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Biology > core practicals paper 1 > Flashcards

core practicals paper 1 Flashcards

1
Q 
topic 1 
core prac 1
effect of caffeine concentration on Daphnia heart rate 
variables 
(5 control)
A

independent: caffeine concentration
dependent: heart rate of daphnia
control variables:
- temperature
- volume of solution
-stress of daphnia
- size of daphnia
- time of acclimatisation

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2
Q

topic 1
core prac 1
effect of caffeine concentration on Daphnia heart rate
method and outcomes

A

method
- remove 1 dapnia and place in cavity slide replace pond water with distilled, leave for 5 mins to acclimatise
- count heart rate under microscope for 30s then multiply by 2 to get beats per min. repeat with 2 more daphnia
- repeat again a 5 different caffeine concentrations
outcome
- as caffeine increases, heart rate increases

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3
Q

topic 1
core prac 1
effect of caffeine concentration on daphnia heart rate
possible evaluation issues

A
  • ensuring daphnia are the same size
  • left too long under microscope, temp increases due to lamp effecting heart rate
  • ensuring enough data is collected
  • too high conc. of caffeine kills daphnia
  • counting heart beat inaccurate
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4
Q 
topic 1
core prac 2 
measuring the content of vitamin c in fruit juice 
variables 
(4 control)
A

independent: fruit juice
dependent: volume of juice required to decolourise 1 cm3 of DCPIP
control:
- temperature
- concentration of DCPIP solution (1%)
- shake each tube same number of times
- same end point colour. i.e until the blue colour of DCPIP just disappears.

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5
Q

topic 1
core prac 2
measuring the content of vitamin C in fruit juice
methods and calculations

A

method
- 1 cm3 blue DCPIP into test tube. using burette add 1% of vitamin C solution drop by drop. shake tube gently
- continue until blue colour just disappears. record volume needed to decolourise the DCPIP.
- repeat further 2 times and calculate mean result. repeat procedure with different fruit juices.
calculations:
1 cm3 of 1% vitamin C solution contains 10mg of vitamin C, therefore mass in 1cm3 = 10mg x volume of 1% vitamin C to decolourise 1cm3 of DCPIP
mass in sample = mass of vitamin C to decolourise 1cm3 of DCPIP + volume of sample required to decolourise 1cm3 of DCPIP

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6
Q

topic 1
core prac 2
measuring the content of vitamin C in fruit juice
evaluation points

A
  • difficulty in controlling temperature
  • amount of shacking (too much adds oxygen which slightly restore the DCPIP to blue)
  • end point difficult to judge as needs to be just when blue colour disappears especially in highly coloured juices
  • some loss of solution when transferring from one beaker to another
  • accuracy of measuring equipment
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7
Q

topic 1
core prac 2
DCPIP and vitamin C

A

DCPIP is a redox dye
when oxidised it is blue
when reduced it is colourless
vitamin C is a reducing agent as it reduces DCPIP to colourless.

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8
Q 
topic 2
core prac 3 
the effect of temperature on cell membranes 
variables 
(3 control)
A

independent: temperature of water
dependent:% transmission of light through resulting solution
control
- volume of distilled water
- time left in water
- size of beetroot piece

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9
Q

topic 2
core prac 3
the effect of temperature on cell membranes
method, calculation and outcomes

A

method
- using a cork borer and knife cut pieces of beetroot into 1 cm length cylinders
- place in distilled water overnight to remove dye released on preparation. wash and blot dry
- place 8 boling tubes of distilled water into 8 water baths of different temperature. once at temperature add a piece of beetroot to each and leave for 30 mins.
- remove beetroot and shake tubes to disperse dye.
- set colourimeter to read % absorbance on blue/green filter calibrate using distilled water in a cuvette first
as temperature increased % transmission slightly increased to a point a which it greatly increased due to membrane molecules gaining more heat energy, vibrating more to a point where the vibrations caused large gaps in the membrane enabling the release of dye also protein in membrane denatured leaving large pores.

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10
Q 
topic 2 
practical 4 
the effect of changing enzymes concentration on rate of reaction 
variables 
(5 control)
A

independent: concentration of enzyme
dependent: time taken for enzyme to break down substrate
control:
- temperature
- volume of enzyme
- volume of substrate
- concentration of substrate
- pH

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11
Q

T-2 prac 4
the effect of changing enzyme concentration on rate of reaction.
protease version. method, calculations, conclusions

A

method
- make up different conc. of enzymes using distilled water. set up water bath for temperature to keep constant
- place 1 test tube of 5cm3 casein solution into water bath alongside second test tube containing 2cm3 of 0.2% trypsin.
- allow to acclimatise for 3 min so that at same temperature then add trypsion to casesin.
- time how long it takes ofr casein solution to turn transparent. repeat a further 2 times then repeat for concentration
calculation: rate = 1 / time
as conc of enzyme increase rate of reaction increases until a plateau point where all enzyme has metabolised all substrate

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12
Q

T-2 prac4
the effect of changing enzyme concentration on rate of reaction
using catalase in yeast and hydrogen peroxide
method, calculations, outcomes

A

method
- using 1st conc. of yeast solution, acclimatise to temp along with hydrogen perioxide. set up gas syringe
- add perioxide to yeat and attach syringe. read of volume of oxygen produced every 10 mins until3 reading are the same. repeat 3 times for each concentration of yeast solution.
rate = initial rate of reaction = gradient at steepest point of volume against time for each concentration

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13
Q

T2 prac 4
the effect of changing enzyme concentration on rate of reaction
evaluation points

A

protease
- maintaining constant temperature
- accurately making up the different concentrations
- identifying end point consistently
- difficult to see the cross through the solution
catalase and hydrogen perioxide
- attaching syringe can be slower allowing loss of gas
- inaccurate reading of syringe
- inaccurate reading of syringes in making up dilutions
- reaction going too quickly to read

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14
Q

T3 prac 5
observing mitosis
methods, calculations, outcomes

A

chromosomes stained blue using orcein ethanoic stain
- place test tube of 2cm3 of 1M HCl into 60oc water bath
- cut of 1-2 cm of root tip. place in watch glass containing 2cm3 of acetic alcohol for 12 mins.
- remove then place into another watch glass containing 5 cm3 of ice cold distilled water. leave 4-5 min remove and dry
-place tips into heated HCl for 5 mins then repeat process.
transfer 1 tip to microscope slide gently macerate with mounted needle add 1 small drop of orcein ethanoic stain and leave for 2 mins. add cover slip and blot with filter paper.
- view under microscope to observe mitosis.
calculations: percentage of cells in each stage of mitosis
mitotic index. the number of cell containing visible chromosomes + total number of cells in the field of view.

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15
Q

T3 prac 5
observing mitosis
evaluation issues (3)

A
  • resolution of microscope
  • human error in counting number of cells
  • enough time in the solution to enable successful maceration or staining
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16
Q

T4 prac 6
the strength of plant fibres
variables
(2 control)

A

independent. source and type of fibre
dependent. mass that can be held
control
length of fibre
- size of each individual mass

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17
Q

T4 prac 6
the strength of plant fibres
methods and outcomes

A

method

  • plant material should be left to soak in a bucket of water for a week so fibres can be easily extracted (retting)
  • once fibres are removed, connect between 2 clamp stands and gradually add mass in the middle until the fibre snaps try with individual fibres from different plants and different ways of combining
    outcomes: the more fibres combined together the stronger it is.
18
Q

T4 prac 6
the strength of plant fibres
evaluation issues

A
  • maintaining length of fibres
  • ensuring consistency when twisting or plaiting
  • using fibres of the same age (as they get older they become more brittle)
  • extracting whole fibres that are useful.
19
Q

T4 prac 7
investigating plant mineral deficiencies
variables
(4 controls)

A

independent. minerals present
dependent. physical characteristics of the plant
control
- volume of mineral solution
- species of plant
- size of container
- amount of light received

20
Q

T4 prac 7
investigating plant mineral deficiencies
method

A
  • half fill a tube with all nutrients present solution. cover the tip with foil and push down on covering to create well.
    gently push the geranium roots of Mexican plant plant-let through hole so it is in solution. repeat with solutions lacking in nitrogen, phosphate, potassium, magnesium, calcium or lacking all. wrap all tube sin aluminium fill and place in tube holder on sunny window sill. observe regularly
21
Q

T4 prac 7
investigating plant mineral deficiences
observations

A
  • lacking nitrate. stunted growth with yellowed leaves. NO3- needed to make amino acids, nucleotides, chlorophyll, ATP and some plant growth substances
  • lacking calcium. gives gnarled and misshapen leaves. used in the formation of calcium pectate in the middle lamella, the glue between plant cells
  • lacking magnesium. causes leaves to yellow away from veins but stay green near them. important part of the chlorophyll molecule
22
Q

T4 prac 8
effect of garlic and mint on bacterial growth
variables
(4 control)

A

independent. presence of garlic or mint
dependent. zone of inhibition around disc
control:
- concentration of plant material
- lawn of bacteria on petri dish
- contamination of petri dish by other microbes
- same volume of plant material on each disk.

23
Q

T4 prac 8
effect of garlic and mint on bacterial growth
method and outcome

A

method

  • make plant extract by crushing 3g of plant material with 10cm3 of denatured alcohol. shake occasionally for 10 mins.
  • pipette 0.1 cm3 of extract onto sterile paper disc. allow to dry. meanwhile label agar plates and split into 4 sections.
  • place 1 disc of each extract in each quadrant, close and tape. leave to incubate overnight and observe zone of inhibition. carry out controls with just distilled water on discs
    outcomes: the control discs completely covered with bacteria, some plant extracts will create larger zones of inhibition than others, meaning they are more effective at lower concentrations
24
Q

T4 prac 8
effect of garlic and mint on bacterial growth
evaluation issues

A
  • growth of unwanted microbes on agar plate due to bad aseptic technique
  • not shaking extract enough to ensure enough active ingredient
  • inconsistency when adding plant extract to paper discs
  • contaminating controls
  • using wrong species of bacteria for lawn
25
Q

T4 prac 9
viewing plant fibres
method

A

cut section of a stem, transfer to a watch glass of water, transfer to slide, draw around with crayon add the dye (acidified phloroglucinol) and a cover slip, view under microscope, draw a low power plan

26
Q

T5 prac 10
observing patterns by ecological sampling
control variables

A

abiotic factors

  • light
  • temperature
  • soil water
  • humidity
  • O2 concentration
  • pH, aspect, slope angle
27
Q

T5 prac 10
observing patterns by ecological sampling
3 different methods

A
  1. random sampling
  2. systematic sampling
  3. measuring abundance
28
Q

T5 prac 10
observing patterns by ecological sampling
random sampling
systematic sampling

A

random sampling
set up grid using tape measure, use random number to generate points to place quadrant to collect data
systematic sampling
line transect often used especially to study zonation. a tape measure is laid along several zones to be looked at and quadrants are used to record data at regular intervals

29
Q

T5 prac 10
observing patterns by ecological sampling
measuring abundance

A

density = presence of organisms per quadrant
frequency = percentage of quadrant squares containing organism
percentage cover = percentage of ground covered with organism in a quadrant (usually for plants)
pitfall trap = to collect invertebrates
sweep net = to collect invertebrates in long grasses
pooter = to collect invertebrates into a container
tullgren funnel = to collect organisms from soil or leaf litter
baermann funnel= to collect living organisms from water

30
Q

T5 prac 10
observing patterns by ecological sampling
evaluation issues

A
  • constant changing abiotic conditions
  • movement of organisms
  • sampling taken within a small amount of time
  • limitations of only 1 study
  • consideration for safety of organisms
  • disruption to normal habitats
  • ethics of measuring wild organisms
31
Q

T5 prac 11
the effect of temperature on hatching success of brine shrimp
variables
(5 control)

A

independent. temperature
dependent. no. of hatched shrimp
control:
- light intensity
- pH
- salt concentration
- presence of chlorine from tap water
- oxygen concentration

32
Q

T5 prac 11
the effect of temperature on hatching success of brine shrimp
method

A
  • decide temperature range.
  • place 2g of sea salt into 100cm3 beaker. add 100cm3 of de-chlorinated water and stir until the salt completely dissolves. label the beaker.
  • place a tiny pinch of egg cysts onto a large sheet of white paper. we the piece of graph paper and dab onto the sheet picking up approx 40 eggs. use magnifying glass to count eggs
  • place the paper with 40 eggs into beaker. after 3 minutes remove paper, incubate the beakers at appropriate temperatures, controlling exposure to light.
  • count how many have hatched. by placing light next to beaker. using fine glass pipette catch the brine shrimps. record the number of larvae that have successfully hatched at each temperature
33
Q

T5 prac 11
the effect of temperature on hatching success of brine shrimp
outcomes

A

the majority of the shrimps should hatch at the optimum temperature between 25 and 30oc. (optimum at 28oc).
stats tests could be used to show evidence for data
difference = student T test or mann whitney
correlation= spearman’s rank

34
Q

T5 prac 11
the effect of temperature on hatching success of brine shrimp
evaluation issues

A
  • ethics of hatching shrimp under different conditions
  • use of animals in experiments
  • effect of light intensity, may be a difference in light in each sample
  • fluctuating temperatures
  • no accurate salt measurements
  • may not have counted exactly 40 eggs
  • may miss seeing some of the baby shrimp
  • some eggs may not be viable anymore and wont hatch.
35
Q

T6 prac 13
the effects of different antibiotics on bacteria
variables
(6 control)

A

independent. antibiotic
dependent. diameter of inhibition zone
control:
- concentration of antibiotic
- amount of antibiotic
- disc size
- bacterial species
- temperature

36
Q

T6 prac 13
the effects of different antibiotics on bacteria
method

A
  • wash hands. use aseptic technique
  • prepare an agar plate seeded with bacteria. label the petri dish on the base. flame forceps and use them to pick up antibiotic disk / mast ring and place firmly in the centre of the agar, do not seal completely keep it upside down at 30oc for 48 hours. after incubation, look carefully at the plate but do not open it. where bacteria have grown will look opaque. measure the diameter of the inhibition zones in mm.
    outcome
  • dependent on bacterial species used and antibiotics used the larger the inhibition zone the more effective the antibiotic.
37
Q

T6 prac 13
the effects of different antibiotics on bacteria
evaluation issues (5)

A
  • ensuring that the discs are placed evenly on the petri dish
  • having goof aseptic technique to prevent contamination
  • age of antibiotic, not out of date
  • repeats
  • accuracy of incubation temperature and time.
38
Q

Aseptic technique

general rules

A
  • close window and doors to reduce draughts and prevent sudden movements which might disturb air
  • make transfers over a disinfected surface
  • start operations only when all apparatus and materials are within reach
  • complete operations quickly as possible
  • vessels must be open for minimum amount of time
  • all work must be done close to Bunsen burner
  • on opening of bottle, the neck must be immediately warmed by flaming
  • during manipulations involving petri dish, limit exposure
  • all items which come into contact with microorganisms must be sterilised (by flaming) before and after
39
Q

method for observing mitosis for growth

A
  1. root tops are placed in ethanoic ethanol to preserve the structures of the cell
  2. cut 2-3mm peice from the tip because this is where the dividing cells are located
  3. place this in concentrated HCl to macerate the tissue
  4. the tip is placed on a slide and ethanoic orcein is added to stain the DNA
  5. the coverslip is added and pressed firmly to seperate the cells from each other
40
Q

procedure for investigating the effectiveness of antibiotics

A
  1. a sterile nutrient agar plate seeded with suitable bacteria
  2. apply antibiotics to a sterile filter paper disc. then lay on the bacterial lawn using sterile forceps
  3. seal petri dish allowing for gas exchange
  4. incubate below 30 oc for 24 hours
  5. look for zone of inhibition around discs the larger the area the better the antibiotic
    antiseptic technique should be used.

Biology (13 decks)

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