Biology Paper 2 - CATHOLIC DIOCESE OF KERICHO (CDK) EXAMS – 2018 PRE-MOCK WITH MARKING SCHEME

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BIOLOGY
PAPER 2
TIME: 2HOURS
MARCH 2018

CATHOLIC DIOCESE OF KERICHO (CDK) EXAMS – 2018
PRE-MOCK
BIOLOGY PAPER 2
TIME: 2 HOURS

INSTRUCTIONS TO CANDIDATES

• 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.

1.  
   1. Eye colour in fruits flies is sex-linked. Red eye color R is dominant to white eye color r. A heterozygous red-eyed female fly was crossed with a white eye male
      1. Show the parental genotypes (1mk)
      2. By means of a genetic cross, determine the genotypic ratio of the offspring (4mks)
      3. Explain why the actual phenotype ratio obtained from this cross could differ from the expected (1mk)
   2. Name two disorders due to non-disjunction (2mks)
      
      
2. The diagram below shows a section through the mammalian skin
   
   
   
   
   1. Name the parts labeled W and X (2mks)
   2. State the function of the parts labeled Y and Z (2mks)
   3. Explain the changes that occur on the skin when it is cold (4mks)
      
      
3. Examine the diagram below and answer the questions that follows
   
   
   
   
   1. Name the parts labeled A-D (4mks)
   2. State the type of germination exhibited by the seedling above (1mk)
   3. State and explain three environment condition necessary for germination (3mks)
      
      
4. The diagram below represents a food web in an ecosystem
   
   
   
   
   1. From the food web above, construct a food chain ending with a quaternary consumer (1mk)
   2. State the trophic levels occupied by;
      1. Lizard
      2. Green plants
      3. Antelopes
   3. What would happen if leopards were introduced in the ecosystem (2mks)
   4. Construct a pyramid having the following food chains: leaves of 10 large trees are fed on by millions of caterpillars which are in turn fed on by 50 kites (2mks)
      
      
5. Study the experimental set up below and use it to answer the questions that follow.
   
   
   
   The filter pump is used to suck out air from the apparatus, reducing pressure in the apparatus causing the atmospheric pressure to force in air through jar A and moves through the apparatus as shown by means of arrows to the filter pump and observations are made on the appearance of lime water in Jar B and D
   
   
   1. What aspect of respiration is being demonstrated
   2. State the roles of the following in the experiment
      1. Sodium hydroxide (1mk)
      2. Black clothing covering the bell jar (1mk)
      3. Polythene bag enclosing the plant (1mk)
   3. What observations would you expect to make in the lime water in B and D (2mks)
   4. Account for the results in (c)above (2mks)
   5. Suggest the changes one would make on the apparatus if a small mammal e.g. a mouse was used instead of a potted plant in the experiment (1mk)

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

6. A person had stayed for 24hrs without food. Then he was served with a well-balanced meal after which the concentration of glucose and amino acids in the blood were determined every one hour for the next 8 hours after the meal, the concentration were measured as blood passed through the hepatic portal vein and hepatic vein. The results were as shown in the data below.
   
   

   Time in hours	Concentration of glucose and amino acids in blood (mg/100cm3 of blood)
   	Hepatic Portal vein		Hepatic Vein
   	glucose	Amino acids	glucose	Amino acids
   0	79	1.0	85	1.0
   1	79	1.0	85	1.0
   2	160	1.0	110	1.0
   3	140	4.0	100	3.0
   4	120	6.0	90	3.0
   5	100	5.0	90	2.0
   6	90	2.0	90	1.0
   7	90	1.0	90	1.0
   8	90	1.0	90	1.0

   1. On the same axis plot graphs of glucose concentration in hepatic portal vein and hepatic vein against time (7mks)
   2. Account for the difference in blood sugar level in hepatic portal vein and hepatic vein
      1. Between 0-1 (4mks)
      2. Between 2-4 hours (5mks)
   3. Give one reason that delayed increase in amino acids concentration in hepatic portal vein (1mk)
   4. Account for the difference in concentrations of amino acids in hepatic portal vein and hepatic vein 3rd -6th hrs (2mks)
   5. Name the enzyme that completes fat digestion in man (1mk)
7.  
   1. Describe how gaseous exchange takes place in terrestrial plants (12mks)
   2. Explain how blood clotting occurs (8mks)
      
      
8.  
   1. Describe the structural adaptations of mammalian heart to its functions (10mks)
   2. Explain how the herbivores (organism) are adapted to their mode of feeding (10mks)