Question

John ray system of classification is considered to be a natural system of classification as it is based on
A) The natural relationships between the organisms.
B) Few arbitrary characters.
C) The DNA structures.
D) All of the above.

Answer 1

Classification of living organisms is based on similarities and differences. For example, the presence or absence of notochord in animals, presence or absence of vascular tissues in plants, presence of a different type of photosynthetic pigments in different types of algae.

Complete answer:
Different taxonomists gave different classification systems based on their analysis. Linnaeus classified living organisms into 2 kingdoms- Animalia and Plantae. Whittaker gave 5 kingdom classification- Monera, Protista, Fungi, Plantae and Animalia. Carl Woese divided organisms into 3 domains- Archaea, Eubacteria and Eukarya based on complementarity in 16S/18s rRNA genes.

John Ray was a botanist and naturalist who was a major contributor to classification and taxonomy. John Ray classified the plants into different categories. He divided them according to complexity into trees, shrubs, sub shrubs and herbs. Also, he classified plants as imperfect or lower plants (no seeds) and perfect or higher plants (possess seeds). He further divided trees into 8 groups, shrubs into 2 groups and herbs into 21 groups.

So, the classification was based on arbitrary characters like complexity, presence or absence of seeds, and the number of cotyledons (1 or 2) present. Complementarity between DNA structures of related organisms was analyzed to study the relationship between organisms. Based on the relationship between organisms they were kept in the same or different groups of taxa.

Thus the correct answer is option ‘D’, all of the above.

Note: John Ray studied the structural characters as well as internal anatomy which were the most important part of his classification. For the classification of animals and the study of their relationships, evolutionary constructs were used. To predict the relationships, the DNA structure of the associated species is being studied.