A-level paper 3 mistakes Flashcards

1
Q

Explain how the method of setting up a potometer could be modified to produce accurate readings.

A

Don’t put the leaves under water make sure they’re dry.
Wet leaves reduce diffusion

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2
Q

Explain how a potometer could be modified to obtain repeat readings (when the bubble keeps moving)

A

Attach a syringe
To return bubble to scale

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3
Q

Describe how you would use chromotography to separate pigments in a plant leaf.

A

Add extract to start line
dry and repeat to concentrate the spot
Place paper in a solvent such as propanone
Obtain solvent front

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4
Q

Describe how to prepare a microscope slide of root tissue to show stages of mitosis.

A

Use warm acid
Remove acid using water
Add a stain such as toluidine blue
Tease with a needle
Add a coverslip and squash

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5
Q

Devise a method the student should use to investigate the effect of waterlogged soil on mitosis in root cells.

A

Place plant in water logged and non-water logged soil
Use the same species and age of plant
leave for 2 days
Control temperature and pH
Take cells from the same part of the root tip.

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6
Q

Explain why a lack of oxygen in waterlogged soil could reduce the growth of a plant.

A

Aerobic respiration will be inhibited.
Therefore oxidative phosphorylation
So less ATP synthesised
Less active transport of mineral ions
Less GP

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7
Q

Describe hoe a microscope should be used to observe the stomata using the high power lens.

A

Locate the specimen using a low power lens
Focus using low power objective lens before high power
Only use fine focus with higher power lens

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8
Q

Explain how fewer stomata might affect the growth of coffee plants.

A

Less carbon dioxide will be absorbed
So less GP produced
Less transpiration so less mineral ions
So less cellulose produced

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9
Q

Devise a method to compare the effectiveness of 4 antibiotics on the growth of bacteria.

A

Same species of bacteria
Same volume of antibiotic
Use of agar growth medium
Incubate between 20-25 degrees for 2 days
Measure zone of inhibition
Work near a bunsen flame

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10
Q

In the experiment where potato cubes are put in different concentrations of sucrose, what are 3 ways this experiment can be improved to get a more accurate value for water potential of these potato cells?

A

Use small intervals of sucrose concentration.
Blot cubes dry before weighing to remove extra mass.
Repeat to identify anomalies.
Control temperature as this affects membrane permeability.

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11
Q

Describe the steps that should be taken for the student to be able to see pollen grains using a light microscope.

A

Place pollen grains in water
Use of a coverslip
Use lowest power lens first then increase magnification

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12
Q

Explain why standard deviation may be plotted on a graph.

A

Shows variation around the mean
Therefore gives an indication of significant difference.

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13
Q

stat the difference between the action spectrum and the absorption spectrum.

A

The absorption spectrum shows absorption of light of different wavelengths.
The action spectrum shows rate of photosynthesis at each wavelength.

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14
Q

State how an action spectrum and an absorption spectrum show that chlorophyll is used in photosynthesis.

A

Spectra are similar/they overlap

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15
Q

Explain why smaller mammals have a larger oxygen consumption per kg of body mass compared to larger animals.

A

Mammals need to maintain body temperature.
Smaller mammals have a larger surface area to volume ratio.
Therefore lose more heat.
Heat is produced by respiration so more oxygen required.

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16
Q

Explain how gills are adapted for gas exchange.

A

Large surface area to volume ratio for diffusion.
Thin walls for a shorter diffusion distance.
Countercurrent system maintains concentration gradient.

17
Q

Explain why a low oxygen concentration in water will Lower the pH of the tadpole’s blood.

A

Anaerobic respiration will take place.
Therefore lactic acid will be produced.
Because the pyruvate is reduced.