Classification refers to the identification, naming, and grouping of organisms into a formal system based on similarities in their internal and external structure or evolutionary history. It determines the methods of organizing diversity of life on earth. Therefore, classification helps in understanding millions of life forms in detail. Who started the classification of organisms? Let us explore the history of classification. History of classification
One of the earliest schemes of classification was given by the Greek thinker, Aristotle, around 300 BC. He classified animals according to their habitat – land, air, or water. However, this classification of Aristotle was misleading because animals that live on land include earthworms, mosquitoes, butterflies, rats, elephants, tigers etc. These animals do not resemble each other except that they share a common habitat. Similarly, all aquatic animals do not resemble each other.
Therefore, a new system of classification was developed to classify the vast diversity of organisms present on earth. Principles of classification followed today include:
• Nature of cell: Nature of the cell is considered to be the fundamental feature, as it gives rise to another feature called cellularity. It includes the presence or absence of membrane-bound organelles. Therefore, on the basis of this fundamental characteristic, we can classify living organisms into two broad categories of eukaryotes and prokaryotes. • Cellularity: Unicellular organisms are those organisms whose body is made up of a single cell, whereas multicellular organisms are those organisms whose body is made up of many cells. Multicellular organisms use the principle of division of labour to perform specialized functions. This results in a specific body design that distinguishes multicellular organisms from unicellular organisms. • Mode of nutrition: The mode of nutrition also distinguishes different organisms. The ability to manufacture their own food makes the body design of plants different from that of animals. This further extends our classification as shown below:
Look at the pictures given below.
Different life forms
Can you divide these animals into four groups and can you give reasons for each division? These animals can be grouped as follows:
(i) Seahorse, fish: These are exclusively water-inhabiting animals. They breathe through gills. (ii) Lizard, snake: These are cold-blooded animals. They lay eggs and have scales on their body. They breathe through lungs. (iii) Pigeon, sparrow: These are warm-blooded animals. They lay eggs and have feathers on their body. (iv) Chimpanzee, monkey: They have mammary glands and produce young ones. Conclusion: Characteristics can be compared to find out similarities between various organisms, and then these organisms can be classified into groups. Hierarchy of Classification
Hierarchy refers to the organization or classification of things in order of rank or importance. Who developed the hierarchy of classification?
Carolus Linnaeus developed the hierarchy of classification on the basis of characteristics possessed by an organism. The Linnaeus system of classification is still the basic framework for classifying organisms. According to this system, Kingdom is the highest rank. Linnaeus divided each kingdom into Classes; later it was grouped into Phyla for animals and Divisions for plants. Class is further sub-divided into smaller groups – Order and Family, then Genus, and finally, each Genus is divided into Species. Thus, species is the basic unit of classification. [pic]
Hierarchy of classification
What is species?
A species can be defined as a group of interbreeding organisms that are capable of producing a fertile offspring. |...