User talk:Maiz Wafy

Structural organisation in animals (NCERT Based notes)
Introduction

In unicellular organisms all the basic functions are performed by a single cell. In multicellular organisms, some functions are carried out by a number of cells in a well organised manner. The body of hydra is an example: It is composed of different types of cells doing various functions. The number of these cells may even be in the range of thousands.

In an animal, a group of cells along with intercellular materials performing a certain function constitute a tissue. The term tissue was first introduced by Bichat, the founder of animal histology, but was given by N.Grew. When two or more organs come together through physical and chemical interactions to perform a certain function, they are referred to as an organ system. All this division of labour, from cells to tissues to organs to organ systems contribute to the survival of the organism as a whole.

Animal tissues

The animal body has some twenty types of tissues. However, there are only four basic types, namely:
 * Epithelial tissue
 * Simple and compoud


 * Neural tissues
 * Muscular tissues
 * Cardiac, striated and non striated


 * Connective tissues
 * Loose connective tissue and dense connective tissue