BIO PRACTICALS Flashcards
CPAC 1 - Investigating effect of caffeine on heart rate of daphnia
-Prepare five different concentrations of caffeine solution and a control solution of distilled water
-Add some pond water into the well of a slide and add three drops of distilled water
-Select a large Daphnia and use a pipette to carefully transfer it to the cavity slide
-Place the cavity slide onto the stage of a microscope and observe the animal under low power
-Use a stopwatch to time 20 seconds, and count the number of heart beats. Count the beats by making dots on a piece of paper.
-Count the dots and express heart rate as number of beats per minute. Multiply by three to convert beats per 20 seconds into beats per 60 seconds
CPAC 9 - Garlic and mint as antibiotics
-Crush 3 g of garlic with a pestle & mortar and use a measuring cylinder to add 10 cm³ of denatured alcohol to the mixture. Shake the mixture occasionally for 10 minutes.
-Pipette 0.1 cm³ of the garlic extract solution onto 4 of the sterile paper discs. Allow each disc to dry. Repeat this process for the mint extract solution.
-Label the other Petri dishes for garlic, mint and control solutions – include the date.
-Use the sterile forceps to place all 4 discs of each type of extract onto their corresponding Petri dish. Close each dish and seal with hazard tape. Make sure that a small gap is left so that oxygen can enter and there is no build-up of anaerobic bacteria.
-Leave the cultures to incubate overnight.
-Open each Petri dish and use a ruler to work out the zone of inhibition for each paper disc.
Devise an investigation that would produce quantitative data on the effectiveness of the herbicides on the light-dependent reactions of photosynthesis (6)
-Use different herbicides herbicides
-Control temperature and light intensity
-Ensure all plants are the same age
-Use a range of herbicide concentrations from 0 to 10 ug cm -3
-Use DCPIP to measure light dependent reactions
-Isolate chloroplasts
-Method for controlling abiotic variables
-Use a control of tubes in the dark
-Measure time taken for DCPIP to decolourise
-Statistical analysis to compare effectiveness of herbicides on photosynthesis
-The more effective the herbicide the longer the time taken to decolourise the DCPIP, the herbicide that had the most effect on decolourising the DCPIP at the lowest concentration
The effects of these plant extracts were tested on pathogenic bacteria. It was found that
each extract had an effect on its own, but the effect was greater when used together.
Devise a procedure that scientists may have used to measure the effects of these
extracts on pathogenic bacteria.
(4)
- agar plates seeded with bacteria
- add plant extracts on filter paper discs
- extracts used separately and in combination
- incubate at 37°c for 24 hours
- measure and compare zones of inhibition
Devise a procedure that can be used to investigate the effect of cooking on the
vitamin C content of cauliflower (4)
-Cauliflower extract from same mass (of cooked and uncooked cauliflower) (1)
-Volume of DCPIP added to cauliflower extract until the DCPIP is no longer decolourised
-Using same {volume / concentration} of DCPIP (1)
-Determine the vitamin C content in cooked and uncooked cauliflower by comparing with solution of known vitamin C concentration (1)
Differences in the rate of photosynthesis may be due to the light-dependent
reactions in chloroplasts.
Devise an investigation to compare the rate of the light-dependent reaction in
shade tolerant and shade intolerant plants grown at different light intensities.
(6)
- Use shade tolerant and shade intolerant plants
- Plants grown in the same conditions e.g. temperature, humidity
- Plants grown in either 5% light or 25% light or a range of light intensities
- Take same masses of leaf
- Add to equal volume of isolation medium
- Homogenise (e.g. blend / grind in pestle and mortar) for same length of time
- Filter suspensions of plant material (through muslin) or centrifuge to concentrate chloroplasts
- Expose suspensions to 5% and 25% light intensity
- Keep temperature controlled
- Add DCPIP and record time for DCPIP to decolourise
- Carry out repeats to calculate mean time to decolourise the DCPIP
- If the difference is due to the light dependent reaction, shade tolerant plants would decolourise more quickly at lower light intensity
Devise a procedure to measure the rate of recovery of the peat bog (4)
-Use of quadrats for sampling (1)
-Random sampling technique
Record percentage cover of sphagnum (in each
quadrat) (1)
-Several {quadrats/samples} measured and mean
calculated (1)
-Sample at regular time intervals e.g. week, month(1)
-Calculate the rate of change in sphagnum cover (1)
Devise a procedure, using electrophoresis to compare the amplified DNA from these two types of humans
-Restriction endonuclease enzymes are used to cut DNA into fragments
-DNA samples are loaded onto agarose gel
-Electric current is passed through the gel
-Add fluorescent dye to visualise the bands
-position of bands produced can be compared
Devise a laboratory procedure to compare the effectiveness of penicillin with one of the new antibiotics (6)
-Prepare agar plates with bacterial cultures
-Prepare solutions of new antibiotic and penicillin
-Place onto paper discs
-Control time and temperature of incubation (incubate at 25-37 degrees and incubate for 24-72 hours)
-Use same concentration and volume of each antibiotic
-Measure the area of inhibition
-Repeat for effective antibiotics to calculate mean
-Use a t-test to compare data and see which antibiotic is most effective
-Test range of concentrations to give minimum effective dose
Describe how to carry out a study of the distribution of Epilobium Latifolium from the front edge of this glacier
-Use a transect from the front edge of glacier
-Set distance for sample sites along transect
-Estimate abundance e.g. number of plants
-Use more than one transect
-Record results using a tally chart or table
Devise and investigation to compare species richness of the pants growing under the trees in a deciduous woodland with that of a coniferous woodland (5)
-Random sampling in each woodland using random number generator
-Use of quadrat to sample at least 10 times in each woodland
-Count the number of different species in each quadrat
-Control abiotic factors by using forests in similar locations/same climate/measure temp and PH
-For each woodland calculate the total number of species present
-use a suitable statistical test to compare the data from the two woodlands
Devise and investigation to determine the effect of grazing on the distribution of the hairy vetch plants
-Random sampling in grazed and non-grazed areas
-Measure number of plants
-At least 10 quadrats in each area to calculate mean values
-Record abiotic data at each site
-Use t test or Mann Whitney U test to compare distribution
