Need for classification of living organisms :- Living organisms have evolved on the earth over millions of years. There is a vast variety of living organisms. Living organisms show a wide range of variations.- Some microscopic bacteria are of a few micrometres in size and some like whales and red wood trees are about 30 metres and 100 metres in size.- Some pine trees live for thousands of years while insects like mosquitoes die within a few days.- Some organisms are colourless and even transparent and some are brightly coloured. To understand and study all these organisms is impossible. If they are arranged into different groups based on their similarities in characteristics, then it is easier to study the different groups as a whole.Classification of living organisms :- The arranging of organisms into different groups on the basis of the similarities in their characteristics is called classification of living organisms.

Basis of classification of living organisms :- The main characteristics which are considered for classification of living organisms into different groups are :-- Whether they are made of prokaryotic or eukaryotic cells.- Whether the cells occur singly or they are grouped together and live as an indivisible group.- Whether they produce their own food by photosynthesis or get their food from outside.-Of the organisms which produce their own food (plants) what is the level of organisation of their body ? - Of the animals what is the level of organisation of their body and what are their special organs and their functions ? The characteristics used for classification of plants will be different from the characteristics used for classification of animals because plants make their own food and animals get their food from outside.

Classification and evolution :- The present day complex living organisms have evolved from the earlier simple forms due to the changes in their body designs over millions of years. The body designs of living organisms are gradually changing due to the changes in environment and the need to adapt themselves to the changes in the environment. Some groups of organisms having ancient body designs have not changed much during evolution and have simple forms and structure. These organisms are called ‘primitive or lower organisms’. Some organisms have acquired their body designs relatively recently and have complex forms and structure. These organisms are called ‘advanced or higher organisms’.

The hierarchy of classification – Groups Living organisms have been broadly classified into five main kingdoms. They are :-i) Monera ii) Protista iii) Fungi iv) Plante v) Animalia Each kingdom has been further classified into smaller sub - groups at various levels as :- Kingdom Phylum (for plants) / Division (for animals) Class Order Family Genus Species By arranging organisms on the basis of hierarchy and characteristics into smaller and smaller groups we arrive at the basic unit of classification called species. Species :- is group of organisms which are similar enough to breed and perpetuate.

The basis for grouping organisms into five kingdoms

• i) On the basis of the presence or absence of membrane-bound organelles, all living organisms  are divided into two broad categories of eukaryotes and prokaryotes. This division lead to the formation of kingdom Monera, which includes all prokaryotes.

• (ii) Then, eukaryotes are divided as unicellular and multicellular, on the basis of cellularity. Unicellular eukaryotes form kingdom Protista, and multicellular eukaryotes form kingdom Fungi, Plantae, and Animalia.

• (iii) Animals are then separated on the basis of the absence of a cell wall.

• (iv) Since fungi and plants both contain a cell wall, they are separated into different kingdoms on the basis of their modes of nutrition. Fungi have saprophytic mode of nutrition, whereas plants have autotrophic mode of nutrition. This results in the formation of the five kingdoms

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Five kingdom system of classification

• Robert .H. Whittaker in 1959 proposed a five kingdom classification of living organisms on the basis of Linnaeus’ system of classification encorporating cell structure, mode and source of nutrition and body organisation as main features. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, and Animalia

The Five Kingdom classification of living organisms :-

Organisms

Prokaryotes Eukaryotes

Unicellular Multicellular

Protista

With cell wall Without cell wall

AnimaliaDo not performphotosynthesis

Able to perform photosynthesis

Fungi Plantae

Monera

Monera :-1. They are mostly prokaryotic,2. unicellular3. Do not have a definite nucleus4. May or may not have cell wall5. Mode of nutrition is autotrophic or heterotrophic. Eg :- Bacteria, Blue-green algae, Cyanobacteria, Mycoplasma etc.

Bacteria

Blue-green algae

Cyanobacteria

Mycoplasma

Protista :- They are eukaryotic unicellular Mostly aquatic, some have cilia or flagella which help them in moving Mode of nutrition may be autotrophic or heterotrophic. Eg :- Algae, Diatoms, Protozoans etc.

Algae

Protozoan

Diatoms

Fungi :-• They are eukaryotic, multicellular. •They do not have chlorophyll and cannot prepare their own food and are heterotrophs. They use decaying organic matter as food and so are called saprophytes.• Some of them live in association with algae. They are called lichens.•Eg :- Yeast, Aspergillus, Penicillium, Agaricus, Lichens etc.

Yeast

Agaricus

Lichens

Plantae (Plants) They are multicellular eukaryotes having cell walls. They use chlorophyll for photosynthesis. All plants are included in this group. They are divided into five groups. They are :-Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms..

Animalia (Animals)• They include all organisms which are multicellular,

eukaryotes, • Without chlorophyll and cell walls.• They are heterotrophs. • They are divided into ten groups. • They are :-• Porifera, Coelenterata, Platyhelminthes, Nematoda, • Annelida, Arthropoda, Mollusca, Echinodermata, • Protochordata, and Vertebrata

Classification of plants• (i) The first level of classification depends on whether a plant body is well

differentiated or not. A group of plants that do not have a well differentiated plant body are known as Thallophyta.

• (ii) Plants that have well differentiated body parts are further divided on the basis of the presence or absence of vascular tissues. Plants without specialised vascular tissues are included in division Bryophyta, whereas plants with vascular tissues are known as Tracheophyta.

• (iii) Tracheophyta is again sub-divided into two divisions Pteridophyta and Phanerogams on the basis of the absence/presence of seed formation.

• (iv) Pteridophyta plants do not produce seeds• (iv) Phanerogams plants have well developed reproductive organs that

finally produce seeds. • (v) Phanerogams group is further sub- divided on the basis of whether the

seeds are naked or enclosed in fruits. This classifies them into gymnosperms and angiosperms.

• Gymnosperms are seed bearing, non-flowering plants, whereas angiosperms are flowering plants in which the seeds are enclosed inside the fruit.

•

Classification of plants (Plantae) :- Plants are divided into five groups. They are :- i) Thallophyta ii) Bryophyta iii) Pteridophyta iv) Angiosperms v) Gymnosperms

Thallophyta :- In this group the plants do not have well differentiated body parts. The plants are called algae. They are mostly aquatic. Eg :- Spirogyra, Ulothrix, Cladophora, Chara etc.

Spirogyra Ulothrix Chladophora Chara

Bryophyta :- In this group the plant body is differentiated into stem and leaf like structures but there are no specialised structures for the conduction of water and other substances from one part of the plant body to the other. These plants are called the amphibians of the plant kingdom. Eg :- Moss (Funaria), Marchantia, Riccia etc.

Moss

Marchantia Riccia

Pteridophyta :- In this group the plant body is differentiated into roots, stem and leaves and has vascular tissue for conducting water and other substances from one part of the plant body to the other. Eg :- Ferns, Marsilea etc.

Ferns Marselia

Gymnosperms (Cryptogams) :- The plants of this group bear naked seeds (gymno – means naked and sperma means seed). They are usually perinneal, evergreen and woody.Eg :- Pines (Pinus), Cycas etc.

Pinus Cycas

Angiosperms (Phanerogams) :- The plants of this group bears covered seeds (angio – means covered and sperma – means seed). They are also called flowering plants. The plant embryo in the seed have cotyledons. Angiosperms are divided into two groups on the basis of the number of cotyledons. Plants with seeds having single cotyledon are called monocots. Eg :- rice, wheat, maize etc. green gram, peas, tamarind etc. Plants with seeds having two cotyledons are called dicots. Eg :- green gram, peas, tamarind etc.

Classification of plantsPlants

Do not have differentiatedbody parts

Have differentiated body parts

ThallophytaWithout vascular

tissue

Bryophyta

Bear naked seeds

Do not produce seeds(Cryptogams)

Pteridophyta

Produce seeds(Phanerogams)

Gymnosperms Angiosperms

Bear covered seeds

With vascular tissue

One cotyledon Two cotyledons

Monocots Dicots

Classification of animals (Animalia) :- Animals are divided into ten groups. They are :-Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata, and Vertebrata.

Porifera :- (Sponges)

• They are marine non motile animals attached to some soild support.

• They have pores all over the body forming a canal system which helps to circulate water and bring food and oxygen.

• They have a hard outer skeleton and do not have any tissues.

• Eg :-Spongila, Sycon, Euplectelia etc.

Coelenterata

• They are aquatic animals.• There is a cavity in the body (coelom).• The body has two layers of cells – an outer layer and an inner layer.• Some live in colonies (corals) and others are single.Eg :- Corals, Hydra, Jellyfish, Corals

Examples of coelenterataJellyfish Sea anemone

Corals

Platyhelminthes :- (Flatworms)

1. They have three layers of cells and are called triploblastic.2. They do not have true body cavity.3. They may be free living or parasitic. Eg :- Planaria (free living), Liverfluke, Tape worm (parasitic) etc.1. They have flat body( dorsiventrally flattened) which is bilaterally

symmetrical. (Both right and left half of the body is similar.)Planaria Liverfluke Tape worm

Nematoda :- They have cylindrical body. The body is bilaterally symmetrical and triploblastic. They do not have true body cavity.( Pseudocoelome) They have tissues but no real organs. They are parasitic. Eg :- Ascaris (round worms), Wuchereria ( Filarial mworm) (pin worms) etc. Filarial worm causes Elephentiasis

Ascaris

Wuchereria

Annelida :- Their body is bilaterally symmetrical and triploblastic. They have true body cavity. Their body is segmented. ( Both internally & externally) There is differentiation of organs. They are found in water and on land. Eg :- Earthworm, Nereis, Leech etc.

Earthworm Nereis Leech

Arthropoda• Largest group of animal kingdom• They have bilaterally symmetrical

body.• The body is segmented.• They have an open circulatory

system, The blood does not flow in well defined open spaces

• The body cavity is filled with blood.

• They have jointed legs.( Arthro- Jointed legs )

• Eg :- Prawn, Crab, Cockroach, Spider, Scorpion, Butterfly, Housefly, Centipede etc.

Prawn

Crab

Spider ButterflyHousefly

Cockroach Scorpion Centipede

Arthropoda Examples

Mollusca• Second largest group in

animal kingdom• They have bilateral symmetry.• The coelomic cavity is

reduced.• There is little segmentation.• They have open circulatory

system and kidney like organs for excretion.

• They have feet for moving around.

• Eg :- Snails, Mussels, Chiton, Octopus etc.

Snail (Pila)

Mussel (Unio)

Chiton

Octopus

Mollusca - examples

Mollusca - Examples

Echinodermata• They are spiny skinned

organisms.• They are free living marine

animals.• They are triploblastic and have

coelomic cavity.• The have water filled tube feet

which help in movement.• They have hard skeleton made

of calcium carbonate.• Eg :- Star fish, Sea urchin,

Feather star, Sea cucumber etc

Protochordata :- They have bilateral symmetry and are tiploblastic. The have coelomic cavity. The have a notocord which is a long rod-like structure along its back to which muscles are attached and help in movement. Eg :- Balanoglossus, Amphioxus, Herdemania etc.

Balanoglossus

Amphioxus

Herdemania

Vertebrata• These animals have a true vertebral column and internal

skeleton, allowing a completely different distribution of muscle attachment points to be used for movement. Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs. All chordates possess the following features:

• (i) They have a notochord• (ii) They have a dorsal nerve cord• (iii) They are triploblastic• (iv) They have paired gill pouches• (v) They are coelomate.•

Vertebrata :- (Vertebrates) They have vertebral column and internal skeleton. They have bilateral symmetry and are triploblastic. They have coelomic cavity. Their body is differentiated into tissues and organs. Their body consists of four regions – head, neck, trunk and tail. They have two pairs of fins or limbs. The respiration in aquatic forms is by gills and in land forms respiration is by lungs The sexes are separate. Vertebrates are grouped into five classes. They are :- Pisces, Amphibia, Reptilia, Aves and Mamalia.

Pisces• They are fishes living in water.• Their skin is covered with scales or

plates • They respire using gills. • They have streamlined body and fins

which help them to move in water. • They are cold blooded and their heart

has only two chambers.• They lay eggs from which the young

ones hatch out.• Some fishes have skeleton made of

cartilage like Sharks, Rays etc. and some have skeleton made of bones and cartilage like Tuna, Rohu etc.

• Shark

Tuna

Electric ray Sting ray

Rohu

Pisces - Examples

Amphibia :- (Amphibians)• They are found in land and water.• They do not have scales but have mucous glands on their skin. • They are cold blooded• Heart is three chambered. • Respiration is through gills or lungs. • They lay eggs in water. Eg :- Frogs, Toads, Salamanders etc.

Frog Toad Salamander

Reptilia :-(Reptiles)• They have scales • Breathe through lungs. • They are cold blooded. • Most of them have three chambered heart but crocodiles have four chambered heart. • They lay eggs with hard covering in water. Eg :- Snakes, Turtles, Lizards, Crocodiles etc.

Snake

Turtle

Lizard

Flying lizard

Crocodile

Aves :- (Birds)•They are warm blooded animals. •They have four chambered heart. •They breathe through lungs. •They have an outer covering of feathers. •Their two fore limbs are modified into wings for flying. •They lay eggs. Eg :- Crow, sparrow, Pigeon, Duck, Stork, Ostrich

Crow

Sparrow

Pigeon

DuckStork

Ostrich

Mammalia :- (Mammals)• They are warm blooded animals. • They have four chambered heart. • They have mammary glands for production of milk to nourish their young ones. • The skin has hairs and sweat glands. • Most of them give birth to their young ones. Some of them lay eggs (like Platypus and Echidna). Eg :- Cat, Rat, Dog, Lion, Tiger, Whale, Bat, Humans etc.

Nomenclature :- All living organisms have been given scientific names which can be used to identify them anywhere in the world. The system of scientific naming organisms is called binomial nomenclature. The binomial nomenclature consists of two parts. The first part is the name of the genus and the second part is the name of the species. The system of scientific naming or nomenclature we use today was introduced by Carolus Linnaeus. Eg :- The scientific name of human beings is – Homo sapiens. Homo is the name of the genus and sapiens is the name of the species.Generic name starts with capital letter, specific name starts with small letter