Biodiversity: Classification of Living Organisms

Introduction to Biodiversity:

• Biodiversity refers to the variety of life forms. It is a term commonly used to describe the variety of life forms found in a given area.
• Diverse life forms coexist in the environment and are affected by one another. As a result, a stable community of various species evolves.
• Humans have recently changed the balance of such communities. Of course, the diversity of such communities is influenced by specific characteristics of land, water, climate, and so on.
• There are roughly ten million species on the planet, but we only know about one or two million of them.

Fig No.1 Biodiversity

Classification

• Classification in biology is the process of grouping organisms, both living and extinct, based on similar characteristics.
• Taxonomy is the science of naming and classifying organisms.
• The term comes from the Greek words taxis (arrangement) and nomos (law).
• The Earth is home to a diverse range of life forms, including animals, plants, fungi, microorganisms, and over 30 million species that inhabit the biosphere, ranging from microscopic bacteria to blue whales.

Fig No.2 Different organisms

The Characteristics of Living Organisms

• A classification group is a set of qualifier values for a single type of qualifier.
• A classification group can be used to identify all of the possible values that a qualifier type could have for a specific subsystem.
• Taxonomy is a branch of biology in which all living organisms are classified into taxa (categories), groups, and sub-groups based on their characteristics.
• In a living thing, seven characteristics are present: movement, breath, excretion, growth, sensitivity, and reproduction. Some non-living things may show a single characteristic or even two, but living things display them all.

Fig No. 3 Classification

Diversity in Living Organisms

• Darwin’s impactful and contentious book On the Origin of Species was published in the 1850s and in this book, he proposed that species evolve (or, as he put it, “descent with modification”) and that all living things can be traced back to a common ancestor.
• Ernst Haeckel, a German scientist, was honored for his contributions to the biological sciences in the fields of zoology and taxonomy.
• In 1969, R.H. Whittaker proposed a Five Kingdom Classification. He named the kingdoms he cauterized Monera, Protista, Fungi, Plantae, and Animalia.
• Carolus Linnaeus divided all living organisms into two categories: Animalia and Plantae

The Five Kingdom Classification

• Earlier, organisms were classified into only two kingdoms: Plantae and animals.
• Plants were classified as any living organism that did not eat, move, or grow continuously throughout their lives.
• During this period, the animal kingdom included organisms that moved, ate, and stopped growing after a certain size.
• R. H. Whittaker proposed the Five Kingdom Classification, which simplified the classification of organisms into five kingdoms
• Monera
• Protista 
• Fungi
• Plantae 
• Animalia

The five kingdoms in this widely accepted classification are made up of species with similar growth and functioning characteristics. Organisms are classified into five kingdoms based on general characteristics such as:

Cell type: Organisms can be prokaryotes if they have prokaryotic cells (cells without a membrane) or eukaryotes if they have eukaryotic cells (a membrane that covers genetic material). The kingdom Monera is the only one that is made up of prokaryotes, as the other four kingdoms are made up of eukaryotic organisms.

Cell wall: The kingdoms Monera, Fungi, and Plantae are made up of organisms with cell walls. Some Protista has cell walls as well. Cell walls, however, do not exist in the cells of Animalia organisms.

Nuclear membrane: The cells of the Protista kingdom lack a nuclear membrane, whereas the cells of the others do.

Cell organization: This distinguishes organisms as unicellular or multicellular.

Nutrition mode: The Plantae kingdom is composed of autotrophs, which produce their own food. The kingdoms of Fungi and Animalia are heterotrophs or organisms that rely on others for food. Autotrophs and heterotrophs coexist in Monera and Protista.

Five Kingdoms

Linnaeus divided organisms into two kingdoms based on their forms and constituents: Plantae and Animalia.

• These distinctions were based on nutrition, habitat, and physical appearance.
• Ernst Haeckel, a German scientist, coined the term Protista, which means “first of all or primordial,” in 1866.
• He proposed Protista as a third taxonomic kingdom, alongside Plantae and Animalia that includes all “primitive forms” of organisms.
• In 1938, Herbert F. Copeland proposed a four-kingdom classification. He came up with the Kingdom Monera which housed all prokaryotic organisms.
• Monera are unicellular, prokaryotic organisms found in moist environments, and they are also the only organisms that lack a true nucleus and they found in hot springs, deep seas, and snow, and as parasites in organisms.
• Fungi are eukaryotic organisms that include yeasts, molds, and mushrooms. These organisms belong to the kingdom of Fungi.
• The organisms found in the Kingdom of Fungi have cell wall and are ubiquitous. Among living organisms, they are classified as heterotrophs.

Hierarchy

A hierarchy for animal classification is based on its kingdom, which comprises phyla for cell structure, mood, food source, and body composition.

Fig No. 4 Hierarchy for animal classification

Kingdom

Living organisms are classified into five kingdoms: Animalia, Plantae, Fungi, Protista, and Monera. There are five kingdoms in which living organisms are classified.

Phylum

A phylum is a subgroup of a kingdom and is a more specific classification than a kingdom. For example, Porifera, Chordata, Arthropoda, etc., are phyla in the kingdom Animalia.

Class

Until phyla were introduced, the most general rank in the taxonomic hierarchy was class. Animalia has 108 classes, including Mammalia, Reptilian, and Ave. However, the classes used today differ from those proposed by Linnaeus and are not commonly used.

Order

Class is a more general rank than order and it is made up of one or more similar families. For example – Mammalia is divided into 26 orders, including primates, Carnivora, and so on.

Family

This taxonomic hierarchy category includes several genera that have some similarities. Canidae, Felidae, Ursidae, and other families belong to the order Carnivora.

Genus

A genus is a group of related species. Some genera have only one species, which is known as monotypic, whereas others have multiple species, which is known as polytypic. Lions and tigers, for example, are classified as Panthera.

Species

It is the lowest level of the taxonomic hierarchy and there are approximately 8.7 million different species on Earth. It refers to a group of organisms that are similar in shape, form, and reproductive characteristics. Species are further subdivided into sub-species.

Binomial Nomenclature

Fig No. 6 Binomial nomenclature

• Carolus Linnaeus pioneered binomial nomenclature, a simplified system for naming organisms.
• It is a technique for naming each species using two words.
• The first name is the generic name for the genus, while the second name is the specific name for the species.
• The species name is printed in tiny letters, whereas the genus name is written in capital letters.
• Italicized or underlined versions of both names are appropriate.

Summary

• In our environment, there are both living (organisms) and non-living things.
• Plants, animals, and microorganisms are the three major groups of organisms.
• The primary characteristics of living organisms are growth, nutrition, respiration, movement, and reproduction.
• There are numerous distinctions between plants and animals.
• Both animals and plants have a wide range of diversity.
• Plants and animals can be classified and identified using a dichotomous key.
• Ernst Haeckel, a German scientist, was honored for his contributions to the biological sciences in the fields of zoology and taxonomy.
• There are five kingdoms, according to R. H Whittaker, who named them in 1969.
• Carolus Linnaeus divided all living organisms into two classifications: Plantae and Animalia.
• The hierarchical order of taxonomic categories is a sequence of categories from kingdom to species in decreasing or increasing order.
• The highest rank is kingdom, followed by division, class, order, family, genus, and species. Species is at the bottom of the hierarchy.
• Kingdom: The highest taxonomic level. Kingdom Animalia, for example, includes all animals. A taxon is a classification unit that denotes the grouping of organisms based on observable features.
• Phylum: This is a term for animals, whereas its synonym division is for plants. It is a collection of classes that are similar. The class Mammalia is part of the animal phylum Chordata, which also includes birds, reptiles, and amphibians.
• A class is made up of one or more orders. All mammals, including bats, rodents, kangaroos, whales, great apes, and humans, are classified as Mammalia.
• An order is composed of one or more similar families.
• A family is defined as a grouping of related genera. It can be distinguished from other genera based on reproductive and vegetative characteristics. Cats and leopards, for example, are members of the same family.
• A genus is defined as a group of related species.
• Species: A population group that is similar in form, shape, and reproductive features, allowing fertile siblings to be produced.
• As a rule of thumb, chemical nomenclature serves as a way of ensuring that a chemical name doesn’t leave any ambiguity regarding what chemical compound it refers to:
• Every chemical name should refer to a single compound.
• The binomial nomenclature defines the biological nomenclature as a system of naming organisms when the name consists of two terms: one indicating the genus and one showing the species.