Two kingdom classification and its shortcomings


In this article you will find details of the two kingdom classification and its shortcomings. You will also learn the importance of classification & the system of classification in this article.

Introduction

All the organism on earth exhibit variations in term of their size, external features, internal features, physiological processes, adaptation to environment etc. Variations found in different organisms are called Diversity in life. It is not possible for a man to study all the plants and animals during his life time. Therefore, from the beginning of the human civilization, people felt the necessity for arranging then in different groups by studying not only external features but up to some extent their anatomy also. So by studying a single organism of that group we can form a general idea about the general and anatomical characters of all the members of the group.

Importance of Classification

Classification of organisms is necessary to make their study easy. In addition to it, classification also makes following easy :

  • Classification helps to understand diversity in plants and animals.
  • Classification helps us to establish the natural relationship among organisms.
  • Classification helps us to identify the organism.
  • Classification helps us to understand about origin of the organisms and their relationship.
  • Classification gives us evidence for organic evolution, thus helps us to understand organic evolution.

Principles or System of classification

There are three main system of classification accepted by scientists:

  1. Artificial system of classification: Artificial system of classification is based on only a few characters. All the classifications presented from Aristotle to Linnaeus are artificial in nature.
  2. Natural system of classification: Natural system of classification was proposed by George Bentham and Joseph Dalton Hooker. Natural system of classification was based on many morphological features of organisms so that its exact position and relationship with the other organisms is properly established. Natural system of classification provides all the information required about the organisms.
  3. Phylogenic system of classification: Phylogenic system of classification was given by A. Engleer Kari, A.F. Prantle and John Hutchinson. This system is mainly based on the evolutionary and genetic relationship of the plants. Phylogenic system of classification helps us to find out the ancestors or derivatives of any taxon.

Two Kingdom classification

A Swedish biologist, Carolus Linnaeus (1707-1778) in the 10th edition of his book "systema naturae" published in 1758 classified all the organisms of the living world into two main kingdoms : Plantae (including all the plants) and Animalia (including all the animals).

According to the two system classification , the plants are defined as organisms that photosynthesize and do not exhibit locomotion while animals are organisms that exhibit heterotrophic nutrition as well as locomotion.
So, In two kingdom classification all the animals and plants are divided into two main groups:

  • Plantae : All the plants
  • Animalia : All the animals

Shortcomings of two kingdom classification

Two Kingdoms classification has many shortcomings. Some are as follows:

  1. In two kingdom classification, unicellular organism are put together with multicellular organism.
  2. Two kingdom classification has put together eukaryotes (organism with true nucleus in their cells), with prokaryotes (organism without true nucleus).
  3. Two kingdom classification has put together autotrophs and heterotrophs, such as non -photo synthesizing fungi with photosynthetic green plants.
  4. Two kingdom classification has little regard for diversified form.
  5. Lichens is a peculiar group of dual organisms which are formed by an association between an algae and fungus. They have neither plant character not any animal character.
  6. Group of unicellular algae (e.g. euglenoids, diatoms and dianoflagellates) and protozoa show sufficient degree of resemblance.

Two kingdoms classification was an artificial system of classification. This division was based only on morphological appearance. So, two kingdom classification was rejected by the scientist. The most accepted classification is five kingdom classification proposed by R.H. Whittaker.


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