbon dioxide-nch blood has to reneh The lungs for the carbon dioxide to be mood and the oxygenated blood from the lungs his to be brought back to the heart. This oxygen-rich blood is then to the rest of the body. We can follow this process step by Mirp Oxygen-rich blood from the tongs conies to the flon walled upper chamber of the heart on the left, she left atrium. The left atrium relaxes when it is collecting this blood, It then contracts, while the nest chamber. the left ventricle. Relaxes, so that the blood is transferred to . When the muscular left ventriclessntracts to its turn, the blood is pumped out to the body De oxygenated blood comes from the body to the upper chamber on the night, the right artium,

 Nutrition in Human Beings The alimentary canal is basically a long tube extending from the mouth to the anus. we can see that the tube has different parts. Various regions are specialised to perform different functions. What happens to the food once it enters our body? We shall discuss this process here. We eat various types of food which has to pass through the same digestive tract, Naturally the food has to be processed to generate particles which are small and of the same texture. This is achieved by crushing the food with our teeth, Since the lining of the canal is soft, the food is also wetted to make its passage smooth. When we eat something we like, our mouth waters. This is actually not only water..but a fluid called saliva secreted by the salivary glands. Another aspect of the food we ingest is its complex nature. If it is to be absorbed from the alimentary canal, it has to be broken into smaller molecules. This is done with the help of biological catalysts called enzymes Th

 NUTRITION When we walk or ride a bicycle, we are using up energy. Even when we are not doing any apparent activity, energy is needed to maintain a state of order in our body. We also need materials from outside in order to grow, develop, synthesise protein and other substances needed in the body. This source of energy and materials is the food we eat. How do living things get their food? The general requirement for energy and materials is common in all organisms, but it is fulfilled in different ways. Some organisms use simple food material obtained from inorganic sources in the form of carbon dimade and water. These organisms, the autotrophs, include green plants and some bacteria. Other organisms utilise complex substances These complex substances have to be broken down into simpler ones before they can be used for the upkeep and growth of the body. To achieve this, organisms use bio-catalysts called enzymes. Thus the heterotrophs survival depends directly or indirectly on autotroph

WHAT ARE LIFE PROCESSES? The maintenance functions of living organisms must go on even when they are not doing anything particular. Even when we are just sitting in class even if we are just asleep, this maintenance job has to go on The processes which together perform this maintenance job an We processes . Since these maintenance processes are needed to prevent damage and break-down energy is needed for them. This energy comes from outside the body of the mdhadual organism. So there must be a process to transfer a source of energy from outside the body of the organism which we call food, to the inside, a process we commonly call nutrition If the body size of the organisins is to grow, additional raw material wit also be needed from outside. Since life on earth depends on carbon- based molecules most of these food sources are also carbon-based Depending on the complexity of these carbon sources, different organisms can then use different kinds of nutritional processes The outside sourc

 The elements which have a tendency to form positive ions are known metals. The elements which have a tendency to form negative ions are known non-metals. The elements whose properties fall between those of metals and non-metals ore known metalloids. Metals Metals in their pure state, have metallic lustre. Metals are generally hard. • Some metals can be beaten into thin sheets. This property is called f malleability. ⚫ Metals are ductile, ie, thin wires can be drawn from metals. • Metals are good conductor of heat and electricity and have high melting points. Silver and copper are the best conductor of heat. Metals are solid but mercury is liquid at room temperature. . Their oxides are basic. With dil. HCl or H,SO,, they release H₂ gas. e.g., aluminium, copper, sodium, etc Non-metals . These can be solid, liquid or gas at room temperature. . These are neither malleable nor ductile. These are brittle. These do not conduct heat and electricity. C (graphite) is good conductor of electrici

 Force Force is a push or pull which can change the position of a body as required. It is a vector quantity following all the rules of vector. Forces are of two types 1. Balanced Forces If there are many forces acting on a body, but resultant of all of them is zero, then the forces are called balanced forces. 2. Unbalanced Forces If the resultant of all the forces is not zero, then the forces are called unbalanced forces. Newton's Law of Motion There are three laws of motion First Law "Everybody remains in its state of rest or state of motion, until an external force is applied on it." This law is also known as law of Inertia Inertia is a property by virtue of which, a body tries to retain its state. Inertia are of two types 1. Inertia of Rest If a body is in rest, then it will remain in rest until an external force is applied on it. 2. Inertia of Motion If a body is in motion, then it will remain in motion until an external force is applied on it. There are some examples