In whichever direction we turn or wherever we go, whether in the air, on land, or in the sea, we are surrounded by living creatures. Their very presence presents problems and fills us with curiosity.We ask questions. From where do they come? What is the source of their energy? Why are there so many different kinds? What is our relation to other living things? What is life? Such questions and endless numbers of similar ones kindle the interest of every thinking person. The constant endeavor on the part of man to answer these questions and solve the problems of the origin and nature of life has given us the field of study known as Biology.
Biology is a word derived from two Greek words, bios – ” life” and logos -“discourse”, and is the name universally applied to the study of living organisms and life processes. Since living things fall largely into two general categories, plants and animals, such a study deals with the forms and phenomena exhibited by both.
A biological concept may rest upon observations, which may be changed from day to day by the discovery of new facts, but the biologist, like the chemist or physicist, is justified in holding to a theory or hypothesis as long as it provides a true working basis for further investigation.