# Current Affairs 5th Class

#### Human Body and Nutrition

Human Body and Nutrition   Human Body The organs of our body work together to perform various functions for the body. A group of organs doing some particular jobs for the body form an organ system.                Human body has the following systems performing certain functions:
• Respiratory system is responsible for carrying oxygen. Oxygen is necessary for human life.
• Digestive system breaks the food we eat into simpler forms.
• Skeletal system gives shape to human body and helps in the movement.
• Nervous system performs the functions of thinking, smelling, seeing, tasting, etc.
• Circulatory system helps in transportation of oxygen, carbondioxide, nutrients and other substances to various parts of the body.
• Muscular system helps in movement.
Skeletal System It is the framework of bones which gives support to human body. Adult human skeleton has 206 bones. Different parts of the human skeleton are:   Skull Skull consists of 22 bones which protects the brain. All bones of skull are immovable except the lower jaw. With the help of movable lower jaw, we can talk and eat. In lower and upper jaw, we have teeth for cutting and chewing food.     Rib Cage Ribs make a cage of bones around the chest which is called rib cage. It protects our internal organs. Generally adults have 12 pairs of ribs. There is a long bone at the centre of the chest, which holds the ribs in place, called sternum. Ribs are attached to the backbone. Last two ribs are not attached to the sternum and are known as floating ribs. These floating ribs are attached to the backbone. Backbone It is made up of 33-ring shaped small bones called vertebrae. Backbone is also called as vertebral column. It is a hollow tube through which spinal cord runs.   Limbs All human beings have two pairs of limbs: the forelimbs (arms) and hindlimbs (legs). Both forelimb and hindlimb is made up of 30 bones each. Thigh bone or femur is the longest bone in the body.   Note: The smallest bone of the body called stapes is present in the ear.   Functions of the Skeletal System The skeletal system has the following functions:
• It gives shape and support to our body. Without the skeleton, our body would be floppy like a jelly. Forget about walking, we would not even be able to stand.
• It protects our soft internal organs.
(i) The skull protects the brain. (ii) The rib cage protects the heart and the lungs. (iii) The backbone protects the spinal cord.
• It allows the movement of different body parts.
• Bones contain marrow, where our blood cells are made.
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#### Plants

Plants   Plants are very useful to us. Being a living thing, plants also reproduce to maintain the existence of their species. Plants reproduce in a number of ways: (i)      From their body parts (ii)     From spores (iii)    From seeds   Reproduction through Body Parts Some new plants grow from the parts of the mother plants. They grow from roots, stem and leaf. Such type of reproduction is known as vegetative propagation.   Root A sweet potato is a swollen root of the plant. The new plant of sweet potato can be grown from the roots of the original plant.   Stem Some plants can reproduce by burying a part of stem in the soil. From stem cutting, new shoots grow from buds. For example, Sugarcane, rose plant   Underground Stem Underground stems like potato and ginger have buds on them from where new shoots will grow on planting them in the soil. Potato   Similarly, some plants like onions and lilies grow from their bulb shaped stems.   Leaves In Bryophyllum, new plant grows from their leaves.   Bryophyllum   Reproduction Through Spores The plants like ferns, mushrooms or mosses, which do not have flowers, produce spores which can be grown into a new plant. Mushroom   Reproduction Through Spores The fruit bearing plants have seeds inside fruit. When these seeds fall on the soil, new plants grow from them. For example, Mango, rice, wheat and tomato, etc.   Tomato   Parts of Seed Seed has an upper covering which is called seed coat. Inside the seed coat/there may be one or two seed leaves called cotyledons. Between them, baby plant grows called seedling. Seedling has radicle growing downwards that develops into root and plumule growing upwards towards the sunlight that develops into shoot. Food for the baby plant wheat and rice have only one cotyledon and are monocot plants. Pea and beans have two cotyledons and are dicot plants. The process by which baby plant grows from a seed is called germination. A seed needs water, sunlight and air. A seedling grows into a plant when it gets sufficient water and food from soil, sunlight and air. Germination of seed   Dispersal of Seeds Plants have to disperse their seeds with the help of nature so that all seeds would not fall on one place causing lack of sunlight, water and space to grow Seeds are dispersed by wind, water, animals and explosion of fruits. These all are agents of dispersal.   Wind The seeds which are light and have wings or hairs on them are easily carried by more...

#### Animals

Animals   All animals breathe, feed and move. The place where an animal lives, eats, grows and reproduces is called its habitat.   Breathing All animals need to breathe for their survival. An animal breathes in oxygen and breathes out carbon dioxide, an exchange of gases takes place.   Fish A fish lives in water. The water passes out through a pair of gill-slits on each side of its body. As this water passes over the gills, the fish takes in oxygen and releases carbon dioxide, which flows out with the water. The oxygen gets absorbed into the blood of the fish.   Whale A whale looks like a fish and lives in water; but it is not a fish. A whale does not have gills. It has lungs. To breathe, it must come up to the surface of the water to fill its lungs with air. A whale has very large lungs so that it can take in enough oxygen in one breath to last for some time under the water.   Whale Frog A frog breathes through its lungs on land as well as through its moist skin under water. A baby frog or tadpole breathes through its gills. Frog   Insects Insects like cockroaches, caterpillars and grasshoppers breathe through tiny air holes, called spiracles on their bodies. The spiracles of the body lead to air tubes which form a network that reaches every part of an insect’s body. Air enters the body through this network. The body parts take in oxygen and give out carbon dioxide. The blood of insects does not have the oxygen carrier called haemoglobin. That is why their blood is not red in colour. Some animals like earthworms can take in oxygen through their thin moist skins.                     Grasshopper                   Caterpillars                     Cockroach   Amoeba and paramecium are tiny animals which can be seen only through a microscope. They breathe through their body surface.   Humans Humans too breathe through their lungs. We have a pair of lungs in our chest. We breathe through our nose. When we breathe in air, the lungs expand and fill with air. When we breathe out, the chest contracts and pushes out the air with the carbon dioxide from the body.   Human lungs   Eating Habits All living things need food to get energy, to grow and to stay healthy. Different animals eat different kinds of food. Some animals eat plants. Some eat the flesh of other animals. Some animals eat both plants and other animals. Animals have different types of teeth based on the type to food they eat. Animals are classified on the basis of their eating habits as more...

#### Housing

Housing   Housing People at different places build different types of houses. There are some factors on which building of houses depends.    These are:
• The climate of the place
• Materials used for making houses
• The budget
Climate In place where climate is hot, houses have thick walls and flat roofs. Thick walls keep the houses cool from inside. Flat roofs can be used by people for sleeping outdoors. In places where it rains a lot and climate is hot and damp, houses are built on stilts. These houses, built a few feet above the ground on raised platforms, remain safe from floods. The sloping roofs of houses on hills do not allow rainwater or snow to collect and make the houses damp and cold. Most houses in cold areas have fireplaces to keep their houses warm from inside.   Material Used Bricks and stones keep a house cool in hot places. Building houses in hilly areas may be more challenging and expensive than building on a flat area. Therefore, houses are made of bamboo and wood. Houses are built of wood to prevent more damage in case of collapsing. Mud, bamboo and palm leaves are used to make kachcha houses or temporary house called huts. These materials are cheap and easily available. Some other common building materials are concrete, glass, iron and thatch.   Budget Budget is the money available for building the house. A small hut requires less amount of money. Whereas, a large sum of money is required for making a concrete house. In big cities whereas, a large sum of money is required for making a concrete house. In big cities where space is very less, people build multistorey buildings.   Building a house There are certain factors which are to be remembered before, during and after the construction of a house. We should consult an architect for making a plan of the house depending upon space available and on the needs of the people who are going to build house.
• A sun-facing house gets a lot of sunlight.
• The walls of the house must be strong, damp-proof and well plastered. Insects do not breed on such walls.
• A house can be made safe by fitting the doors and windows with grills.
• Doors and windows must be in a direction such that fresh air and sunlight can enter every room. Wire-netting should be placed in windows to prevent flies and mosquitoes entering into the house.
• The floor of the house must be levelled and made smooth. It must have a good drainage system. Covered drains and outlets seal out foul smells and germs.
We should take care of our house after the construction also. The house should be kept clean. The floor of the house should be swept every day.
• The walls, windows, doors and other parts of the house must be dusted regularly. They need to be painted more...

#### Soil, Rocks and Minerals

Soil, Rocks and Minerals   Rocks The crust of the earth is made up of soil and rock. Rocks are made up of minerals. A rock can have one or many minerals. Rocks are found in the mountains, by seas, on the ground, and under it. Large rocks in the mountains are called boulders. Pebbles are small rocks. Sand is actually very tiny pieces of broken rocks. Depending on their formation, rocks are of three types: igneous, sedimentary and metamorphic.   Igneous Rocks The word igneous means made from fire or heat. Deep inside the earth in some areas it is so hot that even hard things like rocks melt. Molten rock is called magma. Sometimes the heavy rocks around the magma push it upwards towards the earth's crust. The magma comes out through a weak point on the surface of the earth. The place from where magma escapes to the surface of the earth is called a volcano. Hot gases, ash, rocks and magma push their way out through the volcano. The hot magma keeps flowing out of the top of the volcano in the form of a liquid called lava. The lava begins to cool and slowly hardens to form solid rock. This solid rock is called igneous rock. Examples of igneous rocks are granite, pumice, basalt and obsidian. There are different types of igneous rocks.   Granite When the magma cools slowly under the ground, it forms granites, a type of igneous rock. Some beautiful temples in Tamil Nadu are made of granite. Grey or black granite is used for making strong buildings. Highly polished granite is used for flooring.   Pumice Pumice is a light grey or cream coloured rock. It has many tiny holes which are formed by gases trapped inside it at the time of formation. It is formed by very quick cooling of the lava. Pumice is very light. Dentists use powdered pumice for polishing teeth. It is also used to polish furniture, to clean floors, and as a body scrubber.   Basalt Basalt is formed when the lava cools quickly and hardens above the ground. It is a fine-grained rock made up of tiny crystals.   Obsidian Obsidian looks almost like black glass. It is used to make tools.   Sedimentary Rocks Flowing rivers carry soil, sand, pieces of rock and clay into the sea. All these things sink to the bottom of the sea and settle down in layers called sediment. Heavy sediment like rocks, pebbles and gravel make up the bottom layer. The lightest sediment is mud which forms the topmost layer. Sand settles between the two layers. As time passes, more and more layers are formed. The weight of the upper layers presses down on the lower ones. Over hundreds or thousands of years the lower layers slowly harden and form sedimentary rocks. It is possible to see the different layers of sediment in many of these rocks. Examples of sedimentary rocks are conglomerate, more...

#### Work, Force, Energy and Simple Machines

Work, Force, Energy and Simple Machines   Work Work refers to an activity that involves movement of the object when force is applied on it. For example, work is done when a person pushes a car and the car moves.       The formula of work is: $~\mathbf{Work}=\mathbf{Force}\times \mathbf{distance}$ It means that more work is done, if more force is applied to an object, or the object moves larger distance, or both. If a force is applied on an object, but no motion takes place then no work is done. For example, if a person pushes against a wall, then no work is done unless the wall moves in the direction in which it is pushed. The unit of measurement of work is unit of force multiplied by the unit of distance i.e. Newton metre (Nm) or Joule (J). For example, if a stone is pushed with the force of 5 N and it travelled a distance of 3 metre, the work done is 15 Nm or 15 J.   Force A push or pull acting on an object is called a force. A force can be used to:
• Move a stationary object
• Stop a moving object
• Make a moving object move faster
• Slow down a moving object
• Change the direction of a moving object
• Change the shape and size of an object
Types of Force There are different types of force:   Muscular Force Muscular force is applied when we push, pull or lift something with our hand.   Gravitational Force Gravitational force or gravity is the force that attracts objects to the centre of the earth. Because of gravitational force, we are able to stay on the ground.   Frictional Force Frictional force is a force of resistance that tries to stop the movement of objects across a surface. On smooth surfaces less friction is exerted and on rough surfaces more friction is exerted. Due to it we are able to walk.   Elastic Force Elastic force arises when a body deforms. When we stretch a rubber band it regains its original position because of elastic force.   Mechanical Force Mechanical force is used by most of the simple machines. A wedge uses mechanical force to separate two objects.   Buoyant Force Buoyant force is the upward push of water on a floating object. When we push a mug or piece of wood in water, we can feel an upward thrust.   Energy Energy is the capacity or ability to do work. Energy can exist in different forms such as mechanical energy, heat energy, chemical energy, sound energy, muscular energy, solar energy, wind energy, etc.   Forms of Energy Mechanical energy: Mechanical energy of an object is its energy due to its position or its motion or both. Mechanical energy is classified into potential energy and kinetic energy based upon its source of origin.   Potential energy of the object is its energy due to its position. For example, a book more...

#### Our Environment and Natural Calamities

Our Environment and Natural Calamities   Air and water form an essential part of our surroundings. Everything surrounds and affects an organism is known as its environment.   Air All living beings breathe in air. Air is needed for many purposes like lighting a fire, flying kites and inflating tyres. Air is a mixture of gases. More than three fourth of air contains nitrogen, slightly more than one fifth of air is oxygen and rest of the air contains gases like argon, carbon dioxide, ozone, helium, neon, etc. Air also contains dust/ smoke and water vapour.   Components of Air Components of air are as follows:   Nitrogen Nitrogen is the major component of air. Plants get nitrogen from the soil. Animals get nitrogen from plants, meat and fish.   Oxygen It is the most important gas present in air. It forms one fifth of the air. All living things breaths in oxygen. It is also required for burning a fire.   Carbon dioxide This gas is very much important for plants. Plants use carbon dioxide for preparing their food by the process of photosynthesis   Other gases Argon, helium, ozone, neon, etc. are some other gases which are present in very small quantity in air. Helium is filled in gas balloons and neon is used to make glow signs. Argon is used to fill electric bulbs.   Water vapour Water is also present in air in the form of water vapour. Water from rivers, lakes, sea, etc evaporates due to the heat of the sun and forms water vapour. Water vapour in the air form clouds. The water vapour in clouds cools and falls as rain, fog and snow. When water vapour is present in very little amount in air, it is said to be dry. When there are lot of water vapours in air on a hot day, the heat makes you sweat. Such day is called a humid day. Humidity is the amount of water vapours present in the air.   Properties of Air Followings are the properties of air: (i)   Air occupies space. (ii)  Air has weight. (iii) Air exerts pressure.   Water Almost three fourth of earth's surface is covered with water. Therefore, earth is also called ‘The blue planet'. Water is essential for all living beings. About three-fourth of our body is made up of water. Loss of water from human body is called dehydration. Water is also used for cooking, washing, in agriculture, in industries and for generating electricity.   Environmental Pollution Environmental pollution occurs when any undesirable change takes place in the physical, chemical and biological characteristics of air, land and water. Pollution can occur due to natural or man made reasons.   Pollutants Pollutants are the agents that cause pollution. Pollutants can be of two types. These are: (i) Biodegradable pollutants: These pollutants can be broken down into simpler compounds by the action of microbes. For example, kitchen waste and agricultural waste. (ii) Non biodegradable pollutants: more...

#### Our Universe

Our Universe   The universe is vast. The solar system forms a very small part of the universe. Our earth is a one of the eight planets of the solar system. Yuri Gagarin was the first man to go into space Valentina Tereshkova was the first woman to go into space. Rakesh Sharma was the first Indian man and later Kalpana Chawla became the first Indian woman to go into space.   Solar System   Moon As the earth moves around the sun, it is accompanied by the moon. Even though the moor is earth's nearest neighbour in space, it is 3,84,400 km away from the earth. The moon is 4500 million years old, the same age as the earth. The moon is called the earth's natural satellite because it revolves around the earth. Why does the moon shine at night? The moon shines because it reflects the sun's light falling on it. The surface of the moon is made up of plains, valleys and mountains. There are big holes called craters all over the moon. These craters are round and deep. A dark grey dust covers the surface of the moon. Americans Neil Armstrong, Edwin Aldrin and Michael Collins were the first people to visit the moon. They landed on the moon on 21 July 1969 in their spacecraft Apollo 11. Neil Armstrong was the first person to step on the moon.                                                                                                                                                                  Moon   The Moon and Tides The rising and falling of the level of water in the sea are called tides. Tides are caused by the gravitational pulls of the moon and the sun. The moon attracts the ocean water with stronger force of attraction than that of the sun, because the moon is much closer to the earth than the sun.   Eclipse An eclipse is a shadow that makes the sun or the moon totally or partially invisible for some time. The sun is the source of light and the earth and the moon are the objects that come in the path of this light and cast their own shadows. As the earth and the moon keep moving, their positions keep changing. Thus, their shadows also keep changing.   Solar Eclipse Sometimes the moon comes between the sun and the earth. When this happens, the moon obstructs the light of the sun and casts its shadow on the earth. The people living in this part of the earth can see only a part of the sun or not see it at all. This is a solar eclipse. Once the moon moves out of this position, the sun can be seen again. If the complete disc of the sun is covered by the shadow of the moon, it is called a total solar eclipse. If a part of the sun is hidden, it is called a partial solar eclipse.                                                               more...

#### Matter

Matter   Matter Matter is anything that occupies space and has weight. It is classified into three categories. Solid, liquid and gas. All matter can be split into tiny units that are not visible to the naked eye. These small units are called molecules.   Salt molecule is the smallest particle of salt.   Atom A molecule has smaller units called atoms. Atoms are building blocks of matter. There are 117 kinds of atoms known to us. Atoms of same kind form elements. Atoms of different kinds combine and form compounds.   Molecules are constantly in a state of motion and are attracted towards each other. In solids, molecules are tightly packed.   In liquids, molecules are less closely packed compared to solids. In liquid, molecules can move freely and can flow. That is why a liquid has definite volume but no definite shape. In gases, the distance between molecules is large. The molecules in a gas move faster than the molecules in a solid or a liquid. Gas has no definite shape and volume.   Combination of States of Matter States of matters may be combined as follows:   Solid in water Sugar and salt are soluble in water. The molecules of these substances occupy the space between the molecules of water.   Liquids in water When two liquids mix in each other, liquids are said to be miscible. Alcohol is miscible with water whereas kerosene is immiscible with water.   Gases in water Carbon dioxide, nitrogen, oxygen and ammonia dissolve in water. Water in oceans and rivers contains dissolved oxygen and nitrogen. When water is boiled, bubbles are formed of gases which are dissolved in water. Aerated drinks contain carbon dioxide.   Change of State Matter changes its state with change in temperature and pressure. If we heat ice, it changes into water that is state changes from solid to liquid.   Physical change A physical change is a temporary change in which no new substance is formed. Physical changes can also be reversed. For example-                                                        These changes involve change:
• in the state of matter
• that are temporary
• that can be easily reversed
Chemical change In a chemical change, on heating or cooling we get a new substance that cannot be changed into the old one. For example, burning of paper, rusting of iron, etc.   Chemical changes: (i) are permanent. (ii) can not be reversed. (iii) result in the formation of new substances.

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