As mentioned earlier, a pile of bricks do into
represent a house. Similarly, a mass of cells do not form an organism. These
cells must be organized into proper body parts. In all the multicellular
organisms, this process of organizing the cells into the body parts starts
after the differentiation.
All the cells designated to carry out a similar
function will have a similar structure and are grouped together to form a
tissue. Several tissues are organized to form an organ. And several organs into
organs system and finally into organism.
Let us now study the tissue organization..
In unicellular organisms, all the body functions are
carried out by by a single cell. In very primitive multicellular organisms. As in some body of
the algae such as volvox, hundred of cells are grouped together to form a
colony.
In the colony
carryout reproductive and these are called reproductive cells- Thus the work to
be done in the colony is divide among the cells and this is a primitive form of
differentiation. In the modern multicellular organism, this division of work or
labour is much more complicated.
A tissue is a group of cells having similar
structure and carry out a similar function and they have a common origin.
Usually, a tissue has several thousands of cells arranged closely.
These cells are packed in frame work called
extracellular matrix. This is made up of proteins and carbohydrates provide
mechanical support for the cells in the tissues and keeps the cells in
position. All the cells in a tissue communicate with each other to efficiency
carry out the function as single unit. Plant and animal tissues are different
in their structure and functions .
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