Maharashtra Board Class 11 Biology Chapter 2 Systematics of Living Organisms PDF Download

Systematics Of Living Organisms

There is great diversity of organisms around us. Since time immemorial, we humans have been exploiting this wealth for our own benefit. During this process man tried to differentiate between and identify the organisms. Eventually this evolved into a branch of biology known as systematics or classification. The methods of classification dates back to ancient time when Indian, Greek and Roman philosophers have contributed their might to systematise science.

2.1 Systematics

Systematics is the study of kinds and diversity of organisms and their comparative and evolutionary relationship (G. Simpson, 1961).

Taxonomy

Taxonomy means classification following certain rules or principles. Word Taxonomy comes from two Greek words, taxis – meaning arrangement and nomous meaning law or rule. The term taxonomy was first introduced by A. P. de Candolle (Swiss Botanist) [1778-1841].

2.2 Classification

It is the arrangement of organisms or groups of organisms in distinct categories in accordance with a particular and well established plan. This classification is based on similarities and dissimilarities among the organisms.

Artificial

It is the classification that is based on few easily observable and non-evolutionary features such as habit, colour, form, etc.; often irrespective of their affinity (relationship) with other organisms. For example, Linnaeus system of classification.

Natural

It is the classification which is based on objectively significant rather than being selected for convenience like artificial system of classification. For example, Bentham and Hooker's system of classification.

Phylogenetic

It is the classification based on common evolutionary descent. For example, Engler and prantles classification.

In the system of classification the terms like 'taxa' and 'categories' are often used. Each category is referred to as a unit of classification. In fact, it represents a rank and is commonly termed as taxon.

2.3 Three Domains Of Life

It is believed that the life originated on earth in its very simple form. Constant struggle of the early living beings gave rise to more and more perfect forms of life. This struggle and progress is evolution which led to formation of diverse life forms. Carl Woese in 1990 proposed three domains of life to classify life forms. They are Archaea, Bacteria and Eukarya. Domain is an unit larger than Kingdom in the system of classification.

Bacteria and Archaea both have prokaryotic cells where as Eukarya have eukaryotic cell. All the three domains have very unique ribosomal RNA (rRNA). Archaea are known for their survival in very extreme conditions like high temperature, salinity, acidic conditions, etc. Bacteria, though are prokaryotes differ from Archaea in structure of cell wall.

Teacher's Note

In India, we see many different types of animals and plants. Classification helps us understand them better by putting similar ones in same groups.

Exam Trick

Remember: Domain is larger than Kingdom. Think of it like India (Domain) has many states (Kingdom). That is how the three domains have many kingdoms inside them.

Points to Remember

Systematics means studying the variety and types of living things.
Taxonomy means arranging and naming things using rules.
Classification puts organisms into groups based on how similar they are.
There are three domains of life: Archaea, Bacteria and Eukarya.
Domain is a bigger group than Kingdom.

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