History of Classification: Aristotle, Theophrastus, Bentham and Hooker, Linnaeus, Practice Problems and FAQs

You know about biodiversity. Lots of varieties of insects, plants and animals are there in this world. It is necessary to keep a name for each species.

Fig: Organisms

Our Earth is home to millions of species of flora and fauna of which around 1.7 - 1.8 million species have been discovered. Ever wondered how we keep a track of existing species and identify new ones? There is a need to classify these organisms, otherwise it will become difficult for us to study them. There are several scientists who worked on these processes. They created the present system of classification. We must appreciate their efforts. They laid stone for the scientific system of classification.

The process of identifying organisms and placing them into groups or categories, based on their similarities and dissimilarities, is called biological classification. Let’s take a deep dive into the history of biological classification.

List of contents

• History of classification
• Aristotle
• Theophrastus
• George Bentham and Joseph Dalton Hooker
• Adolph Engler and Karl Prantl
• Carolus Linnaeus
• Practice Problems
• FAQs

History of Classification

Man has attempted to classify living organisms around himself since the beginning of civilisation. His initial attempts were not scientific and were mostly based on using the animals for basic needs such as food, clothing and shelter. In the present times, a more scientific approach towards classification has been adopted.

Aristotle

Aristotle was the first person to attempt biological classification based on external features. Aristotle’s system of classification is called the artificial system of classification.

Fig. Aristotle

Classification of Aristotle

He classified plants and animals in the following way:

He classified plants into herbs (with soft stems), trees (with woody stems) and shrubs (with several woody stems). He classified animals into air dwellers, land dwellers and water dwellers based on their habitat. Based on the presence or absence of RBCs, he classified animals into enaima (with RBCs) and anaima (without RBCs) .

Demerit of Aristotle’s classification

A major demerit of Aristotle’s classification was that he did not consider evolutionary relationships. Second is that it was not accurate. For example, his system of classification placed organisms that all fly in the same category, that means air dwellers. But bees, birds, and bats are not related to each other.

Fig: Aristotle’s classification

Theophrastus

Theophrastus is a Greek botanist and known as the ‘Father of ancient plant taxonomy’. He wrote a book named Historia plantarum and gave descriptions and names of 480 plants in the book.

Fig. Theophrastus

Classification of Theophrastus

Theophrastus used an artificial system of classification to classify plants into annuals, biennials, and perennials based on their life span. He classified the plants into four groups based on their habitat, form, and texture as follows :

• Trees
• Shrubs
• Under shrubs
• Herbs

Fig: Classification of Theophrastus

Major contributions of Theophrastus

The major contributions of Theophrastus are as follows:

Theophrastus gave the fundamental differences between dicoty­ledons and monocotyledons. He gave the difference between centripetal or racemose and centrifugal or cymose type of inflores­cences. He proposed the difference between polypetalous and gamopetalous corolla. He also identified the difference between inferior and superior ovaries.

George Bentham and Joseph Dalton Hooker

They used a natural system of classification to classify plants based on the ultrastructure of the cell, anatomy of plants, embryology and phytochemistry (analysis of chemicals within plants). They worked together for about 25 years. They jointly published their research work in Genera Plantarum between 1862-1883 in 3 volumes.

Fig: George Bentham and Joseph Dalton Hooker

They divided the seed plants into two subkingdoms like Cryptogamia and Phanerogamia. Phanerogamia was further divided into two divisions such as Gymnospermae and Angiospermae. Angiospermae was again divided into two classes like Dicotyledons and Monocotyledons.

The Dicotyledons were divided into three subclasses Gamopetalae, Polypetalae, and Monochlamydeae. But they have placed Gymnospermae between Dicotyledons and Monocotyledons.

Adolf Engler and Karl Prantl

Engler and Prantl classified flowering plants on the basis of complexity in floral morphology.

They used a phylogenetic system of classification based on the evolutionary relationship between organisms.

Fig: Adolf Engler and Karl Prantl

Merits of Engler and Prantl’s classification

• Plants are classified with a logical sequence of progressive evolution.
• Gymnosperms are placed before angiosperms.
• Gymnosperms are considered primitive to angiosperms.
• Closely related families were treated as natural clusters.
• Descriptions of each family were given.
• Description of family contains the details of morphological, anatomical, embryological characters and geographical distributions.

Demerits of Engler and Prantl’s classification

• They placed Monocotyledons before dicotyledons, which is against the modern phylogenetic concepts.

• Achlamydeous flowers without calyxes and corolla are treated as primitive in this system.

• They placed naturally unrelated taxa in the same group.

• The system was not strictly phylogenetic.

Carolus Linneaus

Linneaus proposed a two kingdom classification system by grouping plants and animals into separate kingdoms. His book, ‘Systema naturae’ has detailed description of plants. His book ‘Genera plantarum’, has a detailed description of the plant kingdom. In his book ‘Species plantarum’ he described around 4000 plant species and gave the scientific names of plants.

Fig. Carolus Linnaeus

Merits of Linnaeus system of classification

Linnaeus' system of classification helps in the quick and easy identification of plants as it is based on one or a few characteristics.

Demerits of Linnaeus system of classification

• His system of classification was developed on the differences between the sex organs rather the similarities.
• The closely related members get separated and the distantly related members become very close in this system of classification.
• The gymnosperms were placed in an angiosperm family.
• The monocotyledons, dicotyledons and gymnosperms were not considered separately.
• This system of classifica­tion can be considered as a dictionary rather than classification where the words are arranged alphabetically with­out maintaining any relationship.

Practice Problems

Q1. Who was the first person to attempt biological classification based on their external features?

(a) R.H. Whittaker
(b) Linnaeus
(c) Aristotle
(d) Bentham and Hooker

Solution : Aristotle was the pioneer in classifying organisms into plants and animals. He classified plants as shrubs, herbs and trees based on their morphological characters. He classified animals as anaima and enaima based on the presence or absence of RBCs.

Q2. Match column I with column II and find out the correct option.

a. A - II, B - III, C - IV and D - I
b. A - II, B - IV, C - I and D - IV
c. A - III, B - I, C - II and D - IV
d. A - II, B - I, C - IV and D - III

Solution : Linneaus proposed a two kingdom classification system by grouping plants and animals into separate kingdoms. His book ‘Systema naturae’ has a detailed description of the animal kingdom. Theophrastus is a Greek botanist. He wrote a book named Historia plantarum and gave descriptions and names of 480 plants in the book. Engler and Prantl classified flowering plants on the basis of complexity in floral morphology. They used a phylogenetic system of classification based on the evolutionary relationship between organisms. Aristotle was the first person to attempt biological classification based on external features. Aristotle’s system of classification is called the artificial system of classification. Hence option (a) is correct.

Q3. Who proposed the two kingdom classification?

(a) R.H. Whittaker
(b) Linnaeus
(c) Aristotle
(d) Bentham and Hooker

Solution : Carolus Linneaus proposed a two kingdom classification system by grouping plants and animals into separate kingdoms. Hence option (b) is correct.

Q4. Find the odd one from the options given below.

A. Systema naturae
B. Historia plantarum
C. Species plantarum
D. Genera plantarum

Solution : Carolus Linnaeus has written books namely Systema naturae, Species plantarum and Genera plantarum. ‘Systema naturae’ has detailed descriptions of plants. His book ‘Genera plantarum’, has a detailed description of the plant kingdom. In his book ‘Species plantarum’ he described around 4000 plant species and gave the scientific names of plants. Historia plantarum is a book written by Theophrastus. Hence option b is correct.

Q5. Write a short note on classification by Aristotle?
Answer: Aristotle was the first person to attempt biological classification based on external features. Aristotle’s system of classification is called the artificial system of classification. He classified plants into herbs, trees and shrubs. He classified animals into air dwellers, land dwellers and water dwellers based on their habitat. Based on the presence or absence of RBCs he classified animals into enaima and anaima.

Q6. Define anaima?
Answer: The organisms that lack red blood cells or RBCs are called anaima as per the classification of Aristotle.

FAQs

Q1. Write down the major difference between the classification system by Linnaeus and Aristotle?
Answer: Aristotle used the habitat and the physical structure of an organism mainly for classification. Linnaeus used the physical structure of an organism along with the structural similarities of different organisms for classification.

Q2. Why was Aristotle's system of classification replaced?
Answer: Naturalists replaced Aristotle's system of classification because it did not cover all organisms and their characteristics. He used common names of organisms for classification that was problematic.

Q3. Who was the first person to classify animals as per their habitats?
Answer: The Greek philosopher Aristotle is considered as the first person who classified animals according to their habitat. In his system of classification, living things are divided into two classes such as plants and animals.

Q4. When did Theophrastus classify plants?
Answer: Theophrastus classified organisms between 350 BC and 287 BC. He described plants based on their uses, reproductive methods etc.