Diversity in the Living world


The variety of life form seen around us is referred to as bio- diversity. It is the natural biological wealth of the earth.
It is recognized at three levels:
  • Genetic diversity
  • Species diversity
  • Ecosystem diversity


It is a functional science which deals with identification, nomenclature and classification of different kinds of organisms all over the world.
Classification: It is the system of arrangement of organisms into groups showing relationship.
In other words, it is the placing of an organism or a group of organisms in categories according to a particular system and in conformity with a nomenclature system.
Functions of biological classification or taxonomy
  • It recognizes and describes the basic taxonomic units or species.
  • It tells a possible way of grouping these units on the basis of their resemblances and relationships.
Nomenclature means system of naming plants, animals and other objects.
Binomial Nomenclature
  • Carolus Linneous develops a Binomial system of Nomenclature. It was used by him in his book ‘Species Plantarum’ published in 1753.
  • According to this system, the scientific name of an organism has two parts:
  1. The name of the genus or generic name
  2. The name of the species or specific name
Example The botanical name of mango is Mangifera indica. The first word Mangifera indicates the genus of plant and second word indica refers to a particular species of that genus.
Scientific name of Human is Homo sapiens.
Guideline for Naming Organisms: To give specific names to organisms some rules framed by international scientific bodies.
ICBN: International Code of Botanical Nomenclature
For naming plants, rules have been standardized by ICBN.
ICZN: International Code of Zoological Nomenclature
For naming animals
ICBN: International Code of Bacteriological Nomenclature
For naming Bacteria
Basic norms for Scientific name:
  • Plants and animals should be given independent names.
  • Each organism has only one valid name.
  • The genus should have it first letter as capital and species with first letter as small.
  • Scientific names are always printed in italics.
  • The name should be in Latin or can be easily converted into Latin.
  • The biological names are the same all over the world.
  • They are uniformly binomial.
  • They are definite and accepted universally.
  • They are descriptive.
  • They indicate the general relationship.

Taxonomic categories

  • The classification is not a single step process. In its hierarchy of many steps are involved where each represents a rank or taxon.
  • Category is the part of overall taxonomic arrangement, so it is called taxonomic categories and all categories together form taxonomic hierarchy.
  • Each category is basically represented a rank or taxon.
Taxonomic hierarchy:
It is a system of arrangement or a framework for classification in which various taxonomic categories are placed in order of logical sequence.
Hierarchy literally means “ A series of succession of different ranks.” So various species have been arranged into different categories and taxon.
For plants and animals various 7 taxonomic categories are given below:
MANGO: (for plants)

HUMAN: (for animals)
  • The smallest unit of classification in both plants and animals is species.
Species may be defined as a population of individuals with similar structural and functional characteristics, which have common ancestry and in nature breed only with each other.
General characteristics of species:
  • They show similar morphological characters.
  • They can interbreed freely produce fertile offspring’s.
  • A genus may be defined as a group of closely related species.
Eg. Dog, Jackal and Wolf are placed in the same genus Canis, because they are closely related to each other but belong to different species.
A number of genera having several common characters form a family. Eg. Solanum, Petunia and Datura have placed in same family Solanaceae.
  • A group of closely related families form an order. Eg. Families Felidae (cat) and Ursidae (bear) have been placed in a single order Carnivora because they all are carnivores.
  • A class represents a group of related orders. Eg. Class Mammilia includes orders like carnivora, Chiroptera (bat), rodentia (rat) and Primates.
Phylum/ Division:
Many classes with some common characters are included in Phylum. Eg. Phylum Chordata includes classes like Pisces, Amphibia, Mammalia.
It is the highest category of taxonomic Hierarchy. All animal are included in animalia kingdom and all plants are included in plantae kingdom.

Systematic: (taxonomy)

It is a study of classification of different organisms and relationship amongst them.
Need and Scope of Systematic or taxonomy
  1. It provides us knowledge of diversity of plants and animals on earth.
  2. It provides necessary information required to other branches of biology.
  3. It has a great role for applied biology.
  4. Role in plant breeding:
Exact identification of harmful pest and their control helps in plants protection.
  1. Role in human health:
Exact identification of insects helps in controlling the epidemic diseases.
  1. Role in Horticulture and Floriculture:
Several ornamental plants have been introduced due to proper identification and nomenclature.
“Discuss Systematic as Profession”:
Systematic has its relevance in fisheries and for the study of economically and medicinally important plants.
All pharmaceutical studies are based on the world of taxonomists.
Taxonomist are being employed at various position in museums, colleges, research institutes and in various public and private organization. So, it has wide scope as profession also.

Taxonomical Aids/ Tools:

  • Herbarium:
A herbarium is a collection of well dried and nicely preserved plants which are correctly identified and arranged according to an approved system of classification.
Purpose/ Function of Herbarium:
  1. To serve as the reference material modern taxonomical research.
  2. To provide scientific information on plants to the people through exhibition, training courses etc.
  3. To serve as national plant wealth repositories (storage house).
Making of Herbarium:
  1. Collection of plants
  2. Pressing and drying
  3. Poisoning
  4. Mounting and labeling
  5. Storing of the herbarium sheets


  • Botanical Gardens:
Botanical gardens can be described as a living repository of plants arranged and maintained on some scientific basis.
    1. To serve as ‘safe abode’ for the rare and endemic species
    2. To maintain the germplasm collection of selected economic, ornamental and medicinal plants and their wild progenitors
Importance of Botanical Gardens:
  1. Royal Botanical Garden, Kew, England
  2. Indian Botanical Garden, Howrah
  3. National Botanical Research Institute, Lucknow
  • Zoological Parks:
Zoological Parks are those man- made places where animals are provided with conditions as similar as possible to their natural habitats.
  1. Zoological parks are helpful in restoring the degraded ecosystem and in the rehabitation of the threatened species.
  2. These inform about mode of living, feeding, habits and behavior of wild animals.
  • Museums:
Museums are those institutions which have collection of preserved plants and animals for study & reference.
In these, the specimens are preserved for longer duration by placing them in chemical preservatives. Here the plants like algal, fungi, mosses etc. are preserved which cannot be maintained in botanical gardens.
  • Keys:
It presents the scheme for identification of plants and animals. Keys are generally analytical in nature. The basis of the keys in generally similarities and dissimilarities of characters.
The keys are taxonomic literature based on contrasting character, generally a pair called couplet.
At each point in decision process multiple alternates are given, each leading to a result or a further choice. The alternatives are commonly called lead.
Types of Keys:
  1. Yolked or indented Key
  2. Bracketed Key

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