Botanica: BIODIVERSITY AND SYSTEMATICS

THE LIVING WORLD

Life is a unique, complex organization of molecules that expresses itself through chemical reactions which lead to growth, development, responsiveness, adaptation and reproduction. The objects exhibiting growth, development, reproduction, respiration, responsiveness and other characteristics of life are designated as living beings.

Unique features of living organism:-

(a) Growth- Living organisms grow in mass and number. A multicellular organism increases its mass by cell division. In plants growth continuous throughout life in their meristematic area. Unicellular organisms also grow by cell division.

(b) Reproduction- It is the formation of new individuals of the similar kind. Reproduction is not essential for survival of the individuals. It is required for perpetuation of the population. In sexual reproduction two parents are involved to produce more or less similar kinds of individuals. In asexual reproduction single parent is involved and individual is copy of the parent.

(c) Metabolism- The sum total of all types of chemical reactions occurring in an individual due to specific interactions amongst different types of molecules in the interior of cells is called metabolism. There are two types of metabolism- Catabolism and Anabolism. Anabolism includes all the building up reactions to increase the mass of the organism like photosynthesis. In catabolism breakdown reactions are involved, such as respiration, digestion etc

(d) Consciousness- It is the awareness of the surroundings and responding to external stimuli.

(e) Life span- every living organism has a definite life span of birth, growth, maturity, senesce and death.

Living organisms are therefore, self-replicating, evolving and self-regulatory interactive systems capable of responding to external stimuli.

BIODIVERSITY

Vast array of living organisms or biodiversity is the occurrence of variety of life forms differing in morphology, size, colour, anatomy, habitats and habits. Each different kind of plant, animal or microorganisms represents a species.

Currently there are some 1.7 – 1.8 million living organisms known to science. Out of which 1.25 are animals and about 0.5 million are plants.

TAXONOMY AND SYSTEMATICS;-

TAXONOMY;- the term taxonomy was given by A P De Candolle as the combination of two greek words “taxis”-arrangement and “nomos” –rules or laws in his book

theorie elementaire de la botanique. De candolle described the taxonomy as the manipulation of data to produce a system of classification.

Taxonomy is defined as the branch of science dealing with the study of classification including its basis, principles, rules and procedures.

SYSTEMATICS;- the term systematics was given by C. linneus in 1735 in his book systema naturae.

Systematic is defined as the scientific study of kinds and diversity of organisms and all relationships between them. The biologists included the system of classification, naming and evolutionary relationships into systematics and considered taxonomy as a restricted term and systematics as a broader term. The systematics involves the reconstruction of the events of evolution and formation of lineages.

COMPONENTS OF SYSTEMATICS

Identification;- it involves recognizing an unknown specimen with a known taxon. It is done with the help of keys, herbaria, manuals, floras etc. This is carried out by determining similarity with already known organisms.

Description;- it involves the study of diagnostic characters like habit, habitat, type of root, stem, leaf, number and shape of calyx, corolla, androecium and gynoecium.

Botanical Nomenclature;- the system of scientific naming to plants is called botanical nomenclature.

Need of scientific names;- the vernacular names have the following demerits;-

Every plant does not have a vernacular name.
The vernacular names are only applicable in one language.
These names keep on changing with locality.
These names give no indication about the taxon of a plant.
There are many names for the same plant.
The unrelated species are named as same.

In order to overcome these problems a single scientific name is devised for a plant over the whole world. The botanical names are treated Latin regardless of origin because the Latin is a dead language therefore it undergoes no change. It is specific and exact in meaning. It uses roman alphabets. For plants

Scientific names are devised by international code of botanical nomenclature- ICBN.

BINOMIAL NOMENCLATURE;- the concept of binomial nomenclature was given by Casper Bauhin in 1623 and was established by Carolous Linnaeus – (Father of Taxonomy). It involves naming a plant with two parts: - Generic name (Genus) & Specific epithet (Species).

Alphonse de Candolle was the first to set instruction for naming a plant in his book Lois de la nomenclature botanique. The first international botanical congress was held at Paris in 1867 called Paris code (de Candolle rules) and the last till now by ICBN in Melbourne in 2011 called the MELBOURNE CODE.

Guidelines and Principles for Nomenclature:

It should be in Latin / derived from Latin.
If it is written in Italics when types and underlined when handwritten.
It contains two parts, first word is Genus; second word is Species.
Genus name starts with Capital while species name starts with small letters.
Name should be short, precise & easy to pronounce.
Name of the author is written is an abbreviated form after the species name.

Ex. Mangifera indica Linn. (Mango), Homo sapiens (Human), Panthera pardus (Leopard).

TAXONOMIC HIERARCHY

A taxonomic category is a rank or level in the hierarchical classification of organism. Taxonomic groups or taxa are arranged into various categories having a fixed sequence. There are seven obligate categories and some intermediate categories. Since the category is a part of overall taxonomic arrangement, it is called taxonomic category and all categories together constitute the taxonomic hierarchy. In this sequence Similarities decreases while as Differences increase.

Species
Genus
Family
Order
Class
Divisions
Kingdom

Species- Species are the natural population of individuals or a group of population which resemble one another in all essential morphological and reproductive characters and are able to interbreed freely among themselves to produce fertile offspring. The term species was first time used by Aristotle and the first species concept was given by John Ray in 1686. (Biological species concept was given by Mayr). The species name is binomial always. Species are the least inclusive group in taxonomic hierarchy and are placed at the bottom.

Genus- it is a group of related species which resemble one another in certain

Correlated characters. All species of a genus are presumed to have evolved from a common ancestor. The genus was first used as taxa by J. P. De. Tournefort (father of genus concept). A genus may contain a single species (monotypic) or it may contain many species (polytypic)-Euphorbia contains 2100 species.

Family- It is a taxonomic category which contains one or more related genera. All genera of a family have some common features or correlated characters. The suffix “aceae” is used for family. A family may contain a single genus- podophylaceae or many genus- asteraceae (1100).

Order- This category includes one or more related families. The suffix “ales” is used for order.

Class- A class is made of one or more related orders. The class dicotyledoneae of flowering plants contains all dicots which are grouped into several orders. The suffix “opsida” is used for class of plants, “phyceae” for algae and “mycetes” for fungi.

Division/Phylum- The term phylum is used for animals while division is used for plants. They are formed of one or more class. The suffix “phyta” is used for plant division and “mycota” for fungi.

Kingdom - It is the highest taxonomic category. All plants are included in the kingdom Plantae while all animals belong to kingdom Animalia.