Question

How are organisms classified on the basis of number of cells?

Answer 1

The structural and functional unit of all the living beings are cells.Cells are the building blocks of life.All living organisms are made up of cells.The cells are discovered by Robert Hooke in 1665.The cells contain cellular organelles that control the activity of the cell.Based on the no.of cells,organisms can be classified as UNICELLULAR and MULTICELLULAR organisms.

UNICELLULAR ORGANISMS:-also called single celled organisms,made up of a single cell.Being the oldest forms of life,they existed about 3.8 million years ago.The single cell regulates all the activity of the organism.Most of the unicellular organisms are invisible to the naked eye.

Example of unicellular organisms:-Bacteria,protozoa,unicelluar algae and unicellular fungi are the main groups.Organisms like amoeba,paramecium are single celled.

MULTICELLULAR ORGANISMS:-Organisms that consist of more than one cell.These cells identify and attach to each other to form a muticellular. organism,and they are visible to naked eye.

Examples of Multicellular Organisms-Plants and animals..Some algae arise from a single cell and they grow up into a muti-celled organism.