Biology Paper 3 Questions and Answers - Eagle II Joint 2021 Mock Exams

INSTRUCTIONS TO CANDIDATES

• Answer ALL questions in the spaces provided in the question paper.
• You are NOT allowed to start working with the apparatus for the first 15 minutes of the 13/4 Hours allowed for this paper. This time is to enable you to read the question paper and make sure you have all the chemicals and apparatus that you may need.
• All workings MUST be clearly shown where necessary.
• Mathematical tables and silent electronic calculators may be used.

For Examiners use only.

QUESTIONS

1. You are provided with liquids L1, L2, L3, L4
   1.                              
      1. Put 3 drops of L2 on a white tile.
         Add one drop of iodine solution.
         Observation …………………………………………………………………….. [1mk]
         Conclusion ……………………………………………………………………… [1mk]
      2. Put 2cm³ of L2 into the test tube and add equal volume of Benedict’s solution and heat.
         Observation …………………………………………………………………… [1mk]
         Conclusion …………………………………………………………………… [1mk]
   2. Label two test tubes A and B. Into each of the test tubes put 2cm³ of the remaining L2 liquid.
      To test tube A, add 10 drops of liquid L1 and 10 drops of liquid L3.
      To test tube B, add 10 drops of liquid L1 and 4 drops of liquid L4
      Put the two test tubes, A and B in a waterbath maintained at between 38-39ºC for 30 minutes.
      

      Test tube	Observations
      	Iodine test	Benedict’s test
      A
      B

      Repeat iodine and Benedict’s tests in each of the test tubes and record your results in the table below. [4mks]
   3. Account for the results in:
      1. Test tube A
         Iodine test ……………………………………………. [1mk]
         Benedict’s test ………………………………............ [1mk]
      2. Test tube B
         Iodine test …………………………………………… [1mk]
         Benedict’s test ……………………………………… [1mk]
   4. Suggest the identity of liquid L1 [1mk]
   5. Why was the water bath maintained at 38oC [1mk]
2. You are provided with specimens labelled A, B, C and D.
   1. Precisely, classify the specimens [2mks]
      B ______________________________
      D ______________________________
   2.                                
      1. Cut specimen A longitudinally and make a well labelled diagram. [4mks]
      2. Calculate magnification of the drawing in b (i) above. Show your working [2mks]
   3.                          
      1. Name the agent of dispersal of the cut specimen [1mk]
      2. Give two reasons for your answer [2mks]
   4.                          
      1. Open specimen C longitudinally, observe and name the type of placentation shown. [1mk]
      2. With reason, identify the agent of dispersal and give a reason for your answer. [2mks]
3. Study the photographs below and answer the questions that follow.
   
   
   1. Name the type of structures shown by: [2mks]
      1. X & Y ……………………………………………………..
      2. W & Z ……………………………………………………..
   2. State the structural difference between structures X and Y [1mk]
   3. Name the type of evolution shown by structures Q and R [1mk]
   4. State the adaptations of structures W and Z
      W …………………………………………………..
      Z ……………………………………………………
   5. Name the types of skeletons shown by structures X and Y [2mks]
      X ……………………………………………………
      Y ……………………………………………………
   6. By comparing structures Q and R, predict the type of food being fed on by the animals and give a reason in each case. [4mks]
      Q ……………………………………………
      R …………………………………………...
   7. A part from structures X and Y, name two other examples of similar structures in animals. [2mks]

MARKING SCHEME

1. You are provided with liquids L1, L2, L3, L4
   1.                              
      1. Put 3 drops of L2 on a white tile.
         Add one drop of iodine solution.
         Observation colour of iodine solution turns to blue- black [1mk]
         Conclusion starch present [1mk]
      2. Put 2cm³ of L2 into the test tube and add equal volume of Benedict’s solution and heat.
         Observation colour of Benedict’s solution retained/persists [1mk]
         Conclusion reducing sugars absent [1mk]
   2. Label two test tubes A and B. Into each of the test tubes put 2cm³ of the remaining L2 liquid.
      To test tube A, add 10 drops of liquid L1 and 10 drops of liquid L3.
      To test tube B, add 10 drops of liquid L1 and 4 drops of liquid L4
      Put the two test tubes, A and B in a waterbath maintained at between 38-39ºC for 30 minutes.
      

      Test tube	Observations
      	Iodine test	Benedict’s test
      A	Blue black colour	Blue colour persists
      B	Colour of Iodine persists	Colour of Benedict’s soln turns yellow

      Repeat iodine and Benedict’s tests in each of the test tubes and record your results in the table below. [4mks]
   3. Account for the results in:
      1. Test tube A
         Iodine test Starch present because HCl denatured enzyme diastase/amylase [1mk]
         Benedict’s test Reducing sugars absent because HCl dentured diastase hence did not breakdown starch to maltose. [1mk]
      2. Test tube B
         Iodine test Amylase/diastase/invertase digested all starch; (to maltose) [1mk]
         Benedict’s test NaOH provided suitable pH for action of diastase enzyme of diastase enzyme starch to maltose; [1mk]
   4. Suggest the identity of liquid L1 [1mk]
      Diastase/amylase/invertase/starch digesting enzyme
   5. Why was the water bath maintained at 38ºC [1mk]
      Optimum temperature; (for action of diastase)
2. You are provided with specimens labelled A, B, C and D.
   1. Precisely, classify the specimens [2mks]
      B cypsela Rej. Wrong spelling
      D caryopsis rej. Wrong spelling
   2.                                
      1. Cut specimen A longitudinally and make a well labelled diagram. [4mks]
         
         First three clockwise
         No mark for transverse section i.e wrong diagram (wd)
      2. Calculate magnification of the drawing in b (i) above. Show your working [2mks]
         Magnification = drawing length
                                     actual length
   3.                          
      1. Name the agent of dispersal of the cut specimen [1mk]
         Animal dispersal
      2. Give two reasons for your answer [2mks]
         Succulent/juicy
         Brightly coloured
         Conspicuous
         Scented
         Hard seed coat
   4.                          
      1. Open specimen C longitudinally, observe and name the type of placentation shown. [1mk]
         Marginal placentation
      2. With reason, identify the agent of dispersal and give a reason for your answer. [2mks]
         - Self explosive mechanism
         - Presence of sutures /lines of weakness
3. Study the photographs below and answer the questions that follow.
   
   
   1. Name the type of structures shown by: [2mks]
      1. X & Y Analogous
      2. W & Z Homologous
   2. State the structural difference between structures X and Y [1mk]
                                  X                                         Y
      Pentadactyl limb structure         Toughened veins with cuticles
   3. Name the type of evolution shown by structures Q and R [1mk]
      Divergent evolution
   4. State the adaptations of structures W and Z
      W sharp and curved claws/tattoos to grasp and hold prey
      Z webbed feet to wade/swim in water
   5. Name the types of skeletons shown by structures X and Y [2mks]
      X Endoskeleton
      Y Exoskeleton
   6. By comparing structures Q and R, predict the type of food being fed on by the animals and give a reason in each case. [4mks]
      Q Nector – long and slender break to reach nectaries/nector
      R Flesh/meat – strong curved for tearing flesh
   7. A part from structures X and Y, name two other examples of similar structures in animals. [2mks]
      Eyes of man and octopus
      Flipperss in whales and fins in fish

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