CLASS 9 
BIOLOGY
THE FUNDAMENAL UNIT OF LIFE

BASIC NOTES OF CELL 

IMPORTANT FOR EXAMS 

1. INTRODUCTION OF CELL



**The basic unit of life is CELL in living organisms.

**All organisms composed of cells.

ORGANISMS

Unicellular Composed of single cell while Multicellular composed of
 Many cells.


Unicellular organisms important points.

1.Capable of independent existence means they can do their things by own.
2.Must perform the basic functions of life.

So, with these points we can say that CELL is the Basic  and Fundamental unit of life. 

Survival is not possible without Cell.

Now, one more important feature is CELL is the smallest unit of life.

Cell perform functions and with different structure so we can say CELL is the functional and structural unit of life.

We can sum up the definition of CELL now.

CELL is the smallest, basic, fundamental, functional and structural unit of life.


DISCOVERY OF THE CELL



ROBERT HOOKE


Discover cell for the first time but DEAD cell.

ANTON VON LEEUENHOEK 


Saw and describe cell for the first time but LIVE cell.


DISCOVERY OF THE NUCLEUS


ROBERT BROWN

Discover the nucleus.


FATHER OF BIOLOGY



Image based questions asked in exams, so remember these images.

Important things

1. Microscope 
Microscope is an optical instrument consisting of a lens or combination of lenses which renders minute objects distinctly visible.

2.Light microscope is called a compound microscope because it consists of two or more lens systems.

3.The cork cells were the first cells to be observed. They were composed of box-like compartments, forming a honeycomb structure. Cell organelles are found embedded in the cytoplasm.These are smaller in size and bounded by plasma membrane.

4.Magnification of a microscope is calculated by multiplying the powers of eyepiece and objective lenses.
Mathematically, M = P1 × P2, where Pi is the power of eyepiece andP2 is the power of objective.

5.Before 1940, scientists could view the cell only under a light microscope. The invention of the electron microscope in 1940 enabled the scientists to observe the cell in greater detail.

6.An organism is made up of various organ systems like digestive system, nervous system, etc. These organ systems in turn are made up of various organs which are made up of tissues. Also tissues are a group of cells performing the same function. Hence, a cell is the building unit of an organism. Cell → tissue → organ → organ system → organism.


IMPORTANT QUESTIONS RELATED TO CELL INTRODUCTION.

1.Give an example of unicellular organism.

2.Give an example of multicellular organism.

3.What is microscope?

4.Why is light microscope called a compound microscope?

5.Describe the microscopic structure of the cell.

6.How can you calculate the magnification of a microscope?

7.Why were the scientists not able to observe most of the cell organelles before 1940?

8.Do you agree “A cell is a building unit of an organism”. If yes, explain why.

Dr sundiip Singh

Thank you