Biology - Core practical

• Practical 16a: Investigate the effect of one abiotic factor on the distribution of one speciesIn order to investigate the distribution of a species we need to use quadrats. As we are investigating how one abiotic factor affects the distribution of the species, we need to choose an area that has an obvious environmental gradient and then use a transect.
• 16a : Investigate the effect of one abiotic factor on the distribution of one species. Equipment: Quadrat 20 metre tape measure
• Investigate the effect of one abiotic factor on the distribution of one species

  1. Choose an area with a clear gradient of light intensity

  2. Lay a 20m tape measure from the open area to the shaded area

  3. Look along the transect and pick a plant species that clearly changes in number along the line

  4. Begin at one end of the transect and lay the quadrat next to the 0m mark of the tape

  5. Measure the light intensity at ground level

  6. Record the abundance of your chosen species at this point by counting the number present

  7. Move the quadrat 2m along the tape and repeat steps 5 and 6

  8. Continue until you have 10 measurements along the transect

  9. Create two more transects running from the openly lit to the shaded area and repeat steps 4 to 8 to have repeats
• Abiotic factor

  A non-living component of the environment that affects living organisms
• Transect

  A line along which measurements or observations are made
• Alternatively, class data can be shared
• 16a: Investigate the effect of one abitioc factor on the distribution ofone species. Considerations ● Take the readings close together in time to ensure that light intensity does not vary much, e.g. with cloud movement. ● Using an interrupted transect is quicker and can be used to measure a greater distance. ● Instead of recording abundance through counting the number of the species, we can also estimate percentage coverage, but this is less accurate as it is an estimation.
• 16a: Investigate the effect of one abiotic factor on the distribution of one species. We can conclude that there is a relationship between light intensity (our chosen abiotic factor) and the chosen plant species. However, it does not necessarily mean that the light intensity is the cause of the change in distribution, as there are other biotic (such as competition) and abiotic factors (such as soil moisture content) that can also lead to change in distribution.
• Practical 16b: Investigate the effect of one abiotic factor on the morphology of one species Method 1 . 1. You will have to plan and then carry out an investigation. 2. Plan a suitable title and do background research on the chosen topic, looking particularly at up-to-date peer-reviewed articles in scientific journals as these are of a high quality 3. Use your research to form a hypothesis and write your hypothesis and null hypothesis down 4. Write a short paragraph explaining how you reached this hypothesis, referencing your research
• Practical 16b: Investigate the effect of one abiotic factor on the morphology of one species Method 2 5.Create a step-by-step plan for your investigation, including a description of how you will determine the different levels of your independent variable (such as different levels of light intensity) and a detailed description of how you will be measuring your dependent variable (such as number of individuals, equipment used). Explain your decisions, using your research as much as possible. 6. Consider the variables that need to be controlled and why and how you will control them.
• Practical 16b: Investigate the effect of one abiotic factor on the morphology of one species Method 37. Decide which statistical tests you will use to interpret your data and why. 8. Write an equipment list and check with your teacher to make sure that the equipment is available. 9. Carry out a risk assessment. 10. Carry out your investigation and record the results in a table.
• Investigate effect of one abiotic factor on morphology of one species

  1. Draw a graph of results

  2. Carry out an appropriate statistical test

  3. Use a t-test if you are looking for a significant difference between two levels of an independent variable

  4. Use a test for correlation if you are testing for a relationship, using multiple levels of the independent variable

  5. Write a conclusion explaining your results, using biological ideas and your research references

  6. Evaluate your investigation - comment on reliability and validity of data, explain any anomalies, give values for the uncertainty of key measurements

  7. Write a reference list for your research sources
• Considerations for reliable research sources

  • Check whether the authors have any commercial interests that could create bias
  • Check whether the authors have published elsewhere
  • Check whether the publication is widely cited by other authors
  • Check whether the results are backed up by other papers
• Avoiding bias when choosing samples


  • Include in your plan how you will avoid bias when choosing your samples
• Risk


  The likelihood that a person will be harmed, e.g. high risk or low risk
• Hazard


  A potential source of harm
• Practical 16b: Investigate the effect of one abiotic factor on the morphology of one species
• Practical 16b: Investigate the effect of one abiotic factor on the morphology of one species


  1. Risk assessment

  2. Be careful when handling quadrats and ensure that they are not thrown

  3. Cover cuts and wash hands after fieldwork to stop any risk of infection from plants or soil that could have possibly been contaminated with animal faeces

  4. Use sunscreen if you will be working in area with high UV levels for long periods of time

  5. Do not enter water and ensure that you can be seen by others at all times

  6. Wear gloves if working with nettles

  7. Inform your teacher if you feel unwell due to possibility of allergic reaction from pollen
• Abiotic factor


  A non-living component of the environment that can influence the growth and development of living organisms
• Morphology


  The physical form and structure of an organism
• Effect of abiotic factors on morphology

  • Light intensity on the morphology of plants
  • Height on the shore or wave exposure on the morphology of rocky shore organisms
  • Mineral ion availability and morphology of seedling growth
• Investigating the effect of one abiotic factor on the morphology of one species

  1. Choose a method of measuring growth, e.g. mass, root length, leaf area

  2. Research the function of the mineral chosen

  3. Use Sach's culture medium to compare to a solution where one mineral is deficient

  4. Alternatively, compare solutions with and without the mineral

  5. Control variables, e.g. size of seed, temperature

  6. Grow seeds for around 3 weeks and regularly top up with growth solution

  7. Use germinated barley or mung beans grown in a test tube
• Light intensity and availability affects the rate of photosynthesis and therefore growth
• Many rocky shore species vary in shape or size in relation to abiotic factors, such as period of immersion which is linked to water movements and degree of exposure to waves
• Sach's culture medium is made up of all the key nutrients needed for a plant
• Core Prac 15 sampling methods: The distribution of a species is determined by a range of different variables such as the type of quadrats used when sampling. Different quadrat types of quadrat will give different estimates of population sizes. In this investigation you will use different types of quadrats and quadrats with varying size.
• Core prac 15 samplign methods Equipment 1. 0.5m x 0.5m quadrat 2. 1m x 1m quadrat 3. 2x tape measure 4. Random number generator 5. Clipboard
• Core prac 15 sampling method 1Choose a single species which you want to measure the abundance of. Choose a species that changes in abundance in the sampling area and can be easily identified. 2. Choose a 10x10m area to take samples from. Use two tape measures to create a set of axes off which coordinates can be read. 3. Use a random number generator to generate at least 10 sets of random coordinates. 4. Place the quadrat at each of the coordinates, placing the bottom left corner on the coordinate every time. Start with the smaller 0.5mx0.5m quadrat.
• Sampling methods

  1. Record percentage cover for the chosen species

  2. Record how many of the organisms of the chosen species touch the pins of the quadrat

  3. If using a frame quadrat - record how many intersection points contain the chosen species underneath
• Percentage cover

  Recorded by counting how many of the quadrat's 100 squares contain the organism from the chosen species, where a square should only be counted if half or more of it is covered
• Point quadrat


  A model where the number of intersection points containing the chosen species is recorded
• If your quadrat has 100 smaller squares inside then there will be around 81 intersecting points inside the quadrat
• core prac 15 methods 3 7. Furthermore, record the number of organisms within the quadrat for the chosen species. An organism should only be counted if half or more of it is within the quadrat. This allows us to work out density per square metre. 8. Repeat steps 4-7 with the bigger 1mx1m quadrat
• Core Prac 15 Risk Assessment

  
  

  HAZARD: Biohazard

  RISK Allergies; soil bacteria; contamination

  SAFETY PRECAUTION Wash hands after practical

  IN EMERGENCY Seek assistance

  RISK LEVEL Low

  
  

  HAZARD Slippery surfaces

  RISK Slip hazard

  SAFETY PRECAUTIONWear appropriate footwear; don’t run

  IN EMERGENCYSeek appropriate medical attention

  RISK LEVELLow
• Core Prac 15 Graph/Analysing Data 1. Work out mean percentage ground cover for the frame and point quadrat. 2. Work out the mean density per m for the different sized quadrats 2 3. Construct a bar chart or histogram 4. Statistical test such as t-test
• Core prac 15 Conclusion 1. You should be able to find out if there is a significant difference between density per m^2 for the different sized quadrats. 2. You should be able to find out if there is a significant difference between mean percentage cover for the different types of quadrat.
• Gibberellins are a type of plant hormone, the effects of which include the stimulation of elongation at cell internodes, the growth of fruit, and germination. During germination, the starch stored in the endosperm is converted to glucose. Gibberellins are secreted by the embryo, which has been activated by the absorption of water. They diffuse to the aleurone layer of the endosperm, which stimulates the aleurone layer to produce amylase. Amylase then hydrolyses the starch (amylose and/or amylopectin) into glucose.
• Core prac 14 gibberellins Equipment ● Cereal grains ● Sodium hypochlorite solution ● Muslin ● Beaker ● Scalpel ● Forceps ● Sterile containers to soak the grains ● Tile ● 1M gibberellic acid ● Distilled water ● Petri dishes ● Adhesive tape ● Potassium iodide solution ● Measuring cylinder
• Gibberellins Method

  1. Dilute the stock gibberellin solution to several set concentrations

  2. Place in labelled sample bottles

  3. Collect the required number of seeds and pull any husks off the grains

  4. Cut the seeds in half (one half should contain the embryo and the other half should contain the endosperm)

  5. Discard the half containing the embryo

  6. Sterilise the half containing the endosperm by placing it in the sodium hypochlorite solution and leaving for 3 minutes

  7. Wash the seeds through distilled water 5 times until there is no smell of bleach

  8. Place the seed halves in the gibberellin solution and leave for 12-48 hours

  9. Leave lids of sample bottles loose to so prevent conditions becoming anoxic

  10. Use sterile forceps to move seed halves onto a sterile petri dish with starch agar

  11. Partially tape the lids (to prevent conditions becoming anoxic)

  12. Leave for 12-48 hours

  13. Pour potassium iodide onto the plates

  14. Measure the zone of inhibition/'clear zone; around the seed half
• Core Prac 14 Giberellins Graph ● Plot a graph of the gibberellin concentration against area of zone of inhibition. Conclusion ● As gibberellin concentration increased, the amount of amylase produced by the aleurone layer increased, so area of starch from the agar around the seed half digested also increased. ● Iodine stains starch blue-black, so the area where starch had been digested appeared as a clear area around the seed half.