Organization of tissues in plants and animals and functions of tissues

Organization of tissues in plants and animals

             In unicellular organisms, all the life processes are carried out by a single cell. eg. Chlorella and Amoeba. But in multicellular organisms, similar group of cells specialized as tissue perform common function. Thus they show tissue grade of organization.

         Tissue level of organization is seen for the first time in coelenterata (Hydra) in animal kingdom and in Bryophyta (Moss) in plant kingdom. 

           In Algae and Fungi, cells are grouped together to perform various metabolic activities. In Bryophyta parenchymatous tissue is specialized as epidermal, photosynthetic and storage tissue. In Fern plants (Pteridophyta), parenchyma  tissues are further differentiated into xylem and phloem. These are involved in conduction of water and food materials.

            In lower group of multicellular animals like sponges, cells are grouped to perform various metabolic activities. In the next level of multicellular animals like Hydra, different cells perform different functions. They are grouped to form two tissue layers. In higher animals, cells are highly specialized and differentiated as tissues to perform different function.

Functions of tissues 

In plants

1. Dermal tissue: It forms the covering of the plant body.

2. Ground tissue: It provides mechanical support and stores food material.

3. Vascular tissue: It conducts water and food materials.

In animals

1. Ephithelial tissue: It forms the covering of the body and lines the various cavities, tubes and vessels.

2. Muscle tissue: It helps in movement.

3. Nerve tissue: It enables the organism to understand the surroundings and to adjust itself accordingly.

4. Connective tissue: It attaches muscles to bones 

5. Reproductive tissue: It is involved in reproduction.