– Aristotle classified organisms for the first time.

– Two kingdom system includes – Plantae &Animalia.

Demerits of Two Kingdom system

– No difference in Eukaryotes and Prokaryotes.

– Heterotrophic Fungi kept in Plantae.

– Five kingdom system is given by R.H Whittaker (1969) viz. Monera, Protista, Fungi, Plantae and Animalia.

Kingdom Monera –

– Prokaryotic unicellular organisms.

– Most abundant.

– Also live in extreme habitats viz. Hotsprings, Snow etc. as endoparasite etc.

–  eg. Bacteria.

– Some bacteria are autotrophic others are heterotrophic.

Archaebacteria –

– Cellwall different from other bacteria.

– Live in most harsh habitats eg. Halophile.

– Methanogens are found in the gut of ruminants and produce methane (CH4) gas.

Eubacteria –

– True bacteria.

– Rigid cellwall with or without flagellum.

– Cyanobacteria( Blue green algae) are also included in this group.

– Cyanobacteria are Photosynthetic autotrophs, unicellular, colonial or filamentous, with gelatinous sheath.

– Have Heterocyst for N2fixation eg. Nostoc, Anabaena, Oscillatoria, Rivularia, Gloeotrichia etc.

–  Mostly bacteria are Heterotrophs and are useful and harmfuboth to humans.







– Reproduction occurs by fission. Also by primitive type of sexual reproduction,  by transferring DNA piece from one bacterial cell(+ strain) to other (- strain) (called cell Transduction)









Mycoplasma –

– Smallest unicellular anaerobic organisms having no cellwall.

– Pathogenic in plants and animals.

Kingdom Protista –

– Unicellular eukaryotes.

– Primarily aquatic.

– Some have cilia and flagella.

– Reproduction sexual and asexual both.

Crysophytes –

– Fresh water or marine microscopic Planktons.

– Mostly photosynthetic and cheif producer in ocean eg. Diatomsand Golden algae (Desmids).

– Diatoms with cellwalls in two halves having Silica (indistructible).

– Diatomaceous earth is formed by cellwall  deposits of Diatoms and used in polishing, filtration of oils and syrups, fire bricks and explosives.

Dinofagellates –

– Marine.

– Photosynthetic yellow , green, blue, brown or red in colour.

–  One longitudinal and other transverse two flagella.

– Gonyaulax causes Red tides.

Euglenoids –

– Fresh water forms.

– No cellwall, outer most layer pellicle.

– Two unequal flagella.

– Photosynthetic but also heterotrophic in absence of light ( Mixotroph).

– eg. Euglena.


Slime moulds –

– Saprophytes.

– Body is an aggregation called ‘Plasmodium’( multinucleate, without cellwall, irregular in shape and can spreadover several feet ).

– Plasmodium produces fruiting body having spores with walls which are highly resistant and spread through wind.


Protozoans –

– Fresh water or marine unicellular heterotrophs.

– Primitive relative of animals.


(a) Amoeboid Protozoans –

– Free living or parasites.

– Pseudopodia (false feet) formed eg. Amoeba ,Entamoeba.

(b) Flagellated Protozoans –

–  Free living or Parasitic with flagella eg.Trypanosoma( causessleeping sickness).

(c) Ciliated Protozoans 

– With cilia eg. Paramecium(sleeper animalcule).

(d)Sporozoans –

– Spore like stage in life eg. Plasmodium vivax.

Kingdom Fungi –

– Fungi are a group of achlorophyllous, heterotrophic organisms with cell wall without cellulose.

– Saprophyte or Parasite or Symbiotic.

– Useful and Harmful both.

– Prefer to grow in warm and humid places.

– Unicellular (eg. Yeast) to multicellular filamentous body calledmycelium.

– One unit of   mycelium called hypha .

– Mycelia maybe coenocytic (no septum) or septate.

– Lichens – Symbiotic association of fungus and algae.

– Mycorrhiza – Symbiotic association of fungi with root of higher plants eg. Pinus.

– Reproduction –Vegetative : by fragmentation and by spores.Sexual: by gametes.

– Three steps in sexual reproduction

1) Plasmogamy – fusion of protoplasm.

2) Karyogamy – fusion of nuclei.

3)  Meiosis of zygote.



Phycomycetes –

– Grow on aquatic places or decaying wood or damp places or obligate parasite.

– Mycelium aseptate, coenocytic.- Reproduction –         asexual by zoospores or aplanospores.

Sexual by zygospores.

– eg.   Rhizopus(bread mould) and Albugocandida (causing white rust of crucifers).


Ascomycets (sac fungi)-

– Unicellular  (eg. Yeast) or multicellular

– Saprophytic or parasitic.

– Maybe coprophillus (growing on dung) eg. peziza.

– Mycelium septate and branched.

– Reproduction – asexual by exogenously produced conidia.

sexually by Ascospares produced in asci present in fruiting body called Ascocarp.

– egAspergillus, Claviceps, Neurospora, Saccharomyces (yeast) etc.


Basidiomycetes (club fungi) –

– Grow on soil , logs or parasites ( rusts and smuts).

– Mycelium septate and branched and of two types 1) Uninucleate  2) Dikaryophase.

– Reproduction  vegetative by fragmentation sexualby two somatic cells giving rise to Dikaryophase.

 – Dikaryophase makes fruiting body Basidiocarp having Basidia.

-Inside basidia (singular basidium) – Karyogamy and meiosis occours.

-Meiosis results in formation of four basidiopores.

– eg.  Agaricus (mushroom), Ustilago (smut fungi), Puccinia (rust fungus).


Deuteromycetes (Fungi- imperfectil) –

– It is formed class – Group of Fungi whose complete life cycle is not known.-Saprophyte/parasite , mostly decomposers.- eg. Alternaria, colletotrichum, Trichoderma.

Kingdom Plantae –

– Eukaryotic, chlorophyll bearing autotrophic organisms.

– Only few members partialheterotrophs eg.  Insectivorus plants (Bladder wort and Venus flytrap).

– Few parasites eg. Cuscuta

–  Reproduction – vegetative,asexual and sexual.

– Life cycle shows alternation of generation.

–  eg. Algae, Bryophytes,Pteridophyte, Gymnosperms and Angiosperms.

Kingdom Animalia –

– Eukaryotic, Heterotrophic organisms.

– No chloroplast and no cell wall.

Holozoic mode of nutrition .

– Definite shape and size and capable of locomotion.

– Reproduction –  sexual in general

– eg. frog, cockroach, cow, man etc.

Viruses, Viroids and Lichens –

Viruses –   Connecting link between living and non living.

– Non cellular structure consisting of protein coat and Nucleic acid

– Can reproduce within a host cell.

– Host cell may be killed.

– Viruses which infect bacteria are called Bacteriophage.

– Tobacco Mosaic Virus (TMV)–        

 – Protein coat: – capsid consists of capsomers.

– Viruses can cause diseases viz. Mumps, Small pox, Herpes, Influenza, AIDS etc.


Please enter your comment!
Please enter your name here