BIOLOGY PAPER 3 - KCSE 2019 NYANDARUA PRE MOCK EXAMINATION

1. You are provide with a food solution mixture labeled Y. you are also provided with the following reagents. 1% copper (II) sulphate solution, 10% sodium hydroxide solution, 0.1% DCPIP solution and a filter paper. Carry out tests to determine the food substances present in Y (12 marks)
   

   Food substance being tested	Procedure	Observation	Conclusion

2. The Diagram below shows two organisms (R and S) belonging to the same phylum
   
   
   1. Name the class in which the organisms shown above belong.                                     (2 Mark)
      1. Organism R
      2. Organism S
   2. Other than presence of exoskeleton, listtwo observable similarities between the two organisms (2 Marks)
      

      R	S

   3. Listtwo observable differences between the two organisms (2 Marks)
      

      P	S

   4. Explain how the organism labelled P is adapted to safeguard itself from the predator (2 Marks)
   5.  
      1. Name the gaseous exchange system exhibited by organism S (1 Mark)
      2. State the respiratory surface used by organism S (1 Mark)
   6. Discussfour functions of exoskeleton                                                                        (4 Marks)
3. The following micrographs show images taken from a transverse section of a various stems by a light microscope. Analyze them closely and use them to answer questions that follow.
   
   
   1. On the diagram, label part A, B and C                                                        (3 Marks)
   2. Explain the adaptation of the parts C and D to their functions (2 Marks)
   3. Identifyfive differences between cross section T and Q and record them in the table below. (5 Marks)
      

      T	Q

   4. Explain how part B facilitates the process of secondary growth (4 Marks)

MARKING SCHEME

Question 1.

-4 mark each (12 marks in total). Marks for procedure occur at the end of the collect procedure.

-Reject colour stroking. If procedure is wrong, all the succeeding sections are wrong.

Question 2.

1.  
   1. Arachnida;
   2. Insecta; rej. When word start with small letter.
2. - Jointed appendages;
   - Bilateral symmetry;
   - Have segmented body;
3.  
   

   R	S
   -Body is divided into two parts (Cephalothorax)	- Body is divided into three parts;
   - Two chelicerae each having a craw-like structures	-Does not have chelicerae;
   - Each leg ends into two toothed craw	-Does not have toothed craw;
   - Arachnids have no antennae	-Have a pair of antennae;

4. -The body colour that matches with the surrounding and therefore the predator cannot be able to identify and attack the organism.
   -Lower side of the hind limb/tibia has spikes to strike the predator/any other relevant explanation
5.  
   1. Tracheal system
   2. Tracheole/tracheoles
6. -It provides support to terrestrial arthropods;
   -It also provides point of attachment for body muscles;
   -It prevents desiccation of the body and by secreting wax;
   -It protects the organism from mechanical injury;

Question 3.

1. A-Vascular bundles;   
   B- Intravascular cambium/cambium;  
   C- Sclerenchyma;
   labeling must be done on the diagram, not on the space provided.
2. C- Thickened by lignin to provide mechanical support and strengthening the plants;
   D -Consist of numerous parenchyma cells that store water and food substances;
   -Packed with storage tissues to store of food and water;
3.  
   

   T	Q
   No pith	Pith present
   Vascular bundles scattered	Vascular bundles in a ring
   Numerous vascular bundles	Few vascular bundles
   Cambium Absent	Cambium present
   Small Vascular bundles	Large Vascular bundles

4. -Inner cambium/cambial cells divide and increase in number thereby forming secondary xylem;
   -Secondary xylem push primary xylem cells toward the center;
   -Outer group of cambium/cambial cells divide and increase in number thereby forming secondary phloem;
   - Secondary phloem pushes primary phloem cells toward the periphery;
   - Plant stems increases in girth/diameter
   5 max 4-each point one mark