Analog computer : Analog computer measure the physical properties like voltage in a circuit liquid level temperature etc. these computer measure any value on the basis of comparison.                 Digital computer:        Digital computer in contrast manage a fixed numbers of possible values. The computers which work on binary digits ( 0,1) are called are very popular.                Hybrid computer:  Hybrid computers are the combinations of analog and digital computers in hybrid computers the properties are firstly measured and then converted into numbers.                     Micro computer: all the computers which consist of a micro processor chip can be addressed as micro computers. They are very small in size and make to be used by individuals.                  Mini computer: mini computers are less efficient and store less data than mainframe computers. They have limited range of peripherals.                 Mainframe computer: Mainframe are very powerful computer and they are used as a big network of computer which can store data and resources.

What happens to a drop of water on a leaf or in the ocean?                          Stage - 1.                            It vanishes into the atmosphere as water vapour.                                 Stage - 2.                           As it rises, the water vapour cools and changes into a drop of water again.                        Stage - 3.                            This drop of water along with other drops forms clouds.                                 Stage - 4.                           The clouds become heavy with water and the water falls down as rain.    Definiton { water cycle}.  The movement of water from the earth to the atmosphere and then back to the oceans and seas is called system .       Slide - 5.                            The sun has a important in the water cycle . The natural processes   involved in the water cycle are evaporation and condensation.             Slide - 6.                             Evaporation is the process by which water on heating changes to water vapour . In this case heat is provided by the sun.                              Slide - 7.                             Condensation is the process by which water vapour, on cooling, changes bask to water . Water vapour cools as it rises up wards.                  Slide -  8.                             Think........                         1. Why do washed clothes dry ?                       2. Why do oceans not overflow ?                           3. Why is the water cycle so important ?

Mammals show a very high degree of caring for their young ones. Thos is known as parental care. At a time when babies are young and unable to gather food or protect themselves against the enemies parents take care of them for all matters they hunt and make the food available for the babies.

Each egg has a hard protective outer shell. Inside the shell there is a clear sticky Iiquid called albumen [ also called egg white ). Inside it there is a yellow liquid called yolk that provides food to the body growing inside. This body is called the embryo. The embryo develops into a chicken  only when an egg is kept  warm . The parent bird keeps the egg warm by sitting on it. After 21 days the fully grown chick breaks the egg and comes out. This is called hatching.                                Animals that give birth to young ones produ e milk to feed them are called mammals. These Animals carry their yound ones inside their bodies till they are born. Cow horse tat elephants cat squirrel mongoose etc. belong to this group of Animals Human beings are also mammals.

Bachendri Pal was the first Indian woman and the fifth climbing in the world to climb Mount Everest, in 1984. She was born at Nakuri in Garhwal. At the age of 12, she started mountain climbing with her friends. After her graduation, she joined the Nehru Institute of Mountaineering to be trained as a high altitude  mountaineer. In 1984, she was selected as a member of the fourth indian expedition to Mount Everest. On 23 May 1984 she reached the world highest peak. The base camp also serves as the  entre of operation for climbers. It has normally houses fix machines laptops and other communication equipment. Doctors are available at the camp.

Normally when sunlight falls on the earth some of heat is absorbed by the earth, surface while others are reflected back to space. Carbon dioxide and other gases from a blanket over earth surface trap its heat as a result some heat energy is not allowed to escape. This is known as the green house effect. The increase in the temperature of the earth due to green house effect causes global warming it has become a matter of concern for the environmentantalists. They are finding out ways and techniques to deal with such an alarming situation.

Machinery producing less noise should be used Noisy generators should be kept in a sound proof pollution. Silence zones near schools hospitals residence and offices should should be marked.                                   (  Soil pollution )

The physical and chemical changes in soil that cause harm to plants and animals are called soil pollution. Soil pollution can be caused by excessive use of chemical in agriculture.  Dumping of garbage, polythene bags and plastic in the soil.

Modern water filter used the techraque of RO ( Reverse osmosis). Ans ultraviolet radiation to print water. fresh water in rivers lakes and streams which we. Can readily use forms only 0.3 % all the water available on the earth. we must use water very sensibly we. Should not waist water or pollution water. We can adopt following steps to save water at home: Reuse kitchen water to water plansts in your garden.  Close taps properly after use. Replace or repair leaking taps pipes immediately. Avoid using a shower for bathing as it uses more water. Also avoid the use of a House pipe for washing vehicles. Do not throw plastics and polythene bags into a water sources or a drain. Create awareness about water conservation among people.

In most houses, especially in cities water come through pipes the water is obtained from a nearby water body and sent to a water treatment plant. Once treated and purified the water is distributed throughout the taps in our houses, from where we can get the water supplied through the pipes. In some houses, piped water supply is available only at a certain times in a day. Hence. It is necessary to store water in overhead tanks that it is because freely used all the time.

{Purification of water}

Purification of water is very essential before consuming it. Water can be purified by following methods: 

             Boiling

Water should be boiled for fifteen minutes to kill the germs and bacteria.

          Filtration

It is a common method of water purification. In this method, water is passed through a filering device to remove impurities like dust and germs. The traditional water filter used two or three pots One upon the other to filter water. 

     Water purification 

1. Boiling 2. Chlorination 3. Filtration.

  Chlorination 

Chlorination tablets are mixed in water to kill germs.       

Land thickly covered with trees, bushes and creepers is called a forest. We get many useful things from the trees in a forest such as pulp for paper, fruits, medicines and raw materials for many other products that are produced in factories. Forests are found mainly in areas where there is sufficient rainfall. Ideally, one third of the total area of a country should be one. Fifth of india total area is forest.                         {.Types of forest}

There are different types of forests. These depend on the climate, the kind soil and the amount of rainfall. They are:                1. Tropical Rain Forests.

  2. Mountain Vaetation.

   3. Tropical deciduous forests.

People living in forests  depend on various forest products for living unlike people living in cities or villages. They are called adivasi or tribals. Jarwa, kol, Bhil, Munda , Gond,Khasis,Santhals are some of the adivasi groups living in different forests of India.  Tribal people depend on forest resources for their living women gather various forest products such a tendu leaves, berries bamboo, fruits, sal, seeds, mahua, gum and medicinal plants. From the raw materials collected from the jungles these women make basket mats brooms etc.