KCSE 2015 Biology Paper 3 with Marking Scheme

1. Using the pictures of animals provided below, complete the construction of the dichotomous key by filling the blank spaces. (13 marks)
   
   
   1.     
      1. Animals with a backbone  ............................ go to 2
         
      2. Animals without a backbone ........................
   2.     
      1. Animals with wings ............................ 
      2. Animals without wings .......................
         
         
   3.     
      1. Animals which live in water all the time............................ 
      2. Animals which live in water some time ............................
         
         
   4. 1. Animals with scales.............................
      2. Animals without scales........................
         
         
   5.    
      1. Animals with legs ............................ 
      2. Animals without legs ........................ go to 7
         
         
   6.   
      1. Animals with six legs............................ Butterfly
      2. Animals with eight legs..........................
         
         
   7.     
      1. Animals with a shell ............................ Snail
      2. Animals without a shell.........................
         
         
   8.    
      1. Animals with a jelly-like body ............................ 
      2. Animals without a jelly-like body........................
         
         
   9.    
      1. Animals with a segmented body ............................ 
      2. Animals without a segmented body ....................... Octopus
2. Below are pictures of three mammalian vertebrae.
   
   
   1. Name the type of vertebra labeled
      F ......... (1 mark)
      G ......... (1 mark)
      H .........(1 mark)
   2. Label five parts of the vertebra labeled H. (5 marks)
   3. Name the articular facets labeled K and L.
      K......... (1 mark)
      L ......... (1 mark)
   4. How does each of the parts of a vertebra enable a mammalian skeleton to carry out its functions? (4 marks)
3. You are provided with a 250 ml beaker, four test tubes, solutions labeled D and E, iodine and Benedict’s solution.
   Half fill the beaker with the hot water provided to create a hot water bath.
   
   1. Label the four test tubes as follows:
      
      1. Test tube 1, D + iodine
      2. Test tube 2, D + E + iodine
      3. Test tube 3, D + Benedict’s solution
      4. Test tube 4, D + E + Benedict’s solution
         
   2. Put 1 cm³ of solution D in each of the four test tubes.
   3. To the solution D + Iodine test tube, add only one drop of iodine solution and shake to mix.
   4. To the D + E + Iodine test tube, add 1 cm³ of solution E and two drops of iodine solution and shake to mix.
   5. To the D + Benedict’s solution test tube, add 1 cm³ of Benedict’s solution and shake to mix.
   6. To the D + E + Benedict’s solution test tube, add 1 cm³ of solution E and 1 cm³ of Benedict’s solution. Shake to mix.
   7. Observe the changes in each of the four test tubes.
   8. Put all the four test tubes in the hot water bath and observe carefully for about five minutes.
   1. Record the observations and conclusion for each of the four test tubes in the table below. (8 marks)
      

      NO	TEST TUBE	OBSERVATION	CONCLUSION
      1	D + Iodine
      2	D + E + Iodine
      3	D + Benedict's solution
      4	D + E + Benedict's solution

   2. What was the role of each of the following in the experiment?
      
      1. Solution E (1 mark)
      2. Hot water bath (1 mark)
   3. Give the identity of E in human beings. (1 mark)
   4. Explain the observation made on the reagents tested with Benedict’s solution. (1 mark)

MARKING SCHEME

1.      
   1. (b) go to 5;
   2.    
      1. Eagle;
      2. go to 3;
   3.    
      1. Fish;
      2. go to 4;
   4.    
      1. Tortoise;
      2. Frog;
   5. 1. go to 6;
   6. (b) Spider;
   7. (b) go to 8;
   8.    
      1. go to 9;
      2. Starfish;
   9.    
      1. Earthworm (13 marks)
2.    
   1. F Cervical/Cervical bone; (1 mark)
      G Thoracic/Thoracic bone; (1 mark)
      H Lumbar/Lumbar bone; (1 mark)
   2. 
      
      Labels ⁶/₂ = 3 marks
      Labels touching object = 1 mark
      Labels not crossing = 1 mark
      maximum = 5 marks
   3. K - Tubercular (facet);
      K - Capitular (facet); (2 marks)
   4.      
      • (Large) centrum to support the body vertebrae;
      • Neural arch to protect the spinal cord;
      • (Extended) transverse processes for attachment of (abdominal) muscles;
      • (Long) neural spine for attachment of abdominal muscles/ligaments;
      • Facets for articulation with other vertebrae;
      • Neural canal for passage of spinal cord (4 marks)
3.    
   1. 
      

      NO.	TEST TUBE	OBSERVATION	CONCLUSION
      1	D+Iodine	Turns blue black/blue/black:	Starch present;
      2	D+E+Iodine	Turns colourless/blueblack colour disappears	Starch absent/decreases;
      3	D+Benedict's solution	Remains blue/no colour change;	Reducing sugars absent;
      4	D+E+Benedict's solution	Turns green, yellow, orange, blown/reddish blown	Reducing sugars present;

      (8 marks)
   2.    
      1. Breaks down (hydrolyses) starch; into maltose/reducing sugar; (2 marks)
      2.    
         • Provides optimum suitable temperature; for activity of E/enzymes;
         • Required when testing for reducing sugars using Benedict's solution;
         • Activates enzymes.
   3. Salivary amylase or ptyalin/ amlyse/pancreatic amylase. (1 mark)
   4. Substance D tests negative with Benedict's solution because it is a complex/ polysaccharide; addition of E on heating gives positive results with Benedict's solution, since E hydrolyses, the starch/ complex sugar into simple sugars; testing positive.
      OR
      Starch in D/D is a non-reducing sugar/complex sugar/polysaccharide/not a reducing sugar, startch is hydrolysed/digested/broken down into reducing sugars by E/Amylase in E/Amylase/Diastase/enzyme in E. (2 marks)