Sunday, July 26, 2020

The Living World - Notes (Class 11) - Part 2 Diversity in the Living World

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.

The system of naming with two components is called Binomial nomenclature. It is proposed by Linnaeus.

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 sapiensHomo 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


-   Classification involves hierarchy of steps in which each step represents a taxonomic category (rank).

-   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


Species: 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

Tomato

Solanum

lycopersicum

Brinjal

Solanum

melongena

Lion

Panthera

leo

Tiger

Panthera

tigris

Leopard

Panthera

pardus

Modern man

Homo

sapiens


Genus: 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. 

Class: It is the assemblage of related orders. E.g.

Order Primata, Carnivora etc. is placed in class Mammalia.

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: The assemblage of related phyla. It is the highest category. E.g. Kingdom Plantae, Kingdom Animalia etc.


Organisms with their taxonomic categories


Common name

Man

Housefly

Mango

Wheat

Biological name

Homo sapiens

Musca domestica

Mangifera indica

Triticum aestivum

Species

sapiens

domestica

indica

aestivum

Genus

Homo

Musca

Mangifera

Triticum

Family

Hominidae

Muscidae

Anacardiaceae

Poaceae

Order

Primata

Diptera

Sapindales

Poales

Class

Mammalia

Insecta

Dicotyledonae

Monocotyledonae

Phylum/Division

Chordata

Arthropoda

Angiospermae

Angiospermae

Kingdom

Animalia

Animalia

Plantae

Plantae

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