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AQA GCSE Combined Science Biology Required Practical Revision
1. Microscopy 3. Osmosis 4. Food Tests 5. Enzymes
6. Photosynthesis 7. Reaction Time
9. Field Investigations
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AQA GCSE Triple Science Biology Required Practical Revision
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2. Microbiology 8. Plant Responses
10. Decay
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1. Microscopy – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Answers
Exam Style Question
Quick Questions
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Microscopy
Aim: To use a microscope to observe cells and sub-cellular structures
Apparatus:• Light microscope• Lamp• Microscope slide/Glass slide• Coverslip• Methylene blue stain/Iodine
stain• Pipette• Paper towel• Wooden toothpick/ Cocktail
stick• Onion bulb• Disinfectant• Knife & White Tile• Tweezers • Forceps
Safety:• Take care when handling slides and microscope• Anything that you have put into your mouth should
be placed in disinfectant after use• Wear gloves if using stains• Wear eye protection• Methylene blue is an irritant
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Microscopy
https://www.youtube.com/watch?v=SX6mow1AExI
Click on link below for video
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Microscopy – Quick Questions
1. Draw a labelled diagram of the onion peel cell.
2. A student is observing an ant using a digital microscope. The length of the image is 33mm. The ant's actual length is 3mm. Calculate the magnification of the image.
3. What is 3mm in micrometers?
4. If an earthworm is 19 mm long and it is photographed and the picture is magnified 2.5x how long will it be in the picture?
5. Which has a higher magnification: an electron microscope or a light microscope?
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Microscopy – Exam Style Question
6 Marks
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Microscopy - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Microscopy – Quick Questions - Answers1. Draw a labelled diagram of the onion peel cell.
2. A student is observing an ant using a digital microscope. The length of the image is 33mm. The ant's actual length is 3mm. Calculate the magnification of the image.
3. What is 3mm in micrometers?
4. If an earthworm is 18 mm long and it is photographed and the picture is magnified 2.5x how long will it be in the picture? Give your answer in cm.
5. Which has a higher magnification: an electron microscope or a light microscope?
11x
3000µm
4.5cm
Electron Microscope
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Microscopy – Exam Style Question - Answers
6 Marks
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2. Microbiology (Triple) – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Answers
Exam Style Question
Quick Questions
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2. Microbiology (Triple)Aim: Investigate the effect of antiseptics or antibiotics on bacterial growth using agar plates and measuring zones of inhibition.
Apparatus: a nutrient agar plate
a Bunsen burner
a heatproof mat
a disposable plastic pipette (sterile)
a culture of bacteria (E. coli– K12 or B strain)
a sterile glass spreader
filter paper discs.
three antiseptics (such as mouthwash, TCP, and antiseptic cream or any other suitable antisept)
1% VirKon disinfectant
forceps
clear tape
hand wash
a wax pencil
access to an incubator (set to maximum of 25°C).
Safety:
Ensure that your work spaces and hands are thoroughly cleaned before and after the experiment.
Care must be taken when handling microorganisms such as bacteria. You will use techniques called aseptic techniques during this experiment to avoid contamination.
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Microbiology (Triple)
https://www.youtube.com/watch?v=sI2Dp5fNdDY
Click on link below for video
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Microbiology – Quick Questions
1. What is the name of the glass or plastic dish we grow the microorganism in?
2. What is it called when we kill all unwanted microbes when culturing a microorganism?
3. To ensure no microbes from the air can’t contaminate inoculated Petri dishes, they must be what?
4. What is the name given to the jelly-like material contained in a Petri dish and used to grow bacteria for antiseptic or antibiotic testing?
5. How can contamination occur?
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Microbiology – Exam Style Questions
7 Marks
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Microbiology (Triple) - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Microbiology – Quick Questions - Answers
1. What is the name of the glass or plastic dish we grow the microorganism in?
2. What is it called when we kill all unwanted microbes when culturing a microorganism?
3. To ensure no microbes from the air can’t contaminate inoculated Petri dishes, they must be what?
4. What is the name given to the jelly-like material contained in a Petri dish and used to grow bacteria for antiseptic or antibiotic testing?
5. How can contamination occur?
Petri / Petri dish / Agar plate / Agar dish
Sterilising / Sterilisation
Sealed
Agar / Nutrient agar / Agar jelly / Agar gel
Contamination can occur when microorganisms from:• The surroundings get into your experiment and spoil your results• Your experiment get into the surroundings and cause a potential health hazard
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Microbiology – Exam Style Questions - Answers
7 Marks
Level 3 (5–7 marks):
A coherent method is described with relevant detail, which demonstrates a broad
understanding of the relevant scientific techniques and procedures. The steps in
the method are logically ordered. The method would lead to the collection of valid
results.
Level 2 (3–4 marks):
The bulk of a method is described with mostly relevant detail, which demonstrates
a reasonable understanding of the relevant techniques and procedures. The
method may not be in a completely logical sequence and may be missing some
detail.
Level 1 (1–2 marks):
Discrete relevant points are made which demonstrate some understanding of the
relevant scientific techniques and procedures. They may lack a logical structure
and would not lead to the production of valid results.
0 marks:
No relevant content.
Method:
1. Spraying the bench where you are working with disinfectant spray. Then wipe with paper
towels.
2. Mark the underneath of a nutrient agar plate (not the lid) with the wax pencil
as follows (make sure that the lid stays in place to avoid contamination):
divide the plate into five equal sections and number them 1, 2, 3, 4 and 5 around the edge
place a dot into the middle of each section
around the edge write your initials, the date and the name of the bacteria (E. coli)
3. Wash your hands with the antibacterial hand wash.
4. Put different antiseptics onto the five filter paper discs. This can be done by either soaking
them in the liquid or spreading the cream or paste onto them.
5. Carefully lift the lid of the agar plate at an angle. Do not open it fully.
6. Use forceps to carefully put each disc onto one of the dots drawn on with the wax pencil.
7. Make a note of which antiseptic is in each of the three numbered sections of the plate.
8. Secure the lid of the agar plate in place using two small pieces of clear tape.
9. Do not seal the lid all the way around as this creates anaerobic conditions. Anaerobic
conditions will prevent the E. coli bacteria from growing and can encourage some other
very nasty bacteria to grow.
10. Incubate the plate at 25 °C for 48 hours.
Why there is no growth:
11. Antiseptics diffuse / pass (into agar) and will kill / prevent growth of bacteria or destroy cell
wall / bacteria
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3. Osmosis – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Exam Style Question
Answers
Quick Questions
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OsmosisAim: Investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue.
Apparatus: Potato Cork borer or potato chipper/ vegetable stick
cutter Ruler 10 cm3 measuring cylinder Labels Three boiling tubes Test tube rack paper towels knife White tile Range of sugar solutions Distilled water Balance
Safety:Take care when handling the knifeDo not drink any of the solutions or eat the potatoes
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Osmosis
https://www.youtube.com/watch?v=oieXYuQm_xE
Click on link below for video
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Osmosis – Quick Questions
1. What is the independent variable in the osmosis investigation?
2. What are the control variables?
3. Why is it important to have control variables in this investigation?
4. What is the dependent variable?
5. Is osmosis a type of active transport or a type of diffusion?
6. Draw a table that you could use to record results for 0.25M, 0.5M, 0.75M and 1.0M concentrations of sugar solution.
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Osmosis – Exam Style Question
6 Marks
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Osmosis - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Osmosis – Quick Questions - Answers1. What is the independent variable in the osmosis investigation?
2. List two control variables in this investigation?
3. Why is it important to have control variables in this investigation?
4. What is the dependent variable?
5. Is osmosis a type of active transport or a type of diffusion?
Concentration of sugar solution
Initial length of potato/Initial mass of potato/Type of potato/ Amount of solution in boiling tube/Temperature/Length of time potato is left in solutions
To keep the investigation fair
Final length of potato/Final mass of potato
Type of diffusion
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Osmosis – Quick Questions - Answers
1.0 M sugar
solution
0.75 M sugar
solution0.5 M sugar
solution
0.25 M sugar
solution
Distilled
water
Initial length (cm)
Final length (cm)
Change in length
(cm)
Initial mass (g)
Final mass in (g)
Change in mass in
(g)
6. Draw a table that you could use to record results for 0.25M, 0.5M, 0.75M and 1.0M concentrations of sugar solution.
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Osmosis – Exam Style Questions - Answers
6 Marks
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4. Food Test – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Exam Style Question
Answers
Quick Questions
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Food TestsAim: To use qualitative reagents to test for a range of carbohydrates, lipids and proteins. Apparatus:• Eye protection• Water• Measuring cylinder• Spatula• Powdered foods• Test tubes, racks & bungs• Stirrer• Iodine solution• Benedict’s solution• Potassium Hydroxide solution• Copper sulfate solution• (Or Biuret’s Test)• Ethanol• Cold water• Water bath
Safety:• Wear eye protection• Wash any splashes from skin quickly• Do not taste any of the food substances• Potassium hydroxide can be harmful to the skin and eyes• Take care when using hot water bath to avoid scalding
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Food Tests
https://www.youtube.com/watch?v=akMLGbNA0gE
Click on link below for video
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Food Tests – Quick Questions
1. What is the chemical test for starch?
2. A red colour forms when a solution is heated with Benedict's reagent. What could this solution contain?
3. Biurets reagent is used to test for proteins, what colour changes will take place if protein is present?
4. What test is carried out to test for the presence of fat?
5. List two safety precautions that should be taken when carrying out food tests.
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Food Tests – Exam Style Question
6 Marks
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Food Tests - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Food Tests – Quick Questions - Answers1. What is the chemical test for starch?
2. A red colour forms when a solution is heated with Benedict's reagent. What could this solution contain?
3. Biurets reagent is used to test for proteins, what colour changes will take place if protein is present?
4. What test is carried out to test for the presence of fat?
5. List two safety precautions that should be taken when carrying out food tests.
Iodine test, will turn from an orange colour to a blue-black in the presence of starch.
Glucose
Biurets reagent, will turn from blue to purple in the presence of protein.
Emulsion test, where ethanol is added to the test sample, if fat is present the sample will turn from clear/colourless to cloudy white.
Safety goggles should be worn when carrying out the tests / Wash off spills on skin immediately / No eating or drinking during testing / Care should be taken when handling hot water
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Food Tests – Exam Style Question - Answers
6 Marks
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5. Enzymes – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Exam Style Question
Answers
Quick Questions
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EnzymesAim: To investigate the effect of pH on the rate of digestion of starch by amylase.
Apparatus:• Test tubes• Test tube rack• Water baths (electrical or Bunsen burners
and beakers)• Spotting tiles• 5 cm3 measuring cylinder• Syringes or 10 cm3 measuring cylinders• Glass rod• Stop watch • Starch solution• Amylase solution• Buffered solutions covering a range of pH,
each with a labelled syringe/ plastic pipette• Iodine solution • Thermometers
Safety:• Safety goggles should be worn
throughout.• Take care with boiling water.
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Enzymes
https://www.youtube.com/watch?v=8Yqbu56ImXk
Click on link below for video
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Enzymes – Quick Questions1. What is an Enzyme?
2. What happens to an enzyme when its active site changes shape irreversibly?
3. A student is asked to investigate the effect of pH on the enzyme amylase, which variables should be controlled in order to ensure that this investigation is fair?
a) What is the dependent variable in this investigation?b) What will be the independent variable?
4. What substance is used to test for the presences of starch in this investigation?
5. Draw a table to record your results.
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Enzymes – Exam Style Question
6 Marks
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Enzymes - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Enzymes – Quick Questions - Answers
1. What is an Enzyme?
2. What happens to an enzyme when its active site changes shape irreversibly?
3. A student is asked to investigate the effect of pH on the enzyme amylase, which variables should be controlled in order to ensure that this investigation is fair?
a) What is the dependent variable in this investigation?
a) What will be the independent variable?
A protein molecule that acts as a biological catalyst
It becomes denatured
Enzyme Concentration / Temperature
The time taken for the starch to break down
The pH
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Enzymes – Quick Questions - Answers
4. What substance is used to test for the presences of starch in this investigation?
5. Draw a table to record your results.
Iodine
pH of solution
Time taken for amylase to
completely break down the starch in
seconds (s)
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Enzymes – Exam Style Question - Answers
6 Marks
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6. Photosynthesis – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
E
Exam Style Question
Answers
Quick Questions
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Photosynthesis
Aim: To investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed.
Apparatus:
a boiling tube
freshly cut 10 cm piece of
pondweed
a light source
a ruler
a test tube rack
a stop watch
0.2% solution of sodium
hydrogen carbonate solution
a glass rod.
Safety
Care should be taken:
when handling glassware
with the use of lamps that may get hot
with the presence of water and the electrical power
supply for the lamp.
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Photosynthesis
https://www.youtube.com/watch?v=id0aO_OdFwA
Click on link below for video
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Photosynthesis – Quick Questions
1. Write down the word and symbol equation for photosynthesis.
2. What name is given to a factor which prevents an increase in the rate of photosynthesis?
3. What variables must be controlled in this investigation?
4. What is the independent variable in this investigation?
5. What is the dependent variable in this investigation?
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Photosynthesis – Exam Style Questions
6 Marks
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Photosynthesis - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Photosynthesis – Quick Questions - Answers1. Write down the word and symbol equation for photosynthesis.
2. What name is given to a factor which prevents an increase in the rate of photosynthesis?
3. A student wants to investigate the affect of light intensity on the rate of photosynthesis on pondweed, what variables must be controlled in this investigation?
4. What is the independent variable in this investigation?
5. What is the dependent variable in this investigation?
Carbon Dioxide + Water -> Glucose + Oxygen CO2 H2O C6H12O6 O2
Limiting Factor
Amount of pondweed / Temperature / Carbon dioxide concentration / Time
The distance away from light intensity
Number of oxygen bubbles produced
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Photosynthesis – Exam Style Question - Answers
6 Marks
Level 3 (5–6 marks):
A coherent method is described with relevant detail, which demonstrates a broad
understanding of the relevant techniques and procedures. The steps in the method are
logically ordered. The method would lead to the production of valid results.
Level 2 (3–4 marks):
The bulk of the method is described with mostly relevant detail, which demonstrates a
reasonable understanding of the relevant scientific techniques and procedures. The
method may not be in a completely logical order and may be missing some detail.
Level 1 (1–2 marks):
Simple statements are made which demonstrate some understanding of some of the
relevant scientific techniques and procedures. The response may lack a logical structure
and would not lead to the production of valid results.
0 marks:
No relevant content
Method: 1. Set up a test tube rack containing a boiling tube at a distance of 10 cm away from the light
source 2. Fill the boiling tube with the sodium hydrogen carbonate solution. 3. Put the piece of pondweed into the boiling tube with the cut end at the top. Gently push the
pondweed down with the glass rod. 4. Leave the boiling tube for 5 minutes. 5. Start the stopwatch and count the number of bubbles produced in one minute.
6. Record the results in a table
7. Repeat the count twice more. Then use the data to calculate the mean number of bubbles
per minute. 8. Repeat steps 1‒7 with the test tube rack and boiling tube at distances of 20 cm, 30 cm and
40 cm from the light source.
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7. Reaction Time – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Exam Style Question
Answers
Quick Questions
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Reaction TimeAim: Plan and carry out an investigation into the effect of a factor on human reaction time.
Apparatus:
a metre ruler
a chair
a table
a partner
Safety:
Care should be taken to avoid injury from the
falling ruler.
Drop test
attempts
Ruler measurements in cm Reaction times in seconds
Person 1 Person 2 Person 1 Person 2
1
2
3
4
5
6
7
8
9
10
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Reaction Time
https://www.youtube.com/watch?v=Ws5qVXYHRnQ
Click on link below for video
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Reaction Time – Quick Questions
1. What is a reflex reaction and why are they important?
2. What are effectors?
3. A student is asked to investigate whether practice reduces human reaction times, what variables should be kept the same to ensure the investigation is fair?
a) What is the dependent variable in this investigation?
b) What is the independent variable?
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Reaction Time – Exam Style Question
6 Marks
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Reaction Time - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Reaction Time – Quick Questions - Answers
1. What is a reflex reaction and why are they important?
2. What are effectors?
3. A student is asked to investigate whether practice reduces human reaction times, what variables should be kept the same to ensure the investigation is fair?
a) What is the dependent variable in this investigation?b) What is the independent variable?
A fast reaction that bypasses the brain / to protect you from harm
Muscles & Glands
The height the ruler is dropped from/Hand used
Reaction time
The number of attempts
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Reaction Time – Exam Style Question - Answers
6 Marks
Level 3 (5–6 marks):
A coherent method is described with relevant detail, which demonstrates a broad
understanding of the relevant scientific techniques and procedures. The steps in the
method are logically ordered. The method would lead to the collection of valid results.
Level 2 (3–4 marks):
The bulk of a method is described with mostly relevant detail, which demonstrates a
reasonable understanding of the relevant techniques and procedures. The method may
not be in a completely logical sequence and may be missing some detail.
Level 1 (1–2 marks):
Discrete relevant points are made which demonstrate some understanding of the relevant
scientific techniques and procedures. They may lack a logical structure and would not lead
to the production of valid results.
0 marks:
No relevant content.
Method:
1. use decaffeinated coffee as control
2. control volume of coffee
3. blind trial or do not tell students which coffee they are drinking
4. left for standard time between drink and test
5. at least 10 minutes
6. control start position of ruler
7. control other factors such as light in the room
8. same person for different concentrations
9. repeat for each caffeine concentration
10. use a range of caffeine concentrations
11. start with lowest concentration of caffeine
12. use caffeine solution instead of coffee to control for other ingredients
13. repeat investigation with more people and calculate means
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8. Plant Responses (Triple) – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Answers
Exam Style Question
Quick Questions
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8. Plant Responses (Triple)
Aim: Investigating the effect of light intensity on the growth of mustard seedlings
Apparatus:
white mustard seeds
petri-dishes
cotton wool
a ruler
water
access to a light windowsill and a
dark cupboard
Safety:
Wash hands after handling seeds
DayHeight of seedling in full sunlight in mm
1 2 3 4 5 6 7 8 Mean
1
2
3
4
5
6
7
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Plant Responses (Triple)
https://www.youtube.com/watch?v=fEo21LbnJJM
Click on link below for video
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Plant Responses – Quick Questions
1. What term is used to describe a growth movement in plants?
2. What chemicals control growth movements in plants?
3. What is the name of the hormone that controls phototropism and gravitropism?
4. When investigating the effect of light intensity on the growth of mustard seedlings, list two variables that need to be controlled to make this investigation fair.
5. What would be the dependent variable in this investigation?
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Plant Responses – Exam Style Questions
6 Marks
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Plant Responses (Triple) - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Plant Responses – Quick Questions - Answers
1. What term is used to describe a growth movement in plants?
2. What chemicals control growth movements in plants?
3. What is the name of the hormone that controls phototropism and gravitropism?
4. When investigating the effect of light intensity on the growth of mustard seedlings, list two variables that need to be controlled to make this investigation fair.
5. What would be the dependent variable in this investigation?
Tropism
Auxins / Plant hormones / Growth hormones
Auxins
Type of seed / Nutrients / Volume of water given / Number of seeds
Height of seedlings
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Plant Responses – Exam Style Questions - Answers
6 Marks
Level 3 (5–6 marks):
A coherent method is described with relevant detail, which demonstrates a broad
understanding of the relevant scientific techniques and procedures. The steps in the
method are logically ordered. The method would lead to the collection of valid results.
Level 2 (3–4 marks):
The bulk of a method is described with mostly relevant detail, which demonstrates a
reasonable understanding of the relevant techniques and procedures. The method may
not be in a completely logical sequence and may be missing some detail.
Level 1 (1–2 marks):
Discrete relevant points are made which demonstrate some understanding of the
relevant scientific techniques and procedures. They may lack a logical structure and
would not lead to the production of valid results.
0 marks:
No relevant content.
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9. Field Investigations – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
E
Exam Style Questions
Answers
Quick Questions
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Field InvestigationsAims:
1. Investigating the population size of a plant species using random sampling.
2. Investigating the effect of a factor on plant distribution using a transect line.
Apparatus:
a 25cm x 25cm quadrat
2 x 30 m tape measure
a clipboard
a pen
Paper
Optional: Identification
charts and pencil
Safety:• Consider the safety
aspects of your chosen site, such as poisonous plants, animal faeces or open water and take appropriate precautions while working.
• Wash hands after investigation.
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Field Investigations
https://www.youtube.com/watch?v=yLHz2Ea10Mg
Click on link below for video
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Field Investigations – Quick Questions
1. Environments are sometimes sampled along a straight line.
What is such a line called?
2. Two students visited two locations and measured the lichens on nine trees in each place. Their results are below.
Calculate the mean for each location. Give your answer to one decimal place.
3. A student wants to investigate the population size of daisies in trampled and un-trampled parts of a school field, what variables should be controlled in this investigation?
Location Tree 1 Tree 2 Tree 3 Tree 4 Tree 5 Tree 6 Tree 7 Tree 8 Tree 9
London 4 6 11 13 4 2 6 2 4
N. Wales 21 13 18 7 16 2 5 19 1
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Field Investigations – Exam Style Questions
7 Marks
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Field Investigations - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Field Investigations – Quick Questions - Answers
1. Environments are sometimes sampled along a straight line.
What is such a line called?
2. Two students visited two locations and measured the lichens on nine trees in each place. Their results are below.
Calculate the mean for each location. Give your answer to one decimal place.
3. A student wants to investigate the population size of daisies in trampled and un-trampled parts of a school field, what variables should be controlled in this investigation?
Location Tree 1 Tree 2 Tree 3 Tree 4 Tree 5 Tree 6 Tree 7 Tree 8 Tree 9
London 4 6 11 13 4 2 6 2 4
S. Wales 21 13 18 7 16 2 5 19 1
Transect Line
London mean = 5.8 South Wales mean = 12.9
Type of species / Size of quadrat
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Field Investigations – Exam Style Questions - Answers
7 Marks
Level 3 (5-7 marks):
A very detailed and coherent description is given as to how quadrats are used and an
explanation is given which makes logical links between clearly identified relevant points as
to why daisy growth may be limited.
Level 2 (3–4 marks):
A detailed and coherent explanation is given. Logical links between clearly identified
relevant points are made to explain why daisy growth may be limited.
Level 1 (1–2 marks):
Discrete relevant points are made. The logic may be unclear.
0 marks:
No relevant content
How quadrats should be used:
(placed) randomly 1
sufficient number (of quadrats) used 1
count (daisies) in each quadrat 1
use mean number of daisy, area of quadrat and area of field to estimate population
accept (area of field / area quadrat) × mean number of daisies per quadrat
1 Factors that may be considered:
competition for resources including:
• light • water
• space
• mineral ions (allow nutrients / salts / ions from the soil) 1
Why growth may be limited:
• (light) energy for photosynthesis
• water as a raw material for photosynthesis / support
• surface area exposed to light
• sugar / glucose produced in photosynthesis
• (space) to grow bigger
• (space) for growth of root system
• (mineral ions) for growth
• (mineral ions / sugar) for production of larger molecules or named
example 2
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10. Decay (Triple) – Topic Menu
Required Practical Tutorial
Aims, Apparatus & Safety
Answers
Exam Style Question
Quick Questions
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10. Decay (Triple)Aim: Investigating the effect of
temperature on the rate of decay of fresh
milk by measuring pH change.
Apparatus: a small beaker containing full fat milk or single cream
a small beaker containing sodium carbonate solution
a small beaker containing lipase solution
250 cm3 beakers, to be used as water baths
test tubes
a test tube rack
a marker pen
10 cm3 plastic syringes
a stirring thermometer
a stop clock
Cresol red or Phenolphthalein indicator
an electric kettle, for heating water
ice, for investigating temperatures below room temperature.
Safety:
Sodium carbonate solution is an irritant
above certain concentrations
There is an allergen risk with all
enzymes for some individuals, care
should be taken when handling.
Note: The natural process of decay in milk is to slow to monitor in normal class time. Therefore this procedure should serve as a model for the investigation of decay in milk.
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Decay (Triple)
https://www.youtube.com/watch?v=zSx83-D-LYE
Click on link below for video
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Decay – Quick Questions1. An experiment into decay was carried out at three different
temperatures: 10°, 15° and 20°. At which temperature would you expect the rate of decay to be fastest?
2. True or false? Decay happens fastest in the absence of oxygen.
3. Microorganisms digest waste material faster in conditions that are aerobic, warm and what else?
4. When investigating the effect of temperature on the rate of decay of fresh milk by measuring pH change, list two variables that must be kept the same to ensure the experiment is fair.
5. What is the dependent variable in this investigation?
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Decay – Exam Style Questions
6 Marks
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Decay (Triple) - Answers
Quick Questions - Answers
Exam Style Question - Answers
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Decay – Quick Questions - Answers1. An experiment into decay was carried out at three different temperatures: 10°,
15° and 20°. At which temperature would you expect the rate of decay to be fastest?
2. True or false? Decay happens fastest in the absence of oxygen.
3. Microorganisms digest waste material faster in conditions that are aerobic, warm and what else?
4. When investigating the effect of temperature on the rate of decay of fresh milk by measuring pH change, list two variables that must be kept the same to ensure the experiment is fair.
5. What is the dependent variable in this investigation?
20
False
Moist / Damp
Volume of milk / amount of lipase enzyme added / volume of sodium carbonate solution
Time taken for the solution to change colour indicating decay
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Decay – Exam Style Questions - Answers
6 Marks
Level 3 (5–6 marks):
A coherent method is described with relevant detail, which demonstrates a broad
understanding of the relevant scientific techniques and procedures. The steps in
the method are logically ordered. The method would lead to the collection of valid
results.
Level 2 (3–4 marks):
The bulk of a method is described with mostly relevant detail, which demonstrates
a reasonable understanding of the relevant techniques and procedures. The
method may not be in a completely logical sequence and may be missing some
detail.
Level 1 (1–2 marks):
Discrete relevant points are made which demonstrate some understanding of the
relevant scientific techniques and procedures. They may lack a logical structure
and would not lead to the production of valid results.
0 marks:
No relevant content.
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