BIOLOGY

Nutrition:
All living organisms need food,which is used as a sources of energy,and mateials for the process of life,such as growth.Only two sources of energy are used by living organisms,namely light and chemical energy.Those organisms specialised for using light energy carry out photosynthesis and contain pigments,including chlorophyll,which obserb light.They include plants,algae and simple organisms including bacteria.These organisms which use chemical energy must obtain it from other living organisms.They include animals and fungi.Different methods of nutirtion are responsible for some of the most fundamental difference between organisms.
Respiration:
All life process requires energy and much of the food obtained by nutrition is used as a source of this energy.The energy is released during the breakdown of certain energy rich compound in the process of respiration.The energy released is stored in molecules of adenosine,triphosphate(ATP).This compound had been found to occur in all living cells and is sometimes referred to as the 'universal energy carrier'.


Irritability:
Living organisms have the ability to respond to changes in both the internal and external environments and thus ensure that they maximize their chances of survival.For example the blood vessels in the skins of a mammal dilute(increase in diameter) in response to a rise in body temperature and the consequent heat loss brings about a return to the optimum temperature of the body.A green plant on a window still in a room grows towards light coming through the window,thus ensuring maximum exposure to light from photosynthesis.


Movement:
Some living organisms,such as animals and some bacteria,have the ability to move from place to place,that is they locomote.This is necessary in order for them to obtain their food,unlike other organisms such as plants,which can manufacture their own food from raw materials obtained n one place.Nevertheless,some movement of whole body structures can occurs in plants,as when a leaf grows towards the sun or a flower closer at light.


Excretion:
Excretion is the removal from the body of waste products of metabolism.For examples,the process of aerobic respiration produces a waste product,carbon dioxide,which can be harmful in excess and must be elilminated.Animals takes in a excess of protin during nutrition and since this material can not be stored,it must be broken down and excreted.Animal excretion is,therefore,largly nitrogenous excretion.


Reproduction:
The life span of organisms is limited,but they all have the ability to perpetulate'life'offspring have the same general characteristics as the asexual or sexual reproduction.The 'reductionist'search for the explanation of this inheritance has revealed the existance of molecules,known as nucleic acids{ ribonucleic acid,(DNA) and deoxy ribonuleic acid(RNA)},which contains the coded information passed between organisms from one generation to the next.


Growth:
Non-living objects,such as a crystal or a stalagmite grow by the addition of new material to their outside surface.Living organisms,however,grows from within using food that they obtains from nutrition.The molecules are formed into new living materials.