17. Investigation: Effect of Exercise on Pulse Rate
Procedure: Work in pairs with one partner as the subject and the other as the observer. Locate the pulse by placing three fingers firmly on your partner’s wrist, avoiding excessive pressure that could obstruct blood flow.
Shift finger positions until you detect rhythmic movement against your fingertips – this represents the arterial pulse. Count the number of pulse beats felt during one complete minute while your partner remains at rest, recording this baseline measurement.
Ask your partner to walk briskly around the classroom block, maintaining a steady pace. Immediately after walking, relocate the pulse and count beats for one minute, recording this measurement.
Next, have your partner run around the classroom block at a faster pace. Upon completion, quickly measure and record the pulse rate for one minute. Compare all three measurements to analyze exercise effects.
Expected Results: Resting pulse rate shows the lowest values, typically ranging from 60-80 beats per minute for healthy individuals. Walking increases pulse rate moderately as the heart responds to increased oxygen demands from active muscles.
Running produces the highest pulse rates as cardiovascular system works maximally to supply oxygen and nutrients to heavily exercising muscles. The heart rate increase reflects the body’s adaptation to increased metabolic demands during physical activity.
Conclusion: Exercise significantly increases pulse rate as the cardiovascular system responds to increased oxygen and nutrient demands of active muscle tissue.
18. Investigation: Effect of One-sided Illumination on Growing Shoots
Procedure: Select two identical potted seedlings of the same species and age for comparative analysis. Place the first seedling inside a cardboard box with a small hole cut at the seedling’s height level, creating unidirectional light exposure.
Position the second seedling in an identical box setup but mount it on a slowly rotating clinostat device. The clinostat ensures continuous rotation, providing equal light distribution to all sides of the growing shoot.
Place both setups in the same environmental conditions with identical temperature, humidity, and overall light intensity. Monitor both seedlings over several days, observing and recording growth direction changes.
The clinostat rotation eliminates the effects of unidirectional light by constantly changing the shoot’s orientation relative to the light source.
Expected Results: The seedling on the clinostat continues growing straight upward because auxin hormones remain evenly distributed throughout the shoot. Equal auxin distribution promotes uniform cell elongation on all sides of the stem.
The stationary seedling in the box exhibits clear bending growth toward the light source. Unidirectional light causes auxin accumulation on the darker side of the shoot, leading to faster cell elongation on that side and resulting in bending toward light.
Conclusion: One-sided illumination causes shoots to exhibit positive phototropism by bending toward the light source due to uneven auxin distribution.
19. Investigation: Root Response to Water Stimulus (Hydrotropism)
Procedure: Place a porous clay pot at the center of a large basin or water trough. Fill the basin with dry sand or sawdust, ensuring it completely surrounds the clay pot while leaving the pot’s rim exposed.
Plant seeds approximately 3cm deep in the dry sand, positioning them about 5cm away from the clay pot in various directions. Avoid adding any water to the surrounding sand or sawdust medium.
Fill the porous clay pot with water, allowing some water to seep slowly through the pot walls into the immediately surrounding sand. This creates a localized moisture gradient around the pot.
After 2-3 days of germination, carefully excavate the sand around each developing seedling and observe the direction of radicle (root) growth patterns.
Expected Results: The developing radicles show clear directional growth toward the moist sand surrounding the clay pot rather than growing randomly in all directions. This demonstrates positive hydrotropism as roots actively grow toward the water source.
Roots furthest from the pot show more dramatic curvature as they bend toward the moisture gradient. The water creates a chemical signal that attracts root growth, overriding normal gravitropic responses.
Conclusion: Roots exhibit positive hydrotropism by growing toward water sources, demonstrating their ability to respond to moisture gradients in soil.
20. Investigation: Identifying the Light-Sensitive Part of Shoots
Procedure: Select three identical potted seedlings and prepare different covering treatments. Cover the growing tip of the first seedling completely with aluminum foil, ensuring no light reaches the apical region.
Cover the middle section of the second seedling with aluminum foil while leaving the tip and lower portions exposed to light. Leave the third seedling completely uncovered as a control specimen.
Place all three seedlings in a cardboard box and illuminate them from one side using a consistent light source. Ensure equal light intensity and environmental conditions for all specimens.
Monitor the seedlings for several days, observing and recording any changes in growth direction or bending responses toward the light source.
Expected Results: The seedling with its tip covered continues growing straight upward without showing any bending response toward the light. This indicates the tip contains the light-sensing mechanism necessary for phototropic responses.
Both the seedling with covered middle section and the uncovered control specimen bend toward the light source, demonstrating normal phototropic behavior. The tip region must remain exposed for proper light detection and response.
Conclusion: The growing tip of shoots contains the light-sensitive cells responsible for detecting light direction and initiating phototropic bending responses.
21. Investigation: Root Response to Gravity Stimulus (Gravitropism)
Procedure: Pin several germinated seedlings to large cork stoppers, ensuring radicles are clearly visible and positioned horizontally. Place the cork stoppers in the mouths of glass jars to secure the seedlings.
Set up one jar in a horizontal position so that the radicles remain in horizontal orientation throughout the experiment. Mount the second jar setup on a rotating clinostat device for continuous rotation.
Place both experimental setups in complete darkness to eliminate any phototropic responses that might interfere with gravitropic observations. The darkness ensures gravity is the only directional stimulus affecting root growth.
Monitor both setups for approximately two days, observing and recording the direction of radicle growth and any curvature responses.
Expected Results: Radicles on the clinostat continue growing horizontally because continuous rotation prevents consistent gravitational stimulus direction. Equal auxin distribution maintains straight horizontal growth patterns.
Radicles in the stationary horizontal jar show clear downward curvature as they respond to gravitational pull. Gravity causes auxin accumulation on the lower side of roots, inhibiting cell elongation there while promoting faster growth on the upper side, resulting in downward bending.
Conclusion: Roots exhibit positive gravitropism by growing downward in response to gravity, ensuring proper soil penetration and anchorage.
22. Investigation: Effect of Exercise on Breathing Rate
Procedure: Organize students into pairs with one partner serving as the subject and the other as the observer. Have the subject stand quietly in a relaxed position for several minutes to establish baseline conditions.
Count and record the number of complete breathing cycles (inhalation and exhalation) over a 5-minute period while the subject remains standing at rest. Calculate the breathing rate per minute by dividing the total breaths by 5.
Instruct the subject to skip rope vigorously 20 times at a consistent pace, ensuring moderate to intense physical exertion. Immediately after completing the skipping exercise, count breathing cycles again for 5 minutes.
Calculate the post-exercise breathing rate per minute and compare it with the resting rate to analyze the effect of physical activity on respiratory function.
Expected Results: Resting breathing rates typically range from 12-20 breaths per minute for healthy individuals, representing the body’s baseline oxygen requirements. The respiratory system operates efficiently at rest with minimal effort.
Post-exercise breathing rates increase significantly, often doubling or tripling resting rates as the body attempts to meet increased oxygen demands. Active muscles consume oxygen rapidly and produce excess carbon dioxide that must be eliminated.
The increased breathing rate helps restore oxygen levels in blood and tissues while removing metabolic waste products generated during intense physical activity.
Conclusion: Exercise substantially increases breathing rate as the respiratory system adapts to meet the increased oxygen demands and carbon dioxide removal needs of active muscle tissue.
23. Investigation: Effect of Time of Day on Memory Performance
Procedure: Prepare two identical lists containing 20 different words each on separate sheets of paper. Choose words of similar difficulty and length to ensure fair comparison between morning and evening testing sessions.
In the morning after waking up, spend exactly 5 minutes memorizing the first word list, focusing intently on each word. At noon, write down as many words as possible from the morning list without looking at the original.
During the evening after school activities, spend 5 minutes memorizing the second word list using the same concentration techniques. Before going to sleep, write down as many words as possible from the evening list.
Compare the number of correctly recalled words from morning versus evening memorization sessions to analyze time-of-day effects on memory consolidation.
Expected Results: Morning memorization sessions typically result in higher word recall scores because the brain is fresh and alert after nighttime rest. Mental fatigue is minimal, allowing for better concentration and information processing.
Evening memorization shows lower recall performance as the brain experiences accumulated fatigue from daily activities and stress. Mental energy reserves are depleted, reducing the efficiency of memory formation and consolidation processes.
The difference in recall performance demonstrates how circadian rhythms and mental fatigue influence cognitive abilities throughout the day.
Conclusion: Time of day significantly affects memory performance, with morning hours providing optimal conditions for learning and information retention compared to evening periods.
24. Investigation: Effect of Practice on Target Accuracy
Procedure: Set up a dartboard or target at an appropriate distance and mark a specific target area clearly. Begin with the first round of 10 attempts, carefully aiming at the designated target mark using arrows or balls.
Record the number of successful hits during this initial round, noting accuracy levels when motor skills are unpracticed. Continue for 10 complete rounds, totaling 100 attempts while maintaining consistent throwing conditions.
Record the number of hits achieved in each successive round, creating a data table showing accuracy progression over time. Maintain identical throwing distance, target size, and environmental conditions throughout all rounds.
Analyze the pattern of improvement by comparing early rounds with later rounds to demonstrate practice effects on motor coordination and accuracy.
Expected Results: Initial rounds show relatively low hit rates as the nervous system learns proper muscle coordination and timing for accurate throwing. Hand-eye coordination requires time to develop precision through repetition.
Progressive rounds demonstrate steadily increasing accuracy as the brain develops neural pathways for coordinated movement patterns. Motor memory formation improves with each practice session, leading to more consistent performance.
Later rounds show significantly higher hit rates as practiced movements become more automatic and precise. The cerebellum and motor cortex adapt to repeated stimuli, enhancing coordination accuracy.
Conclusion: Practice significantly improves target accuracy as repeated exposure allows the nervous system to develop more efficient motor coordination and muscle memory patterns.
25. Investigations: Effects of Environmental Factors on Microorganism Growth
A. Effect of Temperature on Microorganism Growth
Procedure: Boil distilled water thoroughly to eliminate all existing microorganisms and create a sterile medium. Prepare glucose solution by dissolving glucose powder in the sterile distilled water for yeast nutrition.
Label three test tubes A, B, and C, then add 40ml of glucose solution and one spatula of yeast powder to each tube. The yeast represents living microorganisms for growth observation.
Place test tube A in a hot water bath maintained at 35°C, representing optimal growth temperature. Position test tube B at room temperature (approximately 25°C) on a laboratory bench.
Place test tube C in a cold environment such as a refrigerator or ice bath to create low-temperature conditions. Observe all three setups after 20 minutes for signs of microbial activity.
Expected Results: Test tube A shows the most vigorous bubbling and frothing, often spilling over due to rapid yeast fermentation at optimal temperature. The 35°C temperature closely matches ideal conditions for yeast metabolism and reproduction.
Test tube B demonstrates moderate bubbling with less intensive frothing compared to the heated sample. Room temperature allows some yeast activity but at reduced rates compared to optimal conditions.
Test tube C shows no bubbling or frothing activity because cold temperatures inhibit yeast metabolism and virtually stop reproduction processes. Low temperatures slow molecular movement and enzyme activity.
Conclusion: Temperature critically affects microorganism growth rates, with optimal temperatures promoting rapid growth while extreme temperatures inhibit or prevent microbial activity.
B. Effect of pH on Microorganism Growth
Procedure: Prepare sterile sugar solution using boiled distilled water and dissolved sugar for microbial nutrition. Label two test tubes X and Y for pH comparison studies.
Add 40ml of sugar solution and one spatula of yeast to test tube X. Create acidic conditions by adding 5ml of hydrochloric acid to establish low pH environment.
Add identical amounts of sugar solution and yeast to test tube Y. Create alkaline conditions by adding 5ml of sodium hydrogen carbonate solution for high pH environment.
Place both test tubes in a water bath at 35°C to maintain optimal temperature while isolating pH as the variable factor. Observe both setups for signs of microbial growth activity.
Expected Results: Test tube X with acidic pH shows active bubbling and frothing, indicating that yeast thrives in slightly acidic conditions. Many microorganisms, including yeast, prefer acidic environments for optimal metabolic function.
Test tube Y with alkaline pH shows little to no bubbling or frothing activity. High pH conditions inhibit yeast growth and metabolism because alkaline environments disrupt enzyme function and cellular processes.
The pH difference demonstrates how chemical environment significantly influences microbial survival and reproduction capabilities.
Conclusion: pH levels critically affect microorganism growth, with specific organisms requiring particular pH ranges for optimal survival and reproduction.
C. Effect of Moisture on Microorganism Growth
Procedure: Obtain two identical slices of bread for moisture comparison studies. Thoroughly dry one bread slice by exposing it to sunlight or using air circulation until moisture content is minimized.
Keep the second bread slice moist by lightly splashing it with clean water, ensuring dampness without oversaturation. Avoid adding excessive water that might create anaerobic conditions.
Place both bread slices in separate dry containers to prevent cross-contamination and position them on a laboratory bench at room temperature. Leave both setups undisturbed for two days.
Observe both bread samples after the incubation period, noting any visible changes in appearance, color, or microbial growth patterns.
Expected Results: The moist bread slice develops visible mold colonies appearing as fuzzy growths in various colors including green, black, or white. Moisture provides essential conditions for spore germination and hyphal growth.
The dry bread slice remains relatively unchanged with no visible mold development because insufficient moisture prevents spore activation and germination. Microorganisms require water for metabolic processes and reproduction.
The dramatic difference demonstrates moisture’s critical role in supporting microbial life cycles and growth processes.
Conclusion: Moisture is essential for microorganism growth, as water is required for spore germination, metabolic processes, and reproductive activities.
26. Investigations: Components of Exhaled Air
A. Detection of Carbon Dioxide in Exhaled Air
Procedure: Obtain a small plastic bottle with a secure plastic cover and fill it halfway with fresh lime water solution. Lime water serves as a sensitive indicator for carbon dioxide presence.
Create two appropriately sized holes in the bottle cover using a sharp tool, ensuring holes are large enough for straw insertion. Seal the bottle with the perforated cover.
Insert a long drinking straw through one hole, pushing it down until it extends well into the lime water solution. The second hole allows air circulation during the experiment.
Blow air steadily through the straw into the lime water for several minutes, ensuring consistent airflow. Observe any color changes in the lime water solution during and after air bubbling.
Expected Results: The clear lime water gradually changes to a milky white color as carbon dioxide from exhaled air reacts with calcium hydroxide in the lime water. This chemical reaction forms calcium carbonate precipitate.
The intensity of the milky appearance increases with continued breathing, demonstrating the continuous presence of carbon dioxide in human respiratory output. The reaction confirms metabolic production of CO₂.
Conclusion: Carbon dioxide is present in exhaled air as demonstrated by the lime water test, indicating cellular respiration and metabolic processes in the human body.
B. Detection of Water Vapor in Exhaled Air
Procedure: Position a clean mirror directly in front of your face at close range. Take a deep breath and exhale forcefully onto the mirror surface several times to maximize water vapor contact.
Allow a few minutes for observation and note any changes in the mirror’s appearance. Look for cloudiness or fogging that indicates water vapor condensation on the cool mirror surface.
Obtain cobalt chloride paper, which serves as a sensitive indicator for water presence. Gently wipe the cobalt chloride paper across the mirror surface where condensation appeared.
Observe any color changes in the cobalt chloride paper, which will indicate the presence of liquid water from condensed water vapor.
Expected Results: The mirror surface becomes cloudy or foggy as warm, moist exhaled air contacts the cooler mirror surface, causing water vapor to condense into tiny water droplets.
The cobalt chloride paper changes from blue to pink color when wiped across the condensed moisture on the mirror. This color change specifically indicates the presence of liquid water.
The combination of visible condensation and cobalt chloride color change provides definitive evidence of water vapor in human breath.
Conclusion: Water vapor is present in exhaled air as demonstrated by condensation on cool surfaces and positive cobalt chloride testing, indicating metabolic water production and respiratory humidity.
27. Investigation: Distribution of Stomata in Leaves
Procedure: Using a sharp scalpel tip, carefully peel a small piece of epidermis from the upper leaf surface, ensuring the tissue remains intact and thin. Remove any attached mesophyll tissue to isolate the epidermal layer.
Mount the upper epidermis specimen on a microscope slide with a drop of water to prevent tissue dehydration. Cover with a coverslip to create a proper microscopic preparation.
Examine the specimen under low magnification objective lens, systematically scanning the tissue and counting visible stomata within defined viewing areas. Record the stomata count for the upper surface.
Repeat the identical procedure using epidermis peeled from the lower leaf surface, maintaining consistent preparation and counting methods. Compare stomatal densities between upper and lower leaf surfaces.
Expected Results: Microscopic examination reveals significantly more stomata on the lower leaf surface compared to the upper surface. This distribution pattern is common in most terrestrial plants.
The lower epidermis typically shows 2-10 times more stomata than the upper surface, reflecting evolutionary adaptations to environmental conditions. Stomata appear as kidney-shaped guard cell pairs with central pores.
Upper leaf surfaces often show fewer stomata or none at all, which reduces water loss from direct sun exposure while maintaining gas exchange capacity.
Conclusion: Stomata are distributed unevenly in leaves, with higher concentrations on lower surfaces to optimize gas exchange while minimizing water loss from sun exposure.
28. Investigation: Distribution of Microorganisms Around School
Procedure: Prepare sterile agar solution by dissolving agar powder in distilled water and boiling thoroughly to eliminate existing microorganisms. Clean four Petri dishes with soap and disinfectant solution.
Fill each sterilized Petri dish with warm agar solution and label them A, B, C, and D for identification. Allow the agar to cool and solidify completely before use.
Keep Petri dish A tightly sealed as a sterile control and store it in a clean cupboard without opening. Moisten one hand and touch various classroom surfaces to collect microorganisms.
Open Petri dish B briefly and run your contaminated hand across the agar surface in a line pattern. Close immediately to prevent additional contamination.
Place Petri dish C outside the classroom with the lid open for several minutes to collect airborne microorganisms, then close and return to the laboratory.
Use moist cotton wool to sample toilet surfaces, then open Petri dish D slightly and touch the agar with the contaminated cotton wool. Close immediately.
Place all Petri dishes in a warm laboratory location and incubate for 48 hours before examining results.
Expected Results: Petri dish A (control) shows no microbial growth because it remained sterile throughout the experiment. This confirms proper sterilization techniques and agar preparation.
Petri dishes B, C, and D display various colored colonies representing different microorganism types. The diversity and density of colonies varies significantly between sampling locations.
Toilet samples typically show the highest microbial diversity and density, while classroom surfaces show moderate contamination. Air samples reveal airborne microorganisms present in different environments.
Conclusion: Microorganisms are distributed differently throughout school environments, with higher concentrations in areas with more human contact and organic matter.
29. Investigation: Comparing Microorganisms on Washed vs. Unwashed Hands
Procedure: Prepare sterile agar solution and clean two Petri dishes thoroughly with soap and disinfectant. Label the dishes A (unwashed) and B (washed) for clear identification.
Fill both Petri dishes with sterile agar solution and allow complete cooling and solidification. Ensure one hand remains unwashed while keeping the other hand available for washing.
Open Petri dish A and run your unwashed hand across the agar surface in a clear line pattern. Close the dish immediately to prevent additional contamination from air exposure.
Thoroughly wash your hands with soap and warm water, scrubbing for at least 20 seconds to remove surface microorganisms. Rinse completely and allow hands to air dry.
Open Petri dish B and run your washed hand across the agar surface using identical technique and pressure as the unwashed hand test. Close immediately.
Incubate both Petri dishes in warm conditions for 48 hours, then examine and compare microbial growth patterns between the two samples.
Expected Results: Petri dish A shows extensive microbial growth with numerous different colored colonies representing diverse microorganisms collected from daily activities and environmental contact.
Petri dish B demonstrates significantly reduced microbial growth with fewer colonies and less diversity, indicating effective removal of surface microorganisms through proper handwashing.
The dramatic difference in colony numbers and types illustrates the effectiveness of soap and water in removing potentially harmful microorganisms from skin surfaces.
Conclusion: Unwashed hands contain significantly more microorganisms than washed hands, demonstrating the importance of proper hand hygiene in preventing disease transmission.
30. Investigation: Effect of Transpiration on Plant Water Uptake
Procedure: Prepare three test tubes and fill each approximately three-quarters full with clean water. Select three seedlings of identical age and species for comparative analysis.
Prepare the first seedling by allowing it to dry completely until it shows signs of wilting or death. Remove most leaves from the second seedling, leaving only two healthy leaves attached.
Keep the third seedling intact with all original leaves remaining for maximum transpiration surface area. Place each seedling in its respective water-filled test tube.
Add a thin layer of oil on top of the water in each test tube to prevent direct evaporation from the water surface. This ensures that any water level changes result from plant uptake rather than evaporation.
Monitor all three setups over several hours, carefully measuring and recording water level changes in each test tube to analyze uptake patterns.
Expected Results: The test tube with the dried/dead seedling shows no change in water level because dead plant tissue cannot actively transport water through vascular systems.
The seedling with two remaining leaves shows moderate decrease in water level as limited leaf surface area allows some transpiration and corresponding water uptake through roots.
The intact seedling with all leaves shows the greatest decrease in water level because maximum leaf surface area promotes rapid transpiration, requiring increased water absorption to replace lost moisture.
Conclusion: Transpiration in leaves directly affects plant water uptake, with greater leaf surface area leading to increased water absorption to replace water lost through stomatal transpiration.