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.