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LAB IN A BOX – BOX 1 Lab in a Box 1 MICROSCOPE AND CELL Page 1 of 34 LAB IN A BOX – BOX 1 Inventory S.No 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. Materials Glassware Beakers – glass, 500 ml Cover slips Microscopic slides Petridish - plastic Watch glass Equipment/Material Microscope Forceps Painting brush (small) Chemicals and Reagents Iodine solution Methylene blue Saffranine Charts Onion cell chart Buccal cells chart Internal structure of feather chart Internal structure of hydrilla leaf Starch granules in potato chart Internal structure of Dicot stem Internal structure of Monocot stem Models Animal cell model Plant cell model Consumables Onion Blades Ice cream sticks/spoons Needles Cutters Tissue papers Quantity 2 1 box 1 box 2 5 1 5 5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 pack 1 pack 2 2 1 pack Page 2 of 34 LAB IN A BOX – BOX 1 CONTENTS Sl. No. Topic Page Parts of Microscope 4 1.1 Working of Microscope 7 1.2 Using and handling of Microscope 8 Observing Onion cell 10 2.2 Observing cheek cells 12 2.3 Plant cell and Animal cell 15 2.4 Observing Hydrilla leaf 19 2.5 Observing starch granules in potato 21 2.6 Observing the internal structure of feather 24 Meristamatic tissues 27 Permanent tissues 30 1 2.1 3.1 3.2 `Microscope Experiment/ Activity Cell Plant tissues Page 3 of 34 LAB IN A BOX – BOX 1 1. MICROSCOPE Microscope is the first powerful tool in the history of biology. It is an instrument used to magnify (enlarge) objects. Structures that are too small to be seen by the unaided (naked) eye can be observed using a microscope. Page 4 of 34 LAB IN A BOX – BOX 1 1.2 PARTS OF COMPOUND MICROSCOPE Parts of microscope can be categorized as mechanical and optical parts, which are as follows Mechanical Parts – The parts which deals in handling of microscope. 1. Base and pillar: The base is generally horse shoe shaped, usually base attached pillar are made heavy in order to minimize vibrations. 2. Inclination joint: It joins the arm of microscope to the pillar. This joint permits the tilting of the microscope 3. Arm: The arm is slightly curved and is a solid piece of metal. It is attached at one end to the pillar by the inclination joint and at the other end holds the body tube. 4. Stage: This is called the table of the microscope, where the slide or specimen is placed for observation 5. Body tube: It is a cylindrical tube, to which the principle optical systems are attached. 6. Nose piece: It is a circular rotating disc attached to the body-tube. 7. Coarse adjustment knob: A pair of large knob positioned one on each side of the body. Rotations of these knobs move the body tube with lenses. It is used to focus the specimens or objects. 8. Fine adjustment knob: This is a smaller round knob on the side of the microscope. It is used for slight and fine adjustment of the body tube. Optical Parts – The parts which deals with the magnification and image formation 1. Condenser: Condenser consists of several lenses that concentrate light on the slide. 2. Iris diaphragm: it is a mechanical device mounted underneath the condenser and controls the amount of light entering the condenser. Page 5 of 34 LAB IN A BOX – BOX 1 3. Mirror: Mirror is placed below the condenser and iris. It collects the light from the natural (sun) or artificial (bulb) and reflects rays into the condenser. 4. Objective lenses: These are attached to the nose piece. They magnify and form the primary image of the specimen. There are three i.e., 10X, 45X and 100X. Our microscope has 10X and 45X objective lenses. 5. Eye piece: Eye piece is the upper optical component that further magnifies the primary image and brings the light rays to a focus at the eye point. Page 6 of 34 LAB IN A BOX – BOX 1 1.3 WORKING OF MICROSCOPE Microscope magnifies and resolves the specimens/objects seen though it. Microscope increases the size of retinal image (the image formed on the retina of eye) of the specimen. The ratio of increased image to that formed on retina of an unaided eye is termed as magnification of the microscope. How many times does our microscope enlarge an image? The magnification power of microscope depends on the lenses which are used. The microscope has 10X and 45X objective lenses and a 10X/15X eye piece. The product of objective lens and eye piece gives the magnification. Magnification = Magnification of objective lens x Magnification of eye piece When you are observing with an eye piece of 10X and objective lens of 10X, then the magnification would be 100 times. If you switch to 45 X objective lens, then the magnification would be 450 (10 x 45) times. Resolution The term resolution (or resolving power) refers to the ability to distinguish two close points as two separate points. Note: Human eyes have a limited resolving power and cannot distinguish the object smaller than 0.1 mm (100 micron), hence to study the structures which are smaller than 0.1 mm, microscopes are used. Page 7 of 34 LAB IN A BOX – BOX 1 1.3 USING AND HANDLING OF MICROSCOPE Aim To study, how the microscope should be handled and care of microscope Materials Required Microscope Procedure Step 1 Carry the microscope by holding the arm with one hand and supporting the base with the other hand. Place the microscope at the centre of the desk or table. Step 2 Rotate the nose piece and select the objective lens with low magnification (10X). Step 3 Adjust the light by turning the mirror towards the source of light and also by moving the condenser. Step 4 Place the prepared slide on the stage and adjust the object just over the stage aperture. Step 6 By looking though eye piece, slowly rotate the coarse adjustment knob till you get a clear image. Step 7 For more detailed structure, switch to 40 X objective lens. Use only fine adjustment at this stage. Page 8 of 34 LAB IN A BOX – BOX 1 Precautions Handle the microscope carefully. Place the microscope in maximum diffuse light. Direct sunlight is harmful for the eyes. Before and after the use, all the lenses and metal parts including the stage should be cleaned. The lenses should be cleaned with soft tissue paper or muslin cloth. Microscope should be kept covered when not in use. Page 9 of 34 LAB IN A BOX – BOX 1 2.1 OBSERVING ONION CELLS Aim To observe onion peel under the microscope Materials Required Fresh or preserved material of onion peel, forceps, iodine solution, saffranine, dropper, slides, cover slip, microscope, tissue paper and onion cells chart. Procedure Step 1 Divide the students into 5 groups and distribute the materials. Step 2 Cut a small piece of onion and using forceps peel off the inner layer from the cut piece. Step 3 Transfer the removed peel on the slide, (spread the peel flat) and add 1 or 2 drops of iodine/saffranine Step 4 Place the coverslip using the needle, make sure that there are no air bubbles. Remove the excess stain using tissue paper. This makes the temporary slide (or temporary mount) of onion peel. Step 5 Place the slide on the stage of microscope and observe first under low power objective lens and then switch to high power objective lens. Page 10 of 34 LAB IN A BOX – BOX 1 Step 6 Draw your observations, also refer to the onion cells chart. Observation Inference Onion peel has closely packed rectangular structures. These structures look similar to each other. These structures are called cells, which are the basic building units of the onion bulb. Together they form a big structure like an onion bulb. Not only onions, but all organisms that we see are made up of cells. Page 11 of 34 LAB IN A BOX – BOX 1 2.2 OBSERVING THE CHEEK CELLS Aim To observe the cheek cells under microscope. Materials Required Ice cream spoon, methylene blue, dropper, slides, cover slip, microscope, tissue paper Procedure Step 1 Divide the students into 5 groups and ask one person from each group to wash/rinse his/her mouth before the activity. He/she will be the donor of cheek cells Step 2 Gently scrap the inner surface of the cheek with one end of the ice cream stick or ice cream spoon. Do not use tooth pick. Step 3 Transfer the scraping collected on to a clean slide and add a drop of methylene blue stain over it. Step 4 Place the coverslip using the needle. Make sure that there are no air bubbles. (Remove the excess stain using tissue paper) Step 5 Page 12 of 34 LAB IN A BOX – BOX 1 Place the slide on the stage of microscope and observe first under low power objective lens and then switch to high power objective lens. Step 6 Draw the figure of your observations. Is the outer covering of onion peel cells and these cells are similar? Observation Inference The cheek cells are roughly polygonal. These are called as buccal mucosa cells. The boundary of a cheek cells is the cell membrane. This gives a shape to the cell and selectively allows substances to pass through it. In the case of onion peel, the outer covering is clearer than in the cheek cells because there is another layer present over the cell membrane, called cell wall. This gives rigidity to the cell. Both the cells have dense round body called nucleus. In cheek cells, nucleus is present more or less at the center of the cell. Whereas in the onion cells it is scattered. The jelly like substance between the nucleus and the cell membrane is Page 13 of 34 LAB IN A BOX – BOX 1 called the cytoplasm, which contains several structures called cell organelles, which carry out major functions within the cell. Page 14 of 34 LAB IN A BOX – BOX 1 2.3 PLANT CELL AND ANIMAL CELL Aim To study the similarities and differences between plant and animal cells Materials Required Plant cell model, animal cell model, onion cells chart, buccal cells chart. Procedure Step 1 Ask the students to compare the slides/observation of animal and plant cells and list out the similarities and differences. Step 2 With help of animal cell model and plant cell model, explain the various cell organelles present in the plant and animal cell. Page 15 of 34 LAB IN A BOX – BOX 1 Inference Animal cell and plant cell are different yet share some common features. Similarities A basic similarity is the cell organelles, many organelles are found in both types of cells. They are both Eukaryotic cells. Many of the organelles serve for the same purpose. Both divide to create new cells Differences Even though most of the parts are the same, not all are. The shape of the cell is different, a plant cell is rectangular, and an animal cell is roughly spherical. Only the plant cell performs the process of photosynthesis. Only a plant cell has a cell wall. Even though both have a vacuole, the vacuole in a plant cell is much larger, it can take up to 90% of the space in the cell. Still, the vacuole serves for the same purpose. Cell organelles Cell wall Most commonly found in plant cells Keeps cell turgid Extracellular structure surrounding plasma membrane Plasma membrane Outer membrane of cell that controls cellular traffic Page 16 of 34 LAB IN A BOX – BOX 1 Contains proteins that move through the membrane and allows the passage of materials Nucleus One or more per cell Spherical shape Denser than surrounding cytoplasm Nuclear membrane Surrounds nucleus Composed of two layers Numerous openings for nuclear traffic Nucleolus Spherical shape Visible when cell is not dividing Chromosomes Usually in the form of chromatin Composed of DNA and contains genetic information Number specific (species - i.e. 23 pairs for human) Cytoplasm Collective term for Cytosol and contains organelles Colloidal suspension Cytosol mainly composed of water with free-floating molecules Endoplasmic reticulum Tubular network attached to the nuclear membrane Runs through cytoplasm onto cell membrane Stores, separates, and serves as cell's transport system Rough type: ribosomes embedded in surface Smooth type: lacks ribosomes Page 17 of 34 LAB IN A BOX – BOX 1 Golgi apparatus Protein 'packaging plant' A membrane structure found near nucleus Composed of numerous layers forming a sac Lysosome Digestive 'plant' for proteins, lipids, and carbohydrates Transports undigested material to cell membrane for removal Vary in shape depending on process being carried out Generally referred as suicidal bag of cell. Mitochondria Second largest organelle Double-layered outer membrane with inner folds called cristae Energy-producing reactions take place on cristae Controls level of water and other materials in cell Recycles and decomposes proteins, fats, and carbohydrates, and forms urea Ribosomes Each cell contains hundreds of ribosomes Miniature 'protein factories' Composes 25% of cell's mass Vacuoles Membrane-bound sacs for storage Contains water solution Contractile vacuoles for water removal (in unicellular organisms) Chloroplasts A plastid usually found in plant cells Contain green chlorophyll where photosynthesis takes place Page 18 of 34 LAB IN A BOX – BOX 1 2.4 OBSERVING HYDRILLA LEAF Aim To observe Hydrilla leaf under microscope Materials Required Fresh and healthy Hydrilla twigs, forceps, slides, cover slip and microscope Procedure Step 1 Take a fresh and healthy hydrilla leaf and place it on the slide. Step 2 Place the coverslip using the needle, make sure that there are no air bubbles. (Remove the excess stain using tissue/blotting paper) Step 3 Place the slide on the stage of microscope and observe first under low power objective lens and then switch to high power objective lens. Step 6 Draw the figures of your observation. Observation Page 19 of 34 LAB IN A BOX – BOX 1 Inference Hydrilla leaf shows closely packed rectangular cells. The cells show green colour dots, which are chloroplasts, containing chlorophyll. These are the chief centers for photosynthesis. Page 20 of 34 LAB IN A BOX – BOX 1 2.5 OBSERVING STARCH GRANULES IN POTATO Aim To observe the starch granules in potato Materials Required Potato, cutter/spoon, slide, needle, iodine solution, dropper, cover slip, tissue paper, microscope Procedure Step 1 Take a piece of potato and scrape it with the help of spoon/cutter and transfer the scrapping on to a clean slide Step 2 Place the coverslip with the help of needle and observe under microscope. What do you observe? Step 3 Scrape the potato again and transfer to a fresh slide, now add a drop of dilute iodine solution. Step 4 Observe the slide under microscope. Do not put the coverslip, Step 5 After observing the blue spots, add 2 drops of saliva on to the scrapings. Step 6 Now place a coverslip and observe under microscope. Can you make out any difference? Observation Page 21 of 34 LAB IN A BOX – BOX 1 Inference The scrapping shows starch granules (bead like structures). On adding iodine, these starch granules turns into blue spots/dots forming starch-iodine complex. Page 22 of 34 LAB IN A BOX – BOX 1 On adding saliva the blue spots/dots disappear because our saliva contains an enzyme called salivary amylase (or ptyalin) which breaks the starch molecules into simpler molecules like (dextrins and maltoses). Page 23 of 34 LAB IN A BOX – BOX 1 2.6 OBSERVING THE INTERNAL STRUCTURE OF FEATHER Aim To observe the internal structure of feather Materials Required Feather of birds, slide, needle, cover slip, microscope Procedure Step 1 Collect the feathers of birds (hen, pigeon, crow) Step 2 Place the feather as such on the slide and observe under the microscope. What do you observe? Move the slide and observe the complete feather. Step 3 Draw your observations. Step 4 Similarly collect the wings of some insects and observe Observation Page 24 of 34 LAB IN A BOX – BOX 1 Inference Page 25 of 34 LAB IN A BOX – BOX 1 Typical wing feather consists of a central, stiff shaft with the softer vanes on each side. The central shaft of a feather is divided into two regions. The calamus is the part of the shaft closest to the bird's body. It is hollow and does not contain any vanes. The distal end of the central shaft is referred to as the rachis. The rachis is solid and is defined as the area to which vanes are attached. Vanes: The vanes extend from each side of the feather. A series of parallel branches called barbs make up the vane. Extending from the barbs are a series of short branchlets called barbules. Page 26 of 34 LAB IN A BOX – BOX 1 3.1 MERISTAMATIC TISSUES Aim To observe and study the meristamatic tissue in onion (This activity requires about 5 to 6 days for the results, plan accordingly and make it ready during your session) Materials Required Conical flasks/gas jars, onions, cutter Procedure Step 1 Take two conical flasks or transparent jars and label them 1 and 2. Fill the conical flasks (or jars) with water up to the brim. Step 2 Take two similar sized onions, (the onions should be slightly bigger than the mouth of conical flasks/jars) cut the base as shown in the figure. Step 3 Page 27 of 34 LAB IN A BOX – BOX 1 Place one onion in each conical flask (or jar) in such a way that the onion base touches the water in the conical flask(jar). Step 4 Keep the set up undisturbed for 2 days and observe on 3 rd day. You will white roots in both the onions. Step 5 After prominent roots are observed, take out the onion in conical flask 2, cut the root tips by about 1 cm and place the onion with left out roots back in to the conical flask (jar). Step 6 Observe the growth in the two conical flasks day by day. Take care that enough water is present in the conical flasks and roots are submerged well in water. What so you observe? Observation White coloured roots developed in the both the onions, the roots continued growth day by day. Page 28 of 34 LAB IN A BOX – BOX 1 The growth stopped in conical flask 2 after cutting the root tips. Inference The growth in the plants occurs only in certain specific regions. This is because the dividing tissue called as meristamatic tissue is located in these regions. Cells of the meristamatic tissue divide continuously and help in increasing the length and girth of the plant. The tips of the roots (and stems) contain these meristamatic cells (cells of meristamatic tissue) which actively divide and grow (can be seen by increase in length). When the root tips are removed, the growth is stopped as these cells are lost. Depending on the region where they are present, meristamatic tissue are classified as 1. Apical meristems: these are present at the growing tips of stems and roots and increase the length of stem and root. 2. Intercalary meristems: these are located at the base of the leaves or internodes (on either side of nodes) on twigs. 3. Lateral meristems: these are found beneath the bark and cause increase in thickness (or diameter of organs like stem, root) 2 Page 29 of 34 LAB IN A BOX – BOX 1 3.2 PERMANENT TISSUES Aim To study the permanent tissues of a plant through a transverse section of stem Materials Required Fresh material of monocot (maize) stem, dicot (sunflower stem, potato, watch glass, new blade, slides, coverslips, petridish, saffranine, brush, needle and blotting paper Procedure Step 1 Take a 2-3 cm long piece of sunflower stem and place it between potato pieces and hold it horizontally between thumb and first finger of your left hand. Any stem can be used, but the stem should be soft, tender and thin. Step 2 Hold the blade in your right hand, dip it in the water Step 3 Cut the sections of the material quickly and transfer the sections in watch glass containing water. Step 4 Select a thin uniform and complete section and place it in a drop of water on a glass slide. Step 6 Cover the section with coverslip and observe it under microscope. Step 7 Draw your observations. Page 30 of 34 LAB IN A BOX – BOX 1 Step 8 Repeat the activity for the monocot stems like grass stems Observation Page 31 of 34 LAB IN A BOX – BOX 1 Page 32 of 34 LAB IN A BOX – BOX 1 Inference In the transverse section of stem, we can see all the 7 (epidermal, collenchymas, parenchyma, parenchyma, sclerenchyma, xylem, phloem, and cambium) types of cells. All these cells perform different functions. Simple permanent tissues 1. Parenchyma Parenchyma is the widely distributed tissue in the plant body. It is made up of unspecialized cells which are similar in structure and function. Parenchyma tissue is found in the cortex, pith, and ground tissue, mesophyll tissue of leaves and also in vascular bundles. 2. Collenchyma Page 33 of 34 LAB IN A BOX – BOX 1 Collenchymas being a strong and flexible tissue, it is a mechanical tissue of the growing organs. It is found in the peripheral regions of stems and leaves. 3. Sclerenchyma Like collenchyma, sclerenchyma is also a strengthen and mechanical tissue. It is simple tissue, composed of dead cells. Complex permanent tissues 1. Xylem Xylem is a complex tissue consisting of both parenchymatous and sclerenchymatous cells. Hence it consists of living and non living cells. In roots, stems, leaves of higher plants, xylem and phloem usually occur together forming vascular bundles. Main function of xylem is conduction of water. 2. Phloem Like xylem, phloem also consists of parenchymatous and sclerenchymatous cells. Main function is to conduct food materials from the leaves to the other regions of plants and also to storage organs. Protective tissues 1. Epidermis It is present as the outermost layer of the plant body, in the roots, stem, leaves, flowers and fruits. It is usually one cell thick and covered with a waterproof coating or layer called cuticle. 2. Cork In old roots and stems the epidermal tissue at the periphery is replaced by cork. The cork cells are dead and lack intercellular spaces. The walls of cork cells are heavily thick and impermeable to water and gases. Page 34 of 34