EXERCISE 3 COMPARATIVE STUDY OF PROKARYOTIC AND EUKARYOTIC ORGANISMS

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1 EXERCISE 3 COMPARATIVE STUDY OF PROKARYOTIC AND EUKARYOTIC ORGANISMS 3.1 INTRODUCTION In the previous exercise you studied the ultrastructure of prokaryotic and eukaryotic cells with the help of electron micrographs and compared their subcellular organisation. You know that cells of prokaryotes are much smaller than eukaryotes and possess a primitive type of cellular organisation. They lack nucleus and other cell organelles such as chloroplasts and mitochondria. Bacteria and related organisms are prokaryotes and rest of the organisms is Among algae, blue- green algae are prokaryotes and are true bacteria. They are called cyanobacteria because they posses certain accessory pigments such as phycocyanin and phycoerythrin. The presence of these pigments and chlorophyll a together impart characteristic blue colour to these organisms. In Plant Diversity - I course you learnt that algae are not true plants but they are included in this study because traditionally botanists study them. In this exercise you will examine the live specimens of a bacteria and a eukaryotic algae, and a slide of a nitrogen fixing cyanobacteria found in the nodules of leguminous plants. You cannot distinguish between their cell types under a compound microscope because the details observed are substantially limited. However, it is a valuable tool and will enable you to compare cellular organisation of various organisms and help you to distinguish among them. Prior Readings For doing satisfactory work you must read the following before coming to the lab. You will not be allowed to carry the theory course blocks or any other botany book with you to the lab. 4 The course "Plant Diversity - I" (LSE-12), Block 1B Algae, Unit 3: Comparative morphology and cell structure in algae, Sec 3.2 Algal morphology, p If you are short of time, look at the figures 3.1,3.2,3.3 and their captions. Unit 6: Algal habitats and distribution, Sec Algal-symbiotic associations, p In this exercise you should be able to: prepare well stained whole mounts of Lactobacilli and an algae, examine the structure of bacteria in root nodules of legumes and curd and compare the structures of a bacteria with an alga and identify the characteristic features that can help to distinguish among them.

2 Cyanobaeteria, Algae, hnyi anni Lower Plants 3.2 MATERIALS REOUIRED 1. The biology laboratory kit 2. The biology laboratory students kit 3. Fresh curd 4. Permanent slide of root nodules of any leguminous plant showing cells filled with bacteria Freshlp red/pern nanent slide of an alga Crystal - : stain Glycerine 8. 1odine.solution Precautions 1. Always use a brush for holding the mounting material. Do not use forceps. 2. Ensure that your temporary mounts do not dry up. Keep them immerged in the mounting liquid. 3. View the temporary mounts immediately as they tend to dry up or become distorted in a short ~eri0d of time. I 3.3 PROCEDURE 1. To prepare a fresh mount of curd it is best to use the water, which separates in fresh curd. This will give you a good slide as it has limited number of bacteria. Place a drop of curd water on a clean slide and a drop of crystal violet stain. Wait for two minutes and then place a cover slip on the top. 2. If you are provided with freshlpreserved material of alga, prepare a whole mount and stain it with iodine solution. Refer to Exercise 5 for preparation of whole mount of algae. 3.4 RECORD OF OBSERVATIONS Observe the three slides - curd, root nodules and the alga under the low and high power objective lens of compound microscope. Make sure that you focus sharply on the specimen. You should spend enough time on each slide and make a record of the number of cells, their size, shape, colour, cell wall and ground substance etc. in the three materials. Also see if nucleus, chloroplast, pyrenoid, flagella etc are visible. Record your observations according to the format given in Laboratory Report 3. Appendix 3 is provided to guide you fc making observations systematically and correctly. 1 Also compare the features of the three preparations. It is quite unlikely that you will be able to see all organelles listed in the Appendix 3. Therefore do not write in your report what is not visible.

3 Marking Scheme Comparative Study of Proksqotic and Eukaryotic Organisms W.M. of two samples Labelled diagrams and description of the three specimens Comparison of 3 specimens Laboratory skills Viva voce 1x2 = 2 marks 1x3 = 3 marks 3 marks 1 mark 1 mark Total 10 marks

4 Cyanobacteria, Algae, Fungi and Lower Plants --- Appendix 3 Form - microscopiclmacroscopic, unicellular/multicellular Multicellular Organisation of cells - singlelaggregateslclumps, coloniallfilamentous branchedlunbranched Differentiation - main body, holdfast (presentlabsent) Comparative size of cells - unifodnot uniform Shape of cells - round/ oval/ spherical/cylindricall rectangular /square/ indefinite Colour/pigments - green/browrdwhite/black, chlorophyllouslachlorophyllous, pigmented Sub-cellular structures Cell sheath - (visiblelinvisible), mucilaginouslrough, thicklthin Cell wall - (visiblelinvisible), thirdthick, everduneven, lightldark, layeredlnot layered Plasma membrane - (conspicuouslinconspicuous), unifoduneven, extensions Cytoplasm - smooth/granular Nucleus - chromatirdchromosomes (conspicuouslinconspicuous) Nucleoli - (visiblelinvisible) Chloroplast/plastids (visiblelinvisible) - photosynthetic lamellae (visiblelinvisible) Shape of chloroplast - cup-shapedlstar-shapedl girdle-shapedlstellatelspiral Organs of motion - ciliajflagella, number, length Pyrenoid - (visiblelinvisible) Eye spot - (visible/invisible) Vacuole - (visiblelinvisible)

5 LABORATORY REPORT - 3 Name:... Enrol. No.:... Session: I1 Date:... Time allotted: 2 hrs. Time spent:... Comparative Study of Prokaryotic and Eukaryotic Organisms EXERCISE 3 COMPARATIVE STVOY OF PROKARYOTIC AN0 EVKARYOTIC ORGANISMS 1. Materials and Procedure Technique(s) used for slide preparation (W.M., section cutting, smear etc.) Note: You should write this section if you have used a method other than the one given in the manual. Otherwise omit it. 2. Observations Diagram of bacteria (give magnification used) Descri'ption Diagram of the section of nodules containing bacteria (give magnification used) Description Diagram of alga (give magnification used) Description

6 Cyanobacteria, Algae, Fungi and Lower Plants 3. Comparison between prokaryotic and eukaryotic specimens as observed under compound microscope Features Bacteria Cyanobacteria Gross features Unicellular/multicellular Organisation of cells Type of cell(s) Any special features Individual cells Shape Comparative size of individual cells Pigmentation/colour Organs of motion Sub-cellular structures Cell sheath Cell wall Plasma membrane Nucleus/Chromatin Nucleoli Mitochondria Pyrenoid Eye spot Vacuole, S Pained structure(s) Identification (prokaryotic/eukaryotic cell) Alga