THE LIVING WORLD

The earth has a wide range of ecosystems in which huge varieties of animals are found. The most extraordinary thing is different habitats have different diversity of animals living in them. Examples: Camels are found in deserts. fishes are found in the aquatic ecosystem, polar bears live in Arctic region. etc. Diversity is what makes the ecosystem harness the energy needed to live and sustain life to continue. Diversity refers to the different kinds of living organisms found in various habitats on earth All the diverse organisms present are part of biodiversity (bio means living and diversity refers to the variety and range of organisms found on this planet).

NOMENCLATURE AND CLASSIFICATION

Nomenclature

There are so many plants and animals on this planet earth. We identify plants and animals by local names given by us. Their local names can vary from place to place, locality to locality or country to country. Therefore, this world needs standardised names for the organism, so that they can easily be identified by same name all over the world. This is why we need Nomenclature. The nomenclature is the only possible way to recognise the organisms and this is known as identification Nomenclature is the process of naming living organisms, so that they can be known by a single identity all over the world and can be identified by everyone (identification) without any difficulty. International Code for Botanical Nomenclature (ICBN) and International Code of Zoological Nomenclature (ICZN) names the plants and animals respectively on the basis of certain principles and criteria given by the plant and animal taxonomists. Some scientists decided to name the plant based on its origin and discoverer but this idea was not widely accepted. Carolus Linnaeus created the binomial system of nomenclature in order to create a consistent system, for naming species. In this system. the names are usually in Latin language and written in italics.

Every organism has a unique name according to binomial nomenclature, made up of two components, the first component is the Generic name and second component is specific epithet, e.g. Mangifera indica in which Mangifera is the genus name and indica is a specific epithet. This unique system of naming is what helps people all around the globe to identify any species, so that the studies and knowledge could be shared to all without any difficulty or confusion. The nomenclature is not only a means of naming the species but it also sought to help in solving the scientific conflicts among the scientific community and common people. Before naming or writing the name of any organism either plant or animal a certain set of rules should be considered which are globally well-accepted and followed by the entire scientific community. Rules of binomial nomenclature are as follows:

(1) The scientific name generally originated from Latin. As stated earlier, the Latin language is a dead language because this language is not an official or national language of any country anymore and hence, it is safe to use Latin for naming in order to avoid any claim over the named species.

(2) The biological name when printed is written in italics and if hand-written is underlined separately. This is an action performed so that the scientific species name could be distinguished from the rest of other words and the species name itself could be highlighted in the long elaborated text It signifies their Latin origin.

(3) The first name represents the genus and the second name represents the specific epithet. The genus name can include many species but the specific epithet of a genus remains unique. In short, the species name given in binomial nomenclature is unique and cannot be possibly shared with any other species.

(4) The genus (first) name starts with a capital letter and the specific epithet (second) name starts with a small letter as seen in the example of Solanum tuberosum. Although while mentioning any species name in the title of the scientific publication, some authors choose not to use the italic font while writing the species name. This way scientific writing for some might be considered a bit unconventional but actually, it is a matter of editorial discretion to find and accept such kind of scientific writing.

Classification

When we have a large number of individuals to deal with, we tend to classify them for better handling of the situation. In nature, we have numerous organisms and their study is not easy, therefore, if we do not categorize or classify them, the entire study will turn into chaos, to avoid that, we use scientific rules and principles to determine a method of global acceptance to classify all the known organisms present on this planet Classification is the process of dividing organisms into different categories on the basis of observable characteristics.

THREE DOMAINS OF LIFE

In biological classification, the domain is the highest taxonomic rank on category, above the kingdom level It was first introduced in the year 1990. Three domain system of classification was developed by Carl Woese with his colleagues named Otto Kandler and Mark Wheelis. In this system, all the organisms can be classified into 3 domains on the basis of structure of rRNA, its sensitivity to antibiotic lipid structure of cell membrane.

Domain Archaea

Organisms with prokaryotic cells are found in this domain. Nuclear membrane is absent. They have bacterial cell RNA markers in them. The name "archaea" comes from an ancient Greek word that means "ancient things," and it refers to the earliest species of life on Earth They have a unique cell wall that allows them to thrive in severe and harsh environments. Archaea's cell wall is devoid of peptidoglycan.

Examples: Methanogens, Halophiles, etc.

Domain Bacteria

Prokaryotic cells are also present in domain bacteria. They are also referred to as real bacteria or eubacteria Methanogens, Halophiles etc. Peptidoglycan makes up their cell wall Unbranched fatty add chains and glycerol create an ester bond to form their cell membrane. Examples: Cyanobacteria, Eubacteria, etc.

Domain Eukarya

Organisms with eukaryotic cells and membrane bound nucleus belong to the domain Eukarya Cell walls may be present in them. They have a cell wall that is composed of chitin and cellulose. Their cell wall is devoid of peptidoglycans. Protista, Fungi, Plantae, and Animalia are the four kingdoms that make up the domain Eukarya.

SYSTEMATICS

The word 'systematics' is derived from the Latin word 'systema' which means the systematic arrangement of an organisms. This field was also introduced by Linnaeus in his book named Systema Naturae. Systematics is a term often used interchangeably with taxonomy. According to Simpson (1961). Systematics is the science that deals with the diversity of organisms and all their comparative, evolutionary relationships are based on a study of comparative anatomy development, comparative ecology, etc. All the species do share some similarities and differences among them, but what makes them work together in a habitat or a niche actually is the basis of how the ecosystem works. If the relationship between the species was not important then the removal of one species would not have affected the other, but it is a known fact that if one species is removed then the other is directly or indirectly affected by it.

The human involved extinction or Anthropocene extinction or Holocene extinction are caused due to human activities, which are responsible for causing the extinction or endangerment of numerous species. The self-centered activities of humans have caused numerous problems to the environment and ecosystem which is now globally visible to all and the extinction or removal of any species in the ecosystem is simply causing unnatural changes and damage to other species niches.

TAXONOMY AND ITS CATEGORIES

Taxonomy

Society functions on a hierarchy and so does biology. All the organisms on the planet are divided into certain groups and divisions ranging from higher to lower. The lowest ranking (species) shares the most common features than the highest ranking (kingdom) in the hierarchy so that the entire arrangement is maintained within the ecosystem A field was discovered by Carolus Linnaeus to extensively study the nomenclature and characterisation of species called Taxonomy, although the word itself was coined by AP de Candolle.

Taxonomic Hierarchy

Each category is called taxa. All the organisms are categorised on the basis of their characters and are arranged in taxonomic hierarchy. Each category is called a taxonomic category or unit of classification and is commonly referred to as rank or taxon. The taxonomic hierarchy in descending order is:

(1) Kingdom

(2) Phylum or division (for plants)

(3) Class

(4) Order

(5) Family

(6) Genus

(7) Species

Species

Species is a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups. The species are named on the basis of binomial nomenclature. For example: Let us consider Mangifera indica (Mango), Solanum tuberosum (Potato), Panthera leo (Lion) and Homo sapiens (Human beings). In all these names, indica, tuberosum, leo and sapiens represent the specific epithets.

Genus

These are the related species sharing some more common characteristics. There are certain species with a common genus like lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) have common genus named Panthera.

Family

Family includes some related genera with few similar characteristics, e.g.. Solanum, Petunia and Datura belong to the Family Solanaceae. Similarly, Panthera and Felis (cats) belong to the Family Felidae.

Order

It is a higher taxonomic category which includes families sharing some of the common features. Examples: (1) Plant families such as Convolvulaceae and Solanaceae belong to the Order Polymoniales.

(2) Animal families such as Felidae and Canidae are included in the Order Carnivora.

Class

The organisms belonging to the related orders are included in it. For example, Order Primata and Order Carnivora are placed in Class Mammalia.

Phylum or Division

It is a category higher than that of class. The term phylum is used for animals while division is used for plants. A division or phylum is formed of one a more classes. Examples: The Phylum Chordata of animals contains not only the Class Mammalia but also aves (birds), reptilia (reptiles), amphibia, Cyclostomata, Chondrichthyes, Osteichthyes (fishes), etc.

Kingdom

It is the highest category in which all the animals are included under Kingdom Animalia while all the plants are included in Kingdom Plantae.

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