Practicals Flashcards
Describe method for practical identifying stem structures
- Cut transverse sections of the plant stem (on the white tile using a razor, wet to reduce friction) as thinly as possible. Select the thinnest sections.
- Place one section on a microscope slide. to prevent the dye from spreading. Add a few drops of toluidine blue (stains lignin blue/green allowing xylem and schlerenchyma to be seen)
- Rinse in water and place onto microscope slide
- Lower the cover slip down carefully onto the slide. Make sure there are no air bubbles in the slide which may distort the image.
- Place under a microscope and set the objective lens on the lowest magnification, then use the coarse adjustment knob to move the lens down to just above the slide
- Observe and draw the stem.
- Measure the size of the stem diameter and vascular bundle using the calibrated eyepiece graticule.
Describe method for practical investigating effect of nutrient deficiencies
Method
1. Use the measuring cylinder to fill test tubes with each of the nutrient solutions.
2. Cover the top of the test tube with tinfoil. Poke a hole through the tinfoil.
3. Push the roots of the Bryophyllum plantlets through the hole in the tinfoil into the solution.
4. Wrap the test tubes in tinfoil (to prevent light getting in) and place them under a sunny window.
Describe method for tensile strength of plant fibres practical
Method
1. Use the forceps to separate the fibres.
2. Test the tensile strength of the fibres by using suspended masses to compare e.g. types of fibres, internal vs external fibres etc.
Describe method for practical investigating anti microbial properties of plants
Method
1. Carry out aseptic techniques detailed above.
2. Crush 3g of the garlic and mint (separately) with methylated spirit. Shake occasionally.
3. Use a sterile pipette to transfer plant extract to paper disc.
4. Leave paper discs to dry for 10 minutes.
5. Use sterile forceps to place the paper disc onto a petri dish.
6. Lightly tape a lid on, invert and incubate at 25°C for 24 hours. DO NOT tape around the entire dish as this prevents oxygen entering and so promotes the growth of more harmful anaerobic bacteria.
7. Sterilise equipment used to handle bacteria and disinfect work surfaces.
8. Measure the diameter of the inhibition zone (clear circle) for each plant. DO NOT remove lid from agar plate.
9. Work out the area of the inhibition zone using the formula:
What temperature is bacteria incubated at and why?
Bacteria sample is incubated at 25°C as incubating at 37°C (human body temperature) could enable pathogens to grow that are harmful to humans.
Describe method for practical investigating distribution
Method
1. Choose a site where there is an obvious gradient in an abiotic variable. Place the transect down. Select a species that changes in abundance along the gradient.
2. Place the quadrat at each of the marks on the transect, placing the bottom left corner on the mark every time.
3. Record the percentage cover for the chosen species. This can be done by recording how many of the quadrat’s 100 squares contain the chosen species. A square should only be counted if half or more of it is covered.
4. At each coordinate, a measure of the independent variable should be taken.
For example, if investigating light intensity, a photometer can be used to take a reading for the light intensity at each coordinate.
What degree of freedom is used as critical value in statistical tests?
Must be above critical value
- T-test —> (n – 1) + (n – 1)
- Chi-squared —> no of categories – 1
- Spearman’s rank —> no of pairs of data – 2
- Paired t-test —> no of pairs - 1
When is the Students T-test used?
Looking at difference in mean values between sets of independent data
When is Chi squared used?
Comparing observable and expected values, looking at difference between frequencies in discrete categories
When is spearman’s rank used?
Looking at correlation between two variables
When is paired test used?
Looking at difference in mean values of sets of matched data (e.g before and after)
