A LevelBiologyOCRExam Questions1. Development of Practical Skills in Biology1.2 Practical Skills: Endorsement Assessment

Practical Skills: Endorsement Assessment (OCR A Level Biology)

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1
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Which of the following are examples of aseptic technique?

1 Sterilising culture medium when working with microorganisms
2 Working around a lit Bunsen burner
3 Eating and drinking in the lab

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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2
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The diagram below shows a microscope view of a blood sample. An eyepiece graticule and a stage micrometer were used. The smallest divisions on the micrometer measure 10µm. What is the diameter of the erythrocyte shaded in grey?ocr-as-1-2e-mcq-q2-microscope-diagram 

  • 52 µm

  • 10 µm

  • 7 µm

  • 34 µm

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3
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What methods can be used to measure the population of a species using a quadrat?

1 Population density; calculating the number of individuals per m2
2 Percentage cover; counting the abundance within a square quadrat
3 Marking individuals of an insect species to estimate the population

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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4
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What are the benefit(s) of using computer programs to model natural selection?

1 Time can be sped up to study future outcomes of populations.
2 Various factors can be controlled or varied to study the effect on the population.
3 Computers can predict any genetic mutations which might arise, and their effects.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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5
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A student cuts three potato cylinders and places each in a different sucrose solution. The water potentials of the potato cylinders and solutions are recorded in the table below. 

Water potential (MPa)
Potato Solution 1 Solution 2 Solution 3
-0.27 -0.49 -0.61 -0.73

What should the student expect to happen to the water molecules in the potato cells?

  • Water molecules will move out of the potato cells and into the sucrose solution as there is a lower water potential in the potato.

  • Water molecules will move out of the potato cells and into the sucrose solution as there is a higher water potential in the potato.

  • Water molecules will move out of the sucrose solution and into the potato cells as there is a higher water potential in the potato.

  • There will be no movement of water molecules.

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1
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The photograph below shows a blood smear.q3-paper-2-june-2017-ocr-a-level-biology
Which row correctly lists the cells that are visible in the smear?

  erythrocytes lymphocytes monocytes neutrophils
A ✓  x ✓ ✓
B ✓  x  x ✓
C ✓ ✓ ✓  x
D x ✓ ✓ ✓

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    2
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    Scientists wanted to estimate the number of E.coli bacteria in a 25 cm3 sample.

    They carried out a serial dilution with a dilution factor of 103 and then transferred 0.1 cm3 of the solution to an agar plate to obtain a countable sample.

    75 colonies grew on the agar plate.

    Which number provides the best estimate for the number of E.coli bacteria found in the original 25 cm3 solution?

    • 5625

    • 1.875 x 107

    • 1.875 x 104

    • 750 000

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    3
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    The image below shows the stages involved in growing a culture of a bacterial species usually found in the mouth.

    aseptic-technique-1

    Which option correctly explains the reason for incubating the petri dish at 25 °C and no higher?

    • This temperature will ensure maximum growth of bacteria.

    • A temperature of 25 °C will prevent growth of harmful pathogens.

    • This is the optimum temperature for the bacterial growth.

    • This is the most energy efficient temperature.

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    4
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    Some students are dissecting a sheep's heart.

    Before they cut into the heart they decided to examine the structure as a whole and to investigate the action of the valves.

    Stage 1: The students ran water in through the vena cava and pulmonary vein.

    Stage 2: They squeezed the heart from the bottom so that the water moved out through the aorta and pulmonary artery.

    Which of the following correctly describes the position of the valves inside the heart during this process.

      Stage 1 Stage 2
    A Bicuspid valve and aortic valve open Bicuspid valve and aortic valve closed
    B Pulmonary valve and aortic valve open Bicuspid valve and tricuspid valve open
    C Bicuspid valve and tricuspid valve closed Pulmonary valve and aortic valve open
    D Bicuspid valve and tricuspid valve open Pulmonary valve and aortic valve open

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      5
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      A student investigated the effect of temperature on the cells of beetroot. The method followed by the student was as follows:

      1. Cut 6 discs of equal size from beetroot
      2. Place the discs into 6 test tubes with distilled water
      3. Maintain the temperature of the tubes at 20 °C, 30 °C, 40 °C, 50 °C, 60 °C and 70 °C
      4. After 30 minutes remove the beetroot discs and use a colorimeter to measure the percentage of light passing through the water (transmission)

      Which of the following graphs most accurately represents the results the student should expect using this method?

      R_yV1fDZ_membrane-permeability-practical-mcq

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        6
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        A student was using a light microscope to study some cells from an onion. They used an eyepiece graticule and a stage micrometer; the smallest divisions on the micrometer measured 10 μm.

        The image below shows the view through the eyepiece as seen by the students.

        eyepiece-graticule-calculation-mcq

        What is the length of the complete cell in the image?

        • 1.5 mm 

        • 18.5 µm 

        • 185 µm 

        • 74 µm 

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        7
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        Some students used a mark-release-recapture method to estimate the size of an insect population at two different sites in the UK:

        • Site 1 was a natural meadow situated 10 m from a busy motorway.
        • Site 2 was a natural meadow situated 1000 m from the nearest major road.

        The table below shows their results:

        Location Initial number captured in first sample and marked Number captured in second sample Number marked in second sample
        Site 1 321 297 39
        Site 2 57 75 5


        What is the difference in the population estimates of the two sites?

        • 1589.54

        • 3300

        • 1590

        • 2444

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        8
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        Some students carried out a series of biochemical tests on some unknown solutions to identify their contents.

        Which solution contained sucrose?

        Solution Colours observed after testing
        Benedict's test for reducing sugar Benedict's test for non-reducing sugar Iodine test for starch Biuret test for protein
        A Blue Brick red Brown Blue
        B Brick red Brick red Brown Blue
        C Blue Blue Black Blue
        D Blue Blue Brown Lilac

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          9
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          A leafy shoot was attached to a potometer and the time taken for the meniscus to move along the capillary tubing was recorded. The capillary tube had a 0.5 mm diameter.

          In one session the student measured bubble movement at a rate of 3 mm min-1

          The volume of a cylinder can be calculated using the following formula:

          V = πr2l

          To two significant figures, how much water would the plant absorb in 30 minutes at this rate?

          • 18 mm3

          • 90 mm3

          • 45 mm3

          • 17.67 mm3

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          10
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          Two agar blocks of different sizes are cut. The agar contains universal indicator, giving it a purple colour.

          rate-of-diffusion-in-agar-mcq

          The cubes were then placed in hydrochloric acid solution.

          Which of the following statements correctly explains the observations made by the student?

          • Block number 2 will turn red the fastest as it has the largest surface area to volume ratio so the rate of osmosis is faster

          • Block number 2 will turn red the fastest as it has the largest surface area to volume ratio so the rate of diffusion is faster

          • Block number 1 will turn red the fastest as it has the largest surface area to volume ratio so the rate of osmosis is faster

          • Block number 1 will turn red the fastest as it has the largest surface area to volume ratio so the rate of diffusion is faster

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          1
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          A student uses a potometer to investigate the effect of temperature on the rate of transpiration in a plant cutting. All the potometers were left for the same length of time during the investigation.

          The results from the investigation are shown below:

          Temperature (°C) Start point of bubble (mm) End point of bubble (mm) Rate of transpiration (mm/min)
          5 0 8 0.27
          10 2 14 0.40
          15 1 18  
          20 0 22 0.73
          25 1 30 0.97
          30 0 32 1.07

          Which of the following is the correct rate of transpiration at 15°C?

          • 0.57 mm/min

          • 0.60 mm/min

          • 1.67 mm/min

          • 0.56 mm/min

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          2
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          The population of roe deer in a woodland area are estimated using the mark-release-capture method. They were captured and marked with a small plastic ear-tag before being released. After 12 months the population was sampled again.

          The data collected from this study is shown below:

          Number of roe deer captured in first sample 145
          Number of untagged roe deer in second sample 86
          Number of tagged roe deer in second sample  29

           

          Which of the answers below is the correct estimate of the roe deer population in this area?

          • 194 roe deer

          • 430 roe deer

          • 575 roe deer

          • 580 roe deer

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          3
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          Which of the following statements explain why membrane permeability increases as temperature increases?

          1 The phospholipid bilayer may start to melt and break down, increasing the permeability of the membrane.
          2 Cholesterol in the bilayer decreases the fluidity of the membrane at high temperatures.
          3 The volume of water inside the cell expands, increasing the pressure on the membrane and leading to deformation of channel and carrier proteins.
          4 The 3D shape of proteins are affected as the intermolecular forces between amino acids are broken.

          • 1, 2, 3 and 4

          • 1, 2 and 3

          • 1, 3 and 4

          • 1 and 2 only

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          4
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          Which of the answers below explains why a mixture of solvents is used as the mobile phase of chromatography when separating a mixture of amino acids?

          • The different solvents will dissolve both polar and non-polar amino acids.

          • The different solvents will move at different rates to each other.

          • The amino acids will produce different Rf values.

          • The amino acids are pure and will produce a single spot on the stationary phase.

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          5
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          An investigation was completed into the effect of water potential on potato cylinders. The potato cylinders all began with a length of 5cm. The data gathered is shown below:

          Potato cylinder Final length (cm)
          A 5.3
          B 5.0
          C 4.8
          D 4.9
          E 5.2
          F 5.3

          Which of the following observations and conclusions would not be made for potato cylinders C and D?

          1 The solution has a lower water potential than the potato cylinder.
          2 The potato cylinders will feel hard.
          3 Under a microscope, the potato cells will appear plasmolysed.
          4 The potato cells have become flaccid.
          5 The solution has a higher water potential than the potato cylinder.

          • 1 and 2

          • 1, 3 and 4

          • 4 and 5

          • 2 and 5

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