Biology Paper 2 Questions and Answers - Sukellemo Joint Mock Examinations July 2020

INSTRUCTIONS TO CANDIDATES

• Write your Name, School and Index number in the spaces provided. 
• Answer all questions in section A in the spaces provided. In Section B, answer question 6 (compulsory) and either 7 or 8 in the spaces provided after question 8.
• Candidates should answer all the questions in English.

FOR EXAMINERS USE ONLY

QUESTIONS

SECTION A
(Answer ALL questions in this section)

1. In a biology lesson, some students obtained a young stem and split it half way along the length as shown in diagram A. They then placed it in solution Y for two hours before making observations, The results were as shown in diagram B.
   1. What was the nature of solution Y? (1 mk)
      
   2. Explain why the stem curved as shown in diagram B. (4mks)
   3. State three roles of active transport in organisms. (3mks)
2.                                
   1. In human, premature baldness is controlled by a gene on the Y chromosome. Using B to represent the gene for baldness, work out a cross between a bald man and his wife. (4 mks)
   2.                        
      1. What is the probability of their daughters being bald? (1 mk)
      2. Give a reason for your answer. (1 mk)
   3. Name one trait in human beings that is determined by multiple allele (1mk)
   4. Name one genetic disorder affecting the human eye (1 mk)
3. The experiment below was set-up to investigate some physiological processes. The glucose solution was first boiled then cooled. The set-up was left for 24hrs.
   
   
   1. Suggest two aims of the experiment. (2mks)
   2.                                    
      1. State the expected observations after 24 hours. (2mks)
      2. Explain your observations in a (i) above. (1 mk)
      3. Why was glucose solution boiled then cooled? (1 mk)
      4. Suggest a control for the above experiment (1 mk)
      5. State the practical application of the process being investigated in industry (1 mk)
4. The picture below represents an evolutionary phenomenon. Study it and answer the questions below.
   
   
   1. What name is given to the above evolutionary phenomenon? (1 mk)
   2. Account for your observation in pictures A and B
      Observation......................................(2 mks)
      Accounting.......................................(2 mks)
   3. Explain how continental drift is an evidence for organic evolution (3 mks)
5. An analysis was done on the contents of faeces of a cow. The results are as shown in the table below.
   

   Content	Percentage
   Carbohydrates	12
   Proteins	0.8
   Fiber	14
   Fats	1

   1. Name the other component that makes up the faeces of a cow and give its percentage. (1 mk)
   2. Name the substance that contributes the fiber in the faces. (1 mk)
   3. Cow faeces are normally used as fertilizer that increases nitrates in the soil. 
      1. State the component in the faces that yield nitrates. (1 mk)
      2. Describe how the component named in (c)(i) above is converted into nitrates (4 mks)
   4. Explain why the manure would be better if the cows urine was added to the faces. (2 mks)

SECTION B (40 Marks)
Answer question 6(Compulsory) and either question 7 or 8 in the spaces provided after question 8

6. The table below shows how the quantities of sweat and urine vary with external temperature.
   

   External Temperature (°C)	Urine (cm3/hour)	Sweat(cm3/hour)
   0	100	5
   5	90	6
   10	80	10
   15	70	20
   20	60	30
   25	50	60
   30	40	120
   35	30	200

   1. On the grid provided, plot graphs of quantities of urine and sweat produced against external temperature. (7 mks)
      
   2. At what temperature were the amounts of sweat and urine produced equal? (1 mk)
   3. Account for the shape of the graph for: 
      1. Amount of urine produced (3 mks)
      2. Amount of sweat produced. (2 mks)
   4. State two ways in which the skin lowers body temperature. (2 mks)
   5. State the advantages of having constant body temperature in mammals. (3 mks)
   6. State the role of the hypothalamus in thermoregulation. (2 mks)
7. Describe the process of hearing in man. (20 mks)
8.                          
   1. Explain the role of the following plant hormones in growth and development.
      1. Gilberellins (5 mks) 
      2. Cytokinin (5 mks)
   2. Describe the process of fertilization and implantation of the zygote in mammals. (10mks)

MARKING SCHEME

1.                                
   1. hypotonic; (1 mk)
   2. Solution Y was hypotonic to cell sap of the cortical cells; The epidermal cells are covered with waxy cuticle hence do not take in water by osmosis; while the cortical cells with thin walls take in water by osmosis. They therefore become turgid; hence the stem curves outwards. (4mks)
   3. Absorption of end products of digestion in intestines; absorption of salts in the colon; re absorption of substances (any
      correct) in kidney tubules; (3mks)
2.                                    
   1. Parents Man♂/ Wife/♀
      XY^B       X         XX
      Rej - the mark for genotypes if the X is missing
      
      Rej - the mark for fusion lines if they penetrate the gametes. 
   2.                                          
      1. 0; ace - zero/none (1 mk)
      2. The gene for baldness is located on the Y chromosome which the girls lack;
   3. Blood group;
   4. Colour blindness; reject colour blind
3.                                  
   1. To find out whether energy/ heat is released in anaerobic respiration/ fermentation;
      To investigate the gas produced during fermentation/anaerobic respiration; (2marks)
   2.                          
      1. (significant) rise in temperature; color of bicarbonate indicator turns yellow; (2marks) 
      2. Yeast will respire aerobically releasing energy/ and carbon dioxide gas that turn indicator yellow; mark 
      3. Expel / drive out oxygen; 1mark iv) Use glucose solution without yeast cells/ killed yeast cells; 1mark
      4. Brewing; 1 mark 
         Baking; 
         Production of dairy products; Mark any 1
4.                        
   1. Natural selection; (1 mk)
   2. Observation (2 mks)
      • A-Long-necked giraffes survived;
      • B -short-necked giraffes died from starvation;/perished
        Accounting (2 mks)
      • Nature selected those giraffes with long necks allowing them to survive; while rejecting those with short necks thus eliminating them; OR Natural selection favours survival of giraffes long-necked traits, and rejects/eliminates those with short-necked traits; 
   3. Current continents existed as one large land mass/Pangea/ Lauresia; the present continents drifted leading to isolation of organisms; organisms in each continent evolved along different evolutionary lines; (3mks
5.                    
   1. Water; 72.2%;
   2. Cellulose;
   3.                            
      1. Proteins; 
      2. Proteins are broken down to ammonium compounds/ammonia; by saprophytic bacteria /fungi/microorganism; Ammonia is converted into nitrites by Nitrosomonas/Nitrococcus bacteria; nitrites are converted into nitrates by nitrobacter(bacteria);
   4. Urine contains urea/nitrogenous compounds; that add to the protein content of the feaces;
6.                                        
   1.                                  
      
   2. 24 °C (+ 1 or -1); Rej- without units
   3.                        
      1. An increase in temperature leads to decrease in the amount of urine produced; because of increased sweating which increases osmotic pressure of blood; hence more water is reabsorbed in the kidney tubules;
      2. An increase in temperature results to increased sweat production; high temperature increases evaporation rate; hence more sweat is converted to vapour (to cool the body);
   4. Vasodilatation;
      Hair lies flat;
   5. Mammals are active even under cold conditions/always;
      Able to escape from predators/search for food because they are active always;
      Can survive in both hot and cold habitats/ wide range of habitats; 
   6. Contains thermoreceptors that detect changes in temperature (of blood); and generate impulses to the appropriate organs/structures; 
7. The pinna; collects/channels sound waves; into the auditory canal/meatus; Auditory canal concentrates directs sound waves; to the tympanic membrane/ear drum; The sound waves heat the ear drum and cause it to vibrate; The vibrations are transmitted to the ear ossicles/from the ear drum the vibrations are picked by malleus which transmits them to the incus then to the stapes; Stapes passes the vibrationsto the oval window/fenestra ovalis; from where the vibrations are transmitted to the fluid in the cochlea; the vibrations stimulate sensory cell hairs; to generate impulses; which are transmitted to the brain; through the auditory nerve; for interpretation; The intensity of the stimulus transmitted; to the brain enables the brain to interpret the impulse as sound of specific pitch; and loudness; The coiling of the cochlea offers a large surface area; for attachment of the sensory cells; Vibrations in the fluid in the inner ear are dissipated; by the round window; (20mks)
8.                              
   1.                        
      1. Gibberellins;
         Promote cell division /elongation; stem elongation in dwarf plants; Initiates formation of IAA; Promotes formation of side branches on stems; Inhibits growth of adventitious roots; 
         Activates hydrolytic enzymes during germination/promote seed germination /breaks seed dormancy Promote leaf expansion; leaf abscission; 6 max 5mks
      2. Cytokinins 
         Promotes cell division (in presence of auxins/IAA); 
         Promotes root formation on a shoot; 
         Breaks dormancy in some species; 
         Cytokinins plus AA induces formation of callus tissue; 
         Stimulates lateral bud development; 
         Low concentration encourages leaf senescence and enlargement in leaves; 7 mks (5mks)
   2.                                  
      • It occurs at the upper part of the oviduct after copulation; 
      • Sperms are drawn by section of cervix to the uterus 
      • Sperms swim up to the oviduct using their tails 
      • When sperms come into contact with the egg the aerosome bursts
      • Releasing lytic enzymes that dissolve the egg membrane 
      • The aerosome turns inside-out forming a fine filament that penetrates the egg; 
      • The head of the sperm enters the ovum and tail left behind; 
      • Vitelline membrane changes to prevent further entry of sperm to ovum
      •  Male nucleus fuses with female nucleus forming adeploid zygote 
      • Zygote undergoes a series of mitotic divisions forming blastocytes 
      • Blastocytes develop villi which grows into uterus 
      • Villi together endometrium develop the placenta 
      • Blastocytes become embryo after implantation 
      • Implantation take place in the uterus
      • Zygote moves from oviduct to uterus by cilia movements and contractions of smooth muscles along the oviduct