Biology Paper 3 Questions and Answers with confidential - Form 4 End Term 1 Exams 2023

1. You are provided with the following
   25ml Bromothymol blue.
   Solution X.
   A drinking straw.
   2 test tubes.
   10ml measuring cylinder.
   A boiling tube.
   Dilute hydrochloric acid.
   Dilute sodium hydroxide.

1. 1.  Place 2ml of Bromothymol Blue (B.T.B) in a clean test tube.  Add dilute hydrochloric acid drop by drop and shake after each drop till there is a permanent colour change.
      1. State the resulting colour.                        (1mk)
      2. To the mixture obtained above, now add sodium hydroxide solution drop by drop until there is a colour change.  Record your observation. (1mk)
      3. From your observations in (a)(i) and (a)(ii) above what is the nature of Bromothymol blue. (1mk)
   2. Place 10ml of fresh Bromothymol blue in a boiling tube.  Using the drinking straw, bubble air through the bromothymol blue until there occur colour change.
      1. Record your observation. (1mk)
      2. What does the colour obtained in (b)(i) above suggest about the nature of the gas breathed out? (1mk)
   3. Rinse the measuring cylinder and use it to place 2ml of solution X in a clean test tube.  Rinse the drinking straw used in (b) above and use it to bubble air through solution X.
      1. Record your observation. (1 mark)
      2. Suggest the identity of solution X. (1 mark)
      3. Suggest the identity of the gas that gave rise to the observation above. (1 mark)
      1.  Name the physiological process in cells that leads to formation of the  gas named in c(iii) above. (1 mark)
      2. Write down a word equation for the process named in d(i) above. (2 marks)
      3. What is the importance of the identified process in cells of living organisms? (1 mark)
2. Study the photographs and answer the following questions.
   
   1. The photograph in Plate 5 shows the germination process in a species of legume.
      1.  
         1. Name the type of germination shown in the photograph.          (1mk)
         2. Give a reason for your answer. (1 mark)
      2. Other than germination the seedling have shown some responses.
         1. Name two responses shown in the photograph. (2 marks)
         2. State one survival value of each of the response named above. (1 mark)
   2. Examine the photograph in Plate 6 and Plate 7 which show different essential parts  of a flower of a species on two different plants.
      1. Name the flower parts shown in Plate 6 and Plate 7. (2 marks)
         Plate 6
         Plate 7.
      2.  
         1. Name the phenomenon described in the statement above. (1 mark)
         2. Explain the significance of the phenomena stated in (a)(i) above. (1 mark)
      3.  
         1. State the mode of pollination of the flower shown in the photograph. (1 mark)
         2. Give a reason for your answer. (1 mark)
      4.  
         1. State the type of pollination of the flower shown in the photograph. (1 mark)
         2. Give two reasons for your answer. (2 marks)
3. The photographs in Plate J, K and L shows the anterior part of two different animals,  Plate L shows the longitudinal dissection of Plate K.  Examine the photographs and answer  the questions below.
   
   1.  
      1.  State the class to which the animal organ in Plate J belongs. (1 mark)
      2. State the habitat of the animal. (1 mark)
      3. Give a reason for your answer in (ii) above. (1 mark)
   2.  
      1. Name the organ shown in the photograph in Plate J. (1 mark)
      2. State the function of the organ named above (i). (1 mark)
      3. Name the structure that protects the organ named in (b(i) above from mechanical damage. (1 mark)
      4. From observable features only explain three adaptation of the organ to ts function. (3 marks)
   3.  
      1. Identify the structure in the photograph Plate K and L. (1 mark)
      2. Give a reason for your answer. (1 mark)
      3. Using observable features only state three adaptations of the structure to its functions. (3 marks)

MARKING SCHEME

1.  
   1.  
      1.  Yellow ;
      2. Blue ;
      3. PH indicator;
      1.  Colour changes from blue to green / yellow;
      2. The gas is acidic;
      1.  White precipitate formed;
      2. Lime water / Calcium hydroxide;
      3. Carbon (IV) oxide;
      1.  (Aerobic) respiration ;
         Reject anaerobic respiration.
      2. Glucose + Oxygen; →Carbon (IV) Oxide + Water + Energy
      3. For provision of energy
2.    
   1.  
      1.  
         1.  epigeal
         2. cotyledons are above the ground
      2.  
         1. positive hydrotropism in roots
            positive phototropism in shoot.
         2. Positive phototropism
            1. Light causes lateral migration of auxins away from the light side, towards the darker side; high auxin concentration stimulates growth in the shoot ; thus the cells on darker side grew and elongated faster than the cells on the illuminated side ; causing the curvature towards light;
            2. Provides yield energy required by the cell for various functions;
         3. Positive hydrotropism.
            Water causes auxins to migrate towards the side with water / moisture, auxin, are positively hydrotropic; low auxin concentration stimulates growth in roots, auxin high concentration inhibit growth in roots; the cells on the side away from the water grow and elongated faster; leading to curvature towards water.
         4. Phototropism enables plants (shoot) to obtain optimum light for photosynthesis.
            Hydrotropism by roots enables plants to absorb water and mineral salts for metabolic processes.
   2.  
      1. plate 6 - stamen
         plate 7 - pistil
      2.  
         1.  dioecium
         2. facilitates pollination leading to variation within the species and increase in hybrid vigour.
      3.  
         1. wind pollination
         2. mall incospicuous bracts ; that are dull coloured
      4.  
         1. cross pollination.
         2.  
            • male and female parts occur in different plants.
            • the plant pollen grains are sterile to the stigma of the same plant.
3.  
   1.  
      1. Pisces
      2. Aquatic
      3. have gills for gaseous exchange
   2.  
      1. fish gills, gills
      2. Site for gaseous exchange
      3.  Operculum
      4.  
         • Have numerous gill filaments to increase the surface area for gaseous exchange.
         • Have gill rakers to trap food particles and solid materials which may damage the delicate gill filaments.
         • Have thin epithelium (blood visible) to reduce diffusion distance hence faster exchange of respiratory gases.
   3.  
      1. Trachea
      2. It is tubular; hollow ; it has ring of cartilage.
      3.  
         • Tubular/hollow to transport respiratory gases ;
         • Have rings of cartilage to keep the trachea open / prevent from collapsing.
         • Have smooth muscles to allow for stretching hence bending of the neck.