classification of matter

 

NEED FOR CLASsIFICATION

lhe number ot living beings, the plants and animals is enormous. Further many new forms are aiscovered and added every year. Plants, animals or microorganisms have great diversity in their form, structure and mode of ire. lo find an organism of known characters from the vast number of organisms is almost imposible. They need to be divided into groups or subgroups. Arranging and grouping the organisms in a definite principle, makes the study of living organisms easy. Just by selecting a few representatives from each group, a broad idea of lite in this earth can be achieved. Therefore, a good system of classification is must for their identification, study and bringing out relationships amongst themselves.

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So needs for classification are . It is not possible to study every organism at a time. The study of one

Or two organisms of a group give sufficient information about the essential features of the group. 2. All the

types of organisms are not found in one locality. 3. Without a proper system of classification organisms can not be identified. 4. The organisms of the past can not be studied without classification. 5. Classification helps to

know the relationship of the different groups. 6. From classification we can know the evolutionary significance of different groups.

ADVANTAGES OF CLASSIFICATION

1 It makes the study ot ditterent organisms very convenient.

2. It facilitates identitication of organisms.

3. It shows relationship among various groups of organisms.

4. It shovws evolutionary trends in various groups of organisms by revealing gradual increase in the complexity of structure in those organisms.

5. It helps in interpreting the poorly developed structures of the fossil organisms.

6. The study of a few representatives of a group gives the general characteristics of that group as a whole.

7. It is useful in foretelling missing or connecting links through which evolution of one group has occurred

from another.

8. A proper system of classification is useful for studying fossils.

9. It helps to know the organisms of other localities..

PRINCIPLE OF CLASSIFICATION

Classification is the arrangement of plants or animals in a series of groups or categories according to their natural relationship. The main objective of classification of animals and plants lies in the placing of animals and plants of all categories in different groups in such a way that their origin, relationship and structural features may be brought out easily. The principle of classification of plant kingdom is very simple based on only habits of plants like trees, shrubs and herbs.

According to Carolus Linnaeus, artificial systems of plants and animals were simply arranged in groups according to their superficial resemblances without paying any regard to evolutionary relationship. Thus, in such a system, closely related organisms are often placed in different groups, while quite different organisms are placed in the same group, because of the presence or absence of a particular feature. Natural classification may be defined as classification based on characters or groups of characters which indicate natural relationships.

The phylogenetic system classifies organisms according to their evolutionary sequence. In this classification, natural attinities and relationship of organisms are taken into consideration in addition to serveral constant morphological characters. This system shows genetic relationship and helps to determine the ancestors and derivatives.

GUIDELINES FOR CLASSIFICATION

A modern taxonomist uses the following criteria and principles to determine the position of an organusn in the natural system of classification. He studies the similarities and differences in organisms by examinin

many characteristics. These include--1. Morphology, 2. Anatomy, 3. cytology, 4. Physiology, 5. Ontogeny, 6. Reproduction, . Behaviour and Biochemistry, 8. Numerical Taxonomy, 9. Paleontology etc. Considering all such characteristics of an organism, determination of its position in classification would be more natural and scientiic.

RULES AND CODES OF CLASSIFICATION

Classification of organisms should be on the basis of their similarities and dissimilarities in such a way that their origin, relationship and evolutionary sequence (phylogeny) may easily be understood.

2 Taxonomy regulates all the rules, procedures and principles of classification. It maintains diagram, description, identification, nomenclature and documentation of an organism.

3. ICBN (International Code of Botanical Nomenclature) and ICZN (International Code of Zoological Nomenclature)

maintain rules and regulations relating to nomenclature of type specimen in case of related organism. The

system of classification which is followed in the grouping of an organism is also mentioned.

OBJECTIVES OF CLASSIFICATION

1. To identify and describe different kinds of organisms.

o place the organisms in various categories on the basis of their similarities and dissimilarities.

. To build a true natural system of classification which gives an idea of origin and evolution of the sne . Helping an easy identification of species.

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TYPES OF BIOLOGICAL CLASSIFICATION

There are four types of Biological classification. These are . Artificial, Z. Natural, 3. Phylogenetic a 4. Phenetic system of classification.

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1. Artiticial system of classitication :This classification system is based upon superticial resemblance

Detween organisms in traits, habitats or morphological features irrespective of evolutionary history is called

Artificial system of classification, e.g., classification proposed by Carolus Linnaeus (1735-37) and othe d

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classification prior to him.

2. Natural system of classification: This system of classification employs a number of charactes including morphological, anatomical, physiological etc. of organisms to find their natural relationship i m called Natural system of classification, e.g., classification proposed by George Bentham and J. D. Hooke (1862-83). This system of classification is useful for practical value. In India it is the most used system.

3. Phylogenetic system of classification This system of classification is based on evolutionan sequence and the genetic relationship among the organisms in addition to other characters to trace the common ancestry is called phylogenetic system of classification, e.g., classification proposed by Adolf Enge and Karl Prantl (1887-99). This system gives the phylogenetic relationship among organisms.

4. Phenetic system of classitication This system of classification is based on the overall similaritie of organisms evalua ted without regard to phylogeny due to absence of fossil records is called phenetic systen of classification. This system of classification is also called numerical classification. Julian Huxley (1940 introduced the term new systematics. This system obtains supporting evidences from four major branche of taxonomy Cytotaxonomy, Chemotaxonomy, Numerical taxonomy and Cladistic taxonomy.