Chapter 2 - The Variety Of Living Organisms

There is an enormous variety of living organisms. The living organisms are classified into groups by their structure and function. Each group of organisms share common features.

The major groups of organisms are the following:-

▪Plants
▪Animals
▪Fungi
▪Protoctists
▪Bacteria
▪Viruses

Plants


This group or kingdom contains flowering plants as in the picture

on the left of this text. It also contains simpler plants like mosses and ferns.Plants are also multi cellular organisms.

Animals

I think all of us are familiar with this kingdom with homo sapiens in it! Wait, you don't know? 

Oh! I meant humans, homo sapiens is just the scientific name !! Yep, humans are 

People are a mystery!

considered in the animal kingdom because they  share 

common features between animals.

Fungi

Fungi.. I like them, then at the same time I dislike it! Yeast, mushrooms, toadstools and 

moulds. How are these supposed to go together? The are all fungi... Yep, even moulds 

(ewww...). Different species of yeast live everywhere - on the surface of fruits, in soil, water 

and even on the dust in the air. The cells of fungi never contain chloroplasts, so they 

cannot photosynthesise.  Their cells have cell walls. The cell walls are made of chitin, not by cellulose.

Yeast cell, highly magnified.

Yeast cell structure

Protoctists

The dustbin kingdom, that's what it's called. It is called the dustbin kingdom because the organisms don't fit into plants, animals or fungi. Most of them are single - celled organisms and most if them look like animal cells. I'm sure you know Amoeba, it's a protoctist.


Bacteria
Bacteria are small single celled organisms. Bacteria cells are smaller than animal cells, plant cells and protoctists.

Viruses

Viruses are many times smaller than bacteria. They are among the smallest organisms known and consist of a fragment of genetic material inside a protective protein coat.

Viruses can only reproduce inside host cells, and they damage the cell when they do this. A virus can get inside a cell and, once there, take over and make hundreds of thousands of copies of itself. Eventually the virus copies fill the whole host cell and burst it open. The viruses are then passed out in the bloodstream, the airways, or by other routes.