Biology Paper 2 Questions and Answers - Kigumo Mocks 2021 Exams

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INSTRUCTIONS TO CANDIDATES

  • This paper consists of two sections Section A and section B
  • Answer ALL questions in section A
  • In section B answer question 6 (compulsory) and either question 7 or 8

For Examiners use only

Section

Question

Maximum score

Candidates score

A

1

5

 

2

2

 

3

5

 

4

4

 

5

8

 

6

7

 

7

13

 
 

8

20

 

9

20

 

10

20

 
 

Total score

80

 

QUESTIONS

SECTION A

  1. When testing a variegated leaf for starch, the following procedure is important
    1. The leaf is boiled in water
    2.  The leaf is then boiled in methylated spirit
    3. The leaf is taken back to the hot water
    4. The leaf is spread on a white tile and irrigated with iodine solution
      1. Why is the leaf boiled in hot water? (1mk)
      2. Why is the leaf boiled in methylated spirit? (1mk)
      3. Explain why the leaf is dipped in in hot water (1mk)
      4. Explain the observation made when the leaf is irrigated with iodine solution (2mks)
      5. What is a variegated leaf? (1mk)
      6. What is to destarch the leaf? (2mks)
  2. The diagram below represents the lower jaw of a mammals
    2 aghuihad
    1. Name the mode of nutrition of the mammal whose jaws is shown above (1mk)
    2. State one structural and one functional differences between the teeth labeled J and L (2mks)
    3.                                  
      1. Name the toothless gap labeled K (1mk)
      2. State the function of the gap (1mk)
    4. Name the substance that is responsible for hardening of the teeth (1mk)
    5. Distinguish between the terms homodont and hererodent (2mks)
  3. The diagram below shows the gaseous exchange system of a locust
    3 agduyada
    1. Name the structure labeled Q (1mk)
    2. State the function of the part labeled R (1mk)
    3. How is the part labeled S structurally adapted to its function? (2mks)
    4. Identify the structure that perform the same function as one illustrated above in (2mks)
      1. Amoeba
      2. Fish
    5. Name the causative agents for the following respiratory
      Diseases (2mks)
      1. Whooping Cough
      2. Pneumonia
  4. When pure breeding black guinea pigs were crossed with pure breeding white guinea pigs the offspring had a coat with black and white patches
    1. Using letter G to represent the gene for black coat colour and letter H for white colour, workout the genotypic ratio of F2 (5mks)
    2. State the phenotypic ratio of F2 generation (1mk)
    3. Name the term used when two alleles in heterozygous state are fully expressed phenotypically in an organism (1mk)
    4. Give an example of a trait in human beings where the condition whose term is named in (c) above expresses it (1mk)
  5. The diagram below shows an embryo sac
    5 ayguygadga
    1. Name the structures labeled D and E (2mks)
    2. On the diagram label the integuments (1mk)
    3. On the diagram, mark using letter X the point at which the pollen tube enters the embryo sac (1mk)
    4. What is the function of the pollen tube? (2mks)
    5. State two factors that hinders self-pollination in flowering plants (2mks)

SECTION B (40 MARKS)
Answer question 6 (compulsory) and any other one question from this section

  1. 1cm3 of catalase solution was added to equal volumes of hydrogen peroxide solutions at different pH values The time taken to collect 10cm3 of oxygen was measured The results were as follows

    pH solution

    Time taken to collect gas (minutes)

    5.5

    30

    6.0

    20

    6.5

    12

    7.0

    8

    7.5

    5

    8.0

    9

    8.5

    15

    9.0

    25

    1. Plot a graph of time against pH of solution (6mks)
    2. Account for the rate of reaction at:
      1. pH 75 (2mks)
      2. pH 55 (2mks)
      3. pH 90 (2mks)
    3. Write a word equation for the reaction above (1mk)
    4. What is the importance of the reaction you have given in c above? (1mk)
    5. Name an organ in the human body where the above reaction takes place (1mk)
    6. Other than the factor being investigated above name four other factors that affect the rate of enzyme controlled reaction (4mks)
  2. Describe the functions of a mammalian skin (20mks)
  3. Describe the process of double fertilization in a flowering plant (20mks)

MARKING SCHEME

  1. When testing a variegated leaf for starch, the following procedure is important
    1. The leaf is boiled in water
    2. The leaf is then boiled in methylated spirit
    3. The leaf is taken back to the hot water
    4. The leaf is spread on a white tile and irrigated with iodine solution.
      1. Why is the leaf boiled in hot water? (1mk)
        • To kill the protopiasm/ to open up the starch grains.
      2. Why is the leaf boiled in methylated spirit? (1mk)
        • To remove the chlorophyll/ discolour the leaf.
      3. Explain why the leaf is dipped in in hot water. (1mk)
        • To soften the leaf which was hardened by methylated spirit and remove any traces of ethanol.
      4. Explain the observation made when the leaf is irrigated with iodine solution. (2mks)
        • There is formation of blue/black patches; other areas remained brown (colour of iodine); blue/black confirmed presence of starch; brown absence of starch.
      5. What is a variegated leaf? (1mk)
        • A leaf which has some chlorophyll patches while other parts do not have chlorophyll.
      6. What is to destarch the leaf? (2mks)
        • To remove starch from the leaf by keeping it in darkness for 48 hours.
  2. The diagram below represents the lower jaw of a mammals.
    1. Name the mode of nutrition of the mammal whose jaws is shown above. (1mk)
      • Herbivorous
    2. State one structural and one functional differences between the teeth labeled J and L. (2mks)
      • Structural- tooth J is narrow/ sharp/chisel like while tooth L is broad/ridged.
      • Functional- tooth J is used for cutting and biting while tooth L is used for grinding food.
    3. Name the toothless gap labeled K. (1mk)
      • Diastena
    4. State the function of the gap. (1mk)
      • To allow manipulation of food by tongue, separating chewed and newly cut vegetation.
    5. Name the substance that is responsible for hardening of the teeth. (1mk)
      • Calcium Phosphate
    6. Distinguish between the terms homodont and hererodent. (2mks)
      • Homodont- organisms having same/ similar kind/ type of teeth, hence same function.
      • Heterodont- organisms having different type/ kind of teeth hence different function.
  3. The diagram below shows the gaseous exchange system of a locust.
    1. Name the structure labeled Q. (1mk)
      • Spiracle.
    2. State the function of the part labeled R. (1mk)
      • R is the trachea which is air tubes that penetrates the body space carrier oxygen to and carbon (iv) oxide away from tracheoles.
    3. How is the part labeled S structurally adapted to its function? (2mks)
      • Thin walled to reduce the diffusing, molecules. Since it lacks spiral bands of chitin to make the surface permanent to respiratory gases. Moist to dissolve respiratory gases.
    4. Identify the structure that perform the same function as one illustrated above in. (2mks)
      • Amoeba cell membrane
      • Fish- gill filament
    5. Name the causative agents for the following respiratory.
      Diseases. (2mks)
      • Whooping Cough. Bordetella pertussis
      • Pneumonia. Streptococcus Pneumonia.
  4. When pure breeding black guinea pigs were crossed with pure breeding white guinea pigs the offspring had a coat with black and white patches.
    1. Using letter G to represent the gene for black coat colour and letter H for white colour, workout the genotypic ratio of F2. (5mks)
      4 auygdygada
      Genotypic ratio 1GG:2GH:1HH;
    2. State the phenotypic ratio of F2 generation. (1mk)
      • Phenotypic ratio 1 black guinea ; 2 black guinea and white; 1 white
    3. Name the term used when two alleles in heterozygous state are fully expressed phenotypically in an organism. (1mk)
      • Co-dominance
    4. Give an example of a trait in human beings where the condition whose term is named in (c) above expresses it. (1mk)
      • Blood group AB
  5. The diagram below shows an embryo sac.
    1. Name the structures labeled D and E. (2mks)
      • D-polar nuclei; reject nucleus.
      • E- egg cell/ovam.
    2. On the diagram label the integuments. (1mk)
    3. On the diagram, mark using letter X the point at which the pollen tube enters the embryo sac. (1mk)
    4. What is the function of the pollen tube? (2mks)
      • Dissolves the tissue of the stigma, style and ovary as it grows through them; forms a pathway for the male gametes nuclei to reach the embryo sac.
    5. State two factors that hinders self-pollination in flowering plants. (2mks).
      • Protandry;
      • Protogyny;
      • Self-sterility;
      • Heterostyly;
  6. 1cm3 of catalase solution was added to equal volumes of hydrogen peroxide solutions at different pH values. The time taken to collect 10cm3 of oxygen was measured. The results were as follows.
    1. Plot a graph of time against pH of solution. (6mks)
    2. Account for the rate of reaction at:
      1. pH. 7.5 (2mks)
        • Reaction proceeds at maximum rate; optimum pH for enzyme;
      2. pH. 5.5 (2mks)
        • Reaction proceeds at low rate; enzyme denatured;
      3. pH. 9.0 (2mks)
        • Reaction proceeds at a low rate; enzyme denatured.
    3. Write a word equation for the reaction above. (1mk)
      • Hydrogen peroxide water oxgyen
    4. What is the importance of the reaction you have given in c above? (1mk)
      • Convert toxic of metabolism/ hydrogen peroxide into harmless nontoxic substances;
    5. Name an organ in the human body where the above reaction takes place. (1mk)
      • Liver
    6. Other than the factor being investigated above name four other factors that affect the rate of enzyme controlled reaction. (4mks)
      • Temperature;
      • Enzyme inhibitors;
      • Enzyme concentration;
      • Substrate concentration;
      • Enzyme cofactor and coenzymes.
        graph auyguydad
  7. Describe the functions of a mammalian skin. (20mks)
    Mammalian skin
    Parts and functions
    Cornified layer
    • For protecting the skin; against mechanical damage and bacterial infection
    • Protects the skin against water lossy
      Granular layer; 
    • Cells divide to give rise to cornified layer.
      Malphigian layer; 
    • Cells divide to give rise to the granular layer.
    • Contains melanin to protect the skin from harmful UV rays
      Sebaceous glands;
    • Produce an oily secretion called sebumy
      Sebum;
    • Antiseptic
    • Makes skin supple and waterproof
      Blood vessels
    • Bring oxygen and food to the skin
    • Removes waste from the skin
    • Control body temperature
      Nerve endings.
    • Enables mammals to detect changes in external environment. 
      Sweat glands,
    • produce sweat;
    • when sweat evaporates, it brings a cooling effect to the body.
    • Sweat excretes waste products from the body.
      Hairs or fur 
    • maintains body temperature
      Subcutaneous fat;
    • in the dermis.
    • Insulates the body against heat loss or gain. 
    • Act as a store for lipids
    • Site for manufacture of vitamin D
      Erector muscle;
    • Contract and relax making hair erect and lie as to regulate body temperature.
      Hair follicle and hair;
    • Erect and lie as to regulate body temperature.
      Lymphatic vessels
    • Drain excess tissue fluid.
      NB:- Award marks to part only when the function is correctly stated.
      Deny marks if part is wrong, mis-spelt or not stated even function is correct.
  8. Describe the process of double fertilization in a flowering plant. (20mks)
    • Pollen grains land onto the stigma and adhere to it as a result of the stigma cells secreting a sticky substance. It absorbs nutrients and germinates forming a pollen tube which grows down the style to the ovary, deriving nourishment from surrounding tissue. The pollen tube has tube nucleus at the tip and generative nucleus immediately behind it. As the tube grows downwards into the ovary the generative nucleus divides by mitosis/mitotically, to give rise to two male nuclei which represent the males gamete.
      The pollen tube penetrates the ovule/embryo sac/chalaza through micropyle. After the pollen tube enters the embryo sac the tube nucleus breaks down/disintegrates/ degenerates, leaving a clear passage for the entry of the male nuclei. The two male nuclei then enter into the embryo sac, where one fuses with the egg cell nucleus to form a diploid zygote which develop into an embryo. The other male nuclei fuse with the two/both polar nuclei to form triploid nucleus/primary endosperm nucleus which becomes the endosperm. This type of fertilization is called double fertilization.

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