Biology Paper 2 Questions and Answers - Form 4 End Term 2 Exams 2023

• Answer ALL questions in the spaces provided.
• All workings must be clearly shown where necessary.

1. Study the diagram below and use it to answer the questions that follow
   
   1.  
      1. Label parts labelled   (2mks)
         1. K – 
         2. L - 
         3. M- 
      2.  Through which process is structure labeled K in (a) (i) above produced? (1mk)
   2. How is the cell labeled N adapted to perform its functions.     (3mks)
   3. Name the hormone that stimulates the production of cell labeled K.at puberty.    (1mk)
2. Bile and pancreatic juice are important secretions in animal nutrition.
   1. In which part of the digestive system do they exert their influence?         (1mk)
   2.  
      1. For efficient digestion, which of the two secretions should be mixed with the chyme first? (1mk
      2. Explain your answer        (4mks)
   3. Explain why an adult does not need to eat too much protein in a meal/diet. (2mks)
3. The table below shows the approximate distribution of blood groups in a sample of 100 people in a population.
   

   Blood group	Frequency	Rhesus +ve	Rhesus −ve
   A	26	22	4
   B	20	18	2
   AB	4	3	1
   O	50	42	8

   1. Calculate the percentage of Rhesus negative (Rh-ve) individuals in the population? (1mk)
   2. Account for
      1. The large number of blood group O individuals in a population. (2mks)
      2. The small number of individuals with blood group AB. (2mks)
   3. The diagram below represents a blood smear on a glass slide.
      
      1. State the importance of structure C being large numbers in the blood smear. (1mk)
      2. Give a reason why structure C would be found in large numbers in high altitude than in low altitude. (1mk)
      3. Name the process by which structure A would engulf structure B. (1mk)
4.  
   1. Identify organs B and D in photograph T2 and state the class of organism from which they were obtained. (4mks)
      
   2. State the common function of the organs identified in (a) above. (1mk)
   3. Name the parts of the body where B and D in photograph T2 are found. (2mks)
   4. List the adaptations of D to its functions. (3mks)
   5. Using observable features only, state how B is adapted to its function (2mks)
5. The set apparatus was assembled by a group of students to investigate some physiological process. Glucose solution was boiled and oil added on top of it.  The glucose solution was then allowed to cool before yeast was added.
         
   1.  
      1. Give ONE aim of the experiment.           (1mk)
      2. Explain observations expected after 24hrs.            (2mks)
   2.  
      1. Why was the glucose solution boiled  before adding the yeast suspension? (1mk)
      2. What was the importance of cooling the glucose solution before adding the yeast? ( 1mk)
   3. In another investigation, a bird was found to use 10 litres of oxygen to give a respiratory quotient of 0.7 during period of flight.
      1. Name the type of food that was being respired by the bird ( 1mk)
      2. Determine the amount of carbon (IV) oxide produced during the same flight.   (2mk)
6. Mr. Juma has sued Serenity Hospital on grounds that their child was wrongly identified such that they got the wrong one. The child is blood group O. Mr. Juma is blood group AB while Mrs. Juma is heterozygous blood group A.
   1. Work out the possible blood group of their offsprings. (4 marks)
   2. Is Mr. Juma justified in his claims? Explain. (2 mark)
   3. State two blood disorders in humans that result from mutation. (2 marks)

SECTION B: 

Answer question 7 (Compulsory) and either question 8 or 9 in the spaces provided after question 8.

7. A Farmer wished to plant certain species of Erythrina trees on his farm. However, their seeds normally take time to germinate after sowing. To overcome this problem, he put the seeds in hot water maintained at 50°C.
   Batches of 20 seeds were removed at one minute intervals and then planted in trays containing moist soil. After 15 days, the number of seeds that germinated in each tray was counted.
   The results obtained were as shown in the table below.
   

   Batch order	Time intervals(minutes)	Germinated seeds	Percentage of seeds that Germinated.
   1st	0	3
   2nd	1	3
   3rd	2	8
   4th	3	15
   5th	4	18
   6th	5	13
   7th	6	10
   8th	7	6
   9th	8	2
   10th	9	0
   11th	10	0

   1. Calculate the percentage germination rate for each batch and fill in the table. (5mks)
   2. Use your results to plot a graph showing percentage germination against the duration in which the seeds were soaked in hot water. (6mks)
   3. From the graph derive the expected number of seeds that would germinate if soaked for 4.5 minutes. (1mk)
   4. Using the graph briefly explain the effect of hot water treatment on seed germination of Erythrina. (5mks)
   5. Explain why there was no germination of seeds soaked in hot water for nine to ten minutes. (1mks)
   6. Besides hot water treatment, suggest two other methods that can be used to speed up germination in Erythrina. (2mks)
8. Explain the adaptations of parts of the ear in the outer and middle ear. (20 mks)
9. Describe how the kidney Nephron functions. (20 mks)

MARKING SCHEME

1. Study the diagram below and use it to answer the questions that follow
   1.  
      1. Label parts labelled   (2mks)
         1. K – egg/ovum rej. ova
         2. L - Cervix
         3. M- vagina/vaginal canal
      2. Through which process is structure labeled K in (a) (i) above produced? (1mk)
         • Ovulation
   2. How is the cell labeled N adapted to perform its functions.     (3mks)
      • Long tail to propel /propulsion towards egg
      • has numerous mitochrondris – to provide energy for propulsion;
      • has acrosome that has lytic enzymes to digest part of ovum wall to allow sperms to penetration
      • has habloid mucles tofuse with ovum nuclears to maintain chiploidy in zygote;
   3. Name the hormone that stimulates the production of cell labeled K.at puberty.    (1mk)
      • oestrogen
2. Bile and pancreatic juice are important secretions in animal nutrition.
   1. In which part of the digestive system do they exert their influence?         (1mk)
      • Duodenum; acc first part of ileum
   2.  
      1. For efficient digestion, which of the two secretions should be mixed with the chyme first? (1mk
         • Bile juice;
      2. Explain your answer        (4mks)
         • The  salts in it ( sodium tanrocholate/sodium glycocholate) neutralize the acidity in chyme; and create alkaline medium; suitable for pancreatic enzymes( ie pancreatic amylase, lipase);
         • It emulsifies fat/oil ( to create large surface area for lipase enzyme);
   3. Explain why an adult does not need to eat too much protein in a meal/diet. (2mks)
      • Excess protein are not stored in the body; they are deaminated  to produce urea/some coverted to fats   
3. The table below shows the approximate distribution of blood groups in a sample of 100 people in a population.
   1. Calculate the percentage of Rhesus negative (Rh-ve) individuals in the population? (1mk)
       15   x 100 = 15%
      100
   2. Account for
      1. The large number of blood group O individuals in a population. (2mks)
         • The allele O appears in many blood groups/Allele O appears in blood group A, B and O; therefore higher chances of being inherited in a population;
      2. The small number of individuals with blood group AB. (2mks)
         • Allele A and B are co-dominant; hence express themselves only in blood group AB;
   3. The diagram below represents a blood smear on a glass slide.
      1. State the importance of structure C being large numbers in the blood smear. (1mk)
         • To increase the surface area for efficient transport/increase efficiency of delivery of oxygen; (to tissue)
      2. Give a reason why structure C would be found in large numbers in high altitude than in low altitude. (1mk)
         • At high altitude air is less dense/partial pressure of oxygen is low/there is low concentration of oxygen, hence the number of red blood cells/structure C increases to increase oxygen carrying capacity of blood;
      3. Name the process by which structure A would engulf structure B. (1mk)
         • Phagocytosis;
4.  
   1. Identify organs B and D in photograph T2 and state the class of organism from which they were obtained. (4mks)
      

      ORGAN	IDENTITY	CLASS
      B	Trachea/windpipe;	mammalia
      D	lungs:	mammalia

   2. State the common function of the organs identified in (a) above. (1mk)
      • Gaseous exchange.
   3. Name the parts of the body where B and D in photograph T2 are found. (2mks)
      • B - Neck region and the thoracic cavity;
      • D - Thoracic cavity/chest cavity/thorax;
   4. List the adaptations of D to its functions. (3mks)
      • Have a large surface area to ensure diffusion of larger volume of gases;
      • Highly vascularized to transport the diffusing gases; hence maintain a steep concentration gradient;
      • have a thin epithelium to reduce the diffusion distance of gases;
   5. Using observable features only, state how B is adapted to its function (2mks)
      • Have rings of cartilage that prevent it from collapsing; and
      • keeps the lumen fully open even when the neck bends;
5. The set apparatus was assembled by a group of students to investigate some physiological process. Glucose solution was boiled and oil added on top of it.  The glucose solution was then allowed to cool before yeast was added.
   1.  
      1. Give ONE aim of the experiment.           (1mk)
         • To show that energy is released in anaerobic respiration;/
         • To show that carbon (IV) oxide is produced in anaerobic respiration;
      2. Explain observations expected after 24hrs.            (2mks)
         • Increase in temperature/ tthermometer reading since energy/heat is released;
         • Colour of indicator changed to yellow due to acidity/carbon (IV) oxide released changed indicator to yellow;
   2.  
      1. Why was the glucose solution boiled  before adding the yeast suspension? (1mk)
         • Expel dissolved oxygen;
      2. What was the importance of cooling the glucose solution before adding the yeast? ( 1mk)
         • Prevent entry of air/oxygen into glucose solution; (any one)
   3. In another investigation, a bird was found to use 10 litres of oxygen to give a respiratory quotient of 0.7 during period of flight.
      1. Name the type of food that was being respired by the bird ( 1mk)
         • Fat
      2. Determine the amount of carbon (IV) oxide produced during the same flight.   (2mk)
         RQ = vol of CO₂ produced /vol of O₂  used
         0.7 = ^X/₁₀
         X = 7 litres
6. Mr. Juma has sued Serenity Hospital on grounds that their child was wrongly identified such that they got the wrong one. The child is blood group O. Mr. Juma is blood group AB while Mrs. Juma is heterozygous blood group A.
   1. Work out the possible blood group of their offsprings. (4 marks) 
      
   2. Is Mr. Juma justified in his claims? Explain. (2 mark)
      • Yes;
        No possibility of the couple’s child to have blood group O
   3. State two blood disorders in humans that result from mutation. (2 marks)
      • Haemophilia; sickle cell anaemia;

SECTION B: 

Answer question 7 (Compulsory) and either question 8 or 9 in the spaces provided after question 8.