how many cell layers compose a poriferan

All living organisms are composed of structural and functional units called cells. The body of a living organism may be composed of a single cell - as in unicellular organisms or many cells - as in multicellular organisms. The number of c..

All living organisms are composed of structural and functional units called cells. The body of a living organism may be composed of a single cell - as in unicellular organisms or many cells - as in multicellular organisms. The number of cellsh..

It comprises of the nerve cells or the neurons. These nerve cells are bipolar. One end of the bipolar cells, synapses with the rods and cones and the other end synapses with the ganglions present in the next layer. There are certain nerve cells cal..

A cell wall surrounds the plasma membrane in all plant cells. It is a porous covering of about 0.1 milli microns to 10 milli microns in size. The cell wall is chiefly composed of insoluble polysaccharides. The most common constituent is cellulose. Certain oth..

This layer comprises of the ganglions. The dendrites of the ganglions at one end are in contact with the bipolar nerve cells and at the other end, with the optic nerve axon..

A lose gelatinous sheath called slime layer is usually deposited around the bacterial cell wall. It is usually composed of polysaccharides. In some bacteria, the slime layer becomes thick due to the presence of some nitrogen compounds and forms a capsul..

Photoconductive Cell..

It is the outer tough covering around the cell, which provides specific shape and protection to the bacterium. It prevents the cell from swelling and bursting due to osmotic changes. It is composed of a polysaccharide called murein or peptidoglycan. It consists of poly..

Undifferentiated cells or stem cells are unspecialised cells, which give rise to new cells by mitotic divisions. These go to form new tissues or in the maintenance of existing tissues. Examples for these are the Malpighian layer in the epidermis of..

The modified form of cell theory is called cell principle. It applies almost completely and universally to living organisms. The cell principle is also called cell doctrine. Following are the statements of cell principle. Life exists only in ce..