Biodiversity and Classification
- All the properties are specific to a group and the group that shares maximum similarities is usually called “species”.
- the process of categorizing on the basis of a characteristic feature shared similarly by the members of a group is called as “grouping”
- According to historical accounts we find that over a thousand years ago, Aristotle had made attempts towards grouping organisms on the basis of their habitat.
- We find that around the year 1686, John Ray, an English naturalist tried to classify plants on the basis of their external structures.
- After John Ray, it was Linnaeus who tried to classify all plants on earth. His most important contribution is: the use of some specific observable characters like the presence of male and female parts and their number to prepare a simple schema of classification. It is called as sexual system of classification.
- The description of this system is given in his book ‘Systemae Naturae’ published in the year 1735.
- Linnaeus made comparative study of several specimens of plants and animals that he collected.
- He developed such a schema of classification where species of plants and animals could be classified separately. The knowledge that Linnaeus acquired about the structures of animals and plants had a great impact on life sciences. According to his schema, the whole living world could be divided into two categories -Plant kingdom and Animal kingdom.
- Linnaeus first introduced hierarchy in his system. Organisms were arranged on the basis of their characters and developmental history in a definite sequence of groups. Like –
The Linnaean hierarchy for man is –
Kingdom – Animalia (Multicellular, eukaryote, nutrition starts with ingestion of food)
Phylum – Chordata (vertebral column, paired appendages)
Class – Mammalia (hair on body, external ear)
Order – Primate (opposable thumb, 5 fingers each in fore and hind palm)
Family – Hominidae (Bipedal movement)
Genus – Homo (Well developed brain)
Species – sapiens
There were some limitations in the two kingdom classification system. Linnaeus classified organisms as either plants or animals, but several organisms were eventually found to express both animal and plant characters.
- As the knowledge of internal structures of cells increased and new organisms discovered, the basis of classification was also modified. Different ways of classification started finding way. One such schema was suggested by R.H. Whittaker in the year 1969.
- Whittaker classified the whole living world into 5 kingdoms. His classification was based on the following characters –
- 1. The absence or presence of nuclear membrane (prokaryotic or eukaryotic)
- 2. Level of organization (unicellular or multicellular)
- 3. Process of acquiring nutrition (autotrophic or heterotrophic)
Whittaker classified the whole living world into 5 kingdoms
- Kingdom Monera
- Kingdom Protista
- Kingdom Fungi
- Kingdom Animalia
- Kingdom Plantae
- Unicellular organisms that lack a nuclear membrane or are prokaryotes are classified under this kingdom.
- Organisms may be autotrophic or heterotrophic.
- Cell wall is present around the cell membrane.
- Their cell wall is different from that of plants and is mainly made of peptidoglycan
Example: Bacteria, Cyanobacteria
Kingdom Protista –
- All organisms of this kingdom are unicellular with nuclear membrane around the nucleus or eukaryotic cells.
- Organisms can be both autotrophic or heterotrophic.
- All the life processes are carried out within the cell.
Example: Amoeba, Paramecium, Entamoeba, Euglena.
Kingdom Fungi –
- Most fungi are filamentous. They form networks of filaments that are called mycelium.
- Organisms of this kingdom are heterotrophic, unicellular or multicellular eukaryotic forms.
- Chloroplasts are absent in their cells.
Example: Mucor, Yeast, Agaricus (Mushroom), Rhizopus(bread mould), Aspergillus, Pennicilium.
Plant Kingdom –
- All organisms of plant kingdom are multicellular, eukaryotic forms.
- Most plants have chloroplasts in their cells, that help them to photosynthesize thus they are autotrophic.
- These have a cellulosic cell wall.
Example: Spirogyra(Algae)*, Funaria(Moss)
Animal Kingdom •
- Organisms of this kingdom are multicellular, eukaryotic, heterotrophic forms.
- These do not have a cell wall.
- These do not have chloroplasts.
- Mode of nutrition is mainly by ingestion. They have a specialized organ for intake of food. As for example butterflies have juice sucking tubes, humans have mouth, birds have beaks, etc.
- Most of the animals have specialized organs for movement (locomotion: movement in such a way that location changes). Example: Lion, mynah, fish, man, hydra, tapeworm, earthworm,
Need and process of naming organisms –
Linnaeus suggested a system of naming living organisms that could be universally followed. This was a system of scientific naming according to him. According to this system, each organism would have a name comprising two words. This is the system of binomial nomenclature.
In this system
- The first word of the name would represent the genus while the second would represent the species.
- The first alphabet in the name of genus would be in capital letters while the rest would be in small letters. The name of species would be in small letters.
- Both the words in of the name are either underlined or written in italics.
- “Biodiversity and Classification’’ Class-9, SCIENCE 2021-22 (Theory & Practical) Published by “State Council of Educational Research and Training, Chhattisgarh, Raipur’’
- The National Council of Educational Research and Training (NCERT)
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