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Class 11 | CBSE | BIOLOGY
1.2 TAXONOMIC CATEGORIES
Class 11 Biology – Chapter 1: The Living World
1.2 TAXONOMIC CATEGORIES
Introduction: Taxonomic Hierarchy
Classification is not a single-step process. It involves a series of steps, where each step represents a rank or category.
Each rank is called a taxonomic category
All categories together form the taxonomic hierarchy
Each unit of classification is called a taxon
(plural: taxa)
📌 Important Point (Exam Favourite):
Taxonomic categories are real biological entities, not just groups based on appearance.
Taxonomic Hierarchy (Order of Arrangement)
From lowest to highest:
Species → Genus → Family → Order → Class → Phylum / Division → Kingdom
✔ As we move upwards, the number of common characters decreases
✔ As we move downwards, organisms share more similarities
Basis of Classification
To place an organism correctly, we need:
Knowledge of characters
Identification of similarities and dissimilarities
Comparison with other organisms
Modern classification uses:
Morphological characters
Anatomical features
Reproductive features
1.2.1 Species
Definition
A species is a group of individual organisms that:
Share fundamental similarities
Can be clearly distinguished from other species
📌 Species is the LOWEST and MOST IMPORTANT taxonomic category
Examples
| Organism | Scientific Name |
|---|---|
| Mango | Mangifera indica |
| Potato | Solanum tuberosum |
| Lion | Panthera leo |
| Human | Homo sapiens |
indica, tuberosum, leo, sapiens → specific epithets
Mangifera, Solanum, Panthera, Homo → genera
✔ A genus may have one or more species
1.2.2 Genus
Definition
A genus is a group of closely related species sharing more similarities among themselves than with species of other genera.
📌 Genus = aggregate of related species
Examples
Solanum tuberosum (potato)
Solanum melongena (brinjal)
👉 Both belong to genus Solanum
Panthera leo (lion)
Panthera tigris (tiger)
Panthera pardus (leopard)
👉 All belong to genus Panthera
1.2.3 Family
Definition
A family consists of related genera sharing fewer similarities compared to genus and species.
📌 In plants, families are classified using:
Vegetative characters
Reproductive characters
Examples
Plants:
Solanum
Petunia
Datura
👉 All belong to family Solanaceae
Animals:
Panthera and Felis → family Felidae
Dogs → family Canidae
1.2.4 Order
Definition
An order is an assemblage of related families sharing a few common characters.
📌 Similarities are less than in family
Examples
Plants:
Solanaceae
Convolvulaceae
👉 Order: Polymoniales
Animals:
Felidae
Canidae
👉 Order: Carnivora
1.2.5 Class
Definition
A class includes related orders.
Example
Order Primata (monkey, gorilla)
Order Carnivora (lion, dog)
👉 Both belong to class Mammalia
📌 Class Mammalia includes several orders
1.2.6 Phylum / Division
Phylum (Animals)
A phylum includes related classes sharing fundamental features.
📌 Example: Phylum Chordata
Common features:
Presence of notochord
Dorsal hollow nerve cord
Includes:
Fishes
Amphibians
Reptiles
Birds
Mammals
Division (Plants)
In plants, phylum is replaced by division.
Example:
Angiospermae → flowering plants
1.2.7 Kingdom
Definition
Kingdom is the highest taxonomic category.
Major Kingdoms
Kingdom Animalia → all animals
Kingdom Plantae → all plants
📌 All lower categories ultimately fall under a kingdom
Key Concept: Trend in Taxonomic Hierarchy
| Level | Common Characteristics |
|---|---|
| Species | Maximum |
| Genus | Slightly less |
| Family | Fewer |
| Order | Even fewer |
| Class | Much fewer |
| Phylum/Division | Very few |
| Kingdom | Minimum |
✔ Higher category → greater complexity in classification
📊 TABLE 1.1 – IMPORTANT FOR EXAMS
📌 Highly Repeated in Board Exams
|
Common Name |
Man |
House Fly |
|
Biological Name |
Homo sapiens |
Musca domestica |
|
Genus |
Homo |
Musca |
|
Family |
Hominidae |
Muscidae |
|
Order |
Primata |
Diptera |
|
Class |
Mammalia |
Insecta |
|
Phylum/Division |
Chordata |
Arthropoda |
|
Common Name |
Mango |
Wheat |
|
Biological Name |
Mangifera indica |
Triticum aestivum |
|
Genus |
Mangifera |
Triticum |
|
Family |
Anacardiaceae |
Poaceae |
|
Order |
Sapindales |
Poales |
|
Class |
Dicotyledonae |
Monocotyledonae |
|
Phylum/Division |
Angiospermae |
Angiospermae |
EXAM SMART POINTS
✔ Species is the basic unit of classification
✔ Genus includes closely related species
✔ Family includes related genera
✔ As we go higher → similarities decrease
✔ Always write scientific names in italics / underline
📱 Mobile-Friendly Study Tip
Read one category at a time
Revise hierarchy using mnemonic:
Smart Girls Find One Clever Partner Kind
(Species → Kingdom)