Chapter-2 BIOLOGICAL CLASSIFICATION

 Chapter-2

BIOLOGICAL CLASSIFICATION

POINTS TO REMEMBER

SYSTEMS OF • Earliest Classification was given by Aristotle.

CLASSIFICATION Divided plants into herbs, shrubs and trees. Animals into those with RBC’s and those who do not have it.

•Two kingdom classification : Given by Carolous Linnaeus − Plant kingdom and Animal kingdom.

• Five kingdom classification : By R. H.

Whittaker. Monera, Protista, Fungi, Plantae and Animalia are the five kingdoms. Kingdom Monera : • Has bacteria a sole member.

• Bacteria can have shapes like : Coccus (spherical), Bacillus (rod-shaped), Vibrio (comma

shaped) and sprillum (spiral shaped).

• Bacteria found almost everywhere and can be

Photosynthetic autotrophs, Chemosynthetic autotrophs or Heterotrophs.

Archaebacteria : • Halophiles (salt-loving)

• Thermoacidophiles (in hot springs)

Bacteria • Methanogens (in marsh and in gut of ruminant animals. Produce methane gas.)

Eubacteria : • Photosynthetic autotrophs like Cyanobacteria. Some like Anabaena have specialised cells called heterocysts for nitrogen fixation.

• Chemosynthetic autotrophs : Oxidise

various inorganic substances like

nitrates/nitrites, ammonia and use released

energy for their ATP production.

• Heterotrophic bacteria : Decomposes, help in making curd, production of antibiotics, N2

fixation, cause diseases like cholera, typhoid.

Mycoplasma : Completely lack cell wall. Smallest living cells. Can survive without oxygen. Pathogenic in animals and plants.

Kingdom Prostita

(All single celled eukaryotes)

• Forms a link between plants, animals and fungi.

(i) Chrysophytes (Has diatoms and golden algae)

• Cell walls have silica and cell walls overlap to fit together like a soap box.

• Their accumulation forms ‘Diatomaceous Earth’.

• Used in polishing, filtration of oils and syrups.

(ii) Dinoflagellates : • Marine, photosynthetic, cell wall has cellulose.

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

(iii) Euglenoids : • Have protein rich layer ‘pellicle’ which makes body flexible.

• Photosynthetic in presence of sunlight but become heterotrophs if they do not get sunlight.

(iv) Slime Moulds : • Saprophytic protists

• Form aggregates to form plasmodium grows on decaying twigs and leaves.

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

(v) Protozoans : Amoeboid : Catch prey using pseudopodia, e.g., Amoeba. Flagellated : More flagella. Cause disease like sleeping sickness e.g., Trypanosoma. Ciliated : Have cilia to move food into gullet and help in locomotion. e.g., Paramecium Sporozoans : Have infective spore like stage in life cycle,e.g., Plasmodium which causes Malaria.

KINGDOM FUNGI

• Non chlorophyllous hyphae

• Network of hyphae called mycelium

• Cell wall of chitin and polysaccharides

• Grow in warm and humid places

• Saprophytic, parasitic, symbiotic (Lichen)

e.g., Puccinia (rust causing), Penicillium.

CLASSES OF FUNGI

(i) Phycomycetes : • grow on decaying wood

• Mycelium septate

• Spores produced endogenously

• Asexual reproduction by Zoospores or Aplanospores e.g., Rhizopus, Albugo.

(ii) Ascomycetes : • Also known as ‘sac fungi’

• Mycelium branched and septate

• Spores : Asexual spores are called conidia

produced exogenously on the conidiophores.

Sexual spores are called ascospores produced endogenously in ascus produced inside fruiting body called Ascocarp. e.g., Aspergillus, Neurospora.

(iii) Basidiomycetes • Mycelium septate.

• Asexual spores generally are not found.

• Vegetative reproduction by fragmentation.

• Sexual reproduction by fusion of vegetative or somatic cells to form basidium produced in basidiocarp.

• Basidium produced four basidiospores after meiosis. e.g., Agaricus, Ustilago.

(iv) Deuteromycetes • Called as ‘Fungi Imperfecti’ as sexual form (perfect stage) is not known for them.

• Once sexual form is discovered the member is

moved to Ascomycetes or Basidiomycetes.

• Mycelium is septate and branched.

• Are saprophytic, parasitic or decomposers.

e.g., Alternaria, Colletotrichum.

Viruses : • They did not find a place in classification. 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.

• Pasteur gave the term ‘Virus’ i.e., poisonous fluid.

• D. J. Ivanowsky found out that certain microbes caused Tobacco Mosaic Disease in tobacco plant.

• M. W. Beijerinek called fluid as ‘Contagium vivum fluidum’ as

extracts of infected plants of tobacco could cause infection in healthy plants.

• W. M. Stanely showed viruses could be crystallised to form

crystals of protein which are inert outside their specific host.

Structure of Virus : • Its a nucleoprotein made up of protein called

Capsid. Capsid is made up of capsomeres arranged

in halical or polygeometric forms. Have either

DNA or RNA as genetic material which may be

single or double stranded.

• Usually plant viruses have single stranded RNA;

bacteriophages have double stranded DNA and

animal viruses have single or double stranded

RNA or double stranded DNA.

Diseases caused : Mumps, Small pox, AIDS etc. Viroids :

 • Infectious agent, free RNA (lack protein coat)

• RNA has low molecular weight.

• Causes potato spindle tuber disease.

• Discovered by T. O. Diener.

• Lichens : • Symbiotic association between algal component (Phycobiont)

and fungal component (mycobiont). Algae provide food. Fungi

provide shelter and absorb nutrients for alga.

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

QUESTIONS

Very Short Answer Questions (1 mark each)

1. Nostoc and Anabaena have specialised cells called hetercysts. What is the

function of these cells ?

2. Which group comprises of single celled eukaryotes only ?

3. Which organisms are the chief producers in oceans ?

4. Name the fungus which causes disease in wheat (i) rust (ii) Smut.

5. Which Ascomycetes has been used extensively in biochemical and genetic

work ?

Short Answer Questions-II (2 marks each)

6. How are bacteria classified on basis of their shapes ?

7. What is the mode of reproduction in bacteria ?

8. Why are red tides caused and why are they harmful ?

9. Viruses and viroids differ in structure and the diseases they cause. How ?

10. Which class of kingdom fungi has both unicellular as well as multicellular

members ? When is a fungus called coprophilous ?

Short Answer Questions-I (3 marks each)

11. Who gave five kingdom classification ? What was the criteria used by him ?

12. What are the steps in the sexual cycle in kingdom fungi ?

13. Some symbiotic organisms are very good pollution indicators and composed

of a chlorophyllous and a non-chlorophyllous member. Describe them.

Long Answer Questions (5 marks each)

14. Some primitive relatives of animals live as predators or parasites and are divided into four major groups. Elaborate.

15. Differentiate between various classes of kingdom Fungi on the basis of their

(i) Mycelium, (ii) Types of spores and (iii) Type of fruiting body. Also give two examples for each class.

ANSWERS

Very Short Answers (1 mark)

1. Help in nitrogen fixation.

2. Kingdom Protista.

3. Diatoms

4. (i) Puccinia, (ii) Ustilago

5. Neurospora

Short Answers-II (2 marks each)

6. Bacillus (rod-shaped), Coccus (spherical), Vibrium (comma shaped) and Spirillum (spiral shaped).

7. Mainly by fission; Production of spores in unfavourable conditions. Sexual reproduction by DNA transfer.

8. Rapid multiplication of dinoflagellates like Gonyaulax. Harmful as they release toxins which kill marine animals.

9. Refer ‘Points to Remember’

10. Ascomycetes : Yeast (Unicellular), Penicillium (Multicellular), Coprophilous means fungi which grow on dung.

Short Answers-I (3 marks each)

11. R. H. Whittakar. Criteria for classification : Cell structure, thallus

organisation, mode of nutrition, reproduction and phylogenetic relationships.

12. The steps are (i) Plasmogamy : fusion of protoplasm of two motile or non motile gametes.

(ii) Kayogamy : fusion of two nuclei.

(iii) Zygotic Meiosis to form haploid spores.

(iv) Dikaryophase in ascomycetes and basidiomycetes where before karyo

gamy two nuclei per cell (dikaryon) are found.

13. Lichens. Refer ‘Points to Remember’

Long Answers (5 marks each)

14. Protozoans. Refer page no. 21-22, NCERT Text Book of Biology for Class XI

Biology.

15. Refer NCERT Text Book of Biology for Class XI,