Unit of Classification

In accordance with fossil evidence, life on Earth is thought to have begun approximately 3.7 billion years ago. At this time, the world is home to an uncountable number of species, ranging from microscopic microorganisms to massive blue whales. Because the diversity of life is so great, there are many species that have yet to be discovered and studied. So, for example, until a true specimen of the gigantic squid (Architeuthis dux) was captured on camera in 2004, the creature was thought to be nothing more than an urban legend among sailors.

In a similar vein, there are numerous species that have yet to be recognised or found by scientists. We do, however, require a framework for categorising the species that we are already aware of. The reason for this is that the same organism or variations thereof may occur in multiple sites throughout the world. And these organisms are given different names depending on where they are found, despite the fact that they are all biologically the same organism.

Because of this, the concept of biological classification was introduced. We will go into great detail on what biological classification is and what the classification system’s foundations are.

What is the Biological Classification System (BCS)?

Biological categorization is the scientific technique of organising organisms in a hierarchical succession of groups and sub-groups on the basis of their similarities and differences in order to create a more organised system of organisation. A large number of biologists have contributed to this system of classification, which required years for researchers to determine the most fundamental features for the classification to be established.

In later years, biologists began to focus their attention on the classification of living species according to their properties. Characteristics can be explained in a number of different ways. It is possible to classify a group of organisms together based on specific traits if they are sufficiently similar. Characteristics are defined as the appearance/form, as well as the behavior/function, of a thing. These characteristics determine which organisms will be put in which group based on their traits.

A dog, on the other hand, has limbs, whereas a snake has not. Plants, on the other hand, are immobile, unlike dogs and snakes. These are the traits that distinguish various creatures. These behaviours categorise people into separate groups based on their characteristics. The question is, which characteristic should serve as the primary form or function. For example, how should a dog be classified in terms of its physical design or its mode of locomotion, as seen in the above example? As a result, this was not a successful endeavour.

Carolus Linnaeus, a Swedish physician and botanist who lived in the mid-1700s, produced several works on various species of plants and animals during his lifetime. The two-part binomial taxonomy system of categorising creatures according to genus and species was devised by him in accordance with his concept of categorization, which classified organisms based on physical characteristics in common with one another. This method of categorization proved to be useful. Later, his work was integrated with that of Charles Darwin, resulting in the creation of the modern taxonomy that we know today.

Today, some of the traits that are used to classify species include the following, among others:

Cell type 

– either a prokaryotic or a eukaryotic cell

The number of cells is classified as either unicellular or multicellular.

Autotrophs (photosynthetic) or heterotrophs (non-photosynthetic): which kind of nutrition do you prefer? (Non-photosynthetic).

The degree to which organs have been organised and developed.

This class of bacteria includes all types of bacteria that have a prokaryotic cell.

The cell does not have a nucleus, as is commonly assumed.

It is possible to identify several different shapes of bacteria, including spherical cocci, rod-shaped bacillus, comma-vibrios and spiral-spirilla.

They reproduce primarily through fission and spore formation under unfavourable conditions, as well as by DNA transfer from one bacterium cell to another. Because they lack a cell wall, mycoplasma are the smallest cells that can survive in the absence of oxygen.

Archaebacteria are bacteria that can survive in the most extreme environmental conditions, such as salty water, marshy soil, and hot spring water. They are referred to as halophiles, methanogens, and thermoacidophiles, in that order.

Ruminants have methanogens in their guts, which cause them to produce biogas.

Eubacteria- These are true bacteria that have a rigid cell wall and flagella, which are used by motile organisms.

Cyanobacteria and other photosynthetic autotrophs are examples of this type of organism (Blue-green Algae). They contain chlorophyll and carotenoids, among other things. They can be unicellular, filamentous, or colonial in nature, with a mucilaginous sheath covering their bodies. Heterocysts are found in Nostoc and Anabaena, which allow them to fix nitrogen from the atmosphere.

Chemosynthetic Autotrophs- They are important in the recycling of nutrients because they produce them. This energy comes from the oxidation of various inorganic substances such as ammonia, nitrogen oxides, and nitrites, which provide the necessary energy for ATP production.

Heterotrophic bacteria can be found in a wide variety of forms and environments. They perform the function of a decomposer. They are used for a variety of purposes, including nitrogen fixation, curd production, and the production of antibiotics. Many bacteria are pathogens, causing a wide range of diseases in both plants and animals, such as citrus canker, tetanus, typhoid, and cholera, to name a few.

Protists are a type of bacterium.

Unicellular eukaryotes are included in this category.

A photosynthetic protist is an organism that serves as a link between plants and animals.

They are composed of a clearly defined nucleus as well as other membrane-bound cell organelles.

Protozoa, slime moulds, chrysophytes, dinoflagellates, and euglenoids are examples of these organisms.

Chrysophytes 

Include diatoms and desmids in your collection (golden algae)

Because of the presence of silica in their cell walls, they are primarily photosynthetic and have an indestructible cell wall.

As a result, the cell wall forms two thin overlapping shells that fit together like a soapbox on the outside surface.

Diatomaceous earth is a deposit of the cell wall that has accumulated over a period of time. It is employed in the filtration and polishing of water.

Dinoflagellates 

They are both photosynthetic and marine organisms.

Their colour can range from yellow to green to red to blue to brown depending on the amount of pigment in the mixture.

On the cell wall, there are cellulose plates that are stiff.

They reproduce at an alarming rate, resulting in red tide.

Many dinoflagellates emit blue-green light and are bioluminescent, which means they can be seen in the dark.

Euglenoids 

They are flagellated protists that photosynthesise.

Their role is to serve as a link between plants and animals. They are capable of photosynthesis but do not have a cell wall.

The presence of pellicle, a protein-rich layer on the surface of their body, distinguishes them and allows them to be more flexible.

The fungi feed on small organisms when there is no sunlight, and this is known as heterotrophic feeding.

Also see the Euglena Classification System.

Slime moulds 

They are saprophytic protists, which means that they feed on organic materials such as decaying twigs or leaves.

Plasmodium is a slime mould aggregation that forms when the conditions are favourable for the slime moulds to grow.

Fruiting bodies containing spores form at the tip of the plasmodium when the environment is unfavourable to the organism.

These spores are able to survive for an extended period of time in adverse conditions and have true walls.

Kingdom Protozoans.

The group includes all unicellular, eukaryotic heterotrophs that are parasites or predators, as well as all other heterotrophs.

These can be divided into four major categories:

Amoeboid- These organisms are distinguished by the presence of pseudopodia, which are used for movement and prey capture, as in the case of Amoeba. Silica shells are found on the amoeboids of the sea. Some amoeboids are parasites, such as Entamoeba histolytica, which is responsible for amoebic dysentery.

Flagellated- They are distinguished by the presence of flagella on their surface. Some of them are parasites that cause a variety of diseases, such as malaria. Sleeping sickness is caused by the parasite Trypanosoma.

Ciliated- They have thousands of cilia covering the surface of their bodies. The coordinated movement of cilia aids in the steering of water containing food into the gullet (a body cavity that opens outside the body surface), for example, in the case of fish. Paramoecium

Sporozoans are characterised by the formation of spores, which is the infectious stage in the life cycle of certain parasites such as Plasmodium.

Fungi are cosmopolitan in their distribution and can be found everywhere.

They are heterotrophic, meaning that they obtain their nutrients through absorption.

Chitin or fungal cellulose is used to construct their cell walls.

Their mode of nutrition can be classified as saprophytic, parasitic, or symbiotic, and glycogen is their primary food reserve.

Fragmentation, budding, and fission are the three methods of vegetative reproduction.

Asexual reproduction occurs through the formation of spores, which include conidia, zoospores, and sporangiospores.

Sexual reproduction occurs through the formation of oospores, ascospores, and basidiospores in distinct fruiting bodies.

When it comes to sexual reproduction, plasmogamy (the fusion of protoplasm) is followed by karyogamy (the fusion of sperm) (fusion of nuclei)

It is not immediately followed by karyogamy in the basidiomycetes and ascomycetes, and this results in the formation of an isolated cell called a distinct dikaryon (N+N), which contains two nuclei per cell.

Fungi are classified into four major classes based on the types and mode of spore formation that they produce, as well as the structure of their mycelium.

Attributes

Fungi\sClass

Phycomycetes

Ascomycetes

Basidiomycetes

Deuteromycetes

Habitat and habitat are important considerations.

The presence of an obligate parasite on plants in moist, damp conditions

Saprophytic, coprophilous, parasitic, and decomposers are all types of organisms.

Rust and smuts are caused by this organism, which can be found in soil, logs, or as a parasite in plant bodies.

Mineral recycling is assisted by saprophytes, parasites, and decomposers.

The mycelium’s internal structure

Aseptate and coenocytic in nature

Branched and septate Branched and septate Branched and septate Branched and septate

Asexual reproduction is a type of reproduction that does not involve sexual contact.

Zoospores are a type of spore (motile)

Aplanospores are a type of spore (non-motile)

Kingdom Conidia

 It is a genus of plants that are related to the genus Conidia (formed exogenously in conidiophores)

Vegetative reproduction is accomplished through fragmentation; there is no asexual spore formation in conidia.

Sexual Reproduction is a term that refers to the act of reproducing sexually.

Zygospores can be classified as isogamous, anisogamous, or oogamous.

Ascospores are a type of fungus (formed endogenously in ascii)

After the dikaryon phase, no sexual organs are formed in the basidium Karyogamy; instead, basidiospores are produced.

Fungi that are not capable of reproducing sexually have been discovered.

Examples

Mucor, Rhizopus, and Albugo are all types of mushrooms.

Sac-fungi are a type of fungus that is commonly encountered.

Penicillium, Aspergillus, Neurospora, Claviceps, and Yeast are examples of pathogens (unicellular)

Agaricus, Ustilago, and Puccinia are all fungi that are commonly referred to as mushrooms, bracket fungi, or puffballs.

Some Important Fungi

It Includes: Trichoderma, Colletotrichum, and Alternaria.

Yeast is a fermentation agent that is used to make cheese, bread, and beer.

Penicillium is a source of antibiotics.

Wheat rust is caused by the fungus Puccinia.

Smut disease is caused by the fungus Ustilago.

Symbionts include lichens (fungal-algae symbiotic association), mycorrhizae (fungal-algae symbiotic association), and fungi (symbiotic association of fungi with roots of green plants)

Rhizopus is a type of bread mold.

Albugo is a fungus that parasitizes mustard.

Neurospora is a parasite that is widely used in genetic and biochemical research.

Truffles and Morels are edible mushrooms that are regarded as delicacies.

Agaricus is a genus that includes both edible and poisonous species.

Kingdom  Plantae

Eukaryotic organisms that are predominantly autotrophic, chlorophyll-containing, and eukaryotic in origin.

The presence of a rigid cell wall composed of cellulose distinguishes this species.

Insectivorous (Venus flytrap, Bladderwort) and parasitic plants are examples of plants that are partially heterotrophic (Cuscuta)

Kingdom Plantae are Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms, among other groups.

More information about the Plant Kingdom can be found by clicking here.

Kingdom Animalia 

Animalia is composed of all heterotrophic, eukaryotic, and multicellular organisms, and it is classified as a kingdom.

They do not have a cell wall.

More information on the Animal Kingdom can be found here.

In Whittaker’s five-kingdom classification, the following acellular organisms and lichens are not classified as belonging to any of the kingdoms:

Viruses

Dmitri Ivanowsky coined the term “virus” to describe the organism that causes tobacco mosaic disease (TMV)

Beijerinek coined the term “Contagium vivum fluidum” to describe the fluid extracted from diseased tobacco plants, and he observed that it was contagious to healthy tobacco plants.

For the first time, Stanley was able to crystallise TMV (tobacco mosaic virus).

They are acellular and contain a nucleic acid core (which can be either DNA or RNA), which is surrounded by a protein coat known as the capsid, which protects the core from damage.

Viruses replicate inside the host cell by utilising the host’s machinery; however, they also exist in crystalline form outside the host cell.

The parasites are obligate parasites that cause a wide range of diseases in both plants and animals, including the common cold in humans, AIDS, polio, measles, and chickenpox in animals, and various mosaic diseases in plants, including tobacco leaf curling and yellowing of veins in cucumbers and tomatoes, among other things.

Single-stranded RNA (ssRNA) is found in viruses that infect plants.

Bacteriophages, which are viruses that infect bacteria, have double-stranded DNA in their genome.

Viroids are the smallest infectious agents that have been discovered. They are composed of nucleic acid but do not have a protein coat.

Diener discovered viroids as the causative agent of potato spindle tuber disease, which was a free RNA virus at the time of his discovery.

Prions

They contain proteins that have been abnormally folded and have a size that is similar to viruses.

They have the ability to alter the shape of normal proteins by transmitting their misfolded proteins to the normal proteins.

They are responsible for a wide range of neurodegenerative diseases, such as bovine spongiform encephalopathy (BSE) in cattle and Cr-Jacob disease in humans, among others.

Lichens

They are a symbiotic, mutually beneficial association of algae (phycobiont) and fungi that exists to benefit both parties (mycobiont). In contrast to the alga, which is autotrophic and provides food, the fungus provides protection as well as shelter.

Because lichens do not grow in polluted environments, they serve as an excellent pollution indicator.

Conclusion

There are numerous species that have yet to be recognised or found by scientists. We do, however, require a framework for categorising the species that we are already aware of. The reason for this is that the same organism or variations thereof may occur in multiple sites throughout the world. And these organisms are given different names depending on where they are found, despite the fact that they are all biologically the same organism.Because of this, the concept of biological classification was introduced.