Biology notes on Classification of Living Organisms for SSC and WBCS Main Exam

In this article we will discuss about the classification of living organism in different group. This topic is important for various exam conducted by SSC , WBCS Preliminary and  Main and other competitive exam.

Classification of Organism:

• Classification means to categories organism into different groups.
• In 18^th century Linnaeus divide all organisms into two kingdoms – Planate and Animalia in his book “System a Nature”.
• The foundation of modern classification system was laid in the line of classification system started by Linnaeus. Therefore Linnaeus is called ‘Father of Taxonomy’.
• Due to disputed position of organism like bacteria, virus, fungi and euglena, there is a need of reconsideration of system of classification.
• Two kingdom classification was given by Carolus Linnaeus, in which he classified organism into Plantae and Animalia.
• Three kingdom classification was given by Ernest Haeckel i.e. Plantae, Protista and Animalia.
• Four kingdom classification was given by Copeland i.e. Monera, Protista, Plantae and Animalia.
• Five kingdom classification was given by RH Whittaker.
• Latest system of classification is Six Kingdom System given by C Woose, O kandler and Mc Wheels.

Five Kingdom Classification:

• Five Kingdom Classification was proposed in 1969 by R. H. Whittaker.
• The criteria of classifying organism into five kingdoms are its complexity of cell structure, complexity of body of organism, mode of nutrition, life style and phylogenetic relationship
• Classification are as follows:
• Monera : It includes all prokaryotic organism like bacteria, cyanobacteria and archaebacteria, mycoplasma, actinomycetes and rickettsia. Filamentous bacteria also come under this kingdom. All organism of this kingdom are microscopic.
• Protista : This kingdom includes unicellular form usually found in aquatic habitats. On the basis of mode of nutrition they are autotrophic, parasitic, and saprophytic. Diatoms flagellates and protozoa come under this kingdom. Euglena have both heterotrophic and autotrophic mode of nutrition. So, it is placed between plant and animal.
• Fungi : Fungi is a group of unique organism having cell wall of chitin and heterotrophic mode of nutrition. Their body is made up of filaments called hyphae, which form a network called mycelium. Reproduction takes place by fragmentation. Example : Mushroom, Mucor, Albugo etc.
• Planatae : Kingdom plantae includes chlorophyll containing eukaryotic organism. But some plants are insectivorous and parasite. Major characteristic of plants is the presence of cell wall made up f cellulose.
• Animalia : Animals are heterotrophic and multicellular organisms with organs or tissues. Almost every animal comes under this category.

Binomial nomenclature :

• Proposed by Linnaeus in his book Species Pantarum.
• The scientific name of each organism is composed of two names i.e. a generic name and a species name.
• The generic names begin with a special letter and species name begins with small letter.

Scientific Names of some Organisms

Botany

• The study of different types of Trees, Plants is called Botany.
• Theophrastus is called the father of Botany.

Below given classification of Botany is given by Eichler.
Botanical world is mainly classified into two parts which are further classified into various parts

• Cryptogames
• Phanerogames

(A)Cryptogamus plants
There is no flower and seed in these types of plants. These are classified into the following groups:

(1) Thallophyta :

• Largest group of plant kingdom.
• Undifferentiated plant body that has no roots, stems or leaves is called Thallophyta.
• There is no conducting tissue

Algae

• Algae are mostly aquatic.
• They are autotrophic, chlorophyll bearing thalloid plants.
• There reproduction takes by vegetative and sexual means.
• Massive growth of algae is known as algal boom and boom caused by red algae is called red tide.
• Red algae are known as Rhdophyceae.
• Green Algae is known as Chlorophyceae
• Brown algae is known as Phaeophyceae.

Useful Algae :

• As a food : Porphyra, Ulva, Surgassum, Laeminaria, Nostoc etc.
• In making Iodine : Laeminaria ad Macrocystis
• As Biofertilisers : Nostoc, Anabina, kelp etc.
• Antibiotic: Chlorella for making Chlorellin antibiotic
• In Oxygen production for astronauts: Chlorella and Synechococcus

Fungi:

• Mycology is the study of Fungi.
• Chlorophyll is not present in Fungi
• Accumulated food in fungi remains as Glycogen.
• Fungi cell wall is made up of Chitin.

(2) Bryophyta:

• Bryophyta is the Plant Division that contains mosses.
• Plants in this Division have crude stems and leaves, but no roots.
• This is commonly known as amphibians of plant kingdom as they are found both in dry and moist area.
• In byophyta there is lack of Xylem and phloem tissue.
• The moss namely Sphagnum is capable of soaking water 18 times of its own weight. Therefore, gardeners use it to protect from drying while taking the plants from one place to another.
• The Sphagnum moss is used as fuel.
• The Sphagnum moss is also used as antiseptic.

(3) Pteridophyta

• The Pteridophyta Divsion contains ferns.
• Ferns are plants with leaves, roots, and stems; but they do not have flowers like most plants.
• Ferns have special stems, called rhizomes, which grow sideways at the surface or underground.
• Reproduction occurs by spores produced inside the sporangia.
• Examples : Ferns, Azolla, Pteridium, Lycopodium etc

(B)Phanerogamus or Floral plant

The plants in this group are well developed. All the plants in the Group have flowers, fruits and seeds. The plants in this group can be classified into two sub-groups – Gymnosperm and Angiosperm.
(1) Gymnosperm

• Gymnosperms are plants with naked ovules.
• Plants are woody, perennial and tall.
• Its tap roots are well developed.
• Pollination takes place through air.
• They include medium size tree giant redwood tree Sequoia of California(longest tree of plant kingdom)
• The smallest plant is Zaimia Pygmia.
• Living fossils are Cycas, Ginkgo, biloba and Metasequoia.
• Ginkgo biloba is also called Maiden hair tree.
• Ovules and Antherzoids of Cycas is the largest in Plant Kingdom.
• The pollen grains of Pinus are so much in number that later it turns into Sulphur showers.

(2) Angiosperm

• Angiosperms are flowering plants hence , flower is the most important feature of this group.
• Fruit is another major character of angiosperms.
• These group include plant ranges from microscopic Wolfia to tall tree Eucalyptus .
• Angiosperms are divided into dicots and monocots based on the presence of Cotyledons.
• Dicots have two while monocots have one cotyledon.