Current Affairs 4th Class

Plants   We often see beautiful trees, plants full of green leaves, around us. But do we ever think why the leaves of trees are green? Have you ever seen plants having coloured leaves? The leaves of most of the plants are green because their leaves contain a green coloured pigment called chlorophyll. Green leaves are responsible for making food. Thus, they are also known as food factories of the plants. Plants uses carbon dioxide, sunlight and water for making food. Upper surface of a leaf has more chlorophyll for trapping the sunlight. On the undersurface of the leaf, there are tiny pores known as stomata which can only be seen through microscope. The stomata are responsible for exchange of gases in plants. Water and essential minerals are absorbed by the roots of the plant from soil and then It is transported to leaves through Stem. On the undersurface of leaves, there are fine network of lines called veins. Main vein is located at the centre of the leaf called midrib. Main vein has two tubes. One tube carries water and minerals from the stem to the leaf. The other one takes food from the leaf to other parts of the plant. A leaf is attached to the stem by a stalk. Leaves   Photosynthesis The process of making food by plants in the presence of sunlight, water, carbon dioxide and chlorophyll is called photosynthesis. During photosynthesis, plants take carbon dioxide and release oxygen. Food is prepared by plants in the form of glucose. Plants store extra food in fruits and seeds as starch. Trees store food in their trunks in the form of cellulose. Cactus do not have leaves. Photosynthesis occurs in their stems. Cactus   Some plants are not green. For example, mushroom. Another plant like croton plant has red coloured leaves. The red colour of the leaves is due to the presence of anthocyanin. But they have chlorophyll also. Photosynthesis takes place in these plants also.   Croton   Mushrooms do not have chlorophyll. They cannot make their food from photosynthesis. They get food from dead plants and animals.   Classification of Plants Plants are of various types classified on the basis of where they grow.   Terrestrial Plants Plant that grows on land are called terrestrial plants. They are further divided into various types such as:   Mango tree     Plants in hilly areas In hilly areas, plants can make food easily as there is sufficient sunlight and rainfall in these places. Coniferous tree grows on hills and mountains. They have standing branches so that snow which falls on them more...

Animals   Animals are living beings that can move and produce young ones. The process of producing young ones is called reproduction. Different animals reproduce by different methods. Some animals lay eggs and some give birth to young ones.   Egg Laying Animals Several types of animals like birds, reptiles, insects and amphibians lay eggs. An egg is an organic vessel in which an embryo begins to develop.   Birds Birds lay eggs which have a hard, protective shell. It contains a yellow yolk surrounded by white albumen. The yolk provides food to the chick growing inside it. The growing chick is called embryo. The parent bird sits on the egg to keep it warm. The chick breaks the shell and comes out when it has grown. This is called hatching.   Insects Insects also reproduce by laying eggs. Insects like butterfly and housefly have four stages in their life cycle i.e. egg, larva, pupa and adult. The egg is hatched into a larva. The young one looks different from the adult. The larva of a butterfly is known as caterpillar and that of a housefly is called a maggot. The larva first grows rapidly by eating the leaves. Then after sometime, it stops eating and forms a covering around itself called as cocoon. This is called the pupa. The larva changes into an adult inside he pupa and comes out of it after sometime.   Amphibians             Amphibians reproduce by laying eggs in water. The young frog which comes out of the egg is known as tadpole.   Fishes             Fishes also reproduce by laying thousands of eggs in water. But only few eggs grow into baby fishes. Reptiles Reptiles lay eggs in the sand or rotting vegetation. They do not sit on the eggs to keep them warm. The sea makes them warm and the egg is hatched.   Animals Giving Birth to Young Ones             Mammals are the animals which give birth to young ones and produce milk to feed them. They do not lay eggs. Dogs, monkeys, cats and human beings comes under the category of mammals. Bats are flying mammals. Whales and dolphins are also mammals living in water.   Habitat The home or natural environment of a living thing is known as habitat. All living beings changes themselves to survive in the natural world, for example, birds and insects can fly. This is called adaptation.   Classification of Animals on the Basis of Their Habitat             Animals are classified on the basis of the place where they live.   Aquatic Animals Animals which live in water are called aquatic animals. Fishes live in water. They have fins for swimming in water. They have gills for breathing. Aquatic animals like dolphins and whales do not have more...

Functioning of Human Body   All human beings require energy for doing various kinds of activities. They get this energy from food that they eat. The food we eat cannot be used by our body directly. It has to be broken down into a simpler form. Our body has a system for breaking down the food into a simpler form. This system is called digestive system.   Digestive System The process of digestion takes place in the following steps:  

• First, we eat food which goes into the mouth. Our mouth has teeth for chewing and cutting the food into smaller pieces. Thus, the process of digestion begins in the mouth. In the mouth, a digestive liquid called saliva mixes with food to make it a fine paste. Saliva breaks down food into starch and soluble sugar.
• Food then passes into the stomach through the food pipe. The stomach is a hollow, muscular bag-like structure. In the stomach, the food again mixes with some more digestive juices for further break down into simpler form.
• From the stomach, the food passes into long coiled tube called the small intestine. Its wall produces more digestive juices.
• Liver and pancreas also pour their juices into the small intestine. These juices help to digest the food completely.
• Digested food is then absorbed by a network of blood vessels present in the small intestine. The absorbed food is then carried to different parts of the body.
• Body is not able to digest water and roughage. Therefore, they are passed into the large intestine. The blood in the walls of the large intestine absorbs the water and carries it to the kidneys.
• The semi-solid waste is then thrown out from the body through the anus.

Digestive System of Human Body     Health Tips  

• We should eat food at fixed hours.
• We should eat a balanced diet.
• We should wash our hands before eating.
• We should chew the food well before swallowing it.
• We should drink lots of water.
• We should not overeat.
• We should follow a routine to pass out the waste.

  Parts of Teeth A tooth has three parts. Crown, neck and root. Crown:  Crown is that part of tooth that we can see. Neck:  Neck is below the crown. Root:  Through roots, tooth is fixed in the jaw. The gum covers the root. The outer hard layer which covers the tooth is called enamel. Enamel is the hardest thing a human body. Dentine is below it. The core of the tooth is called pulp. Pulp is soft and has blood vessels and nerves in it. The nerves are connected to the gum through a hole in the root.   more...

Measurement   We need to measure many different things in our daily life like length of objects, height, weight (of fruits, vegetables, etc.) amount of milk, water and so on.       Measurement of Length In early days, people used body parts to measure lengths.                      Cubit                                                   Hand span    The metre is what we normally use for measuring lengths. Smaller lengths are measured centimetres. Metre is written as m and centimetre as cm.   Measurement of Mass Mass tells us how heavy or light an object is. We us weighing scales to find the mass an object. Just as we use metre for measuring length, we use kilogram for measuring mass. Smaller weights are measured in grams. Kilogram is written as kg and gram is written as g.   Measurement of Capacity Capacity of a container is the amount of liquid it can hold. Litre is the commonly used unit for measuring capacity. Smaller units are measured in millilitres. Litre is written as / and millilitres as ml.   Some Other Units of Measurement In everyday life, we also need to measure things that do not involve length, mass, and capacity. Time a temperature are two such examples. Time is measured in seconds. Measure of hotness or coldness of an object is called temperature. Temperature can be measured with the help of a thermometer.  

Matter and Materials   Matter Anything that occupies space and has mass is called matter. Everything around us is made up of matter. Matter is made up of atoms. Water bottle, school bag, rubber, pencil are all made up of matter.   States of Matter Matter exists in three forms - solid, liquid and gas. Matter can change from one form in other on heating and cooling.   Changes Around Us Matter is constantly changing around us. Changes are of two types — physical changes and chemical changes. In physical change, no new substance is formed. Breaking of glass, melting of ice into water are some examples of physical change. When ice melts the solid water turned to liquid water. It doesn't turn into food or cold drink or anything new. It remains water. Physical changes can be reversed.in a chemical change, new substance is formed. Changing of milk into curd is an example chemical change. Similarly burning of paper, making of vegetable dishes from raw vegetables, bursting of crackers are some other examples of chemical changes. Unlike physical changes, chemical changes cannot be reversed.   Rocks  

• Our earth is made up of rocks. Rocks are hard stones.
• Pebbles are small pieces of rock
• Rocks are useful to us in many ways. Rocks such as marble, granite and sand?" are used in making buildings.
• World's seventh wonder Taj Mahal is made up of white marble.

  Soil Formation  

• Soil formation starts when rocks break down into smaller pieces due to rain and the sun's heat. These smaller pieces mix with dead and decaying animals and plants to form soil.  It takes thousands of years to form a small amount of soil.
• Different types of soil contain different types of particles. These particles differ in colour and softness.
• Soil contains pebbles, gravel, clay, humus, water and air. The water trapped soil is called moisture.
• Soil provides a bed for both animal and plant life.
• We get many useful minerals such as diamond, granite, marble, and
• Remains of living things found deep under layers of rocks are called fossils.

  Minerals Minerals are chemical substances that occurs in nature. They are formed due to natural processes within the earth. They may be simple substances or very complex Rocks are formed of minerals. Examples of non-metallic minerals are limestone, magnesite, mica, etc. There are metallic minerals also such as gold, silver, iron, etc. Our body needs some minerals such as calcium, sodium and iron in very small quantities for healthy growth. The bulk of minerals is used for industrial needs as manufacturing of building materials, vehicles, for fuels and for making jewellery.

Force, Work and Energy   Whenever we push or pull an object, we apply force. A force can make an object move, can stop a moving object, can change direction of a moving object and can change the shape of an object.   Types of Force There are different types of forces: Muscular Force the force exerted by muscles of our body. For example, lifting a bucket, lifting dumbbells, etc. A Man lifting a dumbbells     Elastic Force It is the force exerted when an elastic material is stretched. For example, stretching of rubber band. Stretching a rubber band   Frictional Force                                                 It is the force exerted by two surfaces on each other in moves over the other, while they are in contact. For example, while walking on a road frictional force is acting between the road and the sole of our shoe. Friction, between shoes and Floor   Gravitational Force The force exerted by the centre of the earth which pulls objects towards it. For example when a ball is thrown in the air, it comes back towards the earth due to gravitational force, an apple falling from a tree, etc.   Falling of an apple due to gravitational force   Electrostatic Force When we rub a comb through dry hair, the comb gets charged and is able to attract tiny bits of paper. The force exerted by charged comb on the bits of paper is called electrostatic force.     Charged hairs exert force on balloon   Work Work refers to an activity that involves applying force on an object and movement the object in the direction of the force. For example, if a man lifts a bucket then some work is done. In this case, due to the force applied by the man, the movement bucket takes place in upward direction. Simple Machines tools which make our work easy are called simple machines. For example, pulley, wheel and axle, lever, inclined plane, etc.   Pulley                                             Inclined-plane   Energy Energy is the capacity or ability more...

Our Environment   Our Environment is composed of physical and biological things surrounding us. It has physical or abiotic factor and biological or biotic factor. Physical components includes air, water, minerals and other non-living things around us. Biological components includes plants, animals and micro- organisms.   Pollution Pollution is the undesirable change in the physical, chemical and biological constituents our surroundings. Pollution is of various types:   Air Pollution Air pollution occurs when the air contains dust particles, gases, fumes in that amount which is harmful for us. The substances causing air pollution are called air pollutants. Industries and vehicles discharge harmful gases into the air making it dirty and unfit for breathing.     Sun has ultraviolet rays which are absorbed by ozone layer present in the atmosphere. These rays can cause skin cancer. Due to air pollution ozone layer is getting depleted.   Effects of Air Pollution Air pollution has various effects which are explained below.   Breathing Problem When we inhale polluted air, it causes breathing problems. Bronchitis and asthma are diseases caused by air pollution.   Global Warming Human inhales oxygen and gives out carbon dioxide, when amount of carbon dioxide increases in air, it causes global warming. Global warming is the heating up of atmosphere due to excessive amount of carbon dioxide in the air   Acid Rain Sometimes harmful gases discharged by factories and vehicles mixes with water vapours in the clouds. When it rains, these harmful gases get mixed with water vapours and comes down as acid rain. It affects forests, soil and human health. Makes soil more acidic. It also damages buildings, monuments etc.   Water Pollution When toxic substances enter lakes, rivers, oceans and other water bodies, it causes water pollution. There are many sources of water pollution. Sewage from cities is thrown it water resources without treatment. Polluted water causes diseases like jaundice, typhoid, diarrhoea etc.   Factories discharges harmful chemicals directly into water which causes damage to aquatic plants and animals.   Soil Pollution Land gets polluted when we dump garbage on it. Wastes are of two types:   Biodegradable: Things like fruits, vegetable peels, paper etc. get decayed by microorganisms and mixes with soil.   Non-biodegradable: Things like plastic, polythene which do not get decayed by microorganisms and remains as it is in the soil and pollute the soil.

Our Universe   Our Universe Our universe consists of number of stars, planets including our earth and moons.   Solar System     The sun and the eight planets belong to a family called solar system. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. All of them revolve in fixed path called orbit. Planets rotate on their axis also. Most planets have their satellites which revolve around them. Satellite does not have its own light. Man has also made ne satellites for weather forecasting and to help in communication which are known as artificial satellites, for example, Aryabhata, Rohini etc.   Stars and Planets A star is a huge ball of hot gases. It gives out heat and light. Planets do not have any or light of their own. They appear bright because they reflect the light of the stars. They revolve around stars. The sun is actually a star because it has its own heat and light. It is a huge sphere of hot gases. The earth and other seven planets that revolve around the sun get heat and from the sun. The sun is the main source of energy in our solar system. The planet Mercury is closest to the sun, followed by Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. They revolve around the sun in fixed path called orbit. Stars are far apart from each other. Distance between stars is measured in light years. The distance travelled by light in year is called light year. The planets also rotate on their axis. Most of the planets have satellites. A satellite heavenly body that revolves around planets. It does not have any light of its own. The moon is a natural satellite of the Earth 3l shines as it reflects sunlight from its surface. The moon does not have an atmosphere to protect it from extreme heat or cold. Some satellites in the sky are artificial. They have been sent up by scientists of different countries to study space, to forecast weather help in communication. The first one of these was Sputnik 1. Some others are Aryabhata, Rohini, INSAT, etc.    

Reasoning and Aptitude   Introduction Learning process is dependent on ones ability to think logically and reason quickly and effectively. So Reasoning and logic skills are an important part in our progress 55 these skills are very useful in our day to day life. In this chapter, we will learn various problems related to reasoning and aptitude.   Problems Based on Patterns Pattern is a list of numbers or letters that follows a certain sequence or a certain rule. To find the missing term or next term in series to continue the given series, first we must have a rule. To solve them all, we have to do is figure out the pattern and come up with the next logical number or letter of the sequence.  

• Example:

The values of A and B in the given number pattern are:   (a) 4,125                      (b) 1,125         (c) 3,243                      (d) 1,243 (e) None of these   Answer (b)   Explanation: Here, pattern followed is: and Therefore, the value of A and B is 1,125           Ø    Example:   Which number will replace the question mark (?) in the number pattern given below?        (a) 31                           (b) 28 (c) 27                           (d) 29 (e) 26   Answer (d)   Explanation: Here, rule followed is: and Therefore, the missing number is 29   Problems Based on Coding and Decoding Coding is a method of expressing something in secret way and decoding is a process to understand a code language.   Word Coding In word coding, some particular words are assigned certain substitute names, a question is asked that is to be answered in the substituted code language.    

• Example:

  If 'India' is called 'Germany' 'Germany' is called 'Japan', and 'Japan' more...

Comprehensions   Reading comprehension is an essential part of any test of English language. In this, a passages is given. You have to read the passage carefully and answer the questions based it.  

•                    Example 1                            

Read the passage carefully and answer the   questions that follow: If you decide to become a paleontologist you would study plants and other organisms that lived in pre-historic times. That would be a time more than 5,500 years ago. Someone might ask how one could study something that is lost and gone. The answer is, by studying fossils. A fossil is the mark, imprint or remain of a plant or an animal left in sedimentary rocks. A fossil is formed after its marks or remains get buried in the mud or sand which is collected at the bottom of rivers, lakes or seas. With time, the weight of the upper layer presses down on the lower layers and turns it into rock.     Paleontologists study fossils to understand how a plant or an animal has changed over the year. They do this by comparing the fossils to what is alive today. But some plants and animals, like the dinosaurs, are not alive today. That makes a paleontologist's job extremely difficult. They have to make sense out of a fossil in much the same way as you would with a jigsaw puzzle. To do this, they also need to understand whether the rocks were formed under the sea or land. They are experts at telling the age of rocks. If you decide to become a paleontologist, you would be of great help to your country in locating oil reservoirs. Oil is often found in rocks that contain certain fossils. Oil companies use such fossils as clues to locate oil reservoirs.   1.            Pre-historic times are ________. (a) times more than 4,500 years ago   (b) times more than 5,500 years ago (c) times less than 4,500ryears ago     (d) times less than 5,500 years ago (e) None of these   2.            more...