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Biodiversity-theory Biology-day-11 Target-ssc-cgl-2018

Biodiversity-theory Biology-day-11 Target-ssc-cgl-2018

Biodiversity-theory Biology-day-11 Target-ssc-cgl-2018


Biological Diversity was coined by Walter G. Rosen in 1986.

It refers to the diverse or varied forms of living beings which differ from one another in external appearance, size, color pattern, behaviour, habitat etc.

Taxonomy – It is biological science which deals with the identification, nomenclature and classification of organisms. It provide the scientific name for every living creature.

Father of Taxonomy – Linnaeus

Linnaeus developed the binomial system of nomenclature and a system of classification.

Binomial nomenclature – The system of naming organisms in which two names are given is called the binomial nomenclature. For example: panthra leo is the name of lion. Here panthra is the genus name (generic name) and leo is the species name (specific name).

Basis Of Classification

The method of arranging the organisms into groups on the basis of their similarities and differences is called classification.

Classification and evolution

Charles Darwin first described the idea of evolution in his book ‘The origin of species’.

The idea of evolution is closely connected to classification. Those organisms with ancient body designs are commonly referred to as “primitive” or “Lower” organisms. The organisms with recent body designs are called “advanced” or “higher” organisms.

Artificial and natural system of classification

Early systems of classification were artificial and were based on size, colour or nature of the organism.

Aristotle classified organisms according to whether they lived on land, sea or air. Theophrastus categorised all plants on the basis of their form, life span and habitat.

Carl Von Linnaeus in his book, Systema Naturae described and named plants, animal and minerals.

The natural system of classification was based on natural affinities between living organisms and indicated all of the similarities and differences between the organisms.

Classification Systems

Two kingdom system of classification: Plant and Animal kingdom. This system of classification was first suggested by Carolus Linnaeus. E.H. Haeckel raised a third kingdom Protista. Robert H. Whittaker proposed the forth kingdom Monera and fifth Fungi.

Five Kingdom system of classification:

-Kingdom Monera [Prokaryotic bacteria and blue green algae]

-Kingdom Protista [unicellular eukaryotic organisms]

-Kingdom Fungi [Multinucleate higher fungi]

-Kingdom Plantae [multicellular green plants and advanced algae]

-Kingdom Animalia [Multicellular organisms]

Carl Woese further divided Monera into Archaebacteria and Eubacteria.


The category or taxa used in the classification of plants and animal kingdom are kingdom, phylum, class, order, family, genus and species.

Species: basic unit to understand taxonomy as well as evolution. It is a group of individuals which are able to breed among themselves and produce off springs of their own kind.

Genus: group of species related and have fewer characters in common. They have identical reproductive organs.

Family: represented by a group of related genera that are more similar to each other.

Order: assemblage of families resembling one another.

Class: organisms of related orders.

Phylum: organisms belonging to different classes having a few characters in common.

Kingdom: organisms who share a set of distinguishing common characters.

Characteristics of five kingdoms

  1. Kingdom Monera

It is divided into two categories:

Archaebacteria :

  • Most of them are autotroph and only a few photosynthesize. They derive energy from the oxidation of chemical energy sources. It can manufacture its own amino acids and proteins. It is further divided into
  • Methanogens : They manufacture methane and are found in swamps and marshes. They die in the presence of oxygen.
  • Thermoacidophiles : they favour extremely hot and acidic environments. Many use hydrogen sulphide as their energy resource.

Halophiles :

they grow in very salty areas.


  • They are prokaryotic cells. Nearly all bacteria are enclosed in porous but rigid cell wall. The most common bacteria shapes are rod like (bacilli), spheres (cocci) and corkscrew (spirilla). The cell wall of bacteria contains peptidoglycan which is composed of chains of sugars.
  • The Gram-staining has dintinguishes two types of cell-wall construction in bacteria i.e. gram negative and gram positive.
  • Many bacteria are motile and contain one or more Flagella. These are made up of protein called flagellin that tend to rotate like propeller of a ship.

Kingdom Protista

It is also known as Protocista and include many types of unicellular eukaryotic organisms. For e.g. unicellular fungi, algae and protozoans. Autotrophic and heterotrophic are the mode of their nutrition.

Phylum protozoa

  • They are Unicellular and mostly aquatic animals
  • Solitary or colonial, Free living or symbiotic
  • Their body are either naked or covered by pellicle
  • Body shape may be irregular, spherical, oval, elongated or flattended
  • Cytoplasm differentiated into outer and inner ectoplasm
  • Nucleate can be uni, bi or multinucleate
  • Nutrition can be heterotrophic

It is divided into five classes:-

Class 1 – Mastigophora – Locomotary organs are flagella. Example – Euglena, Noctiluca, Giardia

Class 2 – Sarcodina – Pseudopodia are chief organelles of locomotion and food cheating. Example – Amoeba, Entamoeba,  Arcella

Class 3 – Sporozoa – All are parasites and lack of locomotary organelles. Example – Plasmodium, Monocystis

Class 4 – Ciliata – Ciliaare the main locomotary and food catching organelles. Example Paramecium, Opalina, Vorticella

Class 5 – Suctoria – They grow up without any Locomotary organelles. Example  – Ephelota

Kingdon Fungi

  • Simple non-green Plants which are not photosynthetic.
  • They are heterotrophic or eukaryotic organisms
  • They are may be unicellular or filamentous and their body is made up of mycelium which is composed of several thread like structures, called hyphae.
  • Cell wall of fungi is made up of chitin cellulose.
  • Glycogen is their food.

Kingdom Plantae

  • They includes multicellular organisms.
  • They have Eukaryotic cell.
  • Their reserve food is starch and lipids.
  • Plant cells are covered by cell organelles called plastids which contain chlorophyll. These are called chloroplast.
  • Photosynthesis is done by the help of autotrophic type nutrition.
  • Their body form is irregular due to presence of branches.

Classification of Kingdom Plantae

1) Division Algae

  • It is simple plant and is in the form of undivided thallus.
  • Most algae are aquatic and have autotrophic cells
  • Their cells is surrounded by cellulose cell walls

2) Division Bryophyta

  • They are multicellular green land plants and are also known as amphibians of the plant kingdom.
  • These plants don’t have vascular system. Their sex organs are multicellular.
  • Their body is flat, green thallus and leafy but they don’t have roots, stems and leaves.

3) Division Pteridophyta

  •  There is absence of flowers. Hence they don’t produce seeds.

4) Division Gymnosperm

  • Sporophylls are aggregated to form cones.
  • Seeds produced are naked.
  • There is no vessel in xylem and no companion cells in phloem.

5) Division Angiosperm

  • Sporophylls are aggregated to form flowers.
  • Seeds are not naked. They are enclosed by a fruit.

Kingdom Animalia

  • They have wall-less eukaryotic cells.
  • Limited growth and stops at maturity
  • They have definite shape and size.
  • Movement in animals is enabled due to the presence of muscular system.
  • Requirement of food and other necessities in animals is fulfilled by locomotion.

Classification of Kingdom Animalia


  • The porifera means organisms with holes.
  • These are non motile animals attached to some solid support.
  • There are holes or pores, all over the body. These leads to canal system that helps in circulating water throughout the body to bring in food and oxygen.
  • The animal is not differentiated into tissues.
  • The body is covered with a hard outer skeleton. These are commonly known as sponges. They are marine animals.
  • Examples: Sycon, spongilla, euplectella, etc.


  • The body is made up of a coelom (cavity) with a single opening.
  • The body wall is made up of two layers of cells (diploblastic).
  • Some of the species live a solitary life while others live in colonies.
  • Examples: Hydra, Jellyfish, Sea anemone, etc.


  • The body is flattened from top to bottom and hence the name platyhelminthes.
  • These are commonly known as flatworms. The body wall is composed of three layers of cells (triploblastic).
  • Because of three layers, it is possible to form some organs as well. But a proper ceolom is absent in platyhelminthes and hence proper organs are absent.
  • They are free-living or parasitic animals.
  • Examples: Planaria, liver fluke, tapeworm, etc.


  • body is bilaterally symmetrical and triploblastic.
  • Pseudo-coelom is present and hence organs are absent.
  • These are very similar as parasitic worms causing diseases, such as worms causing elephantiasis(filarial worms) or the worms in intestines (roundworm or pinworms).
  • Examples: Roundworms, pinworms, filarial parasite (Wuchereria), etc.


  • True body cavity is present in these animals.
  • The body is divided into segments and hence the name annelida.
  • Each segment is lined one after another and contains a set of organs.
  • Examples: Earthworm, leech, etc.


  • The word arthropod means jointed legs.
  • Largest group of animals.
  • Circulatory system is open, which means blood flows in the coelomic cavity.
  • Examples: cockroach, housefly, spider, prawn, scorpion, etc.


  • The animal has soft body; which is enclosed in a hard shell.
  • The shell is made of calcium carbonate.
  • Circulatory system is open and kidney like organ is present for excretion.
  • The body has well developed muscular feet for locomotion. Examples: Snail, mussels, octopus, etc.


  • The body is covered with spines, which gives the name echinodermata.
  • Body is radially symmetrical. The animals have well developed water canal system, which is used for locomotion.
  • Skeleton is made of calcium carbonate.
  • Examples: Starfish, sea urchins, etc.


  • Animals are bilaterally symmetrical, triploblastic and ceolomate.
  • Notochord is present at least at some stages of life.
  • Notochord is a long rod-like structure which runs along the back of the animal.
  • This provides attachment points for muscles.
  • It also separates the nervous tissues from the gut.
  • Examples: Balanoglossus, herdmania, amphioxus, etc.


  • These animals have true vertebral column and internal skeleton.
  • Vertebrates have bilateral symmetry.
  • characteristics of vertebrates:
  • Notochord present; which is replaced by spinal column during embryonic stage.
  • Dorsal nerve chord is present.
  • Animals are triploblastic and coelomate.
  • Animals have paired gill pouches.


  • They are commonly known as fish.
  • Muscular tail is present which assists in locomotion.
  • Body is covered with scales.
  • Paired gills are present; which can breathe oxygen dissolved in water.
  • They are cold-blooded animals.
  • The heart has only two chambers. They lay eggs.
  • Fishes can be bony or cartilaginous.
  • Shark is an example of cartilaginous fish.
  • Rohu and katla are examples of bony fish.

(b). Amphibia:

  • These animals are adapted to live both in water and land.
  • Mucus glands on skin keep the skin moist. The animals breathe through skin when in water and through lungs when on land.
  • The heart has three chambers.
  • These are cold blooded animals.
  • Examples: Frog, toad, salamander, etc.

(c). Reptilia:

  • These animals show crawling movement for locomotion.
  • These animals are cold-blooded, have scales and breathe through lungs.
  • Most of the reptilians have three chambered heart but crocodile has four-chambered heart.
  • They don’t need water to lay eggs, rather eggs are covered with hard shells and laid on land.
  • Examples: snakes, lizards, crocodile, turtle, etc.


  • The body is covered with feathers.
  • Forelimbs are modified into wings. These are warm-blooded animals.
  • The heart has four chambers.
  • Bones are hollow (pneumatic); which assists in flying.
  • All the birds belong to this class.


  • Warm blooded animals with four chambered hearts.
  • The body is covered with hairs.
  • Skin has sweat glands and sebaceous glands.
  • Mammary glands are present in females for the production of milk and are used for nourishing the young ones.
  • Most of the mammalians give birth to young ones and are called viviparous.
  • Some of the mammals lay eggs and are called oviparous.
  • Examples: human, chimpanzee, lion, platypus, horse, etc.


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