Example Lab report
Example Lab report
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It is always good practice to use an example of a good piece of work to see what your teachers/assessors are looking for. This doesn't mean you copy an example of good work, but you use it to get a clear idea of what a good piece of writing looks like.
You can ask your teachers for an example, and use ABEL's example below:
Title of investigation:
Effect of sunlight on plant height
Research question:
How does the amount of sunlight affect the height of a plant?
Background information:
Plants are essential for life on Earth, providing oxygen and food for both humans and animals. It is important to understand the factors that affect their growth and development. One such factor is sunlight, which plays a crucial role in photosynthesis - the process by which plants convert light energy into chemical energy. To carry out photosynthesis, plants need three things - water, carbon dioxide and sunlight (Aces, 2014). If they do not have one of these things then they will die. For a plant to be healthy and strong they also need minerals from the soil.
The glucose made by photosynthesis is used to create other molecules, such as cellulose and starch, which are important for plant structure and storage. Additionally, plants use the energy from glucose to fuel various metabolic processes that support growth and development, such as cell division and protein synthesis (Whiting, 2010). Because photosynthesis allows plants to convert sunlight into the energy and building blocks they need for growth, we can measure the height of a plant to see how the amount of sunlight affects plant growth.
Objective
To answer the research question by changing the amount of sunlight for 3 plants and measuring how much they grow.
Hypothesis
The plant with the most sunlight will grow the most because it can do the most photosynthesis and make the most glucose. I think the plant with no sunlight will not grow because it cannot do photosynthesis.
Variables
Independent variable - I will change the amount of sunlight by putting one plant in a box with no hours of sunlight, one plant in the sunlight for 4 hours/day and another plant in the sunlight for 8 hours/day.
Dependent variable - I will measure the height of the plants with a ruler once a day for a total of 1 week. I will measure from the top of the soil to the top of the highest leaf or stem.
Control variables - I will control the amount of water for each plant by giving each one 20 mL water every day (measured with a measuring cylinder). I will control the amount of gases and the temperature by keeping the plants in the same room. I will control the minerals that each plant receives by using the same soil for each plant. I will control the type of plant by using the same type of seed for each one.
List of materials
9 lentil seeds
3 pots containing the same soil
1 box to cover the first plant
1 ruler
Water
1 measuring cylinder
Method
Place 1 seed in each pot of soil and cover it with a small amount of soil.
Give each plant 20 mL water using a measuring cylinder.
On the first day place Plant 1 in the box, Plants 2 and 3 by the window.
After 4 hours, place Plant 2 in a box.
After 8 hours, place Plant 3 in a box.
Measure the height of each plant with a ruler and write the data in a table.
Repeat this process every day for 1 week.
Results
Table 1. Height of Plants 1, 2 and 3 in Week 1
Calculations
The average is calculated for each plant. To do so, I have to sum all the heights for the same plant and day, and divided between 3.
Table 2. The average of height of Plants 1, 2 and 3
Conclusion
Our hypothesis was correct, as the amount of sunlight increased, the height of the plants also increased. This is because there was more energy available to the plant for growth. As the amount of sunlight increases there is more energy available for photosynthesis, the chloroplasts in the plant’s leaves capture the sunlight energy and convert it into glucose. Glucose is a building block of cellulose, which is used in plant cell walls. If there is more sunlight, more glucose can be made and converted into cellulose which can be made into new cell walls and when these new cells are grown at the top of the plant, its height increases.
This positive correlation can be seen in Graph 1, where the height increases as the amount of light increases, up to a point, where the optimum amount of light has been passed and the height of the plants remain constant. As was described in the Background Information, this is because plants also need water and CO2 to perform photosynthesis, and without increasing these control variables, increasing the amount of light energy cannot produce further growth. This is known as the ‘law of limiting factors’ (Benney et al., 2014). In fact, increasing the amount of light further may damage the plants (BBCbitesize.com, 2018), but we did not see this effect. This finding is therefore in line with the expected results as described by other researchers (Smith, 2011).
Two measurements were repeated due to the values being so different to the others taken during the experiment. This was done so as not to impact the average values. However, as noted in the materials section, the intensity meter had an error of ± 1 W/m2, so although this was used to record every value, this should be taken into account. As the dependent variable measurements do not differ greatly from the averages, our findings can be seen as being reliable and the method robust enough for other people to follow and get similar results. However, the graph shows the optimum amount of sunlight may be in the range of 1200–1400 W/m2, therefore in order to provide an exact optimum value, the method could be revised to focus on this range.
This experiment shows that as plant growth is dependent on the amount of sunlight, this finding may be of use to farmers and commercial fruit growers. In the future, experiments could be designed to calculate the optimum amount of sunlight needed to produce the biggest increase in crops. The following evaluation section looks at specific problems with the method and makes suggestions on how they could be improved.
Evaluation
I think that I carried out this experiment accurately because the results matched my hypothesis and all of the data points are very close to the line of best fit. One error that might have affected my results was that not every day was sunny so sometimes Plants 1 and 2 maybe received less than 6 or 12 hours of sunlight. To improve this I could use a lamp with each plant so that they both received light for the time that they were supposed to. The temperature of Plant 1 might have been higher than 2 and 3 because it was closer to the heater in my bedroom. This might have affected the growth. To improve this I could put all of the plants in exactly the same place.
APA-style reference list
Aces.uiuc.edu (2014). Requirements for Plant Growth. [online] Available at: http://www.aces.uiuc.edu/vista/html_pubs/hydro/require.html [Accessed 1 Jul. 2023].
BBCbitesize.com (2018). The Effect of Light on Plants. [online] BBCbitesize.com/ Available at: http://www.BBCbitesize.com/plantgrowth.html [Accessed 1 Jul. 2023].
Benney, M. et al. (2014). The Law of Limiting Factors. International Plant Journal. vol. 8(3), 207–217.
Smith, J. (2011). Plant growth investigations. Working with plants. vol. 34(1), 1984, pp. 65-89.
Whiting, C. (2010). Plant Growth Factors: Photosynthesis, Respiration, and Transpiration. [online] Ext.colostate.edu. Available at: http://www.ext.colostate.edu/mg/gardennotes/141.html [Accessed 1 Jul. 2023].
Now you be the Teacher!
Now you be the Teacher!
Your teacher will give you a copy of the evaluation criteria that they use, what score would you give the investigation?
Work through each section carefully and honestly.
Write down the areas you do not get top marks for and how you can improve those parts.
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