Biology Paper 3 Questions and Answers with Confidential - Form 3 Mid Term 3 Exams 2023

INSTRUCTIONS TO CANDIDATES:

• Answer ALL the questions.

1. Below is a photograph of an adult human jaw with teeth. Study the diagram and answer the questions that follow.
   
   1. State the mode of nutrition in man. (1mk)
   2. Name the type of teeth labeled I and III. (2mks)
   3. Name the parts of teeth labeled H and J. (2mks)
   4. Identify one distinguishing feature between teeth labeled II and IV. (1mk)
   5. State one function of tooth IV. (1mk)
   6. Write the dental formula from the jaw shown in the photograph. (1mk)
   7. Explain why tooth I would be more prone to dental carries than tooth III, (2mks)
2. Use the hand lens provided to observe specimen K and answer the questions that follow.
   1.  
      1. In the space below draw a fully labeled diagram of representative part of the specimen. (5mks)
      2. Calculate the magnification of your drawing. (2mks)
   2. Identify:
      1. The Kingdom (1mk)
      2. The Division, to which the specimen belongs. (1mk)
      3. Give a reason for your answer in b (ii) above. (1mk)
   3. State the functions of any two parts labeled in your diagram. (2mks)
   4. What is the mode of reproduction in the specimen? (1mk)
   5. Explain the significance of colour observed in the specimen M. (2mks)
3. You are provided with solutions labeled L₁, L₂ and L₃. Note that L₃ is the same as L₂ except that L₃ has been boiled.
   Label three test- tubes A, B and C.
   Into the test- tube labeled A add 1ml of solution L₁.
   Into the test- tube labeled B add 1ml of L₁ and 1ml of L₂.
   Into the test- tube labeled C add 1ml of L₁ and 1ml of L₃.
   1. Withdraw a drop from test – tube A and place it on a white tile. To the drop add one drop of iodine solution. Record your observation in the table below. (3 mks)
      

      Test-tube	Observation	Conclusion
      A
      B
      C

      Repeat the procedure with contents in test – tubes B and C. Record your observations in the table.
      Place the three test –tubes labeled A, B and C into a water bath at 37°C.
      NB. Ensure that the temperature of the water bath does not fall below 35°C or exceed 38°C
   2. After 30 minutes, test the contents of each of the test – tubes labeled A, B and C following the procedure in (a) above. Record your observations in the table below. (6 mks)
      
      

      Test-tube	Observation	Conclusion
      A
      B
      C

   3. Why was test – tube labeled A included in the experiment? (1mk)
   4.  
      1. suggest the identity of solution L2 (1mk)
      2. Give a reason for your answer in (d) i above. (1 mk)
   5. Suggest a part of the alimentary canal in the body of a mammal where the process being investigated in the experiment would take place. (1mk)
   6. Account for the results at the end of the experiment in the test – tube labeled.
      1. B (1mk)
      2. C (1mk)

CONFIDENTIAL

• Moss plant labeled K in a watch glass / peri-dish.
• Showing (Rhizoids, leaves, seta, capsule.
• Hand lens

REQUIREMENTS

Each candidate will require the following:

• 5 test - tubes
• 5ml of solution L₁ – starch solution 0.5%
• 5ml of solution L₂ – diastase solution 10%
• 2ml of solution L₃ – Boiled diastase solution 10%
  NB: boiled for 10 minutes
• Means of labeling – 3 labels
• Water bath
• Thermometer
• Iodine solution
• 3 Droppers
• A White tile
• Means of timing

MARKING SCHEME

Question 1

1.  Omnivorous; (1mk)
2.  
   • I – Molar; (1mk)
   • IIl – Canine; (1mk)
3.  
   • H – Enamel / crown; (1mk)
   • J – Neck; (1mk)
4. Teeth II has flat top / ridged while tooth IV has chisel shaped top. (1mk)
5. Cutting / biting (1mk)
6.  
   x 2 = 32 (1mk)
7. Used more for chewing / has greater contact with food particles; // is flat broad ridged / cusped holds food remains;

Question 2

1.  
   1.  
      
   2. mg = Drawing length  = 20mm
                Objects length     10mm
             = x 2;
2.  
   1. Plantae;
   2. Bryophyta;
   3. Presence of;
      • Rhizoids;
        Male and female branches
3.  
   • Leaves – photosynthesis
   • Capsule – spore producing
   • Rhizoids – anchorage, absorption of water and mineral salts.
   • Green contains chlorophyll for photosynthesis;
4. Sporulation
5. Green hence carry out photosynthesis / autotrophic

Question 3

1.  

   Test-tube	Observation	Conclusion
   A	Blue black/blue /black/bluish black;	Starch present;
   B	Blue black/blue /black/bluish black;	Starch present;
   C	Blue black/blue /black/bluish black;	Starch present;

   ⁶/₂ = 3 marks

2.  

   Test-tube	Observation	Conclusion
   A	Blue black/blue /black/ dark blue / bluish black;	Starch present;
   B	No colour change /brown/yellow colour / colour of iodine;	Starch present;
   C	Blue black/blue /black/bluish black;	Starch present;

   6 marks
3. Control experiment
4.  
   1. Distase / enzyme /starch digesting enzyme/ ptyalin / saliva enzyme /salivary enzyme; (1mark)
   2. Because it is converted / digested / changed starch / can be denatured by boiling / acts within a range of temperature between 35°C – 38°C / optimum temperature; only 1 (1 mark)
5. Mouth / duodenum / ileum;
   NB (f) tied to table (b)
6.  
   1. B – Starch absent / No colour change /colour of iodine remains because starch has been digested / converted / hydrolysed / broken down into glucose / maltose / simple sugar; (1mark)
   2. C - Starch present because boiling denatured enzyme /L2 ; thus starch not broken down / not digested / not acted upon;