Biology Paper 2 Questions and Answers - KCSE 2022 Prediction

Instructions to Candidates

• This paper consists of TWO sections A and B.
• Answer ALL the questions in sections in section A in the spaces provided.
• In section B answer question 6(Compulsory) and either question 7 or 8 in the spaces provided after question 8.

Questions

SECTION A (40MKS)
Answer ALL questions in this section in the spaces provided.

1. The diagram below illustrate a type of chromosome mutation.
   
   
   1.                              
      1. Identify the type of chromosome mutation illustrate above. (1mk)
      2. State two examples of disorders in humans that are caused by the mutation named in a(i) above. (2mks)
      3. Name a disorder of blood that is caused by gene substitution. (1mk)
   2. State three differences between deoxyribonucleic acid (DNA and ribonucleic acid. (3mks)
   3. Define the term mutation (1mk)
2. The diagram below shows part of a longitudinal section of a young root.
   
   1. Name he parts labeled A, B, C and D. (4mks)
   2. State the importance of the cell labeled A. (1mk)
   3. How is the tissue labeled D adapted to the function it performs. (3mks)
3.                          
   1. What is a nerve impulse? (2mks)
   2. The diagram below represents a neuro-junction of a mammal.
      
      On the diagram, indicate with an arrow the direction of impulse transmission. (1mk)
   3. Name the chemical substance that is contained in the synaptic vesicle. (1mk)
   4. State the function of the part labeled K in the diagram. (1mk)
   5. Name two mineral ions that are involved in the transmission of nerve impulses. (2mks)
4. In an experiment to investigate he action of pepsin on egg albumen, equal amounts of pepsin were added to equal amounts of egg albumen in different test tubes. The test tubes were placed in water baths at different temperatures. The graph below shows the time taken for the enzyme to digest protein at each temperature.
   
   1.                              
      1. What is the optimum temperature for the enzyme? (1mk)
      2. Account for the time taken to digest egg albumen at 60ºC. (2mks)
   2. By giving a reason, name the form in which pepsin enzyme is secreted. (2mks)
   3. State three other factors that affect enzyme controlled reactions. (2mks)
5. The graph below shows the relationship between the number of herbivores and carnivores in a park.
   
   
   1. Identify the cure that represent carnivores. Give a reason for your answer. (2mks)
   2. Suggest a reason for the slope of curve X between points A and B. (2mks)
   3.                                        
      1. Name the type of relationship that exist between herbivores and carnivores as indicated in the graphs. (1mk)
      2. State the significance of the relationship you have stated in C(i) above. (1mk)
   4. What will be the long term effect on the park ecosystem if all carnivores were eliminated from the park. (1mk)

SECTION B (40MKS)
Answer question 6(compulsory) in the spaces provided and either question 7 or 8 in the spaces provided after question 8.

6. Research was carried out to determine the growth rate of some boys and girls. Their average mass in
   Kilograms was taken separately for 20 years. Their weight are tabulated as shown in the table below.
   

   Age	Average Mass of (Boys(Kg)	Average mass of girls Kg.
   0 2 4 6 8 10 12 14 16 18 20	2.5 11.1 15.00 18.5 22.1 25.1 27.00 37.00 44.00 47.0 48.5	2.5 11.5 16.0 19.3 27.1 27.2 30.00 36.00 44.00 52.00 55.00

   1. On the same axis, plot graphs of the average mass of the boys and the girls against their age. (7mks)
      
   2. From the graph, determine the
      1. Mass for boys at the age of 11 years. (1mk)
      2. Growth rate for girls between ages 13 and 15. (2mks)
   3. Account for the change in the mass of girls during the age stated in (ii) above. (2mks)
   4. Explain the trend observed in the curves for both boys and girls. (3mks)
   5. Why do girls above 10 years require intake of food that is richer in iron than boys of the same age? (1mk)
   6. Name two other factors, apart from diet, that affect the rate of growth in boys and girls.(2mks)
   7. A part from using average mass to estimate growth in human beings, name two other parameters that can be used. (2mks)
7.                      
   1. What is homeostasis. (2mks)
   2. Discuss the homeostatic functions of the mammalian liver. (18mks)
8. Describe how xerophytes are adapted to their habitats. (20mks)

Marking Scheme

1.                        
   1.                                
      1. Non – disjunction;
      2.  
         • Down’s syndrome;
         • Klinefelter’s syndrome;
         • Turner’s syndrome; (mark 1st two)
      3. Sickle cell aneamia;
   2. 
      

      DNA	RNA
      Is a double strand	Is a single strand;
      Has base thymine	Has base uracil;
      Only present in nucleus	Present in both nucleus and cytoplasm;
      Has deoxyribosugar	Has ribose sugar,

      (mark 1st 3)
   3. Sudden/abrupt/spontaneous, change in the genetic makeup of an organism (that are capable of being inherited).
2.                    
   1. A- Root hair; B- Cortex; C- Endodermis; D- xylem;
   2. Absorption of water containing mineral ions;
   3.  
      • Consists of along tubes that are continuous from the roots to the leaves;
      • Has thick lignified wall to provide support/mechanical support to prevent it from collapsing;
      • Has narrow lumen to increase capillarity;
3.                            
   1. An electrical charges which is conducted/transmitted along a nerve fibre/ an electrical charge arising from changed in ionic concentration across the surface membrane of an axon/dendrite/Dendron;
   2. Diagram
   3. Acetylcholine/Noradrenaline;
   4. Produces/releases(Cellular) energy for the reconstitution of a cetylcholine/noradrenaline, which are used for the transmission of impulses across a synapse;
   5. Sodium(Na+), Potassium (K+), Chloride (Cl-); (any mark 1st two)
4.                    
   1.                    
      1.  35ºC ± 1
      2. At 60ºC digestion takes long; since most enzymes have been denatured (by the high temperature);
   2. Pepsinogen;- to prevent the digestion of the cells that produce it;
   3.  
      • pH;/
      • Presence or absence of enzyme inhibitors;
      • Substrate concentration;
      • Presence of co-factors;
5.                      
   1. Curve X; It starts with a lower population than Y, the herbivore;
   2. Number of predators decreased due to increased completion for food as a result of decrease in the number of prey;
   3.                        
      1. Prey – predator relationship/predation
      2. It maintains the number of prey and predators at the carrying capacity of the habitat/state of balance.
   4.  
      • The number of herbivores will increase (due to reduced predation);
      • The amount of vegetation will decrease (due increased number of herbivore Primary productivity will decrease/lead to soil erosion);
      • Because of increased competition there will be shortage of food for the herbivores.
      • The number of herbivores will decrease due to death or migration;
        (Mark any two correct answers)
6.                            
   1. Graph.
      
   2.                      
      1. (26+-.5)kg;
      2. Girls 15 years – 39
         Girls 13 years – 33
         6 ÷ 2 = 3.0kg/year;
   3. Girls grow faster at adolescence. There is an increase in the size of their hips and breasts.
   4. Girls generally grow faster than boys. Boys grow slowly compared to girls but later, after puberty, the grow more steadily.
   5. Girls above 10 years begin to menstruate. They need more iron to replace the blood lost during menstruation.
   6.  
      • Genetic composition;
      • Sex of the child;
      • State of health;
      • Emotional status;
      • Climatic condition
   7.  
      • Height of the body;
      • Volume of the body;
7.                        
   1. Control and maintenance of a constant internal environment of living organisms;
   2. Regulation of blood glucose level.
      Excess glucose is converted to glycogen by the liver cells under the influence of insulin hormone secreted by the pancreas. While the hormone glucagon produced by the pancreas stimulates liver cells to convert stored glycongen into glucose; when there is less glucose in blood than normal.
      Deamination
      The liver cells breakdown excess amino acids to form ammonia. Ammonia combines with Carbon (IV) Oxide to form urea. Ammonia is formed from the amino group. The carbon skeleton is then converted to glucose that is then used by cells in respiration.
      Detoxification;
      Ammonia from the process, of deamination is converted into less toxic urea in the liver. Bacterial toxins,hydrogen peroxide, alcohol and drugs are converted into less toxic substances by the liver cells.
      Regulation of plasma proteins;
      The liver produces fibrinogen and prothrombin(which are involved in blood clotting) and most of the proteins found in blood. Albumin and some globulins and also produced by the liver. Globulins act as antibodies. Albumin contributes to the maintenance of the osmotic pressure of blood Non-essential amino acids are also synthesized by the liver.
      Storage of fat soluble vitamins A, B, E and K.
      Storage of Iron; Iron is released from the breakdown of worn out erythrocytes is stored in the liver. Iron is stored in form of a compound called Ferritin.
      Heat storage;
      Various metabolic processes that take place in the liver releases energy. This energy is distributed by blood to other parts of the body, hence contribute to maintenance of a constant body temperature.
      Inactivation of hormones and drugs
      Hormones and dugs after performing their function are chemically modified to inactive compounds in the liver. These by-products are got rid of through the kidney and faeces via bile.
      Storage of blood;
      The large size and high capacity for contraction and expansion of the veins in the liver enable it to hold and store a lot of blood. It regulates the volume of blood in the general circulation depending on the body needs.
      Regulation of fat metabolism
      Fats stored in different parts of the body are mobilized and taken to the liver, when carbohydrates are in short supply. The fats are oxidized to release energy or are modified by the liver cells before they are sent to the tissues for oxidation to release energy.;
8. Adaptations of xerophytes to their habitats
   • Some have thick/fleshy/succulent stems/leaves to store water;
   • Some have leaves with thick waxy cuticle to reduce water loss by transpiration;
   • Some have needle like leaves/leaves are reduced to spines to reduce the surface area through which water is lost during transpiration;
   • Some have deep; widespread roots that also water deep in the ground in order to reach water;
   • Some have leaves which are covered with hair or scales that trap a layer of still moist air close to the surfaces of their leaves in order to reduce transpiration.
   • Some have superficial roots that provide a large surface area for maximum absorption of water after light/short showers;
   • Some have rerrenting underground organs like bulbs/corm that store food/water,
   • Some have shallow extensive fibrous root system to absorb water near the surface;
   • Some have short life cycles to maximize the use of the short rainy season to grow and mature;
   • Some role their leaves in dry weather to reduce the surface area exposed to the external environment so as to reduce transpiration;
   • Some produce seed which are resistant to desiccation and remain dormant yet are viable for long period of time;
   • Some have reversed, stomata rhythm ie. Open at night and close during day time to minimize transpiration
   • During hot weather/daytime;
   • Stomata are mainly located on the lower of stomata that come into direct contact with sunlight in order to minimize transpiration.
   • Some have shiny/glossy leaf surfaces to reflect away light in order to reduce the leaf temperature hence reducing rate of transpiration.