Biology Paper 2 Questions and Answers - MECS Cluster Joint Pre Mock Exams 2021/2022

Share via Whatsapp
Download PDF for future reference Get on Whatsapp for 50/-

BIOLOGY
PAPER 2 

SECTION A (40 MKS)

  1. A student boiled some water in a boiling tube and before it cooled down, she covered the surface with a layer of oil. With the water maintained at 37° C. She introduced a mixture of glucose and yeast into the boiling tube. Corked it and fixed a delivery tube, the other end of the delivery tube was immersed into lime water that had been put in a test tube. The set up was left maintained at 37 °C for 30 minutes within which observations were made.
    1. What was the aim of the experiment? (1 mark)
    2. Why was it important to boil the water at the start of the experiment (1mark)
    3. Write down three observations made within the 30 minutes time. (3 marks)
    4. Account for the observations made in (c) above. (3 marks)
  2. The pedigree diagram shows the inheritance of colour blindness (Daltonism) in a family. Colour blindness is sex-linked and is caused by a recessive allele (d). The ability to see colour normally is caused by a dorminant allele (D)
    MECBiop2q2
    1. How many of the male offspring of parents 1 and 2 were normal? (1mk)
    2. State the genotype of:
      1. Individual 2 (1mk)
      2. Individual 5 (1mk)
    3. A person with a recessive allele for colour-blindness may not be colour blind. Explain why males with allele for colour-blindness are always colour-blind. (1mk)
    4. If individual 5 marries a normal male, what percentage of their daughters will have an allele for colour-blindness but will not be colour-blind? Show your working. (4mks)
  3. The following table gives information about concentration of substances in samples of blood plasma, filtrate from the glomerulus and urine.
    Substance  Concentration in sample (g/100cm3)​  
    Blood plasma Glomerular filtrate Urine 
    Glucose  0.10  0.10  0.00
    Protein 8.00  0.00  0.00
    Salts 0.90 0.90 2.70
    Urea 0.03 0.03 1.80

    1. Protein is not filtered out of blood plasma
      1. Use evidence from the table to support this statement. (1mk)
      2. Explain why protein is not filtered out of the blood plasma. (1mk)
    2. The table shows that glucose is present in the filtrate from the glomerulus but not in the urine. Explain why glucose is not present in the urine. (1mk)
    3. Urea is formed by the deamination of excess amino acids. Describe how deamination occurs (5mks)
  4. The diagram below represents a generalized cell structure as seen under an electron microscope.
    MECBiop2q4
    1. Name the structures labeled A,B and C (3mks
      1.          
      2.    
      3.          
    2. How is the structure labeled B adapted to its function (2mks)
    3. What difference would be observed between electron micrograph obtained from cheek cell of a frog and the one above (3mk)
  5. The diagram below represents a nitrogen cycle
    MECBiop2q5
    1. Name the groups of organisms represented by J (1mk)
    2. Name the process represented by R, P M and N (4mks)
      R :
      P :
      M :
      N :
    3. Name one process represented by T (1mk)
    4.          
      1. Name a structure in roots involved in process M (1mk)
      2. State one adaptation of structure named in (d) (i) above to its function (1mk).

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

  1. In an experiment, the population growth of yeast cells in a Petri dish was determined over a period of 75 minutes. The results below were obtained.
    TIME IN MINUTES NUMBER OF YEAST CELLS
    0  4
     5  6
     10  8
     15  10
     25  30
     30  50
     35  80
    40 120
    45 140
    50 150
    55 160
    65 166
    75 166

    1. Using a suitable scale , plot a graph on the grid provided of number of cells against time in minutes (6 marks)
    2. Name the type of the curve you have drawn. (1 mark)
    3. Determine the number of yeast cells after 37 minutes. (1 mark)
    4. After how long was the population of yeast cells 144? (1 mark)
    5. Work out the rate of cell division between 32 minutes and 42 minutes. (2 marks)
    6. Account for the shape of graph between 45th minute and 60th minute. (3 marks)
    7. In a field study to estimate the population of grasshoppers in the school field of 4km2., 60 grasshoppers were caught using sweep nets, marked with red paint and released back to the field. The following day students went back with their sweep nets and caught 100 grasshoppers, in which 20 were found to be already marked.
      1. calculate the population size of grasshoppers in the field. (2 marks)
      2. Calculate the population density of the grasshoppers in the field. (2 marks)
      3. What factors would maintain the population of grasshoppers and yeast cells at the carrying capacity. (2 marks)
  2.            
    1. Describe the process of fertilization in a flowering plant. (15mks)
    2. State the changes that take place in a flower after fertilization (5mks)
  3.            
    1. Describe the adaptation of hydrophytes to their photosynthetic function. [10mks]
    2. Explain how mammalian ileum is adapted to perform its function. [10mks] 

MARKING SCHEME

  1. A student boiled some water in a boiling tube and before it cooled down, she covered the surface with a layer of oil. With the water maintained at 37° C. She introduced a mixture of glucose and yeast into the boiling tube. Corked it and fixed a delivery tube, the other end of the delivery tube was immersed into lime water that had been put in a test tube. The set up was left maintained at 37 °C for 30 minutes within which observations were made.
    1. What was the aim of the experiment? (1 mark)
      • To investigate anaerobic respiration in yeast.

    2. Why was it important to boil the water at the start of the experiment (1mark)
      • To expel any dissolved oxygen from the water.

    3. Write down three observations made within the 30 minutes time, (3 marks)
      • Lime water formed a white precipitate rej. Turned milky.
      • There were bubbles formed in the boiling tube.
      • There was the smell of ethanol in the

    4. Account for the observations made in (c) above. (3 marks)
      • Yeast cells carried out anaerobic respiration; producing carbon (IV) oxide, ethanol and energy / ATP; Carbon (IV) oxide produced reacted with lime water/ calcium hydroxide solution forming .

  2. The pedigree diagram shows the inheritance of colour blindness (Daltonism) in a family. Colour blindness is sex-linked and is caused by a recessive allele (d). The ability to see colour normally is caused by a dorminant allele (D)
    1. How many of the male offspring of parents 1 and 2 were normal? (1mk)
      • 2

    2. State the genotype of:
      1. Individual 2 (1mk)
        • XdXd

      2. Individual 5 (1mk)
        • XdXd

    3. A person with a recessive allele for colour-blindness may not be colour blind. Explain why males with allele for colour-blindness are always colour-blind. (1mk)
      • Since allele is found only on the X – chromosomes, a male has only one allele that is either dominant (normal) or recessive (colour blind)

    4. If individual 5 marries a normal male, what percentage of their daughters will have an allele for colour-blindness but will not be colour-blind? Show your working. (4mks)
      • 100%

  3. The following table gives information about concentration of substances in samples of blood plasma, filtrate from the glomerulus and urine.
    1. Protein is not filtered out of blood plasma
      1. Use evidence from the table to support this statement. (1mk)
        • Concentration in blood plasma is 8.00 while concentration is glucose filtrate and urine is 0.00.

      2. Explain why protein is not filtered out of the blood plasma. (1mk)
        • Proteins have large molecular sizes and cannot be filtered through the tiny pores of the glomerulus.

    2. The table shows that glucose is present in the filtrate from the glomerulus but not in the urine. Explain why glucose is not present in the urine. (1mk)
      • Upon filtration all the glucose is reabsorbed in the proximal convoluted tubule.

    3. Urea is formed by the deamination of excess amino acids. Describe how deamination occurs (5mks)
      • Excess amino acids are broken down to amino group and carboxyl group which is converted to glucose and respired to produce energy; the amino group is reacted with hydrogen to from ammonia, which then reacts with carbon (IV) oxide to form urea; in a series of cyclic reaction called ornithine cycle; catalyzed by enzyme arginase.

  4. The diagram below represent a generalized cell structure as seen under an electron microscope
    1. Name the structures labeled A,B and C (3mks)
      1. Sap vacuole.
      2. Chloroplast
      3. Plasmodesmata

    2. How is the structure labeled B adapted to its function (2mks)
      • Stoma contains enzymes which speed up process of photosynethesis.
      • Lamellae/ granum provide large surface area for accommodation of more chlorophyll molecules that trap light energy.

    3. What difference would be observed between electron micrograph obtained from cheek cell of a frog and the one above (3mk)
      Check cell for log One above
      No cell wall Cell wall present
      Sap vacuole absent Sap vacuole present
      Centriole present Centriole absent
      Chloroplast absent Chloroplast
  5. The diagram below represents a nitrogen cycle
    1. Name the groups of organisms represented by J (1mk)
      • Plants/ autotrophs.

    2. Name the process represented by R, P M and N (4mks)
      • R Denitrification/ nutrition
      • P feeding/ nutrition
      • M Absorption
      • N Decay/ Decomposition

    3. Name one process represented by T (1mk)
      • Fixation by lightning.
      • Bilogical fixation (by bacterias)
    4.     
      1. Name a structure in roots involved in process M (1mk)
        • Root molecule / nodule. Rej nodules
        • Harbour Rhizobium bacteria which convert atmospheric nitrogen into ammonia, which is used by leguminous plants to from nitrogen containing organic compounds/ proteins.
      2. State one adaptation of structure named in (d) (i) above to its function (1mk).
        • Root hair cells are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption.
        • They also contain lots of mitochondria , which release energy from glucose during respiration in order to provide the energy needed for active transport.
  6.        
    1.              
      MECBiop2qa6   
    2. Sigmoid curve.
    3. 98 yeast cells + -1
    4. 47 minutes.
    5. Rate of cell division =
         change in minutes        128 – 60    =         68     = 7 cells/ minute
         Change in time            42 – 32                 10
    6. Rate of cell division of decreasing with the increase in time; due to shortage of oxygen and nutrients; space is limited; accumulation of metabolic wastes which inhibits multiplication.
    7.          
      1. Population =     first marked x second capture      100 x 60     = 300 grasshoppers
                                 Marked released                                    20
      2. Population density =  total population    300     = 75 grasshoppers /km2
                                                 Area                     4
      3. Competition death of those not suitably adapted.
  7.           
    1. Describe the process of fertilization in a flowering plant. (15mks)
      • When pollen grains land on the stigma after pollination; stigma produces chemical substance; which stimulate pollen grain then develops a pollen tube; that grows down the style carrying the tube nucleus and generative nucleus; The generative nucleus divides by mitosis; to produce two male nuclei, on reaching the micropyle, tube nucleus burst open the embryo sac and disintegrate; giving way to the male nuclei; one of the male nucleus fuses with the egg cell nucleus fuses with the two polar nuclei forming primary endosperm nucleus / triploid nucleus; that develops into primary endosperm. This process involves double fertilization; which is unique feature to flowering plants.
    2. State the change that takes place in a flower after fertilization (5mks)
      • Integuments changes into seed coat/testa.
      • Zygote develops into embryo.
      • Ovule develops into seeds.
      • Ovary develops into fruit.
      • Triploid nucleus into endosperm.
      • Style, corolla and stamen dries up / withers.
  8.             
    1. Describe the adaptation of hydrophytes to their photosynthetic function [10mks]
      • Broad / flat lamina/ large; to provide large surface area for carbon (iv) oxide; light absorption.
      • Thin leaf to allow carbon (iv) oxide to pass through a short distance for rapid diffusion of gases.
      • (Presence of) numerous / many stomata; on eth other upper epidermis , ensuring efficient diffusion of carbon ( iv oxide;
      • Cuticle / epidermis transparent to allow penetration of light to palisade/ photosynthetic cell;
      • (Presence of) numerous aerenchyma tissues; which enables the plant to float;
      • Leaves of the completely submerged plants are highly branched/ divided deeply dissected/ truncated; to increase the surface area for photosynthesis;
      • Leaves of submerged plants have increased number of chloroplasts for efficient absorption of light. (14 max 11mks)
    2. Explain how mammalian ileum is adapted to perform its function. [10mks]
      • The inner lining has villi and microvilii which increase the surface area for absorption;
      • Ling/ highly folded; offering a large surface area for the absorption and digestion of food.
      • Has intestinal glands; that secretes intestinal juice that contains digestive enzymes/ maltase , sucrose;
      • Contains villii with numerous blood vessels; to transport absorbed nutrients;
      • Villi contains lacteal lymph vessels; for transport of fatty acid and glycerol;
      • Villii have a thin epithelium/ lining; for faster diffusion of digested food.
      • Have goblets cells; that secrete mucus for lubrication of food and protection of the wall from digestive enzymes. 

Download Biology Paper 2 Questions and Answers - MECS Cluster Joint Pre Mock Exams 2021/2022.


Tap Here to Download for 50/-





Join our whatsapp group for latest updates
Read 5137 times Last modified on Wednesday, 19 January 2022 12:18
Print PDF for future reference