Tissues in Plants and Animals Introduction

Every organism, whether its body is unicellular or multicellular, is capable of performing all vital functions such as respiration, ingestion, excretion and reproduction. In multicellular organisms, because of the increase in body size, it is difficult for each cell to efficiently cope with the vast variety of the physiological needs of the organism. So cells group together to perform definite functions.

A group of cells of the same type or of a mixed type having a common origin and performing similar functions are called tissues.