Chapter Outline.
Includes everything, arranged in a nice way.
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Biological Classification
➢ Criteria for 5 kingdom classification –
- cell structure
- body organisation
- mode of nutrition
- reproduction and
- phylogenetic relationships
❖ kingdom Monera-
➢ Bacteria are the sole members
➢ live in extreme habitats such as hot springs, deserts, snow and deep oceans
➢ based on their shape:
• spherical- Coccus (pl.: cocci),
• rod-shaped - Bacillus (pl.: bacilli)
• the comma-shaped -Vibrium (pl.: vibrio) and
• the spiral - Spirillum (pl.: spirilla)
➢ bacterial structure – very simple,
behaviour- very complex
➢ most extensive metabolic diversity
➢ mode of nutrition-
- autotrophic (some)
- photo autotrophic
- chemoautotrophic
- heterotrophic (vast majority)
➢ Bacteria caused diseases - Cholera, typhoid, tetanus, citrus canker
➢ reproduce mainly by fission
➢ unfavourable conditions- spores.
➢ sexual reproduction by adopting a primitive type of DNA transfer from one bacterium to the
other.
➢ Mycoplasma- completely lack a cell wall.
- smallest living cells
- can survive without oxygen
✓ Archaebacteria
- live in some of the most harsh habitats
salty areas -halophiles
hot springs - thermoacidophile
marshy areas- methanogens
- a different cell wall structure is responsible for their survival in extreme conditions
- Methanogens – present in gut of several ruminant animals such as cows and buffaloes
- responsible for the production of methane (biogas) from the dung of these animals
✓ Eubacteria
- presence of a rigid cell wall, if motile, a flagellum
- cyanobacteria - chlorophyll a, are photosynthetic autotrophs
- cyanobacteria - unicellular, colonial or filamentous, freshwater/marine or terrestrial
algae.
- Nostoc and Anabaena- fix atmospheric nitrogen in specialised cells called heterocysts
- Chemosynthetic autotrophic bacteria oxidise nitrates, nitrites and ammonia and
use the released energy for their ATP production
- role in recycling nutrients like nitrogen, phosphorous, iron and sulphur
- Heterotrophic bacteria-
• important decomposers.
• helpful in making curd
• production of antibiotics
• fixing nitrogen in legume roots
❖ Kingdom Protista –
➢ primarily aquatic
➢ eukaryotes
➢ Some have flagella or cilia
➢ reproduce asexually and sexually by a process involving cell fusion and zygote
formation
✓ Chrysophytes-
- includes diatoms and desmids
- found in fresh and marine water
- are microscopic
- Float passively in water current – (planktons)
- Diatoms:
- The cell walls form two thin overlapping shells, which fit together
- The walls are embedded with silica- Indestructible
- accumulation of cell wall over billions of years- ‘diatomaceous earth
- used in polishing, filtration of oils and syrups.
- chief ‘producers’ in the oceans.
✓ Dinoflagellates-
- mostly marine and photosynthetic
- cell wall- stiff cellulose plates on the outer surface
- mostly have- have two flagella
- red dinoflagellates Example: Gonyaulax
✓ Euglenoids-
- found in stagnant water
- have a protein rich layer called pellicle, makes their body flexible.
- photosynthetic in the presence of sunlight
- deprived of Sunlight- behave like heterotrophs by predating on other smaller organisms
- Example: Euglena
✓ Slime moulds-
- saprophytic protists
- moves along decaying twigs and leaves engulfing organic material.
- Under suitable condition form an aggregation called plasmodium
- Unfavourable condition- plasmodium differentiates and forms fruiting bodies bearing
spores at their tips.
✓ Protozoans-
- are heterotrophs and live as predators or parasites
- Amoeboid protozoans: Amoeba, Entamoeba
- Flagellated protozoans: Trypanosoma. Disease caused- sleeping sickness
- Ciliated protozoans: Paramoecium
- Sporozoans: Plasmodium (malarial parasite)
❖ Kingdom- Fungi
- unicellular fungi- yeast, except these fungi are filamentous
- wheat rust-cause – Puccinia
- source of antibiotics- Penicillium
- grow in warm and humid
- saprophytes or parasites
- Symbionts – in association with algae as lichens and with roots of higher plants as
mycorrhiza.
- The sexual cycle involves-
1. plasmogamy.
2. Karyogamy
3. Meiosis
- vegetative means – fragmentation, fission and budding
- asexual reproduction- conidia, sporangiospores, zoospores
✓ Phycomycetes-
- mycelium is aseptate and coenocytic
- asexual reproduction- zoospores (motile), aplanospores (non-motile)
- spores are endogenously produced in sporangium
- gametes are – isogamous, anisogamous, oogamous
- Examples- Mucor, Rhizopus (the bread mould), Albugo (parasite on mustard)
✓ Ascomycetes-
-sac-fungi
-mostly multicellular
-saprophytic, decomposers, parasitic or coprophilous
-Mycelium- branched and septate
-asexual spores- conidia, produced exogenously on the special mycelium called
conidiophores.
- Sexual spores – ascospores, produced endogenously in asci
- asci are arranged fruiting bodies – ascocarps
- Examples- Aspergillus, Claviceps, Neurospora(genetic work) , yeast, penicillium,
morels and truffles (edible)
✓ Basidiomycetes-
- bracket fungi or puffballs.
- Common form- mushrooms
- Mycelium- branched and septate
- vegetative reproduction – fragmentation
- plasmogamy is brought about by fusion of two vegetative or somatic cells of different
strains or genotypes.
- Dikaryotic structure - rise to basidium
- Karyogamy and meiosis- basidium: four basidiospores
- The basidiospores are exogenously produced on the basidium
- basidia are arranged in fruiting bodies called basidiocarps
- Agaricus (mushroom), Ustilago (smut) and Puccinia (rust)
✓ Deutromycetes-
- imperfect fungi
- only the asexual or vegetative phases are known
- asexual spores - conidia.
- mycelium is septate and branched
- saprophytes, parasites, mostly decomposers- help in mineral cycling
- Examples- Alternaria, Colletotrichum and Trichoderma.
❖ Viruses-
➢ not considered truly ‘living’
➢ inert outside their specific host cell
➢ take over the machinery of the host cell to replicate, killing the host
➢ In addition to proteins, viruses also contain genetic material- RNA or DNA
➢ viruses that infect plants have single stranded RNA
➢ that infect animals could be either single or double stranded RNA or double
stranded DNA
➢ bacteriophages are generally dsDNA viruses
➢ The protein coat called capsid made of small subunits called capsomeres. These
capsomeres are arranged in helical or polyhedral geometric forms.
➢ Diseases in animals- mumps, small pox, herpes and influenza.
➢ Symptos in plants- mosaic formation, leaf rolling and curling, yellowing and vein
clearing, dwarfing and stunted growth
❖ Viroids –
➢ Smaller than viruses
➢ Low molecular weight RNA and no protein coat
➢ Potato spindle tuber disease is caused by potato spindle tuber viroid
❖ Prions-
➢ Consists of abnormally folded protein, similar in size to viruses.
➢ prions cause- bovine spongiform encephalopathy (BSE) commonly called mad cow
disease in cattle and its analogous variant Cr–Jacob disease (CJD) in humans.
❖ Lichens –
➢ are symbiotic associations between algae and fungi
➢ algal component - phycobiont (autotrophic)
- prepare food for fungi
➢ fungal component – mycobiont (heterotrophic)
- fungi provide shelter and absorb mineral nutrients and water for its partner
➢ Lichens are very good pollution indicators – they do not grow in polluted areas.
Important Scientist
➢ Aristotle: earliest to attempt classification, used simple morphological characters to classify
plants into trees, shrubs and herbs.
- He divided animals into two groups with and without red blood cells.
➢ Linnaeus: Two Kingdom classification- Plantae and Animalia
➢ R.H. Whittaker (1969) -Five Kingdom Classification i.e.- Monera, Protista, Fungi, Plantae
and Animalia
➢ Pasteur - gave the name virus, meaning venom
➢ D.J. Ivanowsky – recognized certain microbes causing Mosaic disease of tobacco, named
them virus.
➢ M.W Beijerinek- extract of infected plant can cause infection in healthy plant- Contagium
Vivum fluidum
➢ W.M Stanley- viruses can be crystallized and crystals consists of protein
➢ T.O. Diener- discovered a new infectious agent, smaller than viruses- viroids and caused
Potato spindle tuber disease
YEAR WHY IT IS IMPORTANT?
1892 Recognized virus of Mosaic disease of
tobacco
1898 Infected extract can cause disease in
healthy plant- M.W Beijerinek
1935 W.M. Stanley showed virus can be
crystallized
1971 Discovery of Viroid by T.O. Diener
