THE LIVING WORLD

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DIVERSITY

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• The number of species that are known and described ranges between

1.7-1.8 millions refers to biodiversity.

Number and types of

organisms present on the earth.

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• When explored in new areas and in old ones, new organisms are continuously being identified.

So, how to identify new organisms, lets begin.

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Identification - Nomenclature

• Earlier plants and animals were identified by their local names.

• Local names vary from place to place and within every country.

e.g.

• Millet in Hindi called as mandua.

Tamil called as kelvargu.

Telugu called as ragulu.

Millet

Local names always create

Confusion.

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• Nomenclature provides Scientific name to identified organism.

Hence, there is a need to standardise the names of living organisms so that a particular organism is known by the same name all over the world.

So, this process is

called Nomenclature.

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• Nomenclature is possible when the organism is described properly and accurately identified.

• Identification is to determine whether the collected organism is already known or existing or entirely new one.

In plants, identification can be done directly comparing the characters with its authentic herbarium specimen or indirectly

with the help of keys in flora.

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• In plants, scientific names are based on agreed principles and criteria

which are provided in ICBN.

• Scientific names ensure that each organism has only one name.

Scientific names

People in all over world arrive �at the same name.

• It is to ensure that such name has not been used for any other organism.

Do you know what ICBN means?

International Code for Botanical Nomenclature

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• Biologists follow Universally accepted principles to provide scientific

names to known organisms.

Scientific name has two components

The Generic name

Specific epithet

The naming system given by Carolus Linnaeus

is being followed by biologists all over the world.

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To understand the scientific names better let us take one example.

• The scientific name of ‘Mango’ is written as Mangifera indica.

• In this, Mangifera represents the genus while indica represents particular species or specific epithet.

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• Biological names are generally in Latin and written in italics.

Some of the Universal rules of Nomenclature are

• The first word of biological name represents the genus while second component denotes the specific epithet.

• Both the words in biological name, when hand written are separately underlined or printed in italics to indicate their latin origin.

They are Latinised or derived from Latin

irrespective of their origin.

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• The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter.

• Name of the author [person or scientist who gave that name]

appears after the specific epithet, i.e, at the end of biological name and is written in an abbreviated form.

Mangifera indica Linn.

e.g.

It indicates that this species was first

described by Linnaeus.

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• Classification is the process by which living things are grouped into

convenient categories based on some easily observable characters.

Classification

We easily recognise groups such as plants or

animals or dogs, cats or wheat or rice. The moment we use any of these terms, we associate them with certain characters within the organism in that group. Hence, all these – ‘Dogs’, ‘Cats’, ‘Mammals’ etc.

Each group belongs to one particular category.

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The scientific term for these categories is called Taxon.

• Taxa can indicate categories at very different levels.

‘plants’

Taxon

–

‘wheat’

Taxon

–

‘Dogs’

Taxon

–

‘Cats’

Taxon

–

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• Organisms represents taxon at different levels.

• Hence, based on characteristics, all living organisms can be classified into different taxa.

This process of classification is called taxonomy.

• Thus Characterisation, Identification, Classification and Nomenclature are the processes that are basic components to taxonomy.

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• The study of different kinds of organisms, their diversities and also the relationship among them is referred to as systematics.

Systematics

Systematic arrangement

of organisms.

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• The word systema was first used by Linnaeus for his publication systema nature.

• The scope of systematics further enlarged to include Identification, Nomenclature and Classification.

The word systematics is derived from latin word ‘Systema’.

Systematics take into account evolutionary

relationships between organisms.

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1. A particular organism is known by the same name all over the world. This process is called as….

1) Tissue culture

2) Nomenclature

3) Taxonomy

4) None of these

MCQS

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2. ICBN stands for….

1) International code for botanical nomenclature

2) International conduct for botanical nomenclature

3) International council for botanical nomenclature

4) Indian council for botanical nomenclature

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3. Who introduced the scientific naming system?

1) Linnaeus

2) Aristotle

3) Theophrastus

4) De Candolle

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4. The specific epithet of Mangifera indica is….

1) Mangifera indica

2) Mango

3) indica

4) Mangifera

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5. Identification of plants can be done with the help of using…

1) herbarium only

2) keys in flora, herbarium

3) taxonomic groups

4) genus only

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TAXONOMIC CATEGORIES

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Taxonomic categories

• Classification of organisms involve hierarchy of steps in which each step represents a Rank (or) category.

Order

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• Category is a part of overall taxonomic arrangement, it is called taxonomic category.

All categories together constitute the taxonomic hierarchy.

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• Each category represents a unit of classification and a rank, commonly termed as taxon.

Taxon represents unit of classification or distinct biological entities.

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• Taxonomic categories are not merely morphological aggregates.

Taxonomic study of all known organisms have led to the development

of common categories such as kingdom, division (for plants) or phylum

(for animals) class, order, family, genus and species.

All organisms including those in the plant

and animal kingdoms have species as the

lowest category.

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Species

• A group of individual organisms that have fundamental similarities.

One should be able to distinguish one species from the other based on

Morphological differences.

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• Let us consider the above

• In all the three indica, tuberosum and tabacum represent the specific epithets belong to different species.

• Mangifera indica Mango, Solanum tuberosum Potato and Nicotiana tabacum Tobacco.

Mango

Potato

Tobacco

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• Each genus may have one or more than one specific epithets

representing different organisms but having morphological similarities.

e.g.

Solanum includes species like tuberosum, nigrum and melongena

all belongs to one genus → Solanum

Solanum tuberosum

Solanum nigrum

Solanum melongena

Characters which are common in comparison to species of

other genera.

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Genus

A group of related species or aggregates of closely relating species is called Genus.

e.g.

Potato and brinjal belong to two different species but belong to genus Solanum.

Potato

Brinjal

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Family

• A group of related genera is with still less number of similarities as

compared to genus and species.

• Families are characterised on the basis of both vegetative and reproductive features of plant species.

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• Three different genera Solanum, Nicotiana and Datura are placed under the family Solanaceae.

Solanum

Nicotiana

Datura

Let us consider one e.g.

Similar characters are less in number as compared to different genera included in a family.

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Order

• Assemblage of families which exhibit a few similar characters.

• Order and other higher taxonomic categories are identified based on

the aggregate of characters.

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e.g.

Plant families like convolvulaceae, solanaceae are included in the order polemoniales mainly based on floral characters.

Convolvulaceae members

Solanaceae family members

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Class

Class includes related orders.

Let us consider with one e.g.

• In plant kingdom orders like Malvales, Rosales and polemoniales are included in the class Dicotyledonae.

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Division

• Division includes related classes.

• Dicotyledonae and monocotyledonae (classes) with few similar characters are assigned to a higher category called division (Spermatophyta).

In animals related classes are included in a

Phylum.

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Kingdom

• All the plants belonging to various divisions are assigned to highest category called kingdom.

• In a taxonomic category kingdom is the highest category and species is the lowest.

Kingdom Animalia (for Animals).

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Kingdom

Plylum or Division

Class

Order

Family

Genus

Species

Taxonomic category

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• Taxonomists have also developed sub-categories in the hierarchy to facilitate more sound and scientific placement of various taxa

• In the hierarchial arrangement of Taxonomic categories common character goes on decreasing from species to kingdom.

• Lower the taxon more are the characteristics that the member with in the taxon share.

• Higher the taxon greater is the difficulty of determining the relationship to other taxon at the same level.

Hence, the problem of classification becomes more complex.

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Let us take some examples of Taxonomic Categories

[man, housefly, mango, wheat]

Common

name

Biological name

Family

Man

Housefly

Mango

Wheat

Homo sapiens

Musca domestica

Mangifera indica

Triticum vulgare

Poaceae

Anacardiaceae

Muscidae

Hominidae

Genus

Homo

Musca

Mangifera

Triticum

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Order

Chordata

Arthropoda

Spermatophyta

Primata

Diptera

Sapindales

Class

Poales

Mammalia

Insecta

Dicotyledonae

Monocotyledonae

Common

name

Man

Housefly

Mango

Wheat

Phylum/Divison

Spermatophyta

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1. Classification of organisms involves hierarchy of steps in which each step represents….

1) class

2) order

3) rank

4) all the above

MCQS

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2. A group of individuals with fundamental similarities is called….

1) Species

2) Genus

3) Family

4) Kingdom

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3. Potato and brinjal belong to genus….

1) Mangifera

2) Solanum

3) Cucurbita

4) Ipomea

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4. Assemblage of families which exhibit a few similar characters is called ….

1) class

2) order

3) family

4) kingdom

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5. The unit of classification is….

1) Taxon

2) Class

3) Genus

4) Species

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Thank you…

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