Biology Practicals
- Created by: EmmaHornshaw
- Created on: 17-06-18 18:43
Mineral Deficiencies
IV= minerals present DV= characteristics of plant
CV= vol of mineral solution, species of plant, size of container, amount of light
Method:
- Half fill tube with 'all nutrient'.
- Cover top of tube with foil and create well in centre and push plant through (until in solution)
- Repeat with solution lacking a nutrient e.g. nitrates, Mg, K, Ca, P or lacking all
- Wrap all tubes with foil and place on windowsill in sun
- Observe regularly
Stunted growth= lack of nitrates, Ca or P
Yellow leaves= lack of Mg or K (also can have brown discolouration)
Tensile Strength of Plant Fibres
IV= source and type of fibre DV= mass that can be held
CV= length of fibre, size of each individual mass, same aged fibres
Method:
- Plant material left to soak for about a week can be extracted (retting)/ celery stalks left in coloured water so fibres can be seen and pulled out
- Once removed, connect between 2 clamp stands
- Gradually add mass in middle until fibre breaks
- Try with individual fibres from different plants and different ways of combining fibres
- Can also compare stem to individual fibres
More fibres combined the stronger it is
Eval- ensure consistency of twisting or plaiting fibres
DNA Gel Electrophoresis
Method:
- Mix DNA with desired restriction enzymes and loading dye.
- Prepare agar and pour into electrophoresis mould. Once set fill wells with buffer solution
- Use micropipette to load restriction ladder into first well and the samples with restiction enzymes into other wells
- Connect to electrical supply and leave until dye has moved to opposite end of gel tank
- Swithc off and disconnect supply
- Carefully remove gel from tank and view under UV light
DNA will be seperated out through agar gel. Lightests strands at opposite end and heaviest strands near wells. The DNA resriction laddder can be used as a ruler to measure the different sizes of fragments.
Ecological Sampling
CV= abiotic factors e.g. light, temp, soil, water, oxygen conc, pH, slope angle, aspect, humidity
Random Sampling or Systematic Sampling
Method:
- Random= set up a grid using a tape measure, use random no. generator to generate place to quadrat and collect data
- Systematic= line transect to study zonation, tape measure laid across several zones and quadrat are used to record data at regular interval
- Measuring abundance= % cover, frequency, use pitfall trap (trap invertebrates) or sweepnet or pooter, tuliguen funnel (collect leaf litter) and baerman funnel (collect organisms from water)
Eval- constant changing abiotic factors hard to control, movement of organisms, can take large amount of time, limitations as only 1 study, ethics for organisms. disruption of habitat
Natural Antibiotics (Garlic vs Mint)
IV=presence of mint or garlic DV= zone on inhibition
CV= conc of plant material, lawn of bacteria on petri dish, contamination by other microbes, vol of plant material on each disc
Method:
- Make plant extract by crushing 3g of plant material with 10cm3 denatured alcohol. Shake occassionally for 10 mins
- Pipette 0.1cm3 of extract onto sterile paper disc and allow to dry
- Label petri dish and split into 4 sections (for each type of extract and a control of distilled water)
- Place a disc on each section of agar plate, close and tape
- Leave incubated over night and observe any inhibition
Plant extract will create larger zones of inhibition and are more effective at lower conc (garlic better than mint)
Eval- use aseptic techniques, shake enough to ensure active ingredient
Effect of Temp on Cell Membranes
IV= temp of water DV=% transmission of light
CV= vol of distilled water, time left in water, size of beetroot piece
Method:
- Use a cork borer to cut pieces of beetroot into 1cm3 length cylinders
- Place in distilled water overnight to remove any dye from cutting. Wash and blot dry
- Place 8 boiling tubes of distilled water into 8 differen temps
- Add beetroot and leave for 30 mins
- Remove beetroot and shake to disperse dye
- Set colourimeter to % absorbed on blue/green filter
- Calirate using a curvette of distlled water
- Measure % absorbance at all different temps and record readings
Calculation- % transmitted= 100 - % absorbed
Eval- skin on beetroot affects SA, difficult to maintain temp, accurate of reading on colorimeter, different part of root
Effect of Enzyme Conc on Rate
IV= conc of enzyme DV= time for enzyme to breakdown substrate
CV= temp, vol of enzyme, vol of substrate, cocn of substrate, pH
Method:
- Allow first conc of yeast solution and seperate tube of hydrogen peroxide to acclimatise to desired temp
- Set up gas syringe and set to 0
- Quickly add peroxide to yeast and attach gas syringe
- Read vol of oxygen produced every 10 mins until 3 readings are the same
- Repeat 3 times for each conc of yeast solution and complete for 5 conc
Calculations- initial rate= grad of steepest point on graph of vol against time for each conc
As conc of enzyme increases, rate of reaction increase until plateau point where all enzymes have metabolised all substrate
Eval- loss of gas when attaching syringe, reaction going too quickly to read
Effect of Different Antibiotics
IV= antibiotic DV= diameter of inhibition zone
CV= conc antibiotic, vol antibiotic, disc size, bacterial species, temp, ruler, no contamination, age of bacteria
Method:
- Prepare agar plate seeded with bacteria and label petri dish with type of bacteria
- Flame forceps and pick up antibiotic disc and place in centre of agar in petri dish
- Tape with two pieces to form a cross and keep upsidedown in icubator (30 degrees) for 2 days
- Measure diameter of inhibition zone
- Repeat for other antibiotics
All in aspectic conditions- flame forceps,disinfect surfaces, work in undraught
Depend on bacterical species used (gram + or -). Larger the inhibition zone the more effective the antibiotic against that species
Eval- ensure discs evenly placed on petri dish, aseptic techniques to avoid contamination
Respirometer
CV= no of organisms, temo, time, amount of soda lime
Method:
- Place 5g maggots into tube and replace bung
- Add drop of dye into glass tube and open 3 way tap to move drop to convinient place
- Matk starting position and close connection to syringe and amosphere. Start timing
- Mark position of fluid every minute for 5 mins
- Measure distance travelled each min and calculate mean
Calulation- vol of oxygen= Pi x r^2 x distance travelled
Can work out rate using time
Eval- doesnt allow reset, needs control tube alongside. measurement less accurate
Observing Mitosis
DV= chromosomes stained blue using orcein ethanoic stain
Method:
- Place test tube of 2cm3 of 1M HCl into 60 degree waterbath
- Cut off 1-2cm of root tip from garlic root
- Put in watchglass containing 5cm3 of cold distilled water and leave for 5mins the remove and dry
- Place tips in heated HCl for 5mins then repeat process
- Transfer 1 tip to microscope slide and gently break up with mounting needle
- Add a drop of orcein ethanoic stain and leave for 2 mins
- Add coverslip and blot with filter paper
- View under microscope and identify stages of mitosis
Calculations- % cells in each mitosis stage
Mitotic index= no of cells containing visible chromosomes/ total no of cells in field of view
Eval- resolution of microscope, human error with counting
Identify Vascular Bundle
Method:
- Place a small piece of rhubarb on a watch glass
- Use forceps to pick out one or two vascular bundles from this block of tissue and place them on a microscope slide
- Use mounting needle to tease the vascular bundles apart
- Cover the tissure with a drop of methlene blue and leave for 5 mins
- Draw off extra stain with filter paper
- Place a drop of dilute glycerol on the fibres and mount under a coverslip
- Examine under low, medium and high magnification
Measuring Vit C Content in Juice
IV= fruit juice DV= vol juice to decolourise 1cm3 of DCPIP
CV= temp, conc DCPIP solution (1%), amount of shaking tube, end point colour
Method:
- Pipette 1cm3 DCPIP into test tube
- Use burette to add 1% Vit C solution (control) drop by drop and shake gently after each drop
- Continue until blue colour just disappears
- Record vol of solution needed to decolourise DCPIP
- Repeat 2 times and calculate mean
- Repeat procedure with different fruit juices
Calculations- mass of Vit C= 10mg x vol
Eval- difficulty controlling temp, end point difficult to judge
Effect of Caffeine on Daphnia HR
IV= caffeine conc DV= heart rate
CV= temp, vol of solutions, stress of daphnia, size of daphnia, time of acclimatisation
Method:
- Remove 1 daphnia and place on cavity slide
- Remove pondwater and replace with distilled water (control)
- Leave for 5 mins to acclimatise then observe HR under mircroscope for 30secs
- Repeat with 2 more daphnia
- Repeat for 5 conc of caffeine
As caffeine increases HR increases
Calculation- HR= bpm so if timed for 30sec x2
Eval- light from microscope increases temp=increased HR, high conc of caffeine kills daphnia, counting HR can be inaccurate (human error)
Spirometer
Method:
- Tank of water with air-filled chamber suspended. Set up so adding air makes chamber rise and removing air makes chamber fall. Movements are recorded
- Tubes run from chamber to mouthpiece and back again
- Calibrated so movement corresponds to given vol
- Soda lime canister between mouthpiece and chamber to absorb CO2
- Person tested wears noseclip and need time to acclimatise
- Trace will move move as person breathes
Tidal vol= vol person breathes in and out at rest
Vital capacity= max vol air that can be breathed in and out
BR= no of breaths per min
Minute Ventilation= tidal vol x breathing rate
Habituation
IV= no of stimuli DV= retraction time
CV= replication of stimuli, snails approx same size and age, equal handling history, drying out
Method:
- Place snail on clean and firm surface and allow to acclimatise
- Dampen cotton bud wiht water and touch snail between eye stalks and start timing
- Measure length of time between touch and snail beig fully exposed from shell again
- Repeat procedure for 10 touches
As no of stimuli increases, time taken to re-emerge decreases. With repeated stimuli Ca channels become less responsive so less Ca crosses membrane= less NT released = less likely to result in action potential= less response
Eval- snails handled before may not react same way, hard to determine when fully emerged, lack of moisture encourages snail to stay in shell
Effect of Temp on Enzyme Reaction
IV= temp DV= vol of gas collected
CV= vol hydrogen peroxide, mass of peas, time period, room temp, age of peas, variety of peas
Method:
- Grind known mass of peas in a known vol of distilled water
- Measure a known quality of this solution into a boiling tube
- Add 5cm3 of hydrogen peroxide to solution
- Reconnect boilign tube to apparatus (ensure gas-tight)
- Place the syringe over end of delivery tube and measure oxygen produced while timing
- Measure vol of oxygen produced at regular intervals
- Repeat at range of temps
Calculation- Q10= rate at temp +10 degrees/. rate at temp
Eval- errors of waterbath temp, change in room temp, time limitations
Effect of Temp on Hatching (Brine Shrimp)
IV= temp DV= no of hatched brine shrimp
CV= light intensity, pH, salt content, presence of Cl from tap water, oxygen conc
Method:
- Place 2g of seasalt into a 100cm3 beaker of dechlorinated water and stir until all dissolved
- Label the beaker with seasalt and temp it will be incubated
- Place a pinch of egg cysts onto a large sheet of white paper and wet graph paper with saltwater to pick approx 40 eggs up with
- Put the paper in beaker upsidedown and after 5mins remove paper ensuring eggs washed off
- Incubate at a range of temps from 5 degrees to 35 degrees
- Next day count the no of hatched larvae using a bright light and catching the shrimps wiht a fine glass pipette
Majority hatch between 25-30 degrees
Eval- ethics of hatching in different conditions, use of animals, not accurate salt or egg measurements, human error, some eggs wont hatch
Photosynthesis on Isolated Chloroplasts
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