cells / class -8 / Chapter-8 / New St. Mery English School

 What is cell?

The cell is the smallest structural and functional unit of a living organism. All living organisms are made up of cells. A cell can independently perform all necessary activities to sustain life. Group of Cells make the tissues, Group of tissues make the organs, Group of organs make the  organ systems and Group of organ systems make a living organism. Therefore, the cell is the building block, or the structural unit of the living body.

  Write some important facts about cells.

  Some important facts about cells are

  A cell performs all the important functions of life like respiration, nutrition, growth, reproduction, etc.

  Cells was discovered by Robert Hooke in 1665. He discovered dead cells.

  The word cell is derived from Latin word cellulla. The meaning of cellula is chambers.

  The cells that where observed by Robert Hook was actually dead cells.

  Anton van Leeuwenhoek was the first scientist who observed the living cells. He saw first free living cells in pond water. 

 Anton van Leeuwenhoek is known as father of microbiology.

  The study of structure and composition of cell is known as cytology.

  What are unicellular organisms?

  Those organisms whose body is made up of single cell  are called unicellular organisms. In unicellular organisms, a single cell performs all necessary functions like movement, feeding,               respiration, reproduction etc. 

  Ex:- Amoeba, Paramecium, Euglena etc. 

  What are multicellular organisms?

  Those organisms whose body is made up of many cells  are called multicellular organisms. 

  Ex:- Plants, Animals, Birds, Human beings, etc.

What are tissues?

 A  group of cells having similar structure and performing similar function are known as tissues. A group of tissues forms an organ which performs a single function.

  There are four types of  tissues.

  1:- Connective tissue

  2:- Muscle tissue

  3:- Nervous tissue

  4:- Epithelial tissue 





 

No comments:

Post a Comment

If you have any doubt, please let me know