Biology Paper 3 Questions and Answers - BSJE Mock Exams 2023

• Answer all the questions
• You are required to spend the first 15 minutes of the 1 ¾ hours allowed for the paper reading the whole paper carefully before commencing your work.

                                                                               Answer all the questions.

1. You are provided with specimen K. Use it to answer the questions that follow.
   1. Cut a traverse section of specimen K and draw a well labeled diagram of the cut surface. (3 marks)
   2. State the type of placentation of specimen K. (1 mark)
   3. Apart from the placentation named in (ii), name two other form of placentation. (2 marks)
   4. Squeeze out the juice from two halves of the specimen K and put it in a beaker.  Using the reagents provided, carry out test to identify the food substances present in the juice. (6 marks)
      

      Food substance	Procedure	Observation	Conclusion
      Protein
      Non reducing sugars

2. You are provided with the following:
   • Specimen Y
   • Hydrogen peroxide
   • 2 test tubes in a test tube rack.
   • 2 labels
   • 10ml measuring cylinder.
   • A scalpel.
   • 2 wooden splints.
   • 100ml beaker.
     Procedure
     1. Label two test tubes A and B.
     2. Measure 2cm³ of hydrogen peroxide and put in test tube A.  Repeat the same procedure for test tube B.
     3. Cut a small piece of specimen Y to two smaller pieces using a scalpel.  Place one of the pieces in test tube A and retain the other piece for the subsequent procedure for test tube B.
     4. Immediately, introduce a glowing splint into the mouth of the test tube.  Record your observations in the table below.
     5. Put the other piece of specimen Y in an empty 100ml beaker then add 50ml boiling water from a hot water bath maintained at 80°C. Leave the set up for 5 minutes
     6. Remove specimen Y from the boiling water using a pair of forceps and place in test tube B.  Immediately, introduce a glowing splint at the mouth of the test tube.  Record your observations in the table below.
        1. Record your observations in this table
           

           Test tube	Observations
           	On placing specimen Y	On introducing a glowing splint
           A	(i)                                      (1mark)	(1mark)
           B	(1mark)	(1mark)

        2. Explain your answers in (a).
           1. A (3 marks)
           2. B (1 mark)
        3. State the role of experimental set up in test tube B. (1 mark)
        4. Specimen Y is an organ in animals.  Name the organ and state two other functions apart from the one being investigated above.
           Name of organ (1 mark)
           Functions (2 marks)
3.  
   1. Examine the photograph shown below.
                                                
      1. Name the response shown by the plant labelled X. (1 mark)
         Explain how the response you have stated above occurs. (3 marks)
      2. State one biological significance of the response stated in (i) to the plant X. (1 mark)
      3. Name two tissues in herbaceous plant that enhance support. (2 marks)
   2. The photographs below show two skeletal limbs (A and B) of a certain mammal.
                                   
      1. Which of the skeletons represents a fore limb. (1 mark)
      2. State one observable features on the skeleton to confirm your answer in (i) above. (1 mark)
   3.  
      1. Name the bones labelled. (2 marks)
         J …………………
         K …………………
      2. Which bone forms a second joint with the bone labelled K. (1 mark)
      3. Name the type of joint formed at the part labeled L. (1 mark)
      4. Give one reason for your answer in (v). (1 mark)
      5. A part from the bones, state the function of any one other component of a joint. (2 marks)
         Component                         Function

                                                                                       MARKING SCHEME

1.  
   1.  
             
      Conditions for a biological drawing
      • Continuous outline D1
      • No shading 1 mark
      • Transverse section – D2 1 mark
        Labels
      • Labeling line must touch intended structure
      • Labeling line must be continuous
      • No arrowheads
      • No criss-crossing
      • Label must be singular if 1 labeling line touches 1 structure                    Any 2 correct labels
   2.  Axile (placentation); (1 mark)
   3.  
      • Parietal;
      • Marginal;
      • Basal;
      • Free central;                      Mark 1^st 2 correctly spelled placentation
   4.  
      

      Food substance	Procedure	Observation	Conclusion
      Protein(s)	To (2ml of) food substance, add (equal amount   of) sodium hydroxide solution then add copper   (II) sulphate solution dropwise;                                                        (1 mark)	Blue colour (of copper   (II) sulphate solution)   retained;                                                  (1 mark)	Protein(s)   absent;               (1 mark)
      Non   reducing   sugar(s)	To (2ml of) food substance, add (2 drops   of) hydrochloric acid, heat, cool; add   sodium hydrogen carbonate solution   dropwise until fizzing stop.  Add (equal   amount of) Benedict’s solution then   heat/boil/warm/place in hot waterbath;                                                                                                                                           (2 marks)	Green colour observed;     Yellow/orange/brown;                                                         (1 mark)	Non-reducing sugar(s) present;                     (1 mark)

      
      Distribution of marks:
      • Food substance column – see correct food substance but do not award marks.
      • Procedure – use correct chemical symbols of reagent if words are not used.
      • Observation – reject alternative colours.
      • Conclusion – correctly spelled food substance and traces of for green colour in non-reducing sugar.
2.  
   1.  
      1. (5 marks)
         

         Test tube	Observations
         	On placing specimen Y	On introducing a glowing splint
         A	(i) Formation of foam/production of                         bubbles/effervescence produced                                                            (1mark)	Glowing splint relights/                           rekindles;                                        (1mark)
         B	No foam /no bubbles/ effervescence                   produced                                   (1mark)	Glowing splint does not            relight/ rekindle;                                           (1mark)

      2. Tied to (a)
         1. Catalase (enzyme); breakdown hydrogen peroxide; into water and oxygen; (3 marks)
         2. Boiling denature catalase enzyme; (therefore breakdown of hydrogen peroxide hence no oxygen formed) (1 mark)
      3. Control experiment; reject acts as a control experiment.
      4. Name of organ:  Liver;
         Functions:
         • Blood sugar regulation;
         • Deamination;
         • Thermoregulation;
         • Haemoglobin regulation;
         • Regulation of plasma proteins;
         • Manufacture of red blood cells during foetus stage;
         • Formation and elimination of excess cholesterol;
         • Storage of blood;
         • Storage of vitamins B, C, E, K and mineral; Mark 1st 2
3.  
   1.  
      1. Thigmotropism/haptotropism;
         • Tied to (a) (i).  The contact part on the stem causes auxins to migrate to opposite side; the higher auxin concentration; on the opposite side stimulates faster/rapid cell elongation; leading to coiling/bending; of the stem       4marks maximum 3 
      2. Enables the plant to get support in order to expose the leaves to light for photosynthesis;
         • To get support to expose flowers in position for pollination;
         • To get support to expose fruits for effective dispersal;
      3.  
         • Parenchyma;
         • Collenchyma;
         • Sclerenchyma;
         • Xylem vessels      1st 2 correct  
   2.  
      1. A
      2. Tied to (b) (i)
         • Presence of scapula borne;
         • Presence of olecranon process
   3.  
      1. J – Radius;
         K – Femur;
      2. Hip bone
      3. Hinge joint
      4. Allows movement in one plane/180o 
      5. Component                            Function
         • Cartilage                              - Joins bone and a bone and reduces friction
         • Synovial fluid                       - Lubricates joints, act as shock absorber/reduces friction;
         • Synovial membrane             - Secretes synovial fluid;
         • Ligament                              - Restrains movement of the bones;
         • Tendon                                 - Attaches a muscle to a bone
                      Component is tied to function  (mark 1st one)