Taxonomic Aids - The Living World

Taxonomic Aids

All those collections of actual live specimens or preserved specimens, which help in the identification or verification of a species, are called taxonomic aids.

Some such taxonomic aids are - 

1. Herbaria
2. Botanical Gardens
3. Zoological Parks
4. Museums
5. Monographs
6. Floras
7. Mannuals and
8. Keys.

Herbaria

A herbarium is defined as a collection of plants, that have been dried, pressed and preserved on sheets; these sheets are arranged in accordance with an accepted system of classification and they form a repository for future use.

Steps in the Preparation of Herbarium

• Field visits are made to collect specimens and also to get information about the place, habitat, seasons for collection, environmental condition, human impace in the area and other such general information.
• In the field, there is need for one or more of the following tools, to collect various parts of plants, e.g., digger for digging the soil to collect underground parts, scissors for cutting twigs, knife for cutting any small woody branch and a pole with a hook for collecting samples from tall trees.
• The collected specimens are carried in a box, called vasaculem, to avoid drying up and shrivelling and distortion; polythene bags can also be used for this purpose.
• Sufficient number of of individual specimens of a certain kind are collected and they are assigned a number, called field number. The specimens are spread out and dried by keeping in between fold of newspaper and these paper have to be changed at regular intervals of time to avoid fungal growth; complete specimens can be dried in a plant press.
• The bigger/longer specimens can be folded and preserved; leaves are spread in such a way that some of them show the dorsal surface while some other show the ventral surface.
• The dried specimens are pasted on the herbarium sheets of standard size, i.e., 23 x 41 cm.
• All the pasted specimens are sprayed with fungicides like 0.1% solution of mercuric chloride or DDT to avoid fungal growth.
• Parts like seeds and fruits are kept in a packet and attached to the sheet.
• A label must be put up in each sheet, that carries the following information:

(i) Locality 

(ii) Name of the collector

(iii) Date and time of collection

(iv) Common English name

(v) Vernacular name

(vi) Scientific name

(vii) Name of the family

Note - Vernacular name, Scientific name and Name of the family are written when specie is already identified. 

•  The sheet are then arranged following a particular system of classification and stored in metallic cupboards.
• The are should be disinfected and monitored for humidity to check fungal growth and insect pests.
• The information about the specimens is compiled and published in the form of a book, called Flora.

Vibrant⁺ Learning

# The first Herbarium was set up by Luca Ghini, Pisa, Italy.

Botanical Gardens

Botanical gardens are the collection of living plants maintained as reference for identication and classification; they constitue a natural and economical reference system for taxonomic studies.

International Directory of Botanical Gardens published by Henderson (1983) has documented about 800 important botanical gardens.

Some of them are :

1. Royal Botanical Garden, Kew, London (1600).

2. Padva Botanical Garden, Italy (1545).

3. Berlin Botanical Garden and Museum, Berline (1679).

Some of the Botanical Garden in India are :

1. Indian Botanical Garden, Kolkata.

2. National Botanical Research Institute, Lucknow.

3. Lloyd Botanical Garden, Darjeeling.

Vibrant⁺ Learning

# The first garden for the purpose of scientific study was maintained by Theophrastus in Athens.

# The first modern botanical garden was established in 1544 by Lucan Ghini in Pisa, Italy.

Zoological Park

• Zoological parks are the places where wild animals are protected under conditions very similar to their natural habitats.
• The scientific purpose of such parks is to breed animals under captivity to avoid their extinction.
• Zoological parks helps us to know about wild animals, their food habits, behaviour, etc.

Zoological parks are categorised into large, medium, small and mini depending on the area and number of animals included.

 * Large - 75 hectares, over 750 animals.
 * Medium - 50-75 hectare, 500-750 animals.
 * Small - 20-50 hectare, 200-499 animals.
 * Mini - less than 20 hectares less than 200 animals.

Museums

• Museums are those places which have collection of preserved animals and plants for taxonomic studies.
• The specimens have been correctly identified, labelled and stored; a catalogue of specimens is also prepared for future use.

The specimens are stored in the following ways:

1. Plants and animals specimens are preserved in chemical solutions.
2. They may also be preserved as dry specimens.
3. Insects are preserved in insect boxes, the collected insects are dried and pinned in these boxes.
4. Larger animals like birds and mammals are usully preserved as stuffed specimens.
5. Skeletons of animals are also collected and preserved as dry specimens.

Monographs

Monographs contain a comprehensive accout of the complete compilation of the available information of any family of genus at a time.

Flora

A flora contains the actual description of the habitat and distribution of plants in a given area.

• Several floras are available for identification and comparison of unknown plant materials.

Example: Flora of British India, Flora of Simensis, Flora of Delhi, Flora of Madras, etc.

Manuals

Manuals are those taxonomic aids that contain compiled information about the particular area, key, description of families, genera and species. 

Keys

A key is an analytical scheme for identification of plants and animals based on the similarities and differences.

• The keys are based on the contrasting characters, generally in a pair, called couplet.
• Each couplet actually represents the choice made between two opposite options leading to the acceptance of one; each statements in the key is called a lead.

Keys are of two types —

1. Indented Key : Provides a sequence of choices between two or more statements of characters of species.

Example - An indented key to identify the genera in Ranunculaceae

Carpels single ovuled, fruits achene.

Leaves opposite

             Petals absent, sepals valvate, leaflets not modified into tendrils — Clematis

             Petals many, sepals valvate, leaflets modified into tendrils — Naravelia

Leaves radical / alternate, sepals imbricate.

                                  Petals absent, sepal petaloid.

Flowers have involucre of bracts — Anemone

Flowers have no involucre — Thalictrum

             Petals present, sepal also present — Ranunculus

Carpels many ovuled, fruit follicle.

Carpels united at the base, flowers are regular. — Nigella

Carpels free, flowers are irregular. — Aconitum

Indentation become clear, when viewed in desktop mode.

2. Bracketed key : Where pairs of contrasting characters are used for identification; the number in bracket on the right of statement indicates the next choice of paired statements.

Example : A bracketed key to identify the genera of Ranunculaceae.

1. Carpels single-ovuled, fruit achene (2)

1. Carpels many-ovuled, fruit follicle (3)

2. Leaves opposite, compound (4)

2. Leaves alternate, radical (5)

3. Carpels united at the base — Nigella

3. Carpels free, flowers irregular — Aconitum

4. Petals absent, leaves not modified into tendrils — Clematis

4. Petals many, leaves modified into tendrils — Naravelia

5. Petals absent, sepals petaloid (6)

5. Petals present, many, sepals also present — Ranunculus

6. Flowers have an involucre of bracts — Anemone

6. Flowers have no involucre of bracts — Thalictrum

Importance / Utility of Systematics

1. It makes the study of organisms easy and more scientific; by studying one or a few representative(s) of each group, one gets an idea about the entire group of organisms.
2. It facilitates the identification of organisms.
3. It provides useful information regarding the evloutionary relationship and diversity among organisms.
4. It provides the basic information required in other fields like agriculture, medicines, veterinary sciences, etc.
5. Identification of harmful organisms such as pest and pathogens and their control require knowledge of systematics.
6. Introduction of organisms into a country or a new locality needs the knowledge of systematics.
7. It gives us an idea about organisms which are to be conserved and protected.
8. It helps us to identify the desirable plant varieties for breeding and improving the varieties of crops.

 

You may want to read these Notes :

• The Living World Part I
• The Living World Part II
• The Living World short notes for last minute revision.