There are 7 prescribed lab practicals in IB Biology. Information / skills / understanding of these labs will be assessed in section A of the Paper 3 regardless of the option.
Please review these videos and other resources. Thanks, Mr. A
Note: the potometer / plant transpiration lab is HL only.
Prescribed practical lab 1 video and other resources
Z: Prescribed lab 1: calculation of magnification of drawings, actual size of structures from drawings or micrographs.
Written summaries of the following labs to include (where applicable):
1. the research question
2. identification of the independent variable
3. identification of the dependent variable
4. procedure on a step-by-step basis
5. sample results in a data table
6. processed results and data analysis
7. conclusions including biological explanations
The research question for this lab would be as follows:
What is the effect of magnification on the actual size of structure
The independent variable: no independent variable
The dependent variable: no dependent variable
Calculation of Magnification:
To calculate the linear magnification of a drawing or image, the following equation should be used:
Calculation of Actual Size:
To calculate the actual size of a magnified specimen, the equation is simply rearranged:
Light microscopes use visible light and a combination of lenses to magnify images of mounted specimens
When attempting to draw microscopic structures, the following conventions should be followed:
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Prescribed practical lab 2 video and other resources
Izmah:
Osmolarity is the concentration of a solution expressed as the total number of solute particles per litre.
The osmolarity of a tissue may be interpolated by bathing the sample in solutions with known osmolarities
Osmosis is the movement of molecules from a region of high concentration to a region of low concentration. Solutes that are osmotically active include glucose, sodium ions, potassium ions and chloride ions. These ions are able to move because they are able to form bonds with water. There are many solutes within cells that are osmotically active.
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Prescribed practical lab 3 video and other resources
Ali and Ahmad
Prescribed Lab 3
Ali and Ahmad
IB Biology SL
Research Question: What is the effect of temperature on enzyme activity?
Independent Variable: Temperature
Dependent Variable: Rate of enzymatic activity
7. Like other chemical reactions, the rate of enzyme-catalysed reactions increase as temperature increases. The reaction rate increases with the temperature to a maximum level known as the optimum level. In humans this is around 37 degrees celsius. Following the optimum level, enzyme activity abruptly declines as temperature continues to rise. This is known as denaturing.
In order to convert substrate into a products, enzymes collide with the substrate and bind to it at the active site. The reason the rate of reaction increases is due to the fact that an increase in temperature causes the number of collisions per unit time to increase. The increase in temperature causes an increase in velocity and kinetic energy which is why the number of collisions increases.
Heat may also be converted into chemical potential energy. If the chemical potential energy increase is large enough, some of the weak bonds which determine the shape of the enzymes will be broken. This is what leads to denaturation of the enzyme. This means that too large of an increase in temperature will lead to the reaction rate to decrease due to inactivity of the enzymes.
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Prescribed practical lab 4 video and other resources
Aafia
Research Question: How can we separate photosynthetic pigments using chromatography?
Variables:
Independent - pigment solubility
Dependent - distance that pigments move on chromatography paper
Method:
Two of the most common techniques for separating photosynthetic pigments are:
Conclusion:
If you did a number of chromatographic separations, each for a different length of time, the pigments would migrate a different distance on each run. However, the migration of each pigment relative to the migration of the solvent would not change. This migration of pigment relative to migration of solvent is expressed as a constant, Rf (Reference front). It can be calculated by using the formula:
Rf = distance pigment migrated distance solvent front migrated
Chromatography is the process of separating chemicals in a mixture, where some pigments are more soluble than others and the distance they travel is contingent upon that.
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Prescribed practical lab 5 video and other resources
Armeen and Asma
Prescribed lab 5: attempting to create a sealed mesocosm
Ecosystems have the potential to be sustainable over long periods of time
Mesocosms emulate ecosystems and how they interact with their biotic and abiotic components.
-The main components include: Energy, nutrient availability, and recycling waste.
Mesocosms are enclosed “ecosystems” that allows a small part of a natural environment to be observed under controlled conditions:
A terrarium is a small transparent container, whether it be glass or plastic, in which selected plants or even animals in some cases are kept and observed
1. Building a foundation
2. Selecting the right plants
3. Maintaining appropriate conditions
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Prescribed practical lab 6 video and other resources
Nabhan and Fatima
The research question:
Identification of the independent variable:
Identification of the dependent variable
Procedure on a step-by-step basis
Processed results and data analysis
This graph shows the effect of exercise, which is indicated by treadmill velocity, on ventilation rate. We can see that as the ventilation rate increases so does the ventilation rate, for example, it goes from 20 breaths per minute to 80 breaths per minute by the end. Not only that, but the tidal volume also increases.
Conclusions including biological explanations
As the exercise intensity increases, so does the ventilation rate. Ventilation in humans changes in response to levels of physical activity, as the body’s energy demands are increased. As exercise intensity increases, so does the demand for gas exchange, leading to an increase in levels of ventilation. Exercise will influence ventilation in two main ways: increase ventilation rate (a greater frequency of breaths allows for a more continuous exchange of gases) and an increase tidal volume (increasing the volume of air taken in and out per breath allows for more air in the lungs to be exchanged
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Prescribed practical lab 7 video and other resources
Amir and Sana
Measuring The Rate of Transpiration
1. The research question
How does the rate of transpiration in plants vary between different environmental conditions?
OR
Which environmental conditions allow for the greatest rate of transpiration by plants?
2. Identification of the independent variable
Independent variable: different environments (mist, wind, bright light)
3. Identification of the dependent variable
Dependent variable: transpiration rates (as measured by potometers)
4. Procedure on a step-by-step basis
OR
Compare loss of water in pipettes of potometers between different environments.
5. Sample results in a data table
6. Processed results and data analysis
7. Conclusions including biological explanations
Transpiration describes the movement of water through plants, including the process of water loss. A potometer is a device that measures the rate at which a plant draws up water. Since the plant draws up water as it loses it by transpiration, you are able to measure the rate of transpiration. This rate of transpiration will be affected by different environmental factors, and different environmental conditions can be created for these plants, to determine how the rate of transpiration varies with each.
Evaporation of water through the stomata is a most important factor in pulling water toward the top of a tall tree. Light conditions would generally result in the higher rate of transpiration. Stomata are generally open in the light, and solar energy increases evaporation. A dry environment would result in the higher rate of transpiration because the water potential in the surrounding air would be lowest, resulting in more rapid evaporation. Breezy conditions would increase the rate of evaporation of water from the surface of the leaves, lowering the water potential, and resulting in more rapid evaporation. However, if the plant is subjected to very high wind movement, the stomata may actually close, which prevents water loss. Unless a plant is specially adapted for hot conditions, the rate of transpiration will drop in a hot environment because heat stress may cause the stomata to close, which conserves water. Warm, light-breezy conditions provide an environment for the greatest rate of transpiration in plants. In breezy conditions the rate of transpiration would be very high because of evaporative water loss.
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