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Class 11 | CBSE | BIOLOGY
1.1 Diversity in the Living World | COMPLETE SOLUTIONS
Chapter 1: The Living World
1.1 Diversity in the Living World
If we observe our surroundings carefully, we find an enormous variety of living organisms—plants, animals, birds, insects, pets, and even microscopic organisms that cannot be seen with the naked eye.
The greater the area explored, the greater the diversity observed.
For example, a dense forest has far more species than a garden or roadside.
Each distinct kind of organism is called a species.
👉 Currently known species: approximately 1.7–1.8 million
👉 Many new species are still being discovered, even today.
This vast variety of organisms present on Earth is called biodiversity.
Organisms are known by local or regional names.
These names vary from place to place, even within the same country.
This creates confusion in scientific communication.
To avoid confusion, scientists developed a standardised system of naming organisms, known as nomenclature, so that:
Each organism has one unique name
The name is universally accepted
👉 Naming is possible only after proper identification of the organism.
To ensure uniformity, international rules have been established:
ICBN – International Code for Botanical Nomenclature (Plants)
ICZN – International Code of Zoological Nomenclature (Animals)
These codes ensure:
No two organisms have the same scientific name
One organism does not have multiple scientific names
The universally accepted system of naming organisms is called Binomial Nomenclature.
Proposed by
➡ Carolus Linnaeus
Meaning
“Bi” = two
“Nomial” = names
Each organism has two names:
Generic name (Genus)
Specific epithet (Species)
Example
Mango → Mangifera indica
Mangifera → Genus
indica → Species
Scientific names are Latin or Latinised
Names are written in italics (printed) or underlined separately (handwritten)
Genus name starts with a capital letter
Species name starts with a small letter
Author’s name appears after the species name, abbreviated
Example:
Mangifera indica Linn.
→ Indicates that Linnaeus first described the species
Since it is impossible to study millions of organisms individually, scientists classify them into groups.
Definition of Classification
Classification is the process of grouping organisms into convenient categories based on observable characteristics.
Examples of Grouping
Plants and Animals
Mammals
Dogs, Cats
Wheat, Rice
When we hear a group name, we immediately associate specific characteristics with it.
A taxon (plural: taxa) is a unit or category of classification
Taxa exist at different hierarchical levels
Examples:
Plants → Taxon
Animals → Taxon
Mammals → Taxon
Dogs → Taxon
Wheat → Taxon
👉 These taxa are related in a hierarchical manner
Taxonomy is the science of classification, which includes:
Characterisation
Identification
Classification
Nomenclature
Modern taxonomy uses:
External morphology
Internal anatomy
Cell structure
Developmental processes
Ecological information
Meaning
Derived from Latin word ‘systema’ meaning systematic arrangement
Introduced by Linnaeus in Systema Naturae
Systematics includes:
Identification
Nomenclature
Classification
Evolutionary relationships among organisms
👉 Systematics is broader than taxonomy
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Early humans classified organisms based on utility:
Food
Clothing
Shelter
With scientific advancement, classification became more systematic and evolutionary
Biodiversity – Variety of life forms on Earth
Species – Basic unit of classification
Nomenclature – Scientific naming of organisms
Binomial nomenclature – Two-name system
Taxa – Categories of classification
Taxonomy – Study of classification
Systematics – Study of diversity and evolutionary relationships
Very frequently asked:
Rules of binomial nomenclature
Difference between taxonomy and systematics
Meaning of taxa
Importance of classification
Always underline scientific names properly in written answers.