History of Classification || CH 02 || Biodiversity || Grade 9 || Biology || National Book Foundation

Описание: History of Classification || CH 02 || Biodiversity || Grade 9 || Biology || National Book Foundation


2.3 HISTORY OF CLASSIFICATION

The Greek philosopher Aristotle was the first person who classified the living organisms. In 700s, Abu Usama Aljahiz described 350 species of animals. In the end of 15th century many biologists have worked on classification method.

Chapter 2: Biodiversity

Andrea Caesalpino (1519-1603): He divided plants into fifteen groups and called them genera. John Ray (1627-1705): He published important works on the classification of plants.

Tournefort (1656-1708): He introduced the taxa of class and species Carolus Linnaeus (1707-1778): He grouped species according to similar physical characteristics. According to earlier classification system, organisms were classified into two kingdoms, then three-kingdom and then five-kingdom system.

Classification System

Two kingdom System

Three kingdom System

Five kingdom System

1. Two-kingdom classification system: It is the oldest system and classifies organisms into two kingdoms, the Plantae and Animalia. The kingdom Plantae includes the autotrophs. Bacteria, fungi and algae were also included in the kingdom. The organisms which depend on autotrophs or other heterotrophs are included in the kingdom Animalia.

Many unicellular organisms like Euglena have both plant like (presence of chlorophyll) and animal like (heterotrophic mode of nutrition in darkness and lack of cell wall) characteristics. So separate kingdom was introduced for such organisms.

2. Three-kingdom classification system: The German Scientist Ernst Haeckel proposed a third kingdom, Protista to accommodate Euglena like organisms and to separate unicellular microscopic organisms from multicellular ones.

The organisms which lack nucleus in their cells are called prokaryotes while the organisms which have nucleus in their cells are called eukaryotes.

3. Five-kingdom classification system: In 1937 E-Chatton suggested the terms 'Procariotique' to describe bacteria 'Eucariotique' to describe plant and animal cells. In 1967 Robert Whittekar introduced five-kingdom classification system. The five kingdoms are: Monera, Protista, Fungi, Plantae and Animalia. In the five kingdom system bacteria and archaea were combined in a single kingdom Monera, because they shared the prokaryotic form of cell structure.