Biology Presentation

Group member 1.Babjey2.Jamyang Dorji3.Doe Kumar Kharka4.Ugyen Dorji

1.Aim: To check the conduction of water through xylemMaterials required: - BeakerStandKnifeWaterLeafy shoot/ twig

Hypothesis: Vascular bundles in the stem, root, leaf stalks and leaf veins are all continuous and form an unbroken system of tubes. Collectively, they form the transport system throughout. Water and salt travel upwards mainly through xylem and food substances travel up and down in the plants through phloem.

Procedures:1.Take two leafy shoots (of delicate and fleshy stem)

that has been cut under water.)2.Keep their lower ends dipping in the water3.Remove about 3cm long, outer ring ( phloem) of

the stem ( as in the Beaker A) 4.Keep the central part intact5.Remove an equal length of the central part

( xylem) keeping the outer part intact ( as in the Beaker B)

6.The shoots are then fix to the stands and are allowed to remain for sometimes with their lower ends still immersed in the water.

Beaker Observations

A The leaves of the twig remain turgid and stand out almost normal

B The leaves and twig get wilted and droop down

Result/ Inference: The turgidity and normal standing of the twig in the beaker A indicates that water is conducted through xylemPrecautions:The leafy shoots should be cut under the water to prevent any air bubbles getting in. While removing the outer ring, phloem, the xylem should be kept intact and vice- versa.

Observation table

Difficulty It was challenging to cut the stem in the waterIt was difficult to remove the inner xylem parts.

Beaker A

Beaker B

2.Aim: To prove that temperature is necessary for germination.Materials required: two beakerscotton woolwaterseedsdropper Hypothesis: Very low as well as very high temperature is unsuitable for germination. A very low temperature inhibits the growth of embryo and a very high temperature destroys its delicate tissue. The temperature should be optimum (i.e. 25-350C)

Procedure:1. place the wet cotton wool in beaker2. then place some seeds(maize) on it and marked

it ‘A’3. place the wet cotton wool in second beaker4. place some seeds on it and marked it ‘B’5. place the beaker ‘A’ in normal/ordinary room

temperature6. place beaker ‘B’ in refrigerator whose

temperature is quite low7. then observe it

Beaker Observation (after 2 days) A Germination occurred B No germination occurred

Observation table

Result: we conclude that temperature is necessary for germination Precautions: we added equal amount of water on the cotton.

3.Aim: To prove that water is necessary for germinationMaterials required: two beakerscotton woolwaterseedsdropperHypothesis: Water for seeds is obtained from its environment. The seed absorbs water all over surface through micropyle. The seeds swell and testa ruptures to allow radical elongate and form root system

Procedure1. place the wet cotton wool in first beakers2. then place some seeds( maize) on it and

marked it as ‘A’3. Place dry cotton wool in second beaker.4. place some seeds( maize) on it and

marked it as ‘B’5. keep both the beaker in an ordinary room

temperature.6. observe it

beaker Observation

A Germination occur

B No germination

Observation table

Result: we concluded that water is necessary for germination.Precaution: The temperature should be same for both the beakers

4.Aim: To prove that Oxygen is necessary for germinationMaterials Required:Two conical flaskcotton woolwaterseedsDropperPyrogallic acidHypothesis: For the rapid cell division and cell growth energy is required. The energy required is available only by reparation i.e. usage of oxygen for respiration. Hence the need of oxygen

Procedure:1. Place the wet cotton wool in conical flask 2. Then place some seeds on it and marked it as ‘A’3. Lower the small test-tube in the conical flask A

which it contains alkaline Pyrogallic acid, which absorbs oxygen. (cork it tightly)

4. To second conical flask, place wet cotton wool. Then place seeds on cotton wool and marked ‘B’

5. In the conical flask B lower the test-tube in the same manner except the test-tube should contain plain water.

6. Keep both the conical flask in an ordinary room temperature.

conical flask Observation (after two days)

A Germination has occurred.

B Germination has occurred.

Observation table

Result: in both the case germination take place. The result fail.Precautions: The should not be a single drop of alkaline pyrogallic acid on the seeds and cotton wool while lower with test-tube.There should be equal amount of water spread in the cotton woolFailure and Difficulties: The experiment was a failure because pyrogallic acid doesn’t absorb Oxygen. We tried the experiment for twice but the result was same i.e. germination took place in the both beakers. We have kept pyrogallic acid in open air to check whether it is functional or not. The result was still the same.

5.Aim: To see the uptake of water by plantMaterials required:Ganong’s photometerleafy shootsafraninBeakerHypothesis: It is the device use to see the rate of transpiration(rate at which water is absorb by plant and send out through leaf)

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Procedure: 1. Bring the suitable plant and cut with the sharp

knife2. Fix apparatus as shown in the diagram.3. Air bubble is introduced in the horizontal

graduated capillary tube which is dipping into beaker containing colour water.

4. Observe the process

(In order to bring back the air bubble to its original position, release some water from reservoir into the capillary tube by opening the stop-cock).

Observations: liquid in the capillary tube move very fast. In average it took minimum 47s to complete the capillary tube.Results: We have observed that colour water was moving in the capillary tube due to the transpiration pull.Precautions:Entire apparatus should be filled with water so that no air spaces are present. Difficulties:We face difficult to introduce air bubble

6.Aim: To prove that carbon dioxide is necessary for photosynthesis Materials required:Destarched potted plantConical flaskKOHStandMethyl alcohol or spiritTest-tubePetri dishIodine solutionSpirit lamp Hypothesis: Photosynthesis is the process by which living plants cells, containing chlorophyll, produce food substances (glucose and starch), from CO2 and water by using the light energy.

Procedures:1. We have to destarched the plant for 48 hours

before the experiment 2. Take the destarched leaves3. Insert one of the destarched leaves inside the

conical flask through split cork which it contains KOH( KOH absorbs CO2 )

4. Leave the plant in the sunlight5. After a few hours (3-4), test the leaf and any other

leaf of the plant for starch.

Starch testDip the that leaf in the boiling water for a minute to kill the cellsBoil the leaf in the methylated spirit over a water bath till it becomes pale-white due to the removal of the chlorophyll. Now the leaf becomes hard and brittle.Place the leaf again in the hot water to soften it.Spread the leaf in a petri dish and pour the iodine solution on itThe leaf which was exposed to the atmosphere should turn blue-black and the one inside the conical flask containing KOH should not turn blue-black.

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Result: we concluded that leave that is inside the flask do not turn to dark blue indicating there is no presence of starch.Precaution: we use the soft, fleshy dicot leaf not the rough and hard leaves of dicot.Difficulty: it was very difficult to insert the leaf through the cork into the flask. Not only that our plant was lost and we have to de starch plant for three time. And we do also realize that we must use soft and fleshy dicot leaf

7.Aim: To check the movement of water molecules through cells Materials required:PotatoesSafreninpinsKnifeWaterPetri dishNaCl solution Hypothesis: The movement water molecules across the semi-permeable membrane from dilute solution to concentrated solution.

Procedures:1. Cut the potatoes into cube shape of equal sizes.2. Make holes at the centre of equal height, length

and breadth.3. To the first potato cube add concentrated NaCl

solution and place it in the petri-dish containing plain water.

4. To second potato cube add plain water and place it in the petri-dish containing conc. NaCl solution.

5. To third potato cube add plain water and place it in the petri-dish containing plain water.

6. Observe.

Observation table

Petri-dish Observations

I The level of concentrated solution increased and coloured water too diffused in.

II The level of plain water inside the potato cube decreased

III Remain same.

Results: The diffusion of water from dilute to concentrated solution through cells. Precautions:Size of the potato cube should be equal throughout.We struggle to cut same size of potato cube

III

III

We had tried to do the experiment on the osmotic pressure. We had tried to improvise the piston in thistle funnel but we failed to came up with idea. So we gave up that experiment and instead we had done on potato cubesWe had use only one type of poto meter since the apparatus is not there

The end

Ganong’s potometer

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