Biology Paper 3 Questions, Answers and Confidential - MECS Pre Mock Exams 2023

INSTRUCTIONS TO CANDIDATES

• Answer all questions

• You are required to spend the first 15 minutes of the  hours allowed for this paper reading the whole paper before commencing your work.

• Answers MUST be written on the spaces provided after each question.

• Candidates may be penalized for recording irrelevant information and incorrect spelling especially of technical terms. 

FOR EXAMINERS USE ONLY

 QUESTIONS

1. You are provided with solution M, Dilute Hydrochloric acid ,DCPIP, Benedict’s solution, 1% copper II Sulphate  solution and 10% sodium hydroxide solution. 
   Add 2m1 of hydrochloric acid to solution M and Shake.
   Filter the mixture using the filter paper and filter funnel into a boiling tube provided.
   Wash the residue from the filter paper into a beaker.
   Using the reagents provided carry out food tests on the residue and filtrate. (15 marks) 
   1. Residue
      

      Food substance being tested for	Procedure	Observation	Conclusion
      REDUCING SUGARS
      VITAMIN C
      PROTEINS

   2. Filtrate
      

      Food substance being tested for	Procedure	Observation	Conclusion
      REDUCING SUGARS
      VITAMIN C
      PROTEINS

   3. Account for the observation in (a) and (b) above.   (2mks)
   4. The physiological process demonstrated above occurs in all living things. Name two important processes in animals that depend on it. (2mks)
2. You are provided with specimen R and S 
   1.                              
      1. Give a reason why both R and S are fruits. (1mk)
      2. Why is R also a seed?  (1mk)
      3. Tabulate any two differences between specimen R and S    (2mks)
         

         Specimen R	Specimen S

   2. Using a blade provide; carefully make transverse section of specimen S.
      1. Make a labelled diagram of the cut section. Label any three parts.  (4mks)
      2. Name the type of placentation in S .Reason  (2mks)   
      3. What is the likely agent of dispersal of S? Reason (2mk
3. The photograph below is of mammalian organ
   
   
   1.                  
      1. Name the basic functional units of the organ.   (1mk)
      2. State any function of the organ above. ( 1mk)
   2. Name the parts labelled-
      A
      B
      C    (3mks)
   3. How is the blood vessel E adapted its function.(2mks)
   4. Give two differences between blood flowing through vessel E and D (2mks)
      

      Blood in E	Blood in D

MARKING SCHEME

Residue

Filtrate

Procedure marked once only for first table; 1mk each for procedure, observation conclusion Total 15marks

c) Account for the observation in( a) and (b)above. (2mks)

• Reducing sugars and vitamin c are molecules of small size ; hence diffused through the small pores of filter paper. /Proteins are particles of large molecular size ; hence they could not pass through the small pores of filter paper.

d) The physiological process demonstrated above occurs in all living things. Name two important processes in animals that depend on it. (2mks)

• Excretion/Reabsorption in the nephron
• Absorption of digested food materials
• Predation, Fertilization

2. (c) You are provided with specimen R and S

1.                              
   1.  Give a reason why both R and S are fruits. (1mk)
      • Both have two scars;
      • They have Pericarp
   2. Why is R also a seed? (1mk)
      • Have an Embryo/Cotyledon /Endosperm
   3. Tabulate any two differences between specimen R and S (2mks)
      

      R	S
      Dry/Lack fleshy/ juicy/ succulent pericarp	Has fleshy/succulent/juicy pericarp
      Its white/cream in  colour	Its orange in colour
      Lack scent	scented;
      Has no remains of sepal	Has remains of sepal

2.                         
   1. Diagram/ drawing: no shading/ drawn with free hand and not using geometric instruments, continuous, double outline of epicarp, juice bags, seed/ no openings penalize 1 mark for diagram
      Reject: if exocarp drawn as single line or dots, Transverse section, Mesocarp extending into endocarp, Seed attached onto placenta (rather than on the hollow at the centre of the fruit) 1 mark
      Labelling: plain lines (and not arrows)/ label line touching the structure. If not, encircle/ check for singular and plural. Reject: Pericarp - cancels all marks except for Seed and placenta. Award maximum of 2mks ; penalize 1 mark for any wrong labelling to a maximum of 2.
      [Award a maximum of 4marks]
      
      Magnification. Award 1 mark
      Drawing 1mk
      Labelling 1mk
      Proportionality (Endocarp about 4 times thickness of exocarp) (1mk
   2. Name the type of placentation in S .Reason (2mks)
      • Axile, Placenta centrally placed
   3. What is the likely agent of dispersal? Reason (2mk
      • Animal; Its fleshy/succulent/juicy ; scented; to attract the animal

3. The photograph below is of mammalian organ

1.                                
   1. Name the basic functional units of the organ.
      • Nephron (1mk)
   2. State any function of the organ above.
      • Excretion; Regulation of body pH, Osmoregulation; Ion balance (1mk)
2. Name the parts labelled-
   • A Medulla
   • B Cortex
   • C Ureter (3mks)
3. How is the blood vessel E adapted its function. (2mks)
   • Has a Narrow lumen to maintain high pressure of blood
   • Has thick elastic muscular wall to resist blood pressure and prevent bursting.
4. Give two differences between blood flowing through vessel E and D (2mks)
   

   Blood in E	Blood in D
   Is under high pressure	Blood under low pressure
   Blood rich in Nitrogenous waste eg Urea,	Has less amount of Urea
   Rich in oxygen	Has less oxygen

CONFIDENTIAL

• 20ml of Solution M   -A mixture of Glucose, Ascorbic acid and Egg albumen
• About  5ml of 0.1 M  Hydrochloric acid with a dropper
• Specimen R   --- A Maize grain
• Specimen   S     ----    A Ripe Orange (Orange in colour)
• A scalpel blade
• A filter paper
• A filter funnel
• A boiling tube in a rack
• 10ml Measuring cylinder
• 4 Test tubes in a rack
• A 50ml empty beaker 

• Benedict’s solution 
• 1% copper II Sulphate solution with dropper
• 10%Sodium Hydroxide solution with dropper
• DCPIP solution with dropper
• Distilled water in a wash bottle