Core Practicals

Question 1

Describe the procedure used to test the effect of caffeine on heart rate on daphnia

Answer 1

Remove 1 daphnia and place it on a caviety slide

Remove pond water and replace with distilled water m

Then after time count and observe the heart rate *2 to work out heart rate repeat with 2 more daphnia

Repeat the steps again this time using a small concentration of caffeine solution(increaseing the concentration each time)

Repeat the experiment 3 times for 3 concentrations to obtain average

Question 2

State some control variables in the daphnia experiment and in some cases state how they could be controlled

Answer 2

Temperature
Same species of daphnia
Time(using a stopwatch)
Volume of caffeine solutions(can be obtain by using a pipette

Question 3

Explain why daphnia is used in the experiment on heart rate

Answer 3

They are simple organisms so less likely to feel pain

They are transparent so we can see the heart beat

Question 4

Describe the procedure involved in measuring the content of vitamin c in fruit juice

Answer 4

Pipette 1cm of blue DCPIP into a test tube

using a burette or pippette add 1% of vitamin C solution drop by drop,shake the tube gently after each drop

Continue to do so until the blue colour just starts to disappear

Record the volume of solution needed to decolourise the DCPIP

Repeat twice more in order to calculate the mean result,repeat the procedure with different fruit juices

Question 5

State some control variables in the measuring of the content of vitamin C solution

Answer 5

Temperature
Concentration of DCPIP solution

Shake each tube same number of times

Same end point In which blue colour disappears

Question 6

Describe the procedure involved in measuring the effect of temperature on cell memebranes

Answer 6

Using a cork borer and knife cut pieces of beetroot into 1cm length of cylinders let them dry

Place 8 boiling tubes of distilled water into 8 water baths with different temperatures

Once at temperature add a piece of beetroot to each and leave for 30 mins then remove the beetroot and let the dye disperse

Set the colorimeter to absorbance on blue and green filter and calibrate using distilled water in a cuvette

Then add 2cm3 of beetroot solution from the first temp and place it in a corvette and place it in the colorimeter and read the absorbance

Repeat procedure twice more and obtain an average

Question 7

State some control variables in experimenting the effect of Temperature on membranes

Answer 7

Time left in water

Volume of distilled water

Size of beetroot

Question 8

Describe the procedure used in investigating the effect of changing enzyme concentration on rate of reaction

Answer 8

Using distilled water make up different concentrations of enzymes

Set up a water bath for temperature to keep constant

Place 1 test tube of 5cm3 of casein dilution into water bath alonsise a second test tube containing 2cm of 0.2 trypsin

Allow to acclimatise for 3 mins so they reach the same temperature then add trypsin to casein to start the stop clock time how long it takes for casein solution to turn transparent(mark a X on other side of tube when visible stop clock)

Repeat twice more then repeat for other concentrations

Question 9

State some control variables in the effect of enzyme concentration on rate of reaction

Answer 9

Temperature
Ph
Volume of enzyme and substrate
Condensation of substrate

Question 10

In the experiment that’s investigating change in enzyme concentration of rate if reaction state why different syntinges are used

Answer 10

Different syringes are used to prevent cross contamination

Question 11

Describe the procedure when observing mitosis

Answer 11

Place a test tube of 2cm3 1m HCL into 60 degree waterbath

Cut off 1-2cm of root tip from a garlic root and place it in a watch glass containing 2cm3 of acetic alcohol for at least 12mins

Remove then place in another water glass containing ice cold distilled water

Leave for 4-5 mins then remove and dry and place into heated HCL for 5 mins and then repeat the process all over again

Transfer one tip to a microscope slide gently macerate with a needle add one small drop or precinct ethanoic stain and leave for 2 mins

Add a coverslip and blot with filter paper and view under a microscope and identify each stage of mitosis

Question 12

Describe a procedure to investigate the strength of plants fibres

Answer 12

Leave the plant material in a bucket of water for time

Then extract the fibres

Connect one fibre between two clamp stands and gradually add mass in the middle until the fibre snaps repeat to maintain a mean

Repeat the experiment on other species

Question 13

State control variable in investigating the strength of plant fibres

Answer 13

Length of fibre
Age of fibre
Size of individual mass

Question 14

Describe the procedures investigating plant mineral deficiencies

Answer 14

Fill half a tube with all nutrients present solution cover the tube with foil and push down on covering so there is well in the centre

Gently push the geranium stem into the solution below

Repeat with solutions lacking in nitrogen,potassium,magnesium,phosphate,calcium and lacking in all solutions

Wrap all in aluminium foil and place on a sunny window still and observe regularly

Question 15

State some control variables in the investigation of plant material deficiencies

Answer 15

Volume of mineral solution

Plant species

Size of container
Amount of light revived

Question 16

Describe a procedure for investigating the effect of Garlic and mint on bacterial growth

Answer 16

Make a plant extract by crushing 3G of plant material with 10cm industrial denatured alcohol shake occasionally for 10 mins

Pipette 0.1cm3 of extract into sterile paper disc

Allow to dry on sterile Petri dish

Label agar plat with date and split into 4 sections 1 for each type of plant extract place a disc of each extract into each quadrant of the agar plate

Close the tape with hazard tape

Leave to incubate over night and observe zone of inhibitions

Repeat 3 times

The larger the zone the more effective it is

Question 17

State some control variable in investigating the effect of garlic and mint on bacterial growth

Answer 17

Same volume of plant material on each disc

Concentration of plant material

Lawn of bacteria on Petri dish

Contamination of Petri dish by other microbes

Question 18

State the role of distilled water in investigating the effect of garlic and mint bacterial growth

Answer 18

It acts as a control

Question 19

Describe how you would investigate the distribution of a plant/crop in a field

Answer 19

Using a tape measure mark out 10 by 10m in to different areas of the field

Using random number generator select coordinates in the area and at the coordinates place a quadrant and calculate the percentage cover in that area repeat 20 times in each area

Make sure variables like light,temperature,soil are controlled

Furthermore repeat the experiment again and obtain an average result from percentage cover in each area

Use a statiscal test to back up your findings

Question 20

Describe a practical to test the effect of Tempe the hatching success of bribe shrimp

Answer 20

Decide on a range of temperatures from 5 to 35 to be tested

Place 2g of sea salt into 100cm beaker and add 100 cm of de chlorinated water and stir until the salt has completely dissolved

Label the beaker with sea salt and the temperature at which it will be incubated

Place a tiny pinch of egg cysts onto a large sheet of white paper,wet a piece of graph paper and use it to pick up 40 eggs from the sheet.

Put the paper with 40 eggs into a beaker upside down after 3 mins use forceps to gently remove the paper and make sure the eggs have washed off into the water

Incubate the beakers at different temperatures, the next day count the number of hatched lavre in each beaker

And record the number of larvae that have successor hatched at each temperature

To test for correlation between them use spearmans rank

Question 21

State control variables in the brine shrimp experiment

Answer 21

Ph 
Light intensity 
Salt content 
Oxygen concentration 
Presence of chlorine from Tap water

Question 22

In the brine shrimp practical state how you would count the number of hatched larvae

Answer 22

Place a bright light next to the beaker and any larvae will swim towards the light

Question 23

Describe a practical used to test the effects of different antibiotics on bacteria

Answer 23

First use aseptic techniques such as using placing the forceps in a Bunsen after every use

Prepare an agar plate that’s seeded with bacteria

Label the Petri dish on the base at the edge with the type of bacterium it’s inoculated with

Flame the forceps and use them to pick up an antibiotic disc and place it in the Petri dish and use a tape to seal the Petri dish shut

Keep it at 30 for 48 hours after incubation and look at the zones of inhibition around each antibiotic

The larger zone the more effective the antibiotic against that species

Question 24

Describe a procedure to help identify plant stems in a section

Answer 24

Use a scalpel cut a cross section of the stem and cut the sections as thinly as possible

Use tweezers to remove and place in water

Transfer each section to a dish containing a stain (toluidine blue and leave for a minute)Tbo stains lignin blue green so we can see the position of xylem and scelrencyma

The rest of the phloem remains purple

Question 25

In the mitosis practical state the reason For the use of HCL

Answer 25

To break up middle lamela so it’s easier to macerate

Question 26

State why the root tip is used in observing mitosis

Answer 26

As it’s the site of mitosis in a plant