Friday 5 February 2021

Chapter 2 Biological Classification







CLASSIFICATION is the process of grouping organisms into convenient categories based on some easily observable characters.


1.It makes study of various living organisms easy.

2.Identification of organisms becomes easy.

3.It helps in Knowing relationships among different groups of organisms.ARISTOTLE was the earliest to attempt a scientific basis for classification. He classified plants into trees, shrubs and herbs. He divided animals into two groups: -

1. Animals which had red blood 2. Animals which had not red blood.

LINNAEUS gave the Two Kingdom System in which all organisms have been

classified into two kingdoms - Animalia and Plantae.This system did not distinguish between prokaryotes and eukaryotes.Classification systems for the living organisms have undergone several changes

over time.


It was proposed by R.H. Whittaker in 1969. The five kingdoms are :









Main criteria for classification in this system are :-

1 COMPLEXITY OF CELL STRUCTURE :--Cells are of two types, prokaryotic and eukaryotic.Prokaryotic cells do not have true nucleus, membrane bound organelles, spindle apparatus and 70S ribosomes are present.

Eukaryotic cells have a true nucleus, membrane bound organelles, spindle apparatus, 80S ribosomes are present in cytoplasm and 70S ribosomes are present in mitochondria and plastids.Prokaryotes are placed in Kingdom Monera.Eukaryotes are placed in KingdomsProtista,Fungi,Animalia and Plantae.


2 .COMPLEXITY OF BODY STRUCTURE - Organisms have two types of body structure - Unicellular and multicellular. Unicellular

organisms placed in kingdom monera(prokaryotes )and protista(eukaryotes)Multicellular organisms are placed in Fungi,Animalia and Plantae.


 3 .MODE OF NUTRITION - It is of two main type-

(a) Autotrophy



(a)Autotrophy :-These organisms prepare their own food from inorganic raw material.|t is further of two types :

*«Chemoautotrophic-Energy released from chemical reactions is used to synthesize organic food from organic raw materials.

* Photoautotrophic- Radiant energy is used to synthesize organic food from inorganic raw material.


(b)Heterotrophic - Organisms take readymade food from other organisms.

Types eHolozoic (Ingestive)-Solid food is taken and digested inside the body.eSaprophytic -Absorption of soluble organic remains as food.

eParasitic-Food is absorbed directly from other living organisms


4. PHYLOGENETIC RELATIONSHIP :-The earliest living forms produced prokaryotic organisms (Monerans).Monera gave rise to protists.Fungi,Plants and Animals have developed from early protistians.


In the FIVE KINGDOM SYSTEM OF CLASSIFICATION: -KINGDOM MONERA includes bacteria. These organisms show extensive diversity.

(1) These are prokaryotic unicellular organisms.

(2) Cell wall is noncellulosic (polysaccharides +amino acids)

(3) Nuclear membrane is absent.

(4) Mode of nutrition is autotrophic (chemosynthetic and photosynthetic) and Heterotrophic (saprophytic and parasitic)



Students we know that all living organisms are classified into five kingdoms:-

1 Monera

2 Protista

3 Fungi

4 Plantae

5 Animalia.


Today we will discuss Kingdom Monera in detail. It includes all the prokaryotic unicellular organisms. Prokaryotic organisms are those which lack nuclear membranes i.e. DNA is naked. Genetic material is not organised in nucleus. DNA is coiled and is called nucleoid. Membrane bound organelles are absent.BACTERIA are the sole members of Kingdom Monera.

OCCURRENCE OF BACTERIA.It is found everywhere i.e in soil, air, water, hot springs, deserts, snow, deep oceans,

on and inside other organisms.


1 COCCUS - These are round or spherical bacteria.

2 BACILLUS - These are rod shaped bacteria.

3 VIBRIO - These are comma shaped bacteria.

4 SPIRILLUM - These are spiral shaped bacteria.


1 AUTOTROPHIC: These bacteria synthesise their own food from inorganic

substrates. Bacteria that uses radiant energy to prepare their food are called PHOTOSYNTHETIC AUTOTROPHS. Bacteria that synthesise food from inorganic raw materials with the help of energy released from inorganic chemical reactions are called CHEMOAUTOTROPHIC bacteria.

2 HETEROTROPHIC: These bacteria depend on other organisms or on dead

organic matter for food.



Reproduction in bacteria takes place by following methods: -

A. Fission

B. Forming spores

C. Sort of sexual reproduction by primitive type of DNA transfers from one bacterium to other.



1. Archaebacteria

2. Eubacteria.


They are the oldest form of life. Their cell wall structure is different and this helps them to survive in most harsh habitats.

HALOPHILES: These can live in extremely salty areas

THERMOACIDOPHILES: These can live in hot springs.


METHANOGENS: These can live in marshy areas. These are present in gut of ruminants (cows and buffaloes) and are responsible for methane (biogas) production from the dung.



There are thousands of true bacteria. They have rigid cell wall and if they are motile

then they have flagellum.


1) Cyanobacteria: It is also called blue green algae. It has chlorophyll a. These are PHOTOSYNTHETIC AUTOTROPHS. It may be unicellular, colonial or filamentous,fresh water/marine or terrestrial. Mucilaginous sheath surrounds the colonies. Some of these organisms have specialised cells that fixes atmospheric nitrogen. These cells are called heterocysts, e.g Nostoc and Anabaena.

2) Chemosynthetic autotrophic bacteria helps in recycling of nitrogen,

phosphorous, iron and sulphur.

3) Heterotrophic bacteria are most abundant. Majority of them are

decomposers. These bacteria helps in forming curd from milk, antibiotics formation,fixing nitrogen in legume roots. Some bacteria causes diseases in humans, crops,farm animals and pets.

4) Mycoplasma are groups of monerans that lack cell wall. They are smallest living cells. They can survive without oxygen.






Q1. Round or spherical shaped bacteria is called

(A) Coccus.

(B) Bacillus §

(C) Vibrio.

(D) Spirillum


Q2. Blue green algae is also called

(A) Cyanobacteria

(B) Eubacteria

(C) Both of these.

 D) None of these.

Q3. Bacteria that lives in extremely salty areas are called

(A) Thermoacidophiles.

(B) Halophiles

(C) Methanogens.

(D None of these


Q4. Cyanobacterial cells which are specialised for nitrogen fixation are

(A) Phycobilisomes


(C) Hormogonia.

(D) Trichomes


Q5. The bacterial genome is called

(A) Nucleus

(B) Nucleolus

(C) Nucleoid

(D) None of these



Q1. Prokaryotic cells lacks nuclear membrane.

Q2. Heterotrophic bacteria can produce their own food.

Q3. Virus is responsible for citrus canker disease.



Q1. ---—--are the sole members of Kingdom Monera

Q2. -—---- are the smallest living cells.




Ans 1. (A) Coccus. (Bacillus bacteria is rod shaped)

Ans 2. (A) Cyanobacteria (These are photosynthetic autotrophs)

Ans 3. (B) Halophiles (These can tolerate high salt concentration)

Ans 4. (B) Heterocysts (These are thick walled cells)

Ans 5. (C) Nucleoid (Genetic material is in direct contact with cytoplasm)



Ans 1. True

Ans 2. False. (Autotrophic bacteria can produce the own food)

Ans 3. False. (Bacteria are responsible for citrus canker)



Ans 1. Bacteria.

Ans 2. Mycoplasma. (These can survive without oxygen)



Q1. Give difference between autotrophic and heterotrophic bacteria.

Q2. Write a note on archaebacteria.

Q3. Give characteristics of Kingdom monera.



There are five kingdoms in which all the living organisms are placed.

1. Kingdom Monera

2. Kingdom Protista

3. Kingdom Fungi

4. Kingdom Plantae

5. Kingdom Animalia


We will discuss here Kingdom Protista in detail:--

All single-celled eukaryotes are placed under kingdom Protista. For our convenience, Kingdom Protista is divided into Chrysophytes, Dinoflagellates,Euglenoids, Slime moulds and Protozoans.

(Note: - Out of these five we are discussing first two groups here.)

Members of Protista are primarily aquatic. This Kingdom forms a link with the others,dealing with plants, animals and fungi. Being eukaryotes, the protistan cell body contains a well-defined nucleus and other membrane-bound organelles. Some have flagella or cilia. Protists reproduce asexually and sexually by a process involving cell

fusion and zygote formation.



This group includes diatoms and golden algae (Desmids). They are found in freshwater as well as in marine environments. They are microscopic and float passively in water currents (Plankton).Most of them are photosynthetic. In diatoms the cell wall form two thin overlapping shells, which fit together as in a soap box.The walls are made up of silica and their deposition and accumulation over billions of years is referred to as Diatomaceous Earth.


These organisms are mostly marine and photosynthetic. They appear yellow,green, brown, blue or red depending on the main pigments present in their cells.The cell wall has stiff cellulose plates on the outer surface. Most of them have two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates. Very often red dinoflagellates (like Gonyaulax) undergo rapid-

-multiplication that they make the sea appear red (Red Tides). Toxins released by such large numbers may even kill other marine animals such as fishes.



a) MCQs.:-

Q1. Unicellular eukaryotic organisms are placed in :

(a) Kingdom Animalia

(b) Kingdom Plantae

(c) Kingdom Protista

(d) Kingdom Monera


Q2. Which of the following group not belongs to Kingdom Protista-?

(a) Slime moulds

(b) Protozoans

(c) Archaebacteria

(d) Chrysophytes


Q3. In the Five Kingdom system of Whittaker, how many kingdoms are eukaryotes —

(a) 2

(b) 3

(c) 4



Q4. Toxins released by these can kill other marine animals like -

(a) Diatoms

(b) Golden algae

(c) Dinoflagellates

(d) Slime moulds


Q5. How many flagella are present in dinoflagellates -

(a) 1

(b) 2

(c) 3

(d) 4


(b) FILL UPS.:--

Q1. and golden algae are included in Chrysophytes.

Q2. are responsible for red tides.


(c) TRUE / FALSE:--

Q1. Cell Walls of diatoms form to thin overlapping cells like a soap box.

Q2. Most of the members of Kingdom Protista are terrestrial.

Q3. All Protozoans are autotrophs.



a) MCQs.:—


Ans 1. (c) Kingdom Protista (Protists are Unicellular and have well defined nucleus. )

Ans 2. (c). Archaebacteria (Archaebacteria belongs to Monera.)

Ans 3. (c). 4 (Protista, Fungi, plantae and Animalia are Eukaryotes. )

Ans 4. (c). Dinoglagellates (On rapid multiplication they produce large toxins. )

Ans 5. (b). 2 (Dinoflagellates have two flagella.)


(b) FILL UPS.:-~

Ans 1. Diatoms

Ans 2. Gonyaulax


(c) TRUE / FALSE:~

Ans 1. TRUE

Ans 2. FALSE (Most of the members of Kingdom Protista are Aquatic.)

Ans 3. FALSE (Protozoans are heterotrophs. )



Q1. What do you mean by diatomaceous earth?

Q2. What is the nature of cell wall in diatoms?

Q3. Write a short note on Dinoflagellates.



Kingdom Protista,includes all single celled, eukaryotes.(having true membrane bound nucleus & other organelles and DNA wrapped in Histone proteins.)(Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds and Protozoans).The first tvo groups have been discussed in assignment no.08. Now, we are discussing last three groups here.



Majority of them are freshwater organisms found in stagnant water. Instead of a cell wall they have a protein rich layer called pellicle, which makes their body flexible. They are photosynthetic in the presence of sunlight, when deprived of sunlight they behave like

heterotrophs by predating on other smaller organisms.Interestingly the pigments of euglenoids are identical to those present in higher plants. Example:- Euglena.



Slime moulds are saprophytic protists. The body moves along decaying twigs and leaves engulfing organic material. Under suitable conditions they form an aggregation called plasmodium, which may grow and spread over several feet. During unfavourable conditions the plasmodium differentiates ! and forms fruiting bodies bearing spores at their tips.These spores possess tough walls. They are extremely resistant and survive for many years,even under adverse conditions. The spores are dispersed by air currents.



All protozoans are heterotrophs and live as predators or parasites. They are believed to be primitive relatives of animals. There are four major groups of protozoans,according to mode of locomotion:

 (a) Amoeboid protozoans : These organisms live in freshwater, sea water or moist soil. They move and capture their prey by putting out pseudopodia. as in amoeba. Marine forms have silica shells on their surface.Some of them such as entamoeba are parasites.


(b) Flagellated protozoans: The members of this group are either free living or parasitic. They have flagella. The parasitic forms causes diseases such as sleeping sickness. Example; Trypanosoma gambiens.

 (c) Ciliated protozoans: These are aquatic, ‘actively moving organisms because of the presence of thousands of cilia. They have a cavity gullet, that opens to the outside of the cell surface. The coordinated movement of rows of cilia causes the water laden with food
 to be steered into the gullet.

Example:- Paramecium.

 (d) Sporozoans: This includes diverse parasitic organisms,having no organs for locomotion,and have an infectious sporophytic stage in their life cycle. The most notorious is plasmodium (Malarial parasite) which causes malaria, a disease which has a staggering effect on human population.



(a) MCQs.:--

Q1. Protozoans are believed to be primitive relatives of —

(a) Bacteria

(b) Fungi

(c) Algae

(d) Animals


Q2. Movments of cilia brings food towards gullet in-

(a) Amoeba

(b) Euglena

(c) Paramecium

(d) Slime moulds


Q3. Naked cytoplasm, multinucleated and saprophytic are the characteristics of -

(a) Monera

(b) Protista

(c) Fungi

(d) Slime moulds


Q4. These unicellular eukaryotes are photosynthetic in the presence of sunlight -

(a) Protozoans

(b) Euglenoids


(d) Dinoflagellates


Q5. These form spores during unfavourable conditions -

(a) Dinoflagellates


(c) Euglenoids

(d) Slime moulds


(b) FILL UPS:--

Q1. A protein rich layer which make euglenoids flexible is .

Q2. Amobea moves with the help of .


(c) TRUE / FALSE:-

Q1. Paramecium moves with the help of flagela.

Q2. Plasmodium causes malaria in humans.

Q3. Flagellated protozoans are either free living or parasitic.



(a) MCQs.:--

Ans 1. (d). Animals

Ans 2. (c). Paramecium

Ans 3. (d). Slime moulds (Slime moulds lacks cell wall and secretes slime.)

Ans 4. (b). Euglenoids ( contain photosynthetic pigments. )

Ans 5. (d). Slime moulds


(b) FILL UPS:--

Ans 1. Pellicle

Ans 2. Pseudopodia


(c) TRUE / FALSE:--

Ans 1. FALSE (Most of the members of Kingdom Protista are Aquatic.)

Ans 2. TRUE

Ans 3. TRUE



Q1. How slime moulds surpass unfavourable conditions?

Q2. How amoeba obtain their food?

Q3. Write a short note on ciliated protozoans.




¢ Most of the fungi are multicellular eukaryotic organisms except

yeast(unicellular).¢ Fungi are non-vascular, non-motile organisms.

“ Cell wall is made up of chitin.“« They have no pigments like chlorophyll, so they are not photosynthetic.

“ Most of the fungi are saprophytic (decomposers).

“ Digestion is extracellular.

“ Lack true roots,stems and leaves.

“ Fungi are more related to animals than plant kingdom.

“ Some are parasitic; very few are symbiotic.

“ Body of fungi have thread like structures called hyphae.

“* Hyphae are of two types: Septate and Aseptate.


> Mastigomycetes:

m They produce flagellated cells.

m Asexual reproduction occurs by formation of spores.

= Gametes are usually non-flagellate.

m Sexual reproduction by gametangial contact.

mw They look multinucleate(coenocytic).

ws Examples : Albugo , Phytophthora.


> Zygomycetes:

mw They are found in freshwater and marine water.

= Most zygomycetes live on decaying plants and animal matter.

mw They are non flagellate fungi.

mw They look multinucleate (coenocytic).

mw Asexual reproduction is by means of spores produced in sporangia borne on thehyphae.

mw Sexual reproduction occurs by means of conjugation tube.

ms A Zygote like structure is formed after conjugation.

mw They bear rhizoids which act as roots.

ms Example: Rhizopus stolonifer (bread mold)—which is used for

commercialproduction of fumaric acid.

= Asexual reproduction in Zygomycetes:

Sexual reproduction in zygomycetes:

 It occurs by conjugation.lIsogamous hyphae forms zygote.

 Spores are formed in zygote. Spores grow into hyphae.


A. Very short answer type questions:

A.) MCQ'’s:

Q1. Aseptate fungi are of following types:

a. 1

b. 2

c. 3

d. 4


Q2.Rhizopus(bread mold) is an example of which fungi:

a. Mastigomycetes

b. Zygomycetes

c. Ascomycetes

d. Basidiomycetes


Q3.Lower fungi are:

a. Multinucleate

b. Uninucleated

c. Binucleated

d. Non- nucleated


Q4.Root like structures of fungi are known as:

a. Hyphae

b. Rhizoids

c. Sporangiospore

d. Septa


Q5.Mode of nutrition of fungi is :

a. Autotroph

b. Heterotroph

c. Saprophyte

d. Parasitic


B.) Fill Ups:

1. Cell wallismade up of__.

2. Thread like body of fungi is known as_.

3. Hyphae are of two types and



1. Mastigomycetes are flagellated members of aseptate fungi.

2. During asexual reproduction of zygomycetes, they form spores.

3. Fungi have true roots,stem and leaves.


B.Short answer type questions:

1. Draw flow chart of aseptate division of fungi.

2. Write a note on sexual reproduction of zygomycetes.

3. Write common characters of Kingdom Fungi(eumycetes).

Answer Key

Part A:

a.) MCQ’s:


1. B (Aseptate fungi are of two types: mastigomycetes and zygomycetes)

2. B (Rhizopus is an example of zygomycetes)

3. A (Lower fungi appears multinucleated because septae are absent)

4. B (Root like structures of fungi are known as rhizoids)

5. C (Fungi have saprophytic mode of nutrition)


b.) Fill ups:

1. Chitin

2. Hyphae

3. Septate and aseptate.


c.)True or False:

1. True

2. True

3. False (they lack roots stems and leaves)




 It can be unicellular(yeast) or multicellular(penicillium).

“ Hyphae are divided into cellular compartments by walls called septae.

It consists of three subtypes :





1. Ascomycetes:

It's also known as sac fungi.

It's the largest phylum of fungi.Sexual reproduction takes place by Ascus (ascospores).

Ascus develops from a zygote, 2N vegetative cell or ascogenous hyphae.Cell wall is formed of chitin.Sexual reproduction occurs by gametangial fusion.“« Ascomycetes can be filamentous or unicellular.Fungi with spores produced inside a sac called ascus.

Some ascomycetes are plant pathogens.Ascomycetes make symbiotic relation with algae to form lichens. Asexual reproduction by fission and budding. Some are edible such as Morels and Truffles which are rich in proteins and vitamins. Some are used in food production,such as yeast is used to produce alcohol and make bread. Penicillium species is used in production of citric acid,oxalic acid,fumaric acid

etc. Yeast is also used in genetic research also. Penicillium is used in production of antibiotics.



Yeast is a unicellular fungus used for fermentation and for baking.

Cell wall is made up of Chitin, Phosphoric acid,Glycogen.

Big central vacuole is present.Saprophytic mode of nutrition.

Secrete enzyme Zymase to digest carbohydrates and forms simple

sugars.Asexual reproduction in yeast occurs by budding and fission.



Cell of yeast elongates.Nuclei divides into two nuclei. Plate formation separates cells. Each daughter cell grows separately.

 (Note: Halobial yeast : Yeast which shows asexual reproduction

by budding and fission method). Sexual Reproduction in Yeast: occurs via Hologamy .


2. Basidiomycetes: Basidiomycetes are also known as club fungi.

They are filamentous fungi composed of hyphae. Basidiomycetes reproduce sexually by the formation of club shaped cells called Basidia. Basidia bear external meiospores, known as basidiospores.

Sexual reproduction also occurs by clump connection in few

basidiomycetes, it helps in mating of hyphae of different sexual types.Clamp connection creates genetic variation within the hyphae.

Basidiomycetes are uninucleate when they are in the form of

primary hyphae. Basidiomycetes are binucleate in the form of secondary hyphae(Dikaryotic hyphae).

 Asexual reproduction takes place by :

Spore formationFragmentation of mycelium (hyphae).

Chlamydospore:- it is a thick walled large resting spore which

survives in unfavourable conditions ,such as dry or hot seasons.

Chlamydospore germinates in favourable conditions, it is result of

asexual reproduction. Eg. Mushrooms, Smuts, Rusts , Cryptococcus etc.

Sexual reproduction completed in three steps:-



3) Meiosis

 3.Deuteromycetes : (Fungi imperfecti)

Deuteromycetes are also known as imperfect fungi. No sexual form of reproduction. Only asexual reproduction occurs by the formation of spores(conidia or oidia),known as sporogenesis. Eg. helminthosporium oryzae (causes disease brown spot on leaf in rice)( Note:it is a causal agent of the Bengal famine of 1943. It is considered a Biological weapon used by the US against Japan in world war 2).

Eg. Gibberella fujikuroi It is used as growth hormone accelerating plant growth.

Special Note:Neurospora :

This fungi belongs to the Ascomycetes group of septate fungi.tis also Known as Drosophila of the plant kingdom.Phycomycetes:


Eg. Phytophthora infestans : An oomycete or water mold,

a fungus like microorganism that causes the serious potato and tomato disease known as late blight or potato blight.



Fungi play an important role in yielding antibiotics like

Penicillium. Fungi plays an important role in baking (bread)and brewing (alcohol) eg. Yeast. Organic acids like Citric acid,Oxalic acid and fumaric acid are produced by fermentation.Fungus Aspergilius niger is used for it at commercial level.The yeast Saccharomyces cerevisiae is used as a supplement in diet to increase protein value.

Some no. of molds and yeast are used to synthesise Ergosterol which contains vitamin D. Some species of fungi are edible like mushrooms ,dingri,truffles etc.



Algae + Fungi — Lichen.

It is a symbiotic partnership of algae and fungi.Dominant partner is fungus.They are good environmental indicators(pollution indicator of SO. Fungal partner is known as mycobiont (absorbs nutrients).

Algal partner is known as phycobiont (synthesis of food).Mycorrhiza :

Roots of higher plant + fungus — Mycorrhiza. It's a symbiotic relationship between the roots of higher plants and fungus. They increase the surface area associated with plant roots ,which

increases the intake of nutrients and water from soil.


A.) Very Short Answer Type Questions:

1. MCQ's:


Q1.Sexual reproductive structures of ascomycetes are:

a. Basidium

b. Ascus

c. Spores

d. Hyphae


Q2.In Lichens, Fungus make symbiotic relationship with:

a. Algae

b. Roots of higher plants

c. Bryophytes

d. Yeast


Q3.Basidiomycetes are also known as:

a. Club fungi

b. Sac fungi

c. Lichens

d. Fungi imperfecti


Q4.Dikaryotic Hyphae has no. of nuclei:

a. 1

b. 2

c. 3

d. 4


Q5. Which fungus is used as growth hormone in plants:

a. Gibberella fujikuroi

b. Rhizopus

c. Albugo

d. Agaricus


2. Fill in the blanks:

1. Saccharomyces cerevisiae is a good source of .

2. Roots of higher plants + Fungus— .

3. are good environmental indicators.



1. Yeast is a multicellular fungus.

2. Aspergillus niger is used to form organic acids.

3. Mycorrhizae increases the fertility of soil.


B.)Short Answer Type Questions:

1. Write a short note on asexual reproduction of yeast.

2. Show different types of septate fungi with the help of flow chart.

3. Write uses of fungi.


Answer Key

1. MCQ’s:

1.a (Sexual reproductive structures of ascomycetes are called ascus)

2.a (Fungi and algae make symbiotic relationship to form lichens)

3.b (Basidiomycetes are also known as Club fungi)

4.b (Dikaryotic hyphae have two nuclei)

5.a (Gibberella fujikuroi is used as a growth hormone in plants because it produces gibberellin)


2. Fill in the blanks:

1. Protein

2. Mycorrhizae

3. Lichens


3. True/False:

1. False (Yeast is a unicellular fungus)

2. True




INTRODUCTION:Viruses, viroid, prions and lichen are not mentioned in 5-kingdom system of classification by R.H. Whittaker, because they are acellular and not truly living.


VIRUS:Virus is a microscopic, infectious particle that can reproduce or replicate within the living cell of an organism or host. Viruses cannot reproduce without a host cell. They infect almost all living forms such as animals,plants, and bacteria.In 1898, a Dutch scientist, Martinus Beijerinck discovered the world’s first virus which was the tobacco mosaic virus. He conducted an experiment to show that there is another infectious particle that is smaller than bacteria and responsible for the infection in tobacco plants.In 1892, Dmitri lvanovsky discovered Virus.


Characteristics of viruses:

1. Viruses are obligate intracellular parasites.

2. They are non-cellular.

3. They are on the borderline between living nor non-living.

4. They are parasitic

5. They are microscopic.

6. They are infectious (The genetic material in them is infectious)

7. They require a host. (obligate parasites)

8. They don’t have a metabolism.


Structure of a Virus:Viruses can replicate only inside a living cell. Therefore, it contains only those parts needed to invade and control a host cell.Viruses vary in their individual structure, but all viruses contain two structures.

1. Nucleic acid: DNA “or” RNA (never both)

2. Capsid: protein coat. The protein coat consists of smaller subunits called capsomeres.

3. Envelope: made of lipid. Envelopes are found only in some viruses.

4. Tail: viruses that infect bacteria have a tail which is used for attachment.

Viruses are borderline organisms between living and non living

Viruses can reproduce inside a host just like any other living

organisms, but this ability to reproduce is lost once virus is outside

the host cell. This is because viruses are acellular, they don’t have

a cellular machinery of their own. Also, viruses can be crystallized,

which is a property of non-living things.

viral replication: viruses hijack host cell machinery to reproduce;

Viruses are noncellular and cannot reproduce on their own. Both

enveloped and non-enveloped viruses use their protein coat to

enter attack a host cell and deposit their genetic material inside

host cell. They then hijack host cells machinery to make their own

copies and hence reproduce.

 Virion: It is the “extracellular” infectious form. It must have an envelope and membrane proteins in addition to nucleic acid and capsid.

Consists of nucleic acid and Complete infective form of a protein coat virus: contains envelope as well Priucont (conte mn al

Bacteriophage:Bacteriophage was discovered independently by Federick Twort and Felix d’Herelle independently in 1915 and 1917 respectively. They are viruses that infect bacteria.

 VIROIDS:Viroids are low molecular weight infectious agents with no protein coat and have a low molecular weight RNA as shown in the picture.In 1971, a plant pathologist named Theodor Otto Diener first discovered the Viroids. He found an acellular particle when he was working in an Agriculture Research Service and named this particle as viroid, meaning “virus-like.” At present-33 species of viroid have been identified.


LICHENS:Lichens are a symbiotic association in which algae and fungi live together. Algal component is called a phycobiont and fungal component is called a mycobiont.Algae being autotrophic, prepare food for fungus. Fungi provide shelter and absorb mineral nutrients and water for its partner.

 2. The protein coat of viruses that enclose the genetic material is called

(a) Virion

(b) Capsid

(c) Peplomers

(d) Capsomers


3. Which of the following statements are true about a virion?

(a) Lytic phage

(b) Lysogenic phage

(c) The viral capsid

(d) An infectious and fully formed viral particle


4. Which of the following is the genome of the virus?

(a) DNA

(b) RNA

(c) DNA or RNA

(d) DNA and RNA


5. The viral envelope is made of ............?

(a) Proteins

(b) Glycoproteins

(c) Lipids

(d) All of the above



1. Viroids do not have a protein coat.

2. Viruses are obligate parasites.

3. Lichen is a symbiotic association between plants and fungi.

4. AVirus can have both DNA and RNA



1. Algal component of a lichen is called......

2. Corona virus official name by ICTV is .......

3. ICTV full form is......

4. National Institute of virology isin ....



a) Multiple choice questions:

1. (a) Protein coat and nucleic acid.

2. (b) Capsid.

3. (d) An infectious and fully formed viral particle (Virion is extracellular infectious form having additional components as well: envelope and membrane proteins)

4. (c) DNA or RNA (A virus can never have both).

5. (d) All of the above (Envelope has all three components).


b) True/false:

1. True.

2. True. They can reproduce only when inside a host.

3. False. It's an association between fungus and an Algae.

4. False. A Virus can never have both DNA and RNA together.


c) Fill ups:

1. Phycobiont.

2. SARS-CoV-2.

3. International Committee on Taxonomy of Viruses

4. Pune. (India’s second virology institute is proposed to be set up in Mohali. At present India has only one virology institute)



Ques 1: Label the parts of virus given in following diagram.

Ques 2: Are viruses living or non-living? Comment.



Ques 1. Give a brief account of viruses with respect to their structure and nature of genetic material. Also name 4 common viral diseases.



R.H. Whittaker classified organisms into 5 kingdoms on the basis of:

1. Cell structure- Eukaryotic and prokaryotic

2. Body organisation- unicellular or multicellularity

3. Mode of nutrition- Autotrophic or heterotrophic etc.

4. Mode of reproduction- Asexual or sexual


To appreciate the uniqueness of organisms classified under the 5-kingdom classification, study of differences is must.Hence in this daily dose, we would look at comparisons and differences between

or among different forms.





KINGDOM PROTISTA:Kingdom Protista is further divided on the basis of mode of nutrition,morphology, cell wal! structure etc.



LICHEN:It's unique because it's a symbiotic association between 2- different types of organisms- Fungi (Mycobiont) and an Alga (Phycobiont)



a) Multiple choice questions:


1. Which of the following can be found in extremely saline conditions:

(a) Mycobacteria

(b) cyanobacteria

(c) Archaebacteria

(d) Eubacteria


2. Which of the following statements is false about fungi?

(a) eukaryotic

(b) autotrophic

(c) cell wall made of chitin

(d) none of these


3. Which of the following statements are true about protists?

(a) unicellular mostly

(b) eukaryotic

(c) both (a) and (b)

(d) none of these.


4. Cell wall in bacteria is made up of:

(a) cellulose

(b) fungal cellulose

(c) chitin

(d) peptidoglycan


5. Blue green algae belong to:

(a) protista

(b) prokaryotes

(c) fungi

(d) archaebacteria


b) Eill ups:

1. ....... have siliceous deposits in their cell wall.

2. Proteinaceous covering called pellicle is present in......

3. Asexual spores don't form in ............. subdivision of fungi.

4. Animals store reserve food in the form of.............


c) Irue/false:

1. Archaebacteria are the modern bacteria, most evolved ones.

2. Dinoflagellates have 2 flagella.

3. Mushrooms belong to basidiomycetes division of fungi.

4. Fungi are multicellular, eukaryotic and heterotrophic organisms.

5. Animal cells have a cell wall made of a soft material which makes their body flexible.


a) Multiple choice questions:

1. (c) Archaebacteria: They are primitive bacteria which can survive in extreme conditions

2. (b) autotrophic: fungi are heterotrophic as they lack chlorophyll

3. (c) both (a) and (b): protists are mostly unicellular eukaryotes

4. (d) peptidoglycan: cell wail in bacteria is made of peptidoglycan

5. (b) prokaryotes: Blue green algae or cyanobacteria are prokaryotic.


b) Fill ups:

1. Chrysophytes

2. Euglena

3. Basidiomycetes

4. glycogen

c) True/false:

1. False: Archaebacteria, the most primitive and least evolved forms of bacteria

2. True: They have 2 flagella- one short and one long.

3. True: Mushrooms (Agaricus) belong to basidiomycete fungi.

4. True

5. False: Cell wall is absent in kingdom Animalia.



1. Write major differences between kingdom Monera and kingdom Protista.

2. Differentiate between mycobiont and phycobiont.

3. Compare Chrysophytes with Dinofllagelates.



1. Differentiate the characteristic of various subdivisions of fungi under

(a) mode of nutrition

(b) mode of reproduction.





Classification, in biology, is the establishment of a hierarchical system of categories on the basis of presumed natural relationships among organisms.

Taxonomy: The science of biological classification, that deals with



IMPORTANCE OF CLASSIFICATION: thelps in the identification of living organisms as well as in understanding the diversity of living organisms. To understand and study the features, similarities and differences between different living organisms and how they are grouped under different categories.

Father of Classification:Carolus Linnaeus is known as father of classification. He was the Swedish botanical taxonomist. He introduced two kingdom system, Kingdom Plantae and Animalia.Carolus Linnaeus was the first person to formulate and adhere to a uniform system for defining and naming the world's plants and animals Objectives of Classification:To arrange the species in various categories on the basis of their similarities and dissimilarities.

To evolve a truly natural or phylogenetic system which should indicate

origin and evolution of the species. - Helping in easy identification of organisms.


The main objectives of taxonomy:Obtaining a suitable specimen .(collecting, preserving and, when necessary,making special preparations). Comparing the specimen with the known range of variation of living things.Correctly identifying the specimen if it has been described, or preparing a description.


AIMS OF CLASSIFICATION:Due to classification, there is no need to study each and everythingabout all the living organisms.Classification provides a picture of plants and animals. Classification gives an idea of similarities and differences between various groups example, vertebrates and invertebrates.

 FATHER OF FIVE KINGDOM SYSTEM  Robert Whittaker is known as father of five kingdom system. Earlier Robert Whittaker introduced only four kingdom systems in 1960, Kingdom Monera, Protista, Animalia and Plantae.Later on they introduced fifth Kingdom Fungi.The animal kingdom is the largest kingdom with over 1 million known species. All animals consist of many complex cells. They are also heterotrophs.



1. Discuss how classification systems have undergone several changes over a period of time?

Ans. Linnaeus proposed a two kingdom system of classification with Plantae and Animalia kingdoms was developed that included all plants and animals respectively.It became very difficult to group some living things into one or the other, so early in the past century the two kingdoms were expanded into five kingdoms:Protista (the single-celled eukaryotes); Fungi (fungus and related organisms);Plantae (the plants); Animalia (the animals); Monera (the prokaryotes).


2. State two economically important uses of :

(a)Heterotrophic Bacteria (b) Archaebacteria.

Ans. (a) Economically important uses of Heterotrophic Bacteria:

1. Many bacteria like Lactobacillus helps in the production of curd from milk.

2. They act as decomposers and help in the formation of humus e.g.


3. Many antibiotics are obtained from some species of bacteria like

streptomyces, Bacillus etc.


(b) Economically important uses of Archaebacteria:

1. Since the enzymes from these organisms can survive harsh conditions

they have many industrial applications in biotechnology

2. Many of the thermostable enzymes used in the manipulation of DNA are derived from Archaebacteria.

3. Methanogens of the Archaebacteria are mainly involved in the biogas



3. What is the nature of cell walls in diatoms?

Ans. The cell walls of diatoms are made of silica.Their cell wall construction is known as frustule.When the diatoms die, the silica in their cell walls gets deposited in the form of diatomaceous earth.


4. Find out what do the term ‘Algal Bloom’ and ‘Red Tides’ signify.

Ans. (A) Algal Bloom:

(1) An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, and is often recognized by the discoloration in the water from their pigments.


(2) The term algae encompasses many types of aquatic photosynthetic

organisms, both macroscopic, multicellular organisms like sea weed and

microscopic, unicellular organisms like cyanobacteria.

 (3) An example of a macroscopic algal bloom is a kelp forest.


(B) Red Tides:Red tides are a phenomenon of discoloration of sea surface. Itis a common name for harmful algal blooms occurring along coastal regions, which are resulted from large concentrations of aquatic microorganisms, such as protozoans and unicellular algae (e.g. dinoflagellates and diatoms). Very often Red Dinoflagellates,

GONYAULAX, undergo rapid multiplication to make the sea appear Red.

 6. Describe briefly the four major groups of Protozoa?

Ans. There are four major groups of Protozoa:

1. Amoeboid Protozoans: These organisms lives in fresh water, sea water or moist soil. They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba. Marine forms have silica shells on their surface.Some of them such as Entamoeba are parasites.


2. Flagellated Protozoans: The members of this group are either free living or parasitic. They have flagella. The parasitic form cause diseases such as sleeping sickness. Example: Trypanosoma.

 3. Ciliated Protozoans: These are aquatic, actively moving organisms

because of the presence of thousands of cilia. They have a cavity(gullet) that opens to the outside of the cell surface. The coordinated movement of rows of cilia causes the water laden with food to be steered into the gullet.Example: Paramoecium.


4 .Sporozoan Protozoans: This includes diverse organism that have an

infectious spore like stage in their life cycle. Tne most notorious is

Plasmodium ( Malarial Parasite) which cause Malaria, a disease which has a staggering effect on human populations.



RECAPITULATION:Robert Whittaker is known as father of five kingdom system.Earlier Robert Whittaker introduced only four kingdom systems in 1960, Kingdom Monera, Protista, Animalia and Plantae.

Later on he introduced fifth Kingdom Fungi.

The animal kingdom is the largest kingdom with over 1 million known

species. All animals consist of many complex cells. They are also heterotrophs.


 CHARACTERSTICS:The Monerans are unicellular organisms The cell wall is rigid and made up of peptidoglycan.Asexual Reproduction through binary fission.They contain 70S ribosomes.Flagella serves as the locomotory organ.It lacks organelles like mitochondria, lysosomes, plastids, Golgi bodies,endoplasmic reticulum, centrosome, etc.


ARCHAEBACTERIA:They are present in rumen (first part of stomach) of cattles. This is simple stand most primitive group of bacteria. The cell wall of these bacteria is made of polysaccharides and proteins (peptidoglycans and muramic acid are absent in cell wall). Further branched chain lipids are present in plasma membrane of archaebacteria, due to which these can face extremes of conditions of temperature and pH. Archaebacteria are considered to be ‘oldest of living fossils’. Three main groups of archaebacteria are following Methanogens, Halophiles and Thermoacidophiles


EUBACTERIA:Eubacteria are known as true bacteria, and are cauterized by the presence of a rigid cell wall, and if motile, a flagellum.

The cyanobacteria or blue-green algae have chlorophyll a similar to green plants and are photosynthetic autotrophs.They are unicellular, prokaryotic microscopic cells.Their cell membrane contain lipids made up of glycerol-ester lipids.Chromosome is circular and nucleosomes maybe present.The cell wall is made up of Peptidoglycan (Murein).




CHARACTERSTICS:All protists are eukaryotic organisms.Most protists are aquatic, others are found in moist and damp environments.

Most are unicellular, however, there are a few multicellular protists such as the giant kelp.They may be autotrophic or heterotrophic in nature.




CHARACTERSTICS:Fungi are eukaryotic, non-vascular, non-motile and heterotrophic organisms.They may be unicellular or filamentous.

They reproduce by means of spores.Fungi exhibit the phenomenon of alternation of generation.Fungi lack chlorophyll and hence cannot perform photosynthesis.Fungi store their food in the form of starch.

Biosynthesis of chitin occurs in fungi.The nuclei of the fungi are very small.The fungi have no embryonic stage. They develop from the spores.The mode of reproduction is sexual or asexual.Some fungi are parasitic and can infect the host.Fungi produce a chemical called pheromone which leads to sexual reproduction in fungi.

Examples include mushrooms, moulds, yeast.




CHARACTERSTICS:They are eukaryotic and multicellular.Their cells have cellulose walls.Majority have transport system.They have photosynthesis hence autotrophic.Reproduction is both asexual and sexual.They show alternation of generation.Some examples of plants are trees, flowers, herbs, bushes, grasses, vines,ferns, mosses, and green algae.


CHARACTERSTICS:These organisms are multicellular, eukaryotic and without chlorophyll.The cells possess no cell walls and plastids.

Central vacuoles are absent but small vacuoles may occur.Most of them are free moving (except sponges and some coelentrates)Nutrition is primarily ingestive.Reproduction is generally sexual and the haploid stage is represented only by gametes.Growth of organisms stops when the adult stage is reached.




7. Plants are autotrophic. Can you think of some plants that are partially heterotrophic?

Ans. Mostly all plants are autotrophic in nature as they synthesize their food by photosynthesis in presence of chlorophyll, water, carbon dioxide and sun light but also there are a few members are partially heterotrophic in nature such as insectivorous plants or parasites. They are unable to synthesize their food by photosynthesis due to lack of chlorophyll pigment. Bladderwort and Venus fly trap are examples of insectivorous plants and Cuscuta is parasites.


8. What do the terms Phycobiont and Mycobionts. Signify

Ans. Phycobiont and Mycobionts:

1. Phycobiont refers to the algal component of the lichens.

2. Mycobiont refers to the fungal component of the lichens.

3. Both of these are present in a symbiotic relationship in which algae prepare food for fungi due to the presence of chlorophyll whereas the fungus provides shelter to algae and absorbs water and nutrients from the soil.


9. Give a comparative account of the classes of Kingdom Fungi under the following:

(i) Mode of Nutrition.

(ii) Mode of reproduction.


10. What are the characterstic features of Euglenoids?

Ans. Characterstic features of Euglenoids:

1. Euglenoids (such as Euglena) are unicellular protists commonly found in fresh water.

2. Instead of cell wall, a protein-rich cell membrane known as pellicle is present.

3. They bear two flagella on the anterior end of the body.

4.A small light sensitive eye spot is present.


11. Give a brief account of viruses with respect to their structure

and nature of genetic material. Also name four common viral



1. Viruses are sub-microscopic infectious agents that can infect all living organisms.

2. A virus consists of genetic material surrounded by a protein coat

3.The genetic material may be present in the form of DNA or RNA.

4.Most of the viruses, infecting plants, have single stranded RNA as genetic material.

5. On the other hand, the viruses infecting animals have single or double stranded RNA or double stranded DNA.

6. Bacteriophages or viruses infecting bacteria mostly have double stranded DNA.

7. Their protein coat called capsid is made up of capsomere subunits.

8. These capsomeres are arranged in helical or polyhedral geometric forms.A.|.D.S, small pox, mumps, and influenza are some common examples of viral diseases.


12. Organize a discussion in your class on the topic - are viruses living or non-living?

Ans. Viruses are non-living features intermediate between non-living and living organisms.On the basis of characters, such as non-cellular organization, inactivity outside the host organism, lack of respiration and cellular metabolism, these are caused non-living.

Similar to non-living objects viruses can be crystallized and precipitated.Similar to living beings, they possess genetic material (DNA or RNA), property of mutation, irritability, can grow and multiply inside the host cell.They are intracellular obligate parasites and attack specific hosts.Thus, keeping these points in mind, it is quite difficult to ascertain whether viruses are living or non-living.

Chapter 2 Biological Classification