PLUS ONE BOTANY NOTES- BIOLOGICAL CLASSIFICATION

2. BIOLOGICAL CLASSIFICATION

Systems of classification

ü  Earliest classification was given by Aristotle.

ü  Divided plants into herbs, shrubs and trees.

ü  Animals into those with RBC’s and those who do not have RBC’s.

Two kingdom classification :

ü  Two kingdom classification given by Carolous Linnaeus

ü  He classified living organism into two kingdoms-plant kingdom and animal kingdom.

ü  A large number of organisms did not fall into either category. Hence this classification was found inadequate.

Drawbacks of 2-kingdom classification

ü  Prokaryotes (Bacteria, cyanobacteria) and eukaryotes (fungi, mosses, ferns, gymnosperms and angiosperms) were included under ‘Plants’. It is based on the presence of cell wall. But prokaryotes and eukaryotes are widely differed in other characteristics.

ü  It included the unicellular and the multicellular organisms in same group. E.g. Chlamydomonas and Spirogyra were placed under algae.

ü  It did not differentiate between the heterotrophic fungi and the autotrophic green plants. Fungi have chitinous cell wall while the green plants have cellulosic cell wall.

Five kingdom classification :

ü  Five kingdom classification system proposed by R.H. Whittaker

ü  The five kingdoms are monera, protista, fungi, plantae and animalia

ü  The main criteria for classification include cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships.

ü  Carl Woese classified living organisms into six kingdoms based on Ribonucleic Acid (RNA) studies. He divided the prokaryotes (Kingdom Monera) into 2 groups, called Archaebacteria & Eubacteria. This means that there is no more consolidated Monera Kingdom.

Kingdom Monera

ü  Bacteria is sole member.

ü  They also live in extreme habitats such as hot springs, deserts, snow and deep oceans.

ü  Bacteria  can have shapes like : coccus (spherical), bacillus (rod-shaped), vibrio (comma Shaped) and spirillum (spiral shaped).

ü  Bacterial structure is very simple but they are complex in behaviour and show extensive metabolic diversity.

ü  Some bacteria are autotrophic (synthesize food from inorganic substrates). Majority are heterotrophs (they do not synthesize the food but depend on other organisms or on dead organic matter for food).

Archaebacteria:

ü  These bacteria are live in most harsh habitats

ü  Halophiles (archaebacteria live in salty areas)

ü  Thermoacidophiles (archaebacteria live  in hot springs)

ü  Methanogens are present in the guts of ruminant animals (cows, buffaloes etc). They produce methane (biogas) from the dung of these animals.

Eubacteria 

ü  They have a rigid cell wall, and if motile, a flagellum present.

ü  They also known as blue green algae or Cyanobacteria - photosynthetic autotrophs.

ü 

Cyanobacteria are unicellular, colonial or filamentous, marine or terrestrial algae.

ü  They form blooms in polluted water bodies.

ü  The colonies are generally surrounded by gelatinous sheath

ü  Some cyanobacteria have specialised cells called heterocysts for nitrogen fixation (eg. Nostoc and Anabaena).

ü  Chemosynthetic  autotrophs -oxidise various inorganic

substances like nitrates/nitrites, ammonia and released energy.

ü  They play role in recycling nutrients like nitrogen, phosphorous iron and sulphur.

ü  Heterotrophic  bacteria are decomposes,

ü  Bacteria help in making curd from milk, production of antibiotics, nitrogen fixation and also cause diseases like cholera, typhoid, tetanus, and citrus canker.

ü  Bacteria reproduce mainly by fission

ü  Under unfavourable conditions, bacteria produce spores.

ü  The sexual reproduction by DNA transfer from one bacterium to the other. the process called conjugation.

Mycoplasma :ü 

Completely lack cell wall.

ü  Smallest living cells.

ü  Can survive without oxygen.

ü  Pathogenic in animals and plants.

Kingdom Prostita

ü  Single celled eukaryotes

ü  Prostita  forms a link between plants, animals and fungi.

ü  Protistan cell contains a well-defined nucleus and other membrane-bound organelles

ü  Some have flagella or cilia.

ü  Protists reproduce asexually and sexually (by cell fusion and zygote formation)

ü  Prostita include chrysophytes, dianoflagellates, euglenoids, slime moulds and protozoans

Chrysophytesü 

This group includes diatoms and golden algae (desmids).

ü  They are microscopic and float passively in water currents (plankton).

ü  Most of them are photosynthetic.

ü  Cell walls have silica. Thus the walls are indestructible

ü  Cell walls overlap to fit together like a soap box

ü  Cell wall accumulation of diatoms forms ‘diatomaceous earth’.

ü  Being gritty this soil is used in polishing, filtration of oils and syrups.

ü  Diatoms are the chief ‘producers’ in the oceans.

Dinoflagellates

ü  Marine, photosynthetic, cell wall has cellulose.

ü  They appear yellow, green, brown, blue or red depending on  pigments present in cells

ü  Two  flagella one longitudinal and other transversely in a furrow between wall plates.

ü  Red dianoflagellates (gonyaulax) undergo such rapid multiplication and cause red tides.

ü  Toxins released by dianoflagellate may even kill marine animals such as fishes.

Euglenoids  

ü  They are found in stagnant fresh water.

ü  Have protein rich layer ‘pellicle’ which makes body flexible.

ü  They have two flagella, a short and a long one.

ü  photosynthetic in the presence of sunlight

ü  but become heterotrophs if they do not get sunlight. Eg., Euglena

Slime moulds

ü  Saprophytic protists.

ü  Under suitable conditions, they aggregates to form plasmodium and grows on decaying twigs and leaves.

ü  During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips.

ü  Spores have true walls which are extremely resistant and survive for many years.

ü  The spores are dispersed by air currents.

Protozoans

ü  Protozoans are heterotrophs and live as predators or parasites.

ü  There are four major groups of protozoans.

Amoeboid protozoans

ü  These organisms live in fresh water, sea water or moist soil

ü  Catch prey using pseudopodia,

ü  Marine forms have silica shells on their surface.

ü  E.g., Amoeba,  Entamoeba.

Flagellated protozoansü 

The members of this group are either free-living or parasitic.

ü  They have flagella.

ü  Disease like sleeping sickness caused by  Trypanosoma.

Ciliated protozoans

ü  These are aquatic  and have cilia

ü  Cilia move food into gullet and also help in locomotion.   

ü  E.g., paramecium.

Sporozoans .

ü   Lack any locomotary organelle         

 √ All members are parasitic.

ü  They have infective spore like stage in life cycle,  E.g., plasmodium which causes malaria.

Kingdom Fungi

ü  The fungi constitute heterotrophic organisms

ü  Fungi cause bread mould and orange rot

ü  The common mushroom and toadstools are fungi.

ü  Unicellular fungi (Yeast) are used to make bread and beer.

ü  Puccinia cause  wheat rust

ü  Fungi are source of antibiotics, e.g., Penicillium

ü  Grow in warm and humid places

ü  Fungi are filamentous (except yeast).

ü  Fungi body consist of long, slender thread-like structures called hyphae

ü  Network of hyphae called mycelium

ü  Hyphae with multinucleated cytoplasm are called coenocytic hyphae.

ü  Others have septae or cross walls in their hyphae.

ü  Cell wall composed of chitin and polysaccharides

ü  Most fungi are heterotrophic -

Fungi  absorb soluble organic matter from dead substrates –saprophytic,

Fungi  that depend on living plants and animals are called parasites.

ü  They can also live as symbiotic (lichen) with roots of higher plants as mycorrhiza.

ü  Reproduction- vegetative reproduction- fragmentation, fission and budding.

ü  Asexual reproduction - by spores - conidia or sporangiospores or zoospores

ü  Sexual reproduction- by oospores, ascospores and basidiospores.

ü  The sexual cycle

-Fusion of protoplasms between two motile or non-motile gametes (plasmogamy)

-Plasmogamy leads to two  nuclei per cell this condition is called a dikaryon (n + n)

-Fusion of two nuclei called karyogamy-The meiosis in zygote resulting in haploid spores

ü  Based on the morphology of the mycelium, mode of spore formation and fruiting bodies kingdom fungi divided into various classes.

Phycomycetes

ü  Phycomycetes are found in aquatic habitats and grow on decaying wood

ü  The mycelium is aseptate and coenocytic.

ü  Asexual reproduction by zoospores or Aplanospores

ü  Spores produced endogenously in sporangium

ü  Zygospores are formed by fusion of two gametes.

ü  Gametes are isogamous (similar in morphology) or anisogamous or oogamous (dissimilar) or oogamous.

ü  E.g., Rhizopus (bread mould), Albugo (parasitic fungi on mustard).

    Ascomycetes  

ü  Also known as ‘sac fungi’

ü  They are unicellular, e.g., yeast (Sacharomyces) or multicellular, e.g., Penicillium.

ü  They are saprophytic, decomposers, parasitic or coprophilous (growing on dung).

ü  Mycelium branched and septate

ü  Asexual spores are called conidia produced exogenously on the conidiophores.

ü 

Sexual spores are called ascospores produced endogenously in ascus produced inside fruiting body called ascocarp.

ü  Neurospora is used extensively in biochemical and genetic work

ü  E.g., Aspergillus, Claviceps, Neurospora.

     Basidiomycetes  

ü  Commonly known forms are mushrooms, bracket fungi or puffballs.

ü  They grow in soil, on logs and tree stumps and in living plant bodies as

parasites, e.g., rusts and smuts.

ü  Mycelium is branched and septate.

ü  Asexual spores generally are not found.

ü  Vegetative reproduction by fragmentation.

ü  The sex organs are absent

ü  Sexual reproduction by fusion of vegetative or somatic cells to form basidium

ü  Basidium produced four basidiospores (exogenously produced on the

basidium) after meiosis.

ü  The basidia are arranged in fruiting bodies called basidiocarps.

ü  E.g., Agaricus (mushroom), Ustilago (smut) and Puccinia (rust fungus).

Deuteromycetes

ü  They are called as ‘fungi imperfecti’

ü  The sexual form (perfect stage) is not known for them.

ü  Once sexual form is discovered the member is moved to ascomycetes or basidiomycetes.

ü  They reproduce only by asexual spores conidia.

ü  Mycelium is septate and branched.

ü  They are saprophytic, parasitic or decomposers (decomposes the litter and help in mineral cycling.).      E.g., Alternaria, Colletotrichum and Trichoderma.

Kingdom Plantae

ü  It includes eukaryotic chlorophyll-containing organisms (plants).

ü  Some are partially heterotrophic such as the insectivorous plants(bladderwort and venus fly traps) or parasites(cuscuta).

ü  The plant cells have chloroplasts and cell wall (made of cellulose).

ü  Plantae includes algae, Bryophytes, pteridophytes, gymnosperms and angiosperms.

ü  Life cycle of plants has two distinct phases – the diploid sporophytic and the haploid gametophytic – that alternate with each other(alternation of generation)

Kingdom Animalia

ü  Heterotrophic eukaryotic organisms

ü  They are multicellular and their cells lack cell walls.

ü  They digest their food in an internal cavity

ü  Their mode of nutrition is holozoic – by ingestion of food.

ü  Store food reserves as glycogen or fat

ü  Capable of locomotion.

ü  The sexual reproduction is by copulation of male and female followed by embryological development.

Viruses

ü  They did not find a place in classification.

ü  Take over the machinery of host cell on entering it but as such they have inert crystalline structure. So, difficult to call them living or non-living.

ü  Pasteur gave the term ‘virus’ i.e., venom or poisonous fluid.

ü  D. J. Ivanowsky found out that certain microbes caused tobacco mosaic disease in tobacco plant.ü 

M. W. Beijerinek called fluid as ‘contagium vivum fluidum’ as extracts of infected plants of  tobacco could cause infection in healthy plants.

ü  W. M. Stanely showed viruses could be crystallised to form crystals

ü  of protein which are inert outside their specific host.

Structure of virus

ü  It is a nucleoprotein and the genetic material is infectious.

ü  The protein coat called capsid. Capsid is made up  of capsomeres

arranged in halical or polygeometric forms.

ü  Have either DNA or RNA as genetic material which may be single ordouble stranded.

ü  Usually plant viruses have single stranded RNA;

ü  Bacteriophages(virus that infecting bacteria) have double stranded DNA

ü  Animal viruses have single or double stranded RNA or double stranded DNA.

ü  No virus contains both RNA and DNA.

ü  Diseases caused in amimals: Mumps, Small pox, Herpes Influenza and AIDS etc.

In plants- mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth.

Viroids

ü  Infectious agent, free RNA (lack protein coat)

ü  RNA has low molecular weight.

ü  Causes potato spindle tuber disease.

ü  Discovered by T. O. Diener (1971).

Lichens

ü  Symbiotic association between algal component (phycobiont) and fungal component (mycobiont). Algae provide food. Fungi provide shelter and absorb nutrient for alga.

ü  Good pollution indicators as they do not grow in polluted areas.

Answer the following

       1. Observe the relationship between the first pair and fill in the second pair

a. Extreme salty areas: Halophiles   ::Hot springs: …………..

b. Two –kingdom classification: Linnaeus::Five –kingdom classification: -----------------

c. Ascomycetes: Ascocarp::Basidiomycetes: -------------------------

d) Phycomycetes : Kingdom Fungi ; Chrysophytes : ___________

e) Nostoc: Monera :: Amoeba: ……………..

f) Cellulose; plant cell wall::…………….; fungi.

g) Algal Component: Phycobiont :: Fungal Component: ………………

2. Since the Two kingdom classification of Linnaeus was found inadequate, in 1969 a famous   scientist proposed five kingdom classification, which was phylogenetic also.

a. Who proposed five kingdom classification     b. What were the criteria for this classification

c. Name the five kingdoms    d. What is meant by phylogenetic classification (4 marks)

      3. The place of fungi in class 'Deuteromycetes' is not permanent. That means they may be transferred

          to another class at any time? In what circumstance they are transferred to another class?

     4. Nostoc fix nitrogen with the help of some specialized cells called -----------------

     5. Different types of fungi are given Classify them in to their specific classes

Phycomycetes  Ascomycetes  Basidiomycetes Deuteromycetes

Trichoderma         Neurospora    Mucor                Agaricus   Ustilago              Alternaria Claviceps        Albugo

             

           

    6. On a voyage as part of study tour Mohan and Syam could see a red part of ocean. What will be their identification as the organism which causes the phenomenon?

   7. The Addition of nostoc and anabena increases the yield in Paddy. Give the reason for the increase in field

8. Blue Green Algae can fix atmospheric nitrogen with the help of specialised cells in their thallus

(a) Name the specialised cell for Nitogen fixation                                            ½

(b) Give one example for Nitrogen fixing Blue Green Algae

9. a) Virus are considered as the border line between living and non-living.justify?

b. What is symbiosis?            c.State the economic importance of Lichens

d. Differentiate between virus and viroids.