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There are different types of living organisms in our surroundings, which include unicellular, multi cellular, eukaryotes, prokaryotes,etc. These living creatures are collectively called as organisms, as their body is made up of one or more organs and organelles to carry out various processes in the entire life. The term organism is derived from the Greek word meaning an organ of sense.


Organism Definition

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There are many definitions for the term organism.

It can be defined as a living individual, who develops their ability to perform its function independently and can react to the stimulus, reproduce, grow, metabolizing nutrients, etc. Based on their habituate and other characteristics, they are scientifically divided into five kingdoms, which include – Monera, Protista, Fungi, Plantae and Animalia.

Organism Examples

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Organisms can be unicellular or multicellular- virus, bacterium, fungus, plants and animals. 

Model Organism

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A model organism can be defined as an organism or a species, which are mainly used for research purpose. There are only few selected model organism, such as drosophila, rats, mice from animal kingdom and Escherichia coli from prokaryotes, etc.These animals can be used to study  the development, physiology and behavior. The model organisms have similar functions when compared to other organisms.

Some special features of model organism.
  • They are easy to grow and require minimum space.
  • Require lesser nutrients for growth.
  • They have very short generation time.
  • Resembles to others organisms.
Rat - A model organism

Rat a Model Organism

Organism Classification

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The organism is classified into five kingdoms, which includes – Monera, Protista, Fungi, Plantae and Animalia.

Kingdom Monera:

They are very small and single celled prokaryotic organism, which includes species such as bacteria, archae bacteria, cyanobacteria and Mycoplasma.

Kingdom monera- e.g.: bacteria.

Bacteria Kingdom

Kingdom Protista: 

They are single-celled, eukaryotes and mainly aquatic, which includes species such as diatoms, golden algae, euglena, amoeba, paramecium, etc.

Kingdom Protista- e.g.: paramecium.

Paramecium Kingdom

Kingdom Fungi: 

They are long, thread like structure, eukaryotic organisms, which includes species like lichens, mycorrhiza, aspergillums, mushroom, etc.

Kingdom fungi- e.g.: mushroom.


Kingdom Plantae: 

They are eukaryotic, multicellular, phototrophic organisms with the presence of well developed bounded organelles. It includes all types of plants. 

Kingdom Plantae- e.g.: Mango tree

Mango Trees

Kingdom Animalia:

They are eukaryotic, multicellular, heterotrophic organisms with the presence of well developed bounded organelles. It includes all types of animals.

Kingdom Animalia: The tiger


Unicellular Organism

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An organism, which are composed of only one single cell and are smaller and simpler when compared to multicellular organism. Unicellular organisms carry out all specialized functions within a single cell. The lives, which cannot be seen with the naked eye, are unicellular organisms. 

Examples of unicellular organism.

A unicellular organism includes amoeba, bacteria and some forms of algae such as diatoms. 

Examples of unicellular organism- Amoeba


Multicellular Organism

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An organism, which are composed of many cells and are much larger and more complex compared to unicellular organism.

Multicellular organisms have differentiated cells, which performs specialized functions. 

For example: Nerve cells, blood cells, muscle cells, all performs different functions.

Most of the lives, which can be seen with the naked eye, are multicellular organisms.
Examples of unicellular organism.

A multi cellular organisms includes all organisms from Plantae and Animalia kingdoms - fish, man, tiger, horse, cow, dog, sheep, snakes, whale, elephant, mango tree, rose, plant, herbs, etc.

Examples of multicellular organism.

Animalia Kingdoms
More topics in Organism
Biological Classification
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