BIOLOGY PAPER 3 - KCSE 2019 MOKASA PRE MOCK EXAMINATION

1. You are provided with the following: suspension labeled L, dilute HCl, NaOH, unboiled solution M₁ and boiled solution M₂.
   1. Perform procedures (i) to (iii) and in each procedure maintain the mixture at a temperature of between 34⁰C to 38^oC for 30 minutes and fill in the table that follows.
      1. Mix suspension L with 1ml of solution M₁ and add 1ml of dilute HCl to the mixture.
      2. Mix suspension L with 1ml of solution M₁ and add 1ml of NaOH solution to the mixture.
      3. Mix suspension L with 1ml of solution M₂ and 1ml of HCl to the mixture.
         Fill in the table below:   (3marks)
         

         Procedure	Observation
         i)
         ii)
         iii)

      4. Account for the difference in observation between procedure (i) and (ii)   and (i) and (iii).  (2mks)
   2. Identify solution M and give two reasons for your answer.
      1. Identity (1mark)
      2. Reason(1 mark)
   3. You are provided with specimen K, hydrogen peroxide (H₂O₂) solution, stop watch, motor and pestle. Make two cylinders each measuring 2cm long. Crush one of the potato cylinders to make a paste and add 1ml of H₂O₂ solution to each of the potato paste and cylinder.
      1. Between the two which one takes a longer time to stop producing foam?
      2. Record the time taken by the crushed potato to stop producing foam. (1mark)
      3. Account for the above difference in time taken for foam to stop forming.   (3marks)
      4. Calculate the rate of foam formation in the crushed potato cylinder. (3marks)
2. Study the diagrams below and answer the questions that follow. 
   
   
   1.  
      1. Name the parts labeled A, B, C and D. (4marks)
      2. State the adaptation of the part labeled A to its function. (2marks)
      3. State one function of the part labeled C.                                                     (1mark)
   2. State three adaptations of the parted labeled D.                                           (3marks)
   3. Identify the structures that perform similar function as D, above, in:
      1. Amoeba(1mark)
      2. Fish(1mark)

3. The diagram below illustrates the life cycle of a certain organism.
   
   
   1.  
      1. Giving reasons, name the division to which the organism belongs.
         1. Division (1mark)
         2. Reasons(2marks)
      2. Which portion of the plant’s life is independent?                                      (1mark)
   2.  
      1. Name the parts labeled A and B. (2marks)
      2. State one function of the part labeled B.                                                       (1mark)
   3.  
      1. Define the term alternation of generation.                                               (1mark)
      2. Identify the generations labeled K and L.                                                     (2marks)
      3. In what way is generation L advantageous to generation K?                   (2marks)

MARKING SCHEME

1.  
   1.  
      1. White solution turns colorless.
      2. White solution remained unchanged.
      3. White solution remained unchanged
   2. Between (1 and 2) Albumen was broken by pepsin due to acidic pH which favors the working of pepsin enzyme thus it turned colorless. Between (1and 3) No digestion took place because of an alkaline PH.
   3.  
      1. Pepsin
      2. Works under acidic conditions
   4.  
      1. Uncrushed
      2. 30 minutes
      3. Crushing the potato cylinder increased the surface area for enzyme activity hence it takes a shorter time to foam in the crushed piece, but for the uncrushed the surface area is small taking a longer time.
      4. Rate=Volume/Time.
2.  
   1.  
      1. A –Trachea.     B-Bronchus.         C-Pleural membrane.               D-Alveoli
      2. –Has rings of cartilage that keep it open
         -has cilia that move mucus and dust particles to the top of the trachea
         -lining secretes mucus, which traps dust particles and micro-organism
      3. Secretes pleural fluid that lubricates the lungs.
   2. –moist to dissolve gases
      –Thin membrane for rapid diffusion
      –Highly vascularised to maintain a steep concentration gradient for diffusion of gases.
   3.  
      1. -Cell membrane
      2. -Gill filament
3.  
   1.  
      1. Pteridophyta
         Reasons
         - It has fronds
         –Body differentiated into roots, stems and leaves but no flowers.
         –Has sori.
      2. K
   2.  
      1. A-Rhizome   B. Sori
      2. It contains sporangia that bear spores
   3.  
      1. presence of gametophyte phase and sporophyte phase in lifecycle of an organism.
      2. K-Sporophyte       L – Gametophyte
      3. Produces haploid male and female gametes, that undergo fertilization to produce zygote that develops into a sporophyte.