Basis of Biological Classification: Definition, Overview, Organizing

What Is Biological Classification?

Biological classification is the process through which living organisms are grouped according to their similarities in makeup. It is used in biological classification establishing an order and structure in an environment that is a home to countless living organisms. Aristotle in the early Greek times and Linnaeus in the eighteenth century were perhaps the first to come up with classifications, which focused on the physical characteristics of the items.

Latest: NEET 2024 Paper Analysis and Answer Key 

Don't Miss: Most scoring concepts for NEET | NEET papers with solutions

New: NEET Syllabus 2025 for Physics, Chemistry, Biology

NEET Important PYQ & Solutions: Physics | Chemistry | Biology

This Story also Contains

1. What Is Biological Classification?
2. The Hierarchical System Of Classification
3. Basis Of Classification
4. Types Of Classification Systems
5. Limitations Of Current Systems

These early endeavours became the precursors to contemporary taxonomy, which continuously changes with the newer fields of genetics, molecular biology, and computational tools. Modern systems of classifications not only seek to place organisms in their categories and rank them but also take into account their phylogenetic relations and genetic kinship which gives the scientists the idea of the unity and diversity of creation on this planet.

The Hierarchical System Of Classification

The classification is discussed below

The Linnaean System

The Linnaean systematic arrangement puts organisms in progressive order starting with Kingdom (for instance, Kingdom Animalia) and moving to Phylum (for instance, Phylum Chordata), class, Order, Family, Genus and Species; (for example, Species Homo Sapiens).

As proposed by Linnaeus, binomial taxonomical naming involves the allocation of a two-word scientific name to a species comprising the Genus and Species. The descriptor such as Homo sapiens for humans.

Modern Taxonomic Categories

Additional levels (Domain, Superphylum, Subspecies, etc.)

More advanced classification levels in modern taxonomy are Domain (for example, Eukarya, Bacteria, Archaea), Superphylum (for instance, Lophotrochozoa), and there are subdivisions as well, including Subspecies (for instance, Panthera leo leo African lion).

Examples Of Each Category With Representative Organisms

Domain consists of Eukarya such as Plants, Animals, Fungi, Bacteria including Escherichia co, and Archaea including Methanogens. Superphylum examples are Lophotrochozoa (e. g, Mollusca), and Ecdysozoa (e. g., Arthropoda). Subspecies, for instance, are Panthera leo leo, the African lion, and Panthera leo persica, the Asiatic lion.

Basis Of Classification

The basis of biological classification is listed below

Morphological Characteristics

Structure and form

Morphological characteristics can be described as properties related to the form and external appearance of organisms about shape, size, colour and feelings on the surface.

Importance in early classification

The first taxonomists for instance Linnaeus mainly based on morphological characteristics of the organisms; grouping closely related species based on characters that were easy to observe like the shape of a plant’s leaves or limbs of an animal.

Examples (e.g., plant leaves, animal limbs)

For instance, the leaves of plants are seen in shape and position; broadleaved plants compared to those with needlelike leaves while the position of the leaves may be in an alternating or opposite manner; on the other hand, animal limbs include those that are designed for flying while others are for walking, and so forth. These differences are well represented by diagrams, which can help when it comes to identification or classifying the entities.

Anatomical And Physiological Characteristics

Internal structure and function

One aspect of animals’ morphology is anatomical where the inside and outside of organisms are examined and described based on organs, tissues, and cells that perform functions necessary for the feeding and reproduction of species.

Homologous and analogous organs

Two structures are said to be homologous if despite these dissimilarities the structures were derived from the same basic plan in the course of evolution though each may have been adapted to different uses (for example, the forelimbs of different mammals). On the other hand, homologous organs are the organs that have similar structural plans but are not necessarily structurally related (e.g.; wings of a bird and wings of a bee).

Genetic And Molecular Basis

DNA sequencing and genetic markers

Next-generation sequencing, for example, has transformed biological research through accurate identification of nucleotide sequences. SNPs, standing for single nucleotide polymorphisms, are used as specific points of difference in the genome that are necessary for mapping the traits and analysis of genetic differences within the populations.

Evolutionary relationships

The relatives of evolution are concerned with assembling genetic sequences from different species, in an attempt to make deductions on ancestorship and diversification. Molecular methods enable researchers to analyze systematic transitions and describe the process of evolution, and organisms adaptation and radiation based on natural selection and genetic variation.

Phylogenetic trees and cladograms

Phylogenetic trees as well as cladograms are tree diagrams that display a hierarchy in the evolutionary patterns concerning the genetic information. It shows the directions of branching of the species regarding the presumed order of division and other evolutionary processes. These diagrams assist biologists in understanding the relatedness of various species and identifying associated groups’ evolutionary patterns.

Embryological Evidence

Developmental stages

On the same note, embryological data show pronounced similarities in the developmental steps right from fertilisation to the formation of vital organs. These stages extended from cleavage, gastrulation and neurulation are some of the conservative processes that have significance to the formation of body structures.

Comparison of embryonic development across species

Embryos of different species illustrate that there are similarities in development but also enough differences to establish the principle of convergence. Such similarities of structures that are found in embryos of different animals support the theory of evolution because they indicate that the animals evolved from a common ancestor, while differences indicate that animals evolved to suit their environments and the activities they perform. Such comparisons give information and understanding of relatedness in the evolution of genetic variations and the development of species.

Diagrams Of embryonic stages

Types Of Classification Systems

The classification systems are discussed below:

Artificial Classification

• Artificial classification deals with arranging organisms in groups depending on certain physical aspects that one can easily notice.

• It helps in identification but can cause more distortion of the true evolutionary relationships.

• This method was regarded in the past though advanced molecular techniques have developed later on.

Natural Classification

• Natural classification takes into account more attributes than otherwise, that is; genetic and morphological traits.

• Although its objectives are quite modest, it seeks to classify organisms based on their natural kinship and share a common ancestry.

• Thus, the presented system looks more realistic and reflects the evolutionary relationships much better than artificial classifications.

Phylogenetic Classification

• There is a phylogenetic classification that groups organisms according to their evolution and genetical similarity.

• It employs molecular information data like DNA sequences to create the phylogenetic tree.

• It also aids in the determination of the different species’ evolutionary history and relationship between the species.

Limitations Of Current Systems

The limitations are discussed below

Convergence

One relative drawback is that in the process of convergent evolution, unrelated species over time acquire similar characteristics, and, therefore, the search for close evolutionary kinship solely based on genetic molecular indices is a difficult task.

Divergence

Genetic modification sometimes fails to measure the degree of difference in species of overproduction due to discrepancies in the genetic makeup of species particularly those species that undergo quick genetic changes than the time needed to analyze them.

Hybrid species

The problem of hybridisation between different species complicates the definitive identification of its genetic relations, which may be attributed to the events of hybridization. There is therefore a need for advanced genomic tools to get better and right pictures of hybrid stock ancestry and evolution.