1. THE LIVING WORLD
DIVERSITY IN THE LIVING WORLD
The number and types of organisms present on earth refer to biodiversity.
Number of species described is 1.7-1.8 million.
Taxonomy is the study of identification, classification & nomenclature of organisms.
Systematics (Latin ‘systema’ = systematic arrangement) deals with evolutionary relationships among organisms.
Systema Naturae is the book written by Linnaeus.
Basic processes of taxonomy
- Characterization: It is the understanding of characters of organisms such as external and internal structure, structure of cell, development process, ecological information etc.
- Identification: It is the correct description of the organism so that the naming is possible.
- Classification: It is the grouping of organisms into convenient categories (taxa) based on characters.
- Nomenclature (naming): It is the standardization of names of the organisms such that an organism is known by the same name all over the world.
Botanical names are based on the rules in International Code for Botanical Nomenclature (ICBN).
Zoological names are based on International Code for Zoological Nomenclature (ICZN).
Universal rules of Binomial nomenclature
- Scientific names are in Latin or Latinised and written in italics. When handwritten, they are underlined separately.
- The first word is genus name (Generic name) and second word is the species name (specific epithet).
E.g. Homo sapiens- Homo represents the genus name and sapiens represents the species name.
- The Genus name starts with capital letter and the species name starts with small letter.
- Name of the author (in abbreviated form) appears at the end of the biological name.
E.g., Mangifera indica Linn. It indicates that this species was first described by Linnaeus.
TAXONOMIC CATEGORIES
All categories together constitute a taxonomic hierarchy.
A group of organisms occupying a particular category is called a taxon (pl. taxa). E.g. Class Mammalia.
Each category or taxon represents a unit of classification.
Taxonomic hierarchy in ascending order
| Category | Taxon |
Kingdom | Animalia | |
↑ | ↑ | |
Phylum/Division | Chordata | |
↑ | ↑ | |
Class | Mammalia | |
↑ | ↑ | |
Order | Primata | |
↑ | ↑ | |
Family | Hominidae | |
↑ | ↑ | |
Genus | Homo | |
↑ | ↑ | |
Species | Sapiens |
It is a group of closely related organisms capable of interbreeding to produce fertile offspring.
It is the lowest category. E.g.
|
Common name |
Generic name |
Specific epithet |
|
Mango
|
Mangifera |
indica |
|
Potato
|
Solanum |
tuberosum
|
|
Nightshade
|
Solanum |
nigrum |
|
Brinjal |
Solanum |
melongena |
|
Lion |
Panthera |
leo |
|
Tiger
|
Panthera |
tigris |
|
Leopard |
Panthera |
pardus |
|
Modern
man |
Homo |
sapiens |
It is the aggregates of closely related species. E.g.
- Potato, tomato & brinjal are species of genus Solanum.
- Lion, leopard & tiger are species of genus Panthera. This genus differs from genus Felis (genus of cats).
Family:
It is a group of closely related genera. E.g.
- Family Solanaceae includes Genus Solanum, Genus Petunia and Genus Datura.
- Family Felidae includes Genus Panthera and Genus Felis.
Order:
It is the assemblage of related families. E.g.
- Order Polymoniales includes Family Convolvulaceae and Family Solanaceae.
- Order Carnivora includes Family Felidae & Family Canidae.
It is the assemblage of related orders.
E.g. Order Primata, Carnivora etc. is placed in class Mammalia.
Phylum (Division in case of plants):
Phylum (Division in case of plants):
It is the assemblage of related classes.
E.g. Classes Amphibia, Reptilia, Aves, Mammalia etc. come under phylum Chordata.
Kingdom:
E.g. Classes Amphibia, Reptilia, Aves, Mammalia etc. come under phylum Chordata.
Kingdom:
The assemblage of related phyla.
It is the highest category.
E.g. Kingdom Plantae, Kingdom Animalia etc.
Organisms with their taxonomic categories
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