Wednesday, June 13, 2012

Fibrous root system

  



 In fibrous root  system there are a number of thin fiber like roots of nearly equal size.These roots spread out from the bottom of the stem.Examples of fibrous roots or adventitious roots are roots of grass,wheat,maize and sugar cane.

Tap root system


in tap root system,there is a main root called the primary root.Primary root is bigger in size and goes vertically deep inside the soil.The primary root gives out many smaller branches called secondary roots,which in turn give out even smaller branches called tertiary roots.All these roots from a network inside the soil and fix the plant firmly to the ground. 
 

Xerophytes

These are plants found on dry land,like deserts which get very little amount of water.For examples mango,rose,pee pal,papaya.The roots of saprophytes are very well developer as they have to go deep inside the ground in search of water.Their leaves are reduced to spines which prevent loss of water reducing the surface exposed to sun.

Pure and impure substances



  


A pure substance is one which is made up of only one kind of molecules.It has definite composition and properties.All elements and compounds are pure substances.Some examples are oxygen,hydrogen,gold,silver,copper,common,salt,pure water ,alum.An impure substance is one which is a mixture of two or more kinds of molecules and has no definite composition and properties.for example air,soil,atones and pebbles in food grains,sugar in water,sand in water,fruit juice etc.

Mixture

In the previous lesson, we learned that there are different kinds of substantiates sec in our surrounding.These substances have their own physical which help us to distinguish them from one another. In  some of these substances, we take only the useful components by separating them from useful components.

Force

look at your teacher as he or she enters your class room.The teacher changes the positions .It this case the door,the blackboard,table,students are in the same place or position,but the teacher has changes the positions.Thus,the teacher is in motion.Some other examples are -a ball rolling on the ground,a bird flying,a dog running,all these show motion.Motion is the continuous change in position of a body with respect to bodies around it.You are traveling in a bus,the trees,houses, lamp posts,traffic signals remain where they are.They are said to be at rest.A body is said to be at rest when it does not change its position with respect to bodies around it.However,motion and rest are relative terms.It means that the same body may be at rest with respect to a certain body and in motion with  respect to another body.For example,when you are traveling in a bus,you are in motion with respect to trees,lamp posts,traffic signals etc.But you are at rest at the same time with respect to your fellow passengers as they see you stationary.

Measurement


When you visit a grocery shop and ask for a kilogram of sugar,the shopkeeper puts a certain iron block marked 1kg on one pan of a balance and puts sugar on the other.We add or remove sugar till both balanced.This is measurement.Measurement is the comparison of an unknown quantity with a known quantity.Here,sugar is the unknown quantity.It is compared to the known quantity of 1kg block.Measurement is needed in our day to day life.Your school starts at a certain time.It ends at a contain time.It takes a certain number of kilometers for you to reach the school from your house.The tailor demands a certain length of cloth to stitch your school shirt.These are all based on measurement.Life would be confusing without measurement.In olden times people used simple methods of measurement like heath manna,path,Narnia to name a few.These are local methods of measurement.


Sound

Sound is a form of energy.It needs a medium to travel.It means sound cannot oscillations.When a body moves to and fro it is stalled oscillation.When the guitar is strung,its strings vibrate,which produce sound.When the wings of a bee or a mosquito vibrate,it produces sound.When the tight skin of a medal vibrates it produces sound when a tuning fork prongs are  hit on a rubber pad it vibrates and produces sound.

Natural and artificial magnets

 Lodestone or magnetite is a natural magnet because it is found in nature.It is found in very few places.It looks nothing other than an ordinary stone or rock.thus,it has no regular shape and size.It has a very low attracting power.Artificial magnets are prepared by men using elements like iron cobalt nickel or their  mixture with other elements.They are much stronger than natural magnets.Depending on requirement,these magnets are mad in various shapes and sizes.

History of magnets

There is an interesting story behind how people came  to know about magnets.There was a Greek shepherd named manes.One day he stood resting his staff on a large black rock.He could not move as the iron tip of his staff got stuck to the rock.The Greek named this wonderful  rock magnetite.The Chinese are believed to be the first  to use this rock to indicate direction.The piece of this rock when suspended freely comes to rest in a correction.Ancient chines sailors used piece of this rock for navigation.They give it a chines name  magnet leading stone.later this word was mispronounced as lodestones.The word magnet comes from magnetite which is a type of iron ore found at  different places on the earth.The chemical name of the magnetite is monoxide.


Magnetism

                                                 
  you might  have enjoyed playing with a broken piece of magnet that can get from old magnetic toys  or speakers.have you observed what happens if  you take a magnet near things like thumb pins, safety pins, stapler pins,iron nails?They are attracted to the magnet.When we suspend a magnet freely in the middle,it will come to rest in the north-south direction.Thus magnet is a substance which attracts small pieces of iron towards itself and comes to rest in the north-south direction,when suspends freely.The magnet attracts iron objects by the force called magnetic force.the collective properties of a magnet is called magnetism.

Simple cell

                                                  
                 A simple cell,as its name suggests is very simple in its structure,It consists of a beaker filled with dilute sulfuric acid.Two metal plates of zinc and copper ore dipped in the acid. The copper plate acts as a positive terminal and the zinc plate acts as a negative terminal.If these two terminal are connected by a conducting wire ti an electric bulb,electric current passes from the copper plate to zinc plate through the bulb.The electric circuit is completed.Thus,the bulb glows.A simple cell produces very small amour of electric current.Since it contains liquid.it is not portable.                                                                                           

Electricity

                                              
  We cannot imagine our life without electricity.We use various things in our daily that run on electricity such as lights,radios,television,computer,refrigerator,fans etc.Electricity flows through electric wires.When we turn on a television,electric current passes into it and the television converts it into light and sound energy.Thus,electricity is a form of energy.Electricity is generated in large scales in power stations.Electricity is generated in small scale by cells.

Importance of biology

                                                          
  Biology has greatly helped human beings to find out how we can benefit from plants and animals and improve our lives.We know that plants provide us food,fuels clothe,timber and medicine together with lots of fresh air.Animals provide us food,clothing,help us in agriculture and industry.Research in biology has led to production of better varieties of animals and plants with increase in quantity and quality of food.It has helped to cure and prevent deadly diseases.Study of biology has contributed in conservation of animals and plants as both are interdependent on each other.
                                            

plain

 


A plain is a flat low land.It extends up to 200m from the sea level.There is a stretch of plains in the southern part of our of country. It is called the terrain. There are different kinds of plains may be formed by  the deposition of minerals,humus and fertile substances carried down by the river from the mountains.Such plains are fertile hence there will be dense population.Some plains are formed due to erosion of mountains by wind ,rain river and glacier.Such plains are not fertile.

Lgneous rocks

                                                                 The word igneous is originated from the Greek word 'ignites' which means fire.the igneous rocks are formed by cooling of volcanic matter called the magma. the magma remains in the molten form deep onside the eater's surface due to high pressure and temperature. Igneous rocks are hard and granulated. 
                                                

Well water

                                                    
                 when we dig a hole inside ground to reach the water level,it is called a well is maintained by using concrete rings. this water is drawn out by using a pump set or simply by using suckers.If the well is deep and kept properly covered,the water can be used for drinking.        
                                          

Sea water

                                               
                                        Sea eater is the  largest source of water, but it is not drinkable as it is highly salty.It contains 3.5% of salts mainly sodium chloride or common slat.As the river eventually flow the sea it contains all the impurities of rivers.It is neither good for irrigation nor for industrial use.
                                           

River water

River water is the running  water containing rain water and the melted,snow from the mountains.It also contains many types of impurities both soluble and insoluble.It also contains harmful germs which can cause diseases like jaundice,dysentery and typhoid.It is not fit for drinking.However after purification it is the main source of drinking water,irrigation and production of hydroelectricity.

Rain water

                                      
Rain water is considered as the purest from of water as it is formed by the evaporation of surface water which falls back after condensation.However when it falls the first few showers may contain harmful gases and dust particles mixed with it,but after a few showers it becomes more pure.