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Why Are Living Organisms Classified?

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Key Reasons for Classifying Living Organisms

This world is filled with various kinds of living organisms. But this big complex living world with such diversity is as much a big and difficult task to study as it is interesting. For a proper scientific understanding of their differences and similarities and their typical attributes, there needs to be an organizational system in place that makes it easier for a scientific study. Plus, there is an incredibly high possibility that a particular type of organism is known differently at different places owing to different cultural aspects around the area. Therefore, to avoid such huge factors of confusion and to understand the different properties of the physical and genetic qualities of living organisms, a categorical classification of living things becomes necessary. This is an apt simple explanation for the question of why is classification of living things important.

Classification of Living Organisms

Humans beings share a very close evolutionary relationship and are descendants of monkeys. But this close relationship does not exist between a human being and a cow or cat for that matter. So the typical behavior and development of the biology in a monkey and a human being will be more similar but will be more different with respect to the cow. Such issues of scientific reasoning will fall into trouble when an attempt is made to study the diverse types of living organisms and their wide variety of characteristics. Hence, as mentioned above, the justification for why is it important to classify living organisms stands valid from this point of view as well.

To understand the huge life around us, and to understand their evolutionary process and scientific reasoning for the biological development of different organs and their usability, living things need to be classified. This classification can be done by dividing the organisms into huge groups based upon the fundamental characteristics that are shared between all the living beings in the group. These bigger categories can be divided into further subcategories based upon the increasing number of shared qualities amongst them. Going forward the characteristic may be less defining for the whole bigger group but it will still be important for their own smaller group. For example, if all the animals in a group, will have some fundamental similarities such as the existence of limbs, their multicellularity, etc. But there will be significant differences between a cow, a wolf, a human being, etc. After understanding in good detail why are living organisms classified understanding the basis of classification becomes equally important which is explained further.

Basis of Classification of Living Organisms 

There have been sincere attempts to classify living organisms since ancient times. These attempts are self-explanatory for the question of why is it necessary to classify living things. Aristotle had tried to classify living organisms based on their very generic habitat. He had classified them as organisms living on land, living in water, and living in the air. Even though a very simple and basic classification this type of classification has a huge flaw. The organisms living in water do not share many fundamental similarities except that they reside in water. Even then their similar habitat has not led to the evolution of corals, whales, and octopuses in any similar manner. 

The scientific studies performed after the Aristotle era, explored more physiological qualities of animals, and then to the most recent 19th century it progressed slowly. Hence, the manner in which organisms kept on being classified kept changing. Carl Linnaeus is credited with the idea of the modern system of classification that is followed. There have been quite a few changes in that system but he is well-known for the creation of the modern classification system and correctly credited for the binomial nomenclature of living organisms. The modern system of classification of living organisms is based on the inclusion of several fundamental inter-related characteristics even as basic as the type of cell. Several attributes a few of which given below are taken into account while classifying organisms according to the modern classification systems: 

  • Type of Cell -

Eukaryotic or Prokaryotic based upon the level of organization of the nucleus or the cell organelles

  • Type of Body Organisation - 

Unicellular or Multicellular depending upon how the cells carry out their functions or are there a hierarchy in the multicellular organization of the cells and if yes then what level of organization.

  • Type of Food Generation - 

Plants and Algae and Animals characterized by their ability to make their own food. The presence of pigments like chlorophyll and the organizational level of self food-producing organisms.

A clear difference between plants and animals exists and is visible through the classification system in practice as well. There is also a difference between plants and algae. They both produce their own food and yet are quite different at the type of body and the body organization level. They both in turn are different from unicellular organisms such cyanobacteria which are very very small in size as compared to plants and algae. Thus, a further hierarchy gets created as you move down the classification system when genetic qualities are also included. There are phylogenetic trees showing relationships between organisms of different hierarchies as well. But a classification needs to exist before the relationships can be established. When the classification is considered in the form of a tree then as you move higher and higher from the base classification such as plants and animals the branching happens to be more diversified and more complex.

Modern System of Classification

Why is it necessary to classify living organisms can be clear from the above explanation and also the details provided for the basis of classification. Owing to the difficult efforts given by the scientists for classifying living organisms a modern system of classification has been placed for some time. This system of classification is adaptive to the changing nature in the field of taxonomy - the study of naming and classifying organisms. Although Carl Linnaeus may have paved the way for modern classification biologists, Ernst Hackel, Robert Whittaker, and Carl Woese have made impactful contributions to the modern system of classification. The following level of organization is widely used in modern classification and is also shown in the figure:

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It should be noted that this system of classification closely follows the evolutionary aspects of the living organisms as well. Categorizing the living organisms in this manner not only helps in listing different species of organisms but also in understanding evolutionary ancestors and cross-relationships between them. Thus, it answers clearly as to why the classification of living organisms is important.

Given above is a detailed note on the topic of why are living organisms classified. It explores the reasons for scientific study and understanding of relationships between organisms that need a classification system. It describes the question of why is it important to classify living things, but also gives the basis on which the living organisms are classified. The modern system of classification serves as a prime example and the basis for why is classification of living organisms important.

Fun Facts on Classification of Living Organisms

For students to generally learn about the order of classification of living things, or remember them, the use of mnemonics can be very helpful. One such mnemonic for the classification of living organisms is: King Philip came over for good spaghetti, which stands for Kingdom, Phylum, Class, Order, Family, Genus, and Species.

Another important characteristic is that a species is usually defined as individuals that can reproduce. This also arises from the fact that reproduction is one of the important features of all creatures termed as living things.

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FAQs on Why Are Living Organisms Classified?

1. What is biological classification?

Biological classification is the scientific process of arranging living organisms into groups and subgroups based on their similarities and differences. This systematic arrangement follows a hierarchy of categories, making the study of the vast diversity of life more organised and understandable. It provides a framework for naming, describing, and identifying organisms.

2. What is the primary purpose of classifying living organisms?

The primary purpose of classifying the millions of living organisms on Earth is to make their study more efficient and systematic. Key objectives include:

  • Simplifying Study: It is impossible to study every single organism, so grouping them makes it manageable.
  • Establishing Relationships: Classification reveals the evolutionary and genetic relationships between different life forms.
  • Universal Identification: It provides a universal scientific name for each organism, avoiding confusion caused by local or common names.
  • Predicting Characteristics: Placing an organism in a group allows us to predict certain characteristics it is likely to have.

3. What are the seven main levels in the hierarchy of biological classification?

The seven main obligate categories or ranks in the taxonomic hierarchy, from the broadest to the most specific, are:

  • Kingdom: The highest level, grouping organisms based on fundamental characteristics (e.g., Animalia, Plantae).
  • Phylum (or Division for plants): A group of related classes.
  • Class: A group of related orders.
  • Order: A group of related families.
  • Family: A group of related genera.
  • Genus: A group of closely related species.
  • Species: The most basic unit, representing a group of individuals that can interbreed to produce fertile offspring.

4. What is the five-kingdom classification system?

The five-kingdom classification system, proposed by R.H. Whittaker in 1969, divides all living organisms into five main kingdoms. This classification is based on key criteria such as cell structure (prokaryotic vs. eukaryotic), body organisation (unicellular vs. multicellular), and mode of nutrition (autotrophic vs. heterotrophic). The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

5. What is binomial nomenclature and who is credited with introducing it?

Binomial nomenclature is the formal system of naming species of living things by giving each a name composed of two parts. This system was introduced and popularised by Carolus Linnaeus. The first part of the name identifies the genus (Generic name) and the second part identifies the species (specific epithet). For example, the scientific name for a mango is Mangifera indica.

6. What is the key difference between Taxonomy and Systematics?

While often used interchangeably, Taxonomy and Systematics have a key difference. Taxonomy is concerned with the principles and procedures of identification, nomenclature (naming), and classification of organisms. In contrast, Systematics is a broader field that includes taxonomy but also focuses on understanding the evolutionary relationships (phylogeny) among organisms. Systematics uses this evolutionary history to build a more natural classification system.

7. How does classification help in understanding the evolutionary relationships between organisms?

Modern classification systems, especially phylogenetic ones, are designed to reflect evolutionary history. When organisms are placed in the same taxonomic group, such as a family or order, it implies they share a more recent common ancestor with each other than with organisms in other groups. By studying the hierarchy, scientists can trace the lines of descent and construct phylogenetic trees that map out the evolutionary pathways and connections among the vast diversity of life.

8. Why do classification systems, like the five-kingdom model, change over time?

Classification systems are not static because our scientific understanding is constantly evolving. They change for several reasons:

  • New Discoveries: The discovery of new organisms with unique characteristics can challenge existing systems.
  • Advanced Technology: The development of tools like electron microscopy and biochemical analysis provided deeper insights into cell structure and function.
  • Genetic Evidence: Modern DNA and RNA sequencing techniques offer powerful evidence about the evolutionary relationships between organisms, often leading to major revisions. For example, genetic data led to the creation of the three-domain system.

9. Beyond the five-kingdom system, what is the 'three-domain system' of classification?

The three-domain system is a biological classification model proposed by Carl Woese in 1990 that divides cellular life forms into three domains: Archaea, Bacteria, and Eukarya. This system places more emphasis on molecular evidence, specifically the sequence of nucleotides in ribosomal RNA (rRNA). It revealed a fundamental split in the prokaryotes, separating them into two distinct domains (Archaea and Bacteria), while all eukaryotes are placed in the third domain (Eukarya).

10. What are some limitations in classifying organisms like viruses or lichens within the five-kingdom system?

The five-kingdom system faces challenges with certain organisms:

  • Viruses: They are not included because they are considered to be on the borderline of living and non-living. They lack a cellular structure and can only replicate inside a living host cell, so they do not fit the criteria for any of the five kingdoms.
  • Lichens: These are not single organisms but a symbiotic association of a fungus (from Kingdom Fungi) and an alga or cyanobacterium (from Kingdom Protista or Monera). Classifying this composite organism into a single kingdom is therefore problematic.


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