Biology Paper 3 Questions and Answers - Form 3 End Term 2 Exams 2022

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QUESTIONS

  1. You are provided with
    • Liquid cooking oil 
    • B1
    • B2 
    • Irish potato
      Label two test tubes X and Y. Into each test tube, put 2cm3 of water and 8 drops of liquid cooking oil. To the test tube labeled X add 8 drops of liquid B1, shake both test tubes and allow the content to stand for 2 minutes
      1.      
        1. Record your observations in (2mks)
        2. Name the process that has taken place in test-tube X (1mk)
        3. State the significance of the process named in a (ii) above in digestion (1mk)
        4. Name the digestive juice in humans that has the same effect on oil as liquid B1 (1mk)
        5. Name the region in the digestive system into which the juice is secreted (1mk)
      2. Label two test tubes E and F. Place 2cm3 of liquid B2 into each. Add a drop of iodine solution into each test tube.
        1. Record your observation (1mk)
        2. Suggest the identity of liquid B2 (1mk)
        3. Cut out a cube whose sides are 1cm from the irish potato provided. Crush the cube to obtain a paste and place the paste in the test tube labeled E. Leave the set up for at least 30minutes.
          Record your observation (2mks)
          Contents of test tubes F after 30 min
          Contents of test tube E after 30 min
        4. Account for the results in b (iii) above. (1mks)
      3.      
        1. Cut out another cube whose sides are 1cm from the Irish potato and crush it. Place the crushed paste into a test tube. Carry out food test with the reagent provided. Record the procedure  and results. (2mks)
          Food being tested Procedure Observation Conclusion 
        2. Account for the results in (c) (i) above. (3mks)
  2. The photographs labelled J, K and L are all related to mammalian kidney.
    1  
    1. Name the hormone produced by the structure labelled P. (1 mk)
    2. Name the parts labelled Q, R and T.  (3 mks)
    3. State the process by which wastes are filtered from blood in the structure labelled S. (1 mks)
    4.          
      1. Give two components of blood that that are not filtered at structure S.(2 mks)
      2. Give reason why the components you have named in d (i) above are not filtered. (2mks)
    5. Give two nutrients reabsorbed at the part labelled S. (2 mks)
    6. What two adaptations would be expected in the structure L in a desert animal like a camel. (2 mks)
  3. Below are drawings of specimens from plants. Study them and answer the questions that follow
    2
    1. What is the role of the specimens to the plants. (1mk)
    2. Differentiate the specimen Q from specimen R. ( 2mks)
    3. Label the parts labelled  C and D
    4. Explain what happens to the floral structures after fertilization. (4mks)
    5. With a reason state the class of plants from which the specimens were obtained. (2mks)


MARKING SCHEME

  1.      
    1.    
      1. Test tube X 
        Liquid becomes cloudy/turbid suspension formed/oil broken up into small droplets which are dispersed throughout the liquid. (The oil becomes emulsified)
        Test tube Y 
        Oil floats on the water/two separate/immiscible layers are formed
      2. Emulsification 
      3. Increased surface area for action of enzyme lipase(answer tied to a (ii))
      4. Bile
      5. Duodenum (tied to (a) (ii) and (iv) )
    2.    
      1. Blue black
      2. Starch
      3. Contents of F remain unchanged. Blue black colour in E disappears/fades/changes to pale/light yellow/light brown/orange. (Answer tied to b (ii) ) 
      4. Enzyme/Amylase in potato breaks down starch/converts/hydrolyses/changes/digests starch into maltose/reducing sugars/simple sugars that do not give a blue black colour with iodine.(1mk)
        Procedure
    3.      
      1. Add equal amount of Benedict’s solution to paste and boil in a hot water bath 
        Food being tested Procedure Observation Conclusion
        Reducing sugar

        To the food substance add equal amounts of Benedict’s solution and heat/boil (in a hot water bath) Colour changes from blue to green to yellow to orange and finally brown or colour changes to brown Reducing sugars present 
         
      2. Starch in potato is converted to maltose/glucose/reducing sugar by enzyme amylase/maltose/diastase. Rej ptylin
  2. The photographs labelled J, K and L are all related to mammalian kidney. 
    1. Name the hormone produced by the structure labelled P.:
      Adrenaline ;aldosterone (1 mk)
    2. Name the parts labelled
      Q  - Cortex   
      R –pelvis 
      T- Collecting tubule  (3mks)
    3. State the process by which wastes are filtered from blood in the structure labelled S.
      Ultrafiltration (1 mks)
    4.    
      1. Give two components of blood that that are not filtered at structure S.
        Blood cells / Plasma protein (2 mks)
      2. Give reason why the components you have named in d (i) above are not filtered. (2mks)
        They have very large molecules; structures that can filter through the pores in the glomerulus. 
    5. Give two nutrients reabsorbed at the part labelled S
      Glucose / Amino acids (2 mks)
    6. What three adaptations would be expected in the structure L in a desert animal like a camel. (3 mks)
      • Small glomerulus to reduce filtration of water. 
      • Long loop of Henle  to maximize reabsorption of minerals (sodium salt)
      • Very long distal convoluted lobule to increase surface area for water reabsorption. 
      • Highly coiled distal convoluted lobule to allow more time for water re-absorption. 
  3.    
    1. Reproduction ;

    2. R Q
      Superior  / hypogynous
      Ovary ; 
      Inferior / Ovary;Epigynous ovary 

      Monocarpous    Polycarpous / apocarpous / free capels
    3. C – Anther ;
      D- Sepal / Calyx ;
    4. The petals degenerate / weather and are shed ;
      The ovary develop into a fruit ;
      The ovules develop into seeds
      The ovary wall develop into a pericarp;
    5. Class – dicotyledonae ;
      Reason – The floral structure (anthers ) are in five in Q and 12 ( multiple of 4) in R ;

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