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Biology Classification of Living Organisms

  • Zoology

In this biology classification of living organisms post we have briefly explained about basic classification of living organisms, kingdom Monera, kingdom protista, kingdom fungi, kingdom plantae, kingdom Animalia, other organisms in basic classification of living organisms, taxonomic categories, nomenclature of living organisms.

In earlier day when number of species was limited, Aristotle has used morphological differences as criteria to group into plant and animals.  But as number goes up this kind of basic classification of living organisms didn’t hold and the organism were classified into two kingdom; plantae and animalia. 

This type of basic classification of living organisms was easy to do but several organisms are difficult to classify of either of these kingdoms. Later, R.H. Whittaker has grouped the organisms using five kingdom basic classification of living organisms. The basis of basic classification of living organisms includes cellular structure, body organization, mode of nutrition, reproduction etc.

Classification of Living Organisms

Basic Classification of Living Organisms

Basic Classification of Living Organisms

Kingdom Monera

Bacteria belong to kingdom monera. There are further divided into different catagories base on shapes; Coccus (spherical), bacillus (rod), vibirium (comma shape) and spirillium (spiral). They can be able to grow from soil to extreme conditions such as hot springs, snow and deep ocean. The selected examples of bacterial species belonging to different groups in kingdom monera are as follows:

Archaebacteria

The bacteria belongs to this group has distinct cell wall structure to allow their survival into extreme conditions. These bacterial species live in harsh habitats such as extreme salty areas (halophiles), hot springs (thermoacidophiles) and marshy areas (methanogens). The presence of these bacterial species in the cow dung is responsible for the production of methane (bio-gas).

Eubacteria

These are the true bacteria due to presence of rigid cell wall and a well-defined flagellum for motility. Several species belonging to this group contain chlorophyll a and are photosynthetic autotrophs. In addition, few of the chemosynthetic autotrophs oxidize various inorganic substances such as nitrates, nitrites and ammonia to generate ATP. This property is exploited in industrial setting as well as in environment to recycle nutrients like nitrogen, phosphorous, iron and sulfur.

Kingdom Protista

All unicellular eukaryotes belong to kingdom protista. The organisms in this group has well defined nucleus and other membrane bound organelles. These organisms have mixed properties of plant, fungi, and animals and considered to be responsible for linking organisms in other kingdoms. Protista reproduce mostly asexually and sexually with cell fusion and zygote formation. The selected examples of few of the group from this kingdom are as follows: 

Chrysophytes

Diatoms and golden-brown algae belong to this group. These organisms are present in water and float passively. Diatoms has silica cell wall and they accumulates in the ocean to give diatomaceous earth. This soil is used in polishing, filtration of oils and syrups.

Dianoflagellates

These are photosynthetic marine organisms of different colors depending upon the pigment present in their cell wall. The cell wall has cellulose on its outer surface. Most of the dianoflagellates have two flagella attached to their cell body. Red dianoflagellates multiplication in ocean and gives red color.

Euglenoids

Euglena is the representative organism belonging to this group. These are photosynthetic organism and they perform photosynthesis in the presence of sun light. In the absence of sunlight, it catches tiny preys and behaves like heterotrophs. The cell body has a protein rich layer pellicle and it gives flexibility to the organism.

Classification of Living Organisms

Basic Classification of Living Organisms

Slime Moulds

Slime molds are saprophytic protists. They feed on organic matter from decaying twigs and leaves. During unfavorable condition, they forms spores which are resistant and survive in extreme conditions. Spores of these organisms can survive for several years and be dispersed by air.

Kingdom Fungi

Fungi are heterotypic organisms and constitute a unique kingdom. They exhibit great diversity in morphology, living type and habitat. They are unicellular (yeast) to multicellular (Penicillium) organism. They are universally present in air, water, soli, plant and on animal body.

These organisms are infectious (candida) and non-infectious (yeast). In addition, they live as symbionts; lichens (algae with fungi) and mycorrhiza (plant and fungi). These organisms are commercially being used in fermentation to produce alcohol, antibiotics, vitamin and other products.

Mushroom is used as edible fungi. The cell wall of fungi is composed of chitin and polysaccharides. Reproduction in fungi is mostly by vegetative method such as fragmentation, fission, budding and asexual reproduction by spores.

Kingdom Plantae

All multicellular green plants are part of kingdom plantae. Their cell wall is made up of cellulose. Mostly these organisms are photosynthetic but few insect eater plants are parasitic in nature.

Plants reproduce through asexual vegetative propogation and sexual method. Plants are either bisexual or unisexual with separate male and female. Algae, bryophytes, pteridophytes, gymnosperm and angiosperm are the main groups present in kingdom plant.

Kingdom Animalia

These organisms are heterotrophic multicellular eukaryotic without thick cell wall. They depends on plants for nutrition. They have digestive system, circulatory system and well defined sensory and neuromotor mechanism.

These organisms have a definitive development pattern to acquire defined shape and size in adults. Reproduction in these organism is mostly by sexual mechanism with separate male and female. 

Other Organisms in Basic Classification of Living Organisms

There are organisms which doesn’t falls into five kingdoms due to their unique features. These organisms are not placed and placed into their own group separately. These organisms are as follows:

Virus

These are non-nucleated and acellular organisms. Virus can be stored for year as particle and they are considered to be false living organism. They depend on host organisms to provide cellular machinery for multiplication. They contain genetic material either as DNA or RNA and protein coat. Post infection, they integrate their genetic material into the host genome to control the cellular machinery of host. Virus can use bacteria, plant or animal cells as host. They are mostly pathogenic and be responsible for disease in bacteria, plant and animals.

Viroids

T.O. Diener discovered these organisms which contains only free RNA. They are smaller than virus. It doesn’t contain protein coat as found in virus. 

Lichens

As discussed previously, algae and fungi are associated to give organism known as lichen. In this organism, algae is phycobiont and be responsible for preparing food whereas fungi are absorbing mineral nutrient and water.  The association between both counterparts help each other and this kind of association is known as “symbionts”. Lichen is very sensitive to pollution as they don’t grow in high polluted area.

Taxonomic Categories

Each kingdom is a group of similar organism but this organism are further divided into different taxonomic categories. These categories are as follows:

Classification of Living Organisms

Taxonomic Categories in Basic Classification of Living Organisms

Kingdom

This is the highest taxonomic categories and all organisms are placed in a particular kingdom based on the gross properties as discussed earlier. There are five different kingdoms and few organism as separately kept.

Phylum

Different organisms with similar properties are placed in phylum. For example, phylum chordeta comprises animals containing central notochord for examples: fishes, ambhibians, reptiles, bird etc.

Class

Different classes are present within single phylum. For examples within phylum chordeta, we have individual class for fishes, ambhibians, reptiles etc.

Order

Each class is divided into different order based on the aggregate of character. Each class contains different families. For examples, order carnivore includes families like felidae and cancidae.

Family

Individual order is divided into different families’ basis of related genre. For examples, plants are placed in different families’ basis of reproductive features of the plants.

Genus

It comprises similar species which has common features. For examples, lion, leopard and together are placed within the genus panther.

Species

These are group of organisms with fundamental similarities. Species is the smallest unit in the taxonomic basic classification of living organisms. For examples human belongs to species sapiens.

Nomenclature

The taxonomic basic classification of living organisms is used to nomenclature of the organism. The most popular method of naming organism is known as binomial system which involves the information of genus and species to name each organism.

This system is proposed by carolus Linnaeus where genus and species as first letter and second letter to give the nomenclature of individual organism. For examples, the scientific name of human is Homo sapiens. Here, Homo is the genus and the sapiens is the species.

In case the two organisms has similar species but they belongs to different sub-species.  In these cases, along with species, name of the sub-species is also included. In addition, name of the author appears at the end of biological name, for ex. scientific name of mango is Mangifera indica Linn. It indicates that mango was first discovered by Linnaeus.

Further Readings

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