BIO101 Biology

 BIO101 Biology 

https://drive.google.com/drive/folders/1obBGXfPEt2AWR0e_eIAGQfPV4TcA8gnb?usp=sharing

Cells

Cells- The fundamental Unit of life If you remember, in our previous session we have 

seen the basic difference between a living and a non- living thing and some of the characteristics shown by living organisms.

So today we will be looking at the 1st characteristic in detail i.e the composition of an organism

The trees in the forest the fish in the river the birds in the sky the worm in the soil the tiger 

in the jungle the cactus in the desert your class mate in fact any living thing on this planet is made up of cells which are known to be the building blocks of a living thing. Many many cells come together to form a living organism. Besides this, some organisms like bacteria are made up of only one cell. One celled organism is all together an individual itself which can perform all the functions like any other multi-cellular organism. Every living being performs various functions during its entire lifespan like respiration, digestion, excretion, reproduction etc. the body has specific organs to carry out these functions.

These organs are made up of various types of tissues; and tissues are nothing but a group of cells. So in short we can say that the human body is composed of many cells.Just as bricks form the important part of a building, cells make up an organism. So we can say that cells are the basic fundamental unit of life. In 1665, Robert Hooke discovered cells. He observed dead cells within the cork of the bark of a tree using an old basic microscope. He observed empty spaces contained by a wall and named them cells because they resembled small compartments. So we can say that what Robert Hooke observed looked something similar to a honeycomb structure. We shall take a look at some features of a cell.

So lets get started. No. of cells: Based on the no. of cells an organism can either be unicellular or multi cellular. As the word suggests Uni- is one cell and multi is many cells. Shape of a cell: Cells are of various shapes. Majority of them are round, spherical and elongated. But you know what gives a cell its shape..??? Just like a room gets its shape from its walls a cell gets its shape from a cell membrane which is the outer covering of the cell. Soooo talking about shape of cells u know a unicellular organism named amoeba has no definite shape it is irregular and it keeps changing its shape.

In multi-cellular organisms, cells are of different shapes. Like for eg. A nerve cell is long and branched in structure while a red blood cell (rbc) is spherical and concave.

Size of a cell: Cells are very tiny in size and are not visible by the eye. Hence to view them we use a microscope which is an instrument that magnifies and enlarges the image of a cell. So did you all know that A smallest cell is 0.1 to 0.5 micrometer which is of a bacteria while the largest cell is 170 mm x 130 mm in size which is the egg of an ostrich. You must know that the Size of a cell is based on the function it performs and not on the size of an organism.