Saturday, 30 June 2018

Biology: Organization of life; Cells, Tissue, Organ and complexity

Organization of life

Both plants, animals and simple entities are regarded as organisms, as the word "Organism" is synonymous to life.

Some organisms are made up of a single cell (Unicellular), through out their lives, while some are made up of millions of cells (multicellular) within their body.

For either an unicellular or multicellular organism, the whole body must work together and function together as a single entity.

The complex organisms are called multicellular organisms. For a multicellular organism, either plants or animals have many systems combined within single body system.

If at a point an organ in the body malfunctions, it will invariably affect the  other systems either directly or indirectly.

For Example: the circulatory system and the excretory system combine together to remove the waste products from the body.

READ more: Difference between Mitosis and Meiosis

Watch the video below for more info.


A cell can be defined as the basic for functional unit of life. As mentioned earlier, a cell can be unicellular or multicellular. The starting point from any living thing is formed a single cell which are referred to as unicellular.
Examples of unicellular organisms: Amoeba, paramecium, chlamydomonas, euglema and so on.
Examples of multicellular organisms: humans,  higher plants and animals.


A tissue is a combination of two or more cellular cells performing similar functions. Examples of tissues: mesophyll layer in plant muscles and nervous tissues in animal.


An organ is made up of two or more tissues performing similar functions with the same location of the organism. Examples of organs include: leaf branch, root in plant , kidneys, lungs, hearts, liver in animals and so on.


A system comprises of different organs performing similar functions with the body of organisms.

Examples of systems in plants: the root and shoot system.

Examples of systems in animals: nervous system, excretory system, circulatory system and so on.

The combination of different systems within the body make up the whole organism.

Although, the system functions may be interwoven in some areas. It is on this reason that makes the malfunction of one system to affect the others. This brings about complexity of the organisms, especially multicellular animals.


1) Complex organisms can perform more complicated functions than simple organisms.

2) In complex organisms, there is greater division of labour.

3) Complex organisms can adapt to a variety of environment more than simple ones.

4) Complex organisms can capture, feed on or deal with more complex excretory products.


1) Complex organisms which are normally large in size, require and consume more energy.

2) Complex organism have a small surface area to volume ratio, compared to simple ones.

3) Complex organisms require coordinating systems.
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