NCERT Class 11 Biology Chapter 1 Notes: Diversity in the Living World

Diversity in the Living World refers to the vast variety of life forms on Earth, including plants, animals, and microorganisms. It encompasses the differences in species, habitats, and ecosystems. Biodiversity is essential for the balance of ecosystems and is categorized into different taxonomic ranks, such as species, genus, family, and kingdom. Classification helps organize life forms for better understanding and study. Biodiversity varies across different habitats like forests, oceans, and deserts, contributing to the richness of life on Earth. This article is about NCERT Class 11 Biology Chapter 1 Notes (Diversity in the Living World).

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Diversity in the Living World

Introduction to Biodiversity:

Ø Biodiversity refers to the vast variety of living organisms on Earth, including plants, animals, and microorganisms.

Ø Scientists have identified and described approximately 1.7–1.8 million species, but many remain undiscovered.

Ø Biodiversity varies across habitats such as forests, oceans, mountains, deserts, and lakes.

Need for Classification:

Ø The diversity of life makes it essential to group organisms systematically for easy study and understanding.

Ø Local names for organisms vary geographically, creating confusion.

Ø Scientific classification helps organize species into universally accepted categories.

Identification and Nomenclature:

Ø Identification: Correctly describing an organism to recognize and distinguish it from others.

Ø Nomenclature: Assigning a standardized name to organisms to ensure consistency worldwide.

Ø Follows rules set by the International Code for Botanical Nomenclature (ICBN) for plants and the International Code for Zoological Nomenclature (ICZN) for animals.

Binomial Nomenclature:

Ø Developed by Carolus Linnaeus, Known  as ‘Father of Taxonomy’

Ø Each organism is given a two-part scientific name:

1. Generic Name (Genus): Written with an initial capital letter.

2. Specific Epithet (Species): Written in lowercase.

Ø Names are italicized when printed and underlined when handwritten.

Ø Example: Mangifera indica (Mango).

Taxonomic Categories

Definition of Taxonomy:

Ø Taxonomy is the science of classification, including the identification, naming, and grouping of organisms.

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Taxonomic Hierarchy:

Ø Organisms are arranged in a series of taxonomic ranks, forming a hierarchical structure.

Ø Taxonomic Ranks:

 Species:

Ø The basic unit of classification.
Ø Represents a group of individuals that can interbreed and produce fertile offspring.
Ø Example: Homo sapiens (humans).

 Genus:

Ø Includes related species with shared characteristics.
Ø Example: Panthera (includes lion (Panthera leo), tiger (Panthera tigris), and leopard (Panthera pardus)).

 Family:

Ø Comprises related genera with fewer similarities compared to species or genus.
Ø Example: Felidae (includes genera Panthera and Felis).

 Order:

Ø Groups families with common traits.
Ø Example: Carnivora (includes families Felidae and Canidae).

 Class:

Ø Groups orders with shared features.
Ø Example: Mammalia (includes Primata and Carnivora).

 Phylum (Division in Plants):

Ø Includes classes sharing fundamental characteristics.
Ø Example: Chordata (includes mammals, birds, and reptiles).

 Kingdom:

Ø The highest taxonomic category, representing the broadest grouping of organisms.
Ø Example: Animalia for animals and Plantae for plants.

Taxa and Taxonomic Hierarchy:

Ø Taxa are the categories or ranks in the classification system.

Ø The arrangement of taxa forms the taxonomic hierarchy, moving from broad groups (kingdom) to specific ones (species).

Examples of Classification:

Man: Homo sapiens

 Genus: Homo
 Family: Hominidae
 Order: Primata
 Class: Mammalia
 Phylum: Chordata

Housefly: Musca domestica

 Genus: Musca
 Family: Muscidae
 Order: Diptera
 Class: Insecta
 Phylum: Arthropoda

Mango: Mangifera indica

 Genus: Mangifera
 Family: Anacardiaceae
 Order: Sapindales
 Class: Dicotyledonae
 Phylum: Angiospermae

Species

Ø Fundamental taxonomic unit.

Ø Defined as a group of organisms with similar characteristics that can interbreed to produce fertile offspring.

Examples:

Ø Mangifera indica (mango).

Ø Panthera tigris (tiger).

Ø Homo sapiens (human).

Genus

Ø A group of related species sharing several common features.

Examples:

Ø Panthera includes Panthera leo (lion), Panthera tigris (tiger), and Panthera pardus (leopard).

Ø Solanum includes Solanum tuberosum (potato) and Solanum melongena (brinjal).

Family

Ø Groups related genera with similarities in both vegetative and reproductive features.

Examples:

Ø Family Solanaceae includes genera Solanum, Petunia, and Datura.

Ø Family Felidae includes genera Panthera and Felis.

Order

Ø A higher taxonomic rank grouping related families.

Examples:

Ø Order Polymoniales includes families Convolvulaceae and Solanaceae.

Ø Order Carnivora includes families Felidae and Canidae.
Class

Ø Groups related orders.

Ø Example: Class Mammalia includes orders Primata (monkeys, gorillas, humans) and Carnivora (lions, cats, dogs).

Phylum/Division

Ø Includes classes with shared characteristics.

Ø In plants, the term “division” is used instead of “phylum.”

Ø Example: Phylum Chordata includes classes Mammalia, Aves (birds), and Amphibia.

Kingdom

Ø The highest and most inclusive taxonomic category.

Examples:

Ø Kingdom Animalia: Includes all animals.

Ø Kingdom Plantae: Includes all plants.

Summary

Ø Taxonomy is the scientific study of the classification of organisms into hierarchical categories.

Ø The taxonomic hierarchy includes species, genus, family, order, class, phylum/division, and kingdom.

Ø This system helps biologists study biodiversity, understand evolutionary relationships, and ensure consistency in naming species globally.

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