KCSE 2014 Biology Paper 2 Questions with Marking Scheme

QUESTIONS

SECTION A (40 marks)
Answer all questions in this section on the spaces provided.

1. 1. State four characteristics of fruits dispersed by animals. (4 marks)
   2. State two roles of each of the following hormones in menstruation:
      
      1. luteinising hormone; (2 marks)
      2. oestrogen. (2 marks)
2. The diagram below illustrates the role played by red blood cells in transportation carbon (IV) oxide.
   
   
   
   
   1. Other than carbon (IV) oxide transportation in the red blood cells, name the other form of carbon (IV) oxide transportation in humans. (1 mark)
   2. 1. Name substance F (1 mark)
      2. Name the enzyme marked G and state its role in the reaction. (2 marks)
         Enzyme
         Role
   3. Explain why transportation of carbon (IV) oxide in red blood cells is advantageous. (2 marks)
   4. Explain the role of calcium ions in blood clotting. (2 marks)
3. 1. Describe the mechanism of gaseous exchange in plants through the lenticels. (3 marks)
   2. Explain each of the following:
      1. the tracheoles lack spiral bands of chitin; (3 marks)
      2. the floor of the mouth is lowered during inhalation in a bony fish. (2 mark)
4. 1. How is sex determined in man? (4 marks)
   2. 1. Differenciate between sickle cell anaemia and sickle cell trait. (2 marks)
      2. Explain why people with sickle cell trait have an adaptive survival advantage over normal individuals in malaria endemic regions, (2 marks)
5. The diagram below represents the transverse section of the spinal cord.
   
   
   
   
   1. Name the part labelled H. (1 mark)
   2. State two functions of the fluids found in the part labelled J. (2 marks)
   3. Give a reason for the colour of white matter. (1 mark)
   4. Name and give the function of the enzyme found at the part labelled K.
      Name (1 mark)
      Function (2 marks)
   5. On the diagram, use an arrow to show the direction of the impulse transmission along the neurone labelled I. (1 mark)
                                        SECTION B. (40 marks)
                      Answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after question 8.
      
6. An experiment was done to determine the uptake of nitrogen from the soil by broad bean seedlings. The experiment was done with one set of seedlings M grown in the atmosphere enriched with carbon (IV) oxide and another set up of seedlings N grown in normal atmosphere.
   The amount of nitrogen in each seedling was measured in milligrams at intervals of ten days. The table below shows the results obtained.
   
   
   1. Using the same axis, draw line graphs of nitrogen uptake by the two (M and N) sets of broad bean seedlings against time. (8 marks)
      
      
      
   2. Determine the rate of uptake in Set M between 65 and 85 days. (2 marks)
   3. 1. What is the relationship between carbon (IV) oxide concentration in the air and nitrogen uptake. (1 mark)
      2. Account for the relationship in (c) (i) above. (3marks)
   4. 1. What would happen to the concentration of nitrogen in the seedlings in set M, if after 75 days the seedlings are trasferred to normal atmosphere. (1 mark)
      2. Explain your answer in (d) (i) above. (2 marks)
   5. State three ways in which nitrogen fixation occurs. (3 marks)
7. 1. Explain how each of the following factors affect the rate of photosynthesis:
      1. temperature; (2 marks)
      2. chlorophyll concentration. (2 marks)
   2. Describe the process of cabohydrate digestion in human beings. (16 marks)
8. 1. How does excretion take place in plants? (4 marks)
   2. Describe the role of human skin in homeostasis. (16 marks)

MARKING SCHEME

1.                    
   1.                      
      • Fruit fleshy/juicy/succulent;
      • Fruit brightly coloured/large/inclusters;
      • Fruit scented has sweet smell/sweet aroma;
      • Seeds have tough/hard testa;
      • Some seeds have sticky/mucoid secretions;
      • Fruits have hooks;
        (max 4 marks)
   2.                  
      1. Luteinising hormone:
         stimulates ovulation;
         stimulates the development of remains of the graafian follicle into corpus luteum;
         stimulate corpus luteum to produce progesterone; (max 2 marks)
      2. Oestrogen:
         stimulates healing and repair of uterine lining /endometrium following menstruation;
         stimulates pituitary gland to secrete luteinising hormone; (2 marks)
2.                
   1. Carbonic acid/carbaminohaemoglobin/hydrogen carbonate;(1 mark)
   2.                  
      1. Water;
      2. Carbonic acid; (1 marks)
         Role: catalyses reaction between carbon IV oxide and water to form (weak) carbonic acid; (2 marks)
   3. Prevents accumulation of acidity/maintains pH of blood since hydrogen ions combine with haemoglobim to form Haemoglobinc acids;
      Faster; due to the catalytic effect of carbonic anhydrase;
      (max 2 marks)
   4. Activates thromboplastin; thrombokinase to neutralize heparin/convert prothrombin to thrombin;(2 marks)
3.                            
   1. O₂ concentration is higher outside than inside the lenticels; O₂ diffuses into lenticels; then into the cells;
      CO₂ concentration is higher inside the lenticels than on the outside CO₂ diffuses out of the lenticels into the atmosphere; (4 marks)
   2.                    
      1. To provide a large surface area/ make them thin; for gaseous exchange/ to reduce diffussion distance for respiratory gases;(3 mark)
      2. This increases the volume of the buccal cavity while decreasing the pressure; which forces water to rush into the mouth;(2 mark)
4.                  
   1. Males have two dissimilar chromosomes X and Y/heterogametic;
      Females have two similar chromosomes X and X/homogametic;
      Male gamete/sperms have either X or Y chromosome, while all ova have X chromosome;
      If a sperm with X fuses with an ovum a female is formed and if a sperm with Y fuses with an ovum a make is formed;
      (4 mark)
   2.                          
      1. Sickle-cell trait is heterozygous while sickle cell anaemia is a homozygous condition;(2 marks)
      2. People with sickle cell trait are resistant to malaria; because the plasmodium cannot survive in sickle shaped red blood cells.(2 marks)
5.                    
   1. H - cell body; (1 mark)
   2. Has nutrients for nourishment of neurons, brain, spinal cord;
      Acts as a shock absorber for protection of spinal cord from mechanical damage;(2 mark)
   3. Contains myelin sheaths (of neurons which are made up of fats that make it have a shiny white appearance); (1 mark)
   4. Cholinesterase; (1 mark)
      Breaks down Acetylcholine; to acetic acid and choline;
   5. Correct arrow on neurone 1 points towards the grey matter; (1 mark)
6.                            
   1. Scale 2x1 mark
      Identity of axes 2x1
      mark Plotting of points 2x1
      mark Labelling of curves 1 mark ( 1/2 × 2)
      Smooth curves 1 mark ( 1/2 × 2)
      (2 marks)
   2. At 65 = 395;
      860 - 395
           20
      = 465
         20
      =23.25 ± 1 mg/day
      At 85 = 860 (2 marks)
      
   3.                
      1. The higher the carbon (IV) oxide content in air, the higher the nitrogen uptake and vice versa;(1 mark)
      2. More Carbon (IV) oxide in the air makes the seedlings to photosynthesize more; hence more amino acids/protein; are formed in the dark stage; formation of amino acids/protein requires nitrogen;(max 3 marks)
   4.                    
      1. The concentration of nitrogen would remain constant;(1mark)
      2. Despite decline in CO₂; the nitrogen already absorbed/taken up by the plant will still remain;(3 marks)
      3. Lightning;
         By free-living bacteria/micro organisms;
         By Rhizobium (in root nodules of legumes); (3 marks)
7.            
   1.                            
      1. Reactions in photosynthesis are catalysed by enzymes; at optimum temperature photosynthesis proceeds faster;
         Below optimum temperature the rate of photosynthesis decreases because enzymes are inactivated by the low temperatures / above optimum the rate of photosynthesis decreases because enzymes are denatured; (2 marks)
      2. Chlorophyll traps energy from sunlight for photosynthesis;
         The higher the chlorophyll concentration the higher the rate of photosynthesis and vice versa; (2 marks)
      3. In the mouth;
         Food is chewed; to increase surface area for enzyme activity/saliva contains salivary amylase;
         Saliva mixes with food and provides an alkaline medium; for amylase enzymes;
         Salivary amylase acts on starch and converts them to maltose;
         In duodenum;
         Food is mixed with bile; and pancreatic juice;
         Bile provides alkaline medium; for activity of duodenal enzymes; and neutralizes acidic chyme from the stomach;
         Pancreatic juice contains pancreatic amylase; which converts starch to maltose;
         In the Ileum;
         Epithelial cells in Ileum secrete succus entericus; which contains enzymes; sucrase; which acts on sucrose and converts it to fructose and glucose; Lactase; which acts on lactose and converts it to galactose and glucose; Maltase; acts on maltose and converts it to glucose;
         max 16 marks
8.                                  
   1.                    
      • Diffusion of Carbon (IV) Oxide; and oxygen; through stomata and lenticels;
      • Some wastes are stored in tissues in non-toxic form e.g. calcium oxalate;
      • Some of these tissues or organs drop off from plants e.g. leaves, flowers, fruits and bark of caffeine, nicotine, quinine;
      • Some wastes are released by transpiration through stomata and lenticels such as water vapour;
      • Others are released by guttation through hydathodes as water;
      • Others are released by exudation. (max 4 marks)
   2. When body temperature is lowered below normal;
      arterioles in the skin constrict;
      blood is diverted to a shunt system;
      less blood flows to the skin/less heat is lost;
      when body temperature is raised above normal;
      arterioles in the skin dilate;
      more blood flows to the skin;
      more heat is lost by convection and radiation;
      
      when body temperature is lowered below normal:
      erector-pilli muscles contract, hair stands erect;
      more air is trapped, air is a bad conductor;
      and insulates the body against heat loss;
      when body temperature is raised above normal:
      erector-pilli muscles relax, hair lies on skin;
      less air is trapped, more heat is lost;
      
      when body temperature is lowered below normal:
      less fluids are absorbed by sweat glands;
      less sweating, less vaporisation of water;
      when body temperature is raised above normal:
      sweat glands are more stimulated and more sweat is produced;
      water in sweat evaporates and takes up heat from the body;
      body is cooled/body temperature is lowered;(max 20)