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BTNY-MM: XI 2 BIOLOGICAL CLASSIFICATION

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 Biological classification is the scientific ordering of organisms

into groups.
Aristotle’s classification
 Aristotle (BC 340) classified plants and animals on the basis of
morphological characters.
Living organisms

Plants Animals

Herbs Shrubs Trees Red blooded Non- red

blooded
Two-kingdom classification
 Carlous Linnaeus (1758) classified organisms based on cell wall.
Living organisms Advantages of 5-kingdom classification-
- All disadvantages of 2-kingdom classification
Kingdom Plantae Animalia Disadvantages of 5-kingdom classification-
(with cell-wall) (without cell-wall) - Not mentioned lichens and acellular organisms (Virus, Viroids,
Prions etc.)
Plants (Algae, Mosses, Ferns, Animals
Gymnosperm, Angiosperm) Protozoans Three-domain / Six-kingdom classification
Fungi  Proposed by Carl Woese (1977)
Bacteria (Bluegreen algae)
Some protists Living world
Disadvantages of 2-kingdom classification- Domain Archea Bacteria Eukarya
A. It does not distinguish between -
o prokaryotes and eukaryotes. Kingdom A.bacteria Eubacteria Protista Fungi Plantae Animalia
o unicellular (e.g. Chlamydomonas) and multicellular (e.g.

KINGDOM MONERA
Spirogyra) organisms.
o autotrophs (e.g. green algae) and / heterotrophs (e.g.: fungi).
o cellulosic and non-cellulosic cell wall  Monerans are unicellular prokaryotic organisms. Bacteria and
B. A large number of organisms did not fall into either category. mycoplasma are the members of this kingdom.
 Based on the shape, bacteria are 4 categories:
Five-Kingdom Classification
 It is proposed by R.H. Whittaker (1969).
Living organisms
Kingdom Monera Protista Fungi Plantae Animalia
This classification was based on- (spherical) (rod-shaped) (spiral) (comma-shaped)
Prokaryotic- Cell without true nucleus and membrane bound Monerans are classified into two- Archaebacteria & Eubacteria
organelles (Endoplasmic reticulum, golgi body etc.) /
(i) Cell structure Eukaryotic- Cell with true nucleus and other membrane bound Archaebacteria
organelles Archaebacteria can live in harsh conditions due to presence of
(ii) Body special type of cell wall.
Cellular / Tissue / Organ / Organ system level
organisation
Autotrophic - Organisms that prepare their own nutrition.
Photosynthetic- Synthesis food from inorganic substances Glycan
using solar energy. S-layer Pseudopeptidoglycan /
Chemosynthetic- Energy from oxidation of inorganic matters.
(iii) Mode of Membrane pseudomurein
Heterotrophic- Organisms that depend upon other organism
nutrition lipid
They consists of 3 different groups-
or on dead organic matter for nutrition
Parasitic- Absorb food from a living plant or animal (i) Halophiles- live in salty areas
Saprophytic- Absorb food from dead matters (ii) Thermoacidophiles- live in hot springs
Holozoic- Take solid food through mouth (ingestion) (iii) Methanogens- live in marshy areas and are present in the guts of
(iv) Mode of ruminant animals (cows, buffaloes etc). They produce methane
Sexual / Asexual
reproduction (biogas) from the dung of these animals.
Plantae Animalia
Fungi
(v) Evolutionary
relationships Protista

Monera
Halophiles Thermoacidophiles Methanogen

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Eubacteria (True bacteria)

They have a rigid cell wall and a flagellum (if motile).

S-layer
20 cell wall polymer Lipo-
polysaccharide
Peptidoglycan
Membrane lipid

They include Autotrophs (photosynthetic and chemosynthetic)

and Heterotrophs.
a. Photosynthetic bacteria e.g.: Cyanobacteria / blue-green algae
They are unicellular, colonial or filamentous, freshwater / marine
or terrestrial algae. c. Heterotrophic bacteria:
 The majority are decomposers.
 Economic importance:
- They are used in making curd from milk
- Used in production of antibiotics
- Fixing nitrogen in legume roots etc.
- Some are pathogens causing damage to human beings, crops,
farm animals and pets.
The colonies are generally surrounded by gelatinous sheath. Diseases caused by bacteria-
Gelatinous sheath Mucilaginous sheath Causative
Disease Symptoms
Layer of collagen Covering of glycoprotein bacteria
Function: Function: Severe watery diarrhea, which can
- Protect cells - Protect cell from drying Vibrio
Cholera lead to dehydration and even death if
- Help in locomotion - Help in locomotion cholerae
untreated.
- Provide microenvironment - Binds cells together in colonies
Salmonella High fever, headache, stomach pain,
containing essential nutrients Typhoid
typhi weakness, vomiting and loose stools.
They have chlorophyll a (similar to green plants). Toxins produced by bacteria causes a
They often form blooms in polluted water bodies (Algal bloom). Clostridium person's neck and jaw muscles to
Tetanus
tetani lock, making it hard to open the
mouth or swallow.
Citrus- Xanthomonas Leaves and fruit of citrus trees drop
canker citri prematurely
Reproduction in Bacteria:
 Asexual - By binary fission.

Some of cyanobacteria can fix atmospheric nitrogen in specialized

cells called heterocysts. They symbiotically associate with cycas
in coralloid roots to fix N2.

 Sexual- By DNA transfer from one bacterium to the other.

e.g,

 Under unfavourable conditions, they produce spores.

Nostoc colony Anabaena

b. Chemosynthetic bacteria:
They oxidize various inorganic compounds to release energy for
their ATP production.
They recycle nutrients
Eg: N-bacteria, P- bacteria, Fe- bacteria, S- bacteria.

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Mycoplasma / PPLO
 They are the smallest cells without cell-wall and can survive Examples:
without O2.

Euglena

 Many mycoplasma are pathogenic to plants and animals.

iv. Slime moulds
Body:
KINGDOM PROTISTA Under favourable condition
They form an aggregation called plasmodium which spread over
 Protists are unicellular eukaryotic organisms. several feet.
It includes Chrysophytes, Dianoflagellates, Euglenoids, Slime Under unfavourable condition
moulds and Protozoans. The plasmodium differentiates to fruiting bodies bearing spores at
their tips.
i. Chrysophytes
Habitat: Fresh water, marine water
Body: Microscopic
Nutrition: Photosynthetic (autotrophs)
Locomotory organ: Absent (float passively in water currents)
Examples:

Desmids (Golden algae) Diatoms Diatomaceous earth

Nutrition: Saprophytic
Diatoms-
Locomotory organ: Body moves along decaying twigs and leaves
 Have siliceous cell walls forming 2 thin overlapping shells.
engulfing organic material
 They are the chief ‘producers’ in the oceans.
 The cell wall deposit of diatoms over billions of years is referred v. Protozoans
to as ‘diatomaceous earth’. They are believed to be primitive relatives of animals as they are
This is used in polishing, filtration of oils and syrups. live as predators or parasites. There are 4 groups of protozoans.
a. Amoeboid protozoans
ii. Dinoflagellates Habitat: Fresh water, sea water or moist soil
Habitat: Mostly marine Body: Marine forms have silica shells on their surface
Body: Colour varies depending on the pigments present in their Nutrition: Heterotrophic
cells. Locomotory organ: Pseudopodia
The cell wall has stiff cellulose plates on the outer surface. Examples:
Nutrition: Photosynthetic
Locomotory organ: 2 flagella; One lies longitudinally and the
other transversely.
Examples:

Pseudopodia

Entamoeba

b. Flagellated protozoans
Habitat: Free-living or parasitic
Nutrition: Heterotrophic
Gonyaulax (red dinoflagellates) Red tide
Locomotory organ: Flagella
Gonyaulax- Examples:
 They undergo rapid multiplication that they make the sea appear
red (red tides).
Toxins released by such large numbers may kill fishes.
iii. Euglenoids
Habitat: Fresh water Flagella
Body: Have a protein-rich layer called pellicle which makes their
body flexible Trypanosoma (Cause sleeping sickness)
Nutrition: Photosynthetic, heterotrophic (in the absence of c. Ciliated protozoans
sunlight) Habitat: Aquatic
Locomotory organ: 2 flagella; A short and a long one Nutrition: Heterotrophic
Locomotory organ: Cilia; Movement of cilia causes the water
loaded with food to be directed into the gullet.
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Examples: Cilia Steps of sexual cycle:

When a fungus reproduces sexually, two haploid hyphae of
compatible mating types come together and fuse.
Step 1. Plasmogamy: Fusion of protoplasms between motile or non-
motile gametes.
Step 2. Karyogamy: Fusion of two nuclei. It results in diploid cells (2n).
 In some fungi (ascomycetes and basidiomycetes), the nuclei
do not fuse immediately after plasmogamy. They exist as two
separate nuclei (n + n- dikaryotic stage). Later, the parental
Paramoecium nuclei fuse and the cells become diploid.
d. Sporozoans Step 3. Meiosis in zygote produces haploid spores in fruiting bodies.
Habitat: Endoparasites
Body: Have an infectious spore-like stage in their life cycle
Nutrition: Parasitic
Examples:

Plasmodium (Cause malaria)

KINGDOM FUNGI.
 Fungi are eukaryotic, multicellular, heterotrophic (saprophytic or Kingdom fungi is divided into 4 classes:
parasitic) organisms with chitinous cell wall. i. Phycomycetes
 Fungi occur in air, water, soil and on plants and animals. Habitat: Aquatic, moist and damp places
 Fungi are filamentous, except yeast (unicellular). Nutrition: Saprophyte on decaying wood or as parasites on plants.
Fungal body is called mycelium. It consists of network of long, Morphology of mycelium: Coenocytic
thin thread-like structures called hyphae. Reproduction:
- Asexual- Sporangium endogenously produces zoospores (motile)
or aplanospores (non-motile) and these develop into mycelium.
Fruiting body

- Sexual- Fusion of two gametes (isogamy / anisogamy / oogamy)

produce Zygospore.

Hyphae

Coenocytic / Aseptate Septate

Hyphae that are continuous Hyphae having cross wall /
tubes filled with septa
multinucleated cytoplasm
Some fungi live in symbiotic associations-
 Fungi + algae = lichens
 Fungi + roots of higher plants = mycorrhiza
Plant root

Examples:

Reproduction in fungi
Mucor Rhizopus (breadmould) Albugo (parasite on mustard)

Vegetative Asexual Sexual

fragmentation conidia oospores
fission sporangiospores ascospores
budding zoospores basidiospores
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ii. Ascomycetes / Sac-fungi

Nutrition: Saprophytic, decomposers, parasitic or coprophilous.
Morphology of mycelium: Septate and branched
Reproduction:
- Asexual – Conidiophores on the mycelium exogenously
produce spores called conidia which germinate to produce
mycelium.
- Sexual – At the tip of ascocarps (fruiting bodies) contain a sac
called asci which endogenously produce ascospores.

Examples:

Bracket fungi Puffballs Agaricus (mushroom)

Examples:

Penicillium (source Saccharomyces Morels Truffles Ustilago (smut) Puccinia (rust- cause wheat rust)
of antibiotic) (Yeast- used to make Edible Parasitic
beer and bread)
iv. Deuteromycetes / Imperfect fungi
Nutrition: Decomposers. Some are saprophytes or parasites.
Morphology of mycelium: Septate and branched
Reproduction:
- Asexual- by Conidia
- Sexual- unknown
Aspergillus Claviceps Neurospora
Used in biochemical experiments bcz-
 It has a haploid life cycle that will
show up recessive traits in the
offspring
 Introduced X-ray mutations can be
easily seen
 Can be easily grown in lab

iii. Basidiomycetes
Habitat: Grow in soil
Nutrition: Saprophytic on logs or parasitic on plants. Examples:
Morphology of mycelium: Septate and branched
Reproduction:
- Asexual- not found
- Vegetative- by fragmentation
- Sexual-
Fusion of 2 somatic cells of different mycelium (plasmogamy) 
Mitosis Alternaria Colletotrichum Trichoderma
dikaryotic mycelium basidiocarps (fruiting bodies). Gills of

the basidiocarp contain cells called basidium Karyogamy Zygote

Meiosis
4 basidiospores
(exogenously)

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VIRUSES, VIROIDS, PRIONS swollen lymph nodes.

In plants, the symptoms can be mosaic formation, leaf rolling and
& LICHENS curling, yellowing and vein clearing, dwarfing and stunted
growth.
Some acellular organisms like viruses, viroids, prions and lichens are
not included in the 5-kingdom system of classification.
Viruses
 Viruses are nucleoprotein and obligate parasites
VIRUS

Outside a living cell: Inside a cell: Mosaic formation Leaf rolling Vein clearing
Have an inert Infect a host cell
crystalline structure ↓ Viroids – ‘Virus like’
Take over the machinery of the host  Viroids are infectious RNA.

Replicate Virus Kill the host

 Discovered by T.O. Diener (1971) as causal agent of potato

Milestones in Virology spindle tuber disease.
Year Scientist Contribution
Recognized ‘viruses’ as causal organism Prions
1892 Dmitri Ivanowsky  Prions are abnormally folded infectious proteins.
of the mosaic disease of tobacco.
The name virus (means venom or
poisonous fluid) was given
Demonstrated that the extract of the
1898 M.W. Beijerinek infected tobacco could cause infection in
healthy plants and called the fluid as
Contagium vivum fluidum (infectious
Examples for neurological diseases caused by prions-
living fluid).
1935 W.M. Stanley Showed that viruses could be crystallised. Disease Symptoms
Bovine spongiform
Abnormal behavior, trouble
Structure of Viruses- encephalopathy (BSE)
walking, and weight loss in cattle
It consists of a protein coat and a nucleic acid. / mad cow disease
1. PROTEIN COAT
Difficulty walking, slurred speech,
Creutzfeldt-Jacob numbness in different parts of the
The protein coat (capsid) is made of subunits called capsomeres disease (CJD) body, dizziness, double vision,
Function: Protects the nucleic acid. hallucinations in human
2. NUCLEIC ACID Lichens
The nucleic acid or genetic material is either RNA or DNA.  Lichens are symbiotic associations between algae and fungi.
Function: Cause infection.
Virus infecting- Nucleic acid
Plant ssRNA
Animal ssRNA / dsRNA / dsDNA
Bacteria
dsDNA
(bacteriophages)
 Examples for viral diseases-
Disease Causative virus Symptoms Component Role
Swollen, painful salivary glands,
Mumps Paramyxovirus Phycobiont- algal component - Gives food for fungi
fever, headache and appetite loss.
High fever, Head and body aches, - Provide shelter for algae
Sometimes vomiting, widespread Mycobiont- fungal component - Absorb mineral nutrients and
Small pox Variola virus
skin rash which change into raised water
bumps then fluid filled blisters
Small bumps or blisters around the Ecological Importance
Herpes
Herpes simplex genitals, anus or mouth with pain.  Lichens do not grow in polluted areas. So they act as a good
virus Discharge from the urethra and pollution indicators.
vagina
Fever and chill, cough, sore throat,
Influenza Influenza viruses runny or stuffy nose, muscle or
body aches, headaches, tiredness.
Human Virus multiplies and destroys
AIDS immunodeficiency immune cells, symptoms can
virus (HIV) develop such as fever, fatigue, and
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Mycoplasma

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