Biology Paper 3 Questions, Answers and Confidential - Sukellemo Joint Pre Mock Exams 2022

Instructions to Candidates

• Answer ALL the three questions in the spaces provided
• Spend the first 15 minutes of the 1 hour & 45 minutes to read through the paper carefully before commencing your work
• One may be penalized for recording irrelevant information and for incorrect spelling, particularly of technical terms
• Additional pages must not be inserted

QUESTIONS

1. You are provided with a piece of Irish potato tuber, sodium hydroxide solution, a scalpel, a test tube, hydrochloric acid, iodine solution, hydrogen peroxide and a measuring cylinder
   1. Using the scalpel provided, peel the potato and cut five equal cubes each 1cm3 Label them C1, C2, C3, C4 and C5
      1. Cut C1 into many tiny pieces and put them into a test tube Add 2ml of iodine solution Observe and record your observations (1 mark)
         Observations
      2. Allow the set-up to stand for 30 minutes Observe and record your observations (1 mark)
         Observations
      3. Account for your observations in (i) and (ii) above (2 marks)
   2.                      
      1. Put 5ml of hydrogen peroxide solution into the measuring cylinder provided Put cube C2 into the measuring cylinder and record the volume of foam produced after two minutes
         Volume ................................ cm³ (1 mark)
      2. Empty the measuring cylinder and clean it Cut C3 into smaller pieces and put them into a fresh 5ml hydrogen peroxide solution in the measuring cylinder Record the volume of foam produced after two minutes (1 mark)
         Volume cm³....................................
      3. Account for the difference in volume of foam produced by cube C3 and cube C2 above  (4 marks)
   3.                            
      1. Put 5ml hydrogen peroxide solution into a clean measuring cylinder Add 1ml of the hydrochloric acid provided into the measuring cylinder and place cube C4 inside
         Record your observations after two minutes (1 mark)
      2. Empty the measuring cylinder and clean it Put 5ml hydrogen peroxide solution into the measuring cylinder and add 1ml of sodium hydroxide solution provided Place cube C5 inside and record your observations after two minutes (1mark)
      3. Account for the difference in observations made in (c)(i) and (ii) above (4 marks)
   4. Explain the importance of the enzyme responsible for the observations above in the tissues of living organisms (2 marks)
2. You are provided with specimens H and K Observe the specimens keenly
   1. State two functions of specimen K (2 marks)
   2. Name the division and class to which specimen H belongs
      Division…………………………………………………………………………… (1 mark)
      Reason (1 mark)
      Class ……………………………………………………………………………… (1 mark)
      Reasons (2 marks)
   3. State three adaptations of specimen K for maximum photosynthesis (3marks)
   4. Explain two ways in which specimen H is adapted for survival in its habitat (2 marks)
3. Study the photographs below representing certain processes in insects Use them to answer the questions that follow
   
   
   1. With reasons, name the type of the process represented by plates 1 and 2 (2 marks)
      

      Plate	Name	Reason
      1
      2

   2. Name stages Q, R and D (3 marks)
      Q ………………………………………
      R ………………………………………
      D ………………………………………
   3. Give an advantage of the process in plate 1 over the process in plate 2 (1 mark)
   4. Arrange stages A, B, C and D in their correct sequence (1 mark)
   5. State two differences in the biological activities between the developmental sages R and S (2 marks)
   6. Insects are the most populous and widespread in phylum Arthropoda Give a reason to explain this observation (1 mark)

MARKING SCHEME

1.                        
   1.                        
      1. Colour turns blue black.
      2. Brown/yellow colour of iodine solution observed.
         Accept: blue black colour fades/less blue black/patches of blue black
      3. Starch present in the potato tuber changes iodine solution to blue black. Later starch present is hydrolysed to simple sugars/glucose/reducing sugars/maltose by enzymes (diastase) in potato tissue/cells; hence colour reverted/starts reverting to brown/yellow colour of iodine solution.
   2.                    
      1. 2.5 cm3 ±1
      2. 4.5 cm3±1   
   3. Cutting C3 into smaller pieces increased the surface area of the potato in contact with hydrogen peroxide. C2 had a smaller surface area. Enzyme present/catalase catalysed decomposition of hydrogen peroxide into water and oxygen producing more foam in C3.
   4.                        
      1. Little/no foam produced/ no (or few) bubbles produced
      2. A lot of foam produced/many bubbles produced
      3. Acidic pH conditions provided by HCl denature enzyme catalase present in potato tissue hence hydrogen peroxide not decomposed/decomposed slowly. Maximum activity of enzyme catalase requires alkaline pH conditions provided by NaOH hence faster decomposition of hydrogen peroxide into oxygen and water in (d) (ii) than in (d) (i).
      4. The enzyme breaks down hydrogen peroxide produced in cells during metabolic reactions into oxygen and water otherwise it would be toxic to cells if allowed to accumulate.
         Deny 1mk if student does not mention toxic nature of hydrogen peroxide.
2.                  
   1. Photosynthesis;
      Gaseous exchange;
      Transpiration; mark 1st two.
   2.                        
      • Division Spermatophyta; acc. Spermaphyta  penalize for wrong spelling
      • Reason
      • Body differentiated into roots, stem and leaves;
      • Class Monocotyledonae; penalize for wrong spelling
      • Reasons
      • Fibrous root system; leaves have parallel venation; leaves have sheath-like petiole; mark 1st two
   3.                            
      • Firm/rigid petiole that exposes the leaf/leaflets for maximum trapping of light/gaseous exchange;
      • Many leaflets provide large surface area for photosynthesis; rej broad leaf
      • Upper part is greener/has more chlorophyll to trap more light for photosynthesis; Thin (leaflets) to reduce distance of light penetration (to photosynthetic tissues);
        Mark 1st 3
   4.                      
      • Many / extensive fibrous roots/adventitious roots for anchorage/to absorb surface water;
      • Green leaves containing chlorophyll that traps light for photosynthesis; Hairy leaves reduce transpiration;
      • Numerous nodes allow for propagation of the plant; Mark 1st 2
3.                            
   1. See table below; mark horizontally award 1mk for each row correctly filled; max 2mks
      

      Plate	Name	Reason
      1	Complete metamorphosis	Larval form quite different from adult; accept  Four developmental stages undergone
      2	Incomplete metamorphosis	Larval forms/nymphs resemble the adult; accept three developmental stages undergone

   2. Q: Egg R: Caterpillar; reject larva; D: Nymph Q
   3. There is less competition for food in plate 1(complete metamorphosis) as the larvae and adult forms feed on different foods. There is more competition in plate 2 as both the nymph and adult feed on same food.
      The insect undergoing complete metamorphosis (plate 1) escapes adverse environmental conditions during the pupa stage(S) while the one in plate 2 does not. Mark 1st one
   4. B →D →C →A   
   5. See table below: award mk for any one correctly stated difference; mark 1st two X 2 = max 2mks
      

      R	S
      Highly mobile	Immobile/sessile/stationary
      Feeds a lot	Does not feed
      Very active physically, less active physiologically	Inactive physically, more  active physiologically

   6. Insects undergo internal fertilization after which the female lays many eggs; most have wings that make them very mobile.  

CONFIDENTIAL

Each candidate will require:

• A freshly obtained pinnate/bipinnate leaf labeled specimen K.
• A piece of Irish potato tube (a medium sized potato to be shared between four students)
• A scalpel or other means of cutting
• 5 labels
• One test tube
• A freshly obtained piece of couch grass having 2 to 3 internodes complete with roots and leaves labeled specimen H.
• Distilled water
• Stop watch or access to a wall clock
• About 15ml hydrogen peroxide
• 10ml measuring cylinder
• Access to:
• Iodine solution supplied with a dropper calibrated in ml
• Dilute sodium hydroxide solution supplied with a dropper calibrated in ml
• Dilute hydrochloric acid supplied with a dropper calibrated in ml.