BIOLOGY PAPER 2 - 2019 KCSE STAREHE MOCK EXAMS (QUESTIONS AND ANSWERS)

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INSTRUCTIONS TO CANDIDATES

  • This paper consists of TWO sections; A and
  • Answer ALL the questions in section A in the spaces provided after each question
  • In Section B, answer question 6 (compulsory) in the spaces provided and either question 7 or 8 in the spaces provided after question 8.
  • Candidates should answer all the questions in English.

SECTION A (40 MARKS) 

  1. The diagram below shows a cross section through the female part of a flower.
    b1b1fgrt
    1. Name the structures labeled W, X and Y.       (3 marks)
    2. State two functions of the pollen tube.      (2 marks)
    3. What happens to antipodal cells after fertilization?        (1 mark)
    4. Name the structure labeled K and state their role.  (2 marks)
  1.  
    1. Explain how convergent evolution may occur.                             (3 marks)
    2. The diagrams below show some organism structures that have been used as evidence of the process of evolution.
      BIO2Q2BBBNMHADCSV
      Name the type of evidence and explain it provides evidence to proof that the process of evolution may be taking place.                       (3 marks)
    3. Outline two evolutionary characteristics that adapt man to his environment.                        (2 marks)
  1.  
    1. Name the end products of glycolysis. (1 mark)
    2. The diagram below illustrates an experiment to determine the rate of respiration in a small insect.
      Q3BQSNASADXCCZ
      1. Name the chemical compound labelled X and state its function.                                       (2 marks)
      2. What changes would you expect to observe in the level of the coloured water in the capillary tube after the experiment has run for 10 minutes?      (1 mark)
      3. Explain the changes you have stated in (b) (ii) above.                                                   (3 marks)
    3. Why was it necessary to place the flask in a water bath?                                                   (1 mark)
  1. An investigation was performed by a group of students as shown in the set up below. 
    Q4VCZXADFSGGQ   
    After 30 minutes, the starch suspension had turned blue-black while iodine solution retained its colour.
    1. Name the physiological process that was being investigated in the experiment.                 (1 mark)
    2. Account for the results observed after 30 minutes.                           (3 marks)
    3. Explain what would happen to a red blood cell when placed in distilled water and left to stand for the same duration as for the experiment above.    (3 marks)
    4. Define cell physiology.          (1 mark)
  1. In a plant breeding research, a certain plant species was developed and found to be normally green in colour. A recessive gene for colour (g) causes these plants to be white in the homozygous state. In this state, the gene is lethal causing white plants to die at an early age soon after germination. In the heterozygous state, these plants are pale green in colour and grow to maturity.
    1. Suggest a reason for the early death of the plants with homozygous recessive genes.        (1 marks)
    2. A normal green plant was crossed with a pale green plant; work out the genotypes of the F1 generation. Show your working.             (4 marks)
    3. Seeds from the heterozygous plants were planted. The plant breeders allowed the resulting plants to self-pollinate. Work out the phenotypic ratio of the plants that would grow to become mature.(2 marks)
    4. Give an explanation for the occurrence of the pale green colour in heterozygous plants. (1 mark)

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

  1. A group of students carried out a study to estimate the population of grasshoppers in their school compound. The table below shows the number of grasshoppers that were collected from eight sites within the school compound.
    1.  
      1. Construct a bar graph to represent the number of grasshoppers collected from each site.                                              (6 marks)
      2. In a related exercise, students caught 240 grasshoppers, marked them with ink and then released them. After five days, they caught 160 grasshoppers and found that 40 were marked. Work out the estimated population of grasshoppers in the school compound.                                                (3 marks)
    2.  
      1. Identify the method described in (a)(ii) above.                                                             (1 ma
      2. Identify the instrument the students might have used to get the grasshoppers.                   (1 mark)
      3. State three factors that would influence the results in the method above.                                     (3 marks)
    3. Outline the adaptable observations the students would make on the grasshopper regarding;
      1. Locomotion.        (2 marks)
      2. Protection.    (2 marks)
      3. Feeding.         (2 marks)
  1.  
    1. Name the tissues in flowering plants responsible for secondary thickening (2 marks).
    2. Describe an experiment you would carry out to demonstrate the region of growth in the root of a bean seedling.                      (8 marks).
    3. Explain the role of growth hormones in metamorphosis of a housefly                               (10 marks).
  1.  
    1. Define natural selection. (2 marks)
    2. Natural selection brings about adaptation of a species to the environment. Discuss. (18 marks)


MARKING SCHEME

  1.  
    1. W – Polar nuclei;
      X – Ovum (egg cell);
      Y- Integuments;     (3mks)
    2. -Dissolves the tissues of the stroma, style and ovary; 
      - Forms pathway for the male nuclei to reach the embryo sac;    (2mks)
    3. -They disintegrate ;   (1mk)
    4. -Male nuclei;     carry out double fertilization.  (2mks)
  1.  
    1. Explain how convergent evolution may occur.                             (3 marks)
      Convergent evolution occur when two dissimilar structures /species /organisms with different embryonic origins ; change in response to similar environmental conditions / occupy same environment; and develops similar characteristics / modified to perform similar function.
    2. The diagrams below show some organism structures that have been used as evidence of the process of evolution.
      Name the type of evidence and explain it provides evidence to proof that the process of evolution may be taking place.                 (3 marks)
      (Embryology reveals that) Embryos of different vertebrate groups have similar morphological features during their early stages of development; This suggests a common ancestry; The closer the resemblance between the embryos in early stages, the closer the phylogenetic relationships;
    3. Outline two evolutionary characteristics that adapt man to his environment.                  (2 marks)
      High intellectual capacity / Cranium greatly expanded;
      Reduced incisors and canines unsuitable for killing prey or for self defence;
      Use of speech in communication;
      Locomotion is bipedal /on two limbs / upright;
      Has an apposable thumb for manipulation;
      Has a non-apposable toe in the foot;
  1.  
    1. Name the end products of glycolysis. (1 mark)
      Pyruvic acid;
    2. The diagram below illustrates an experiment to determine the rate of respiration in a small insect.
      1. Name the chemical compound labelled X and state its function.                                     (2 marks)
        Soda Lime / Sodium hydroxide;
        To absorb carbon (IV) oxide produced;
      2. What changes would you expect to observe in the level of the coloured water in the capillary tube after the experiment has run for 10 minutes?    (1 mark)
        Level of coloured water would rise;
      3. Explain the changes you have stated in (b) (ii) above.                                                  (3 marks)
        The Insect respired using oxygen and releasing carbon (IV) oxide; which was absorbed by soda lime;
        Uptake of oxygen caused a decrease in the air pressure within the flask causing a rise in the level of coloured water;
    3. Why was it necessary to place the flask in a water bath?                                                           (1 mark)
      To maintain an almost constant temperature; A slight change in air temperature causes air to expand / contract;
  1. An investigation was performed by a group of students as shown in the set up below                        
    After 30 minutes, the starch suspension had turned blue-black while iodine solution retained its colour.
    1. Name the physiological process that was being investigated in the experiment.                        (1 mark)
      Diffusion;
    2. Account for the results observed after 30 minutes.                                                                    (3 marks)
      Visking tubing is semi-permeable; allowing the smallsized Iodine molecules to pass through; but preventing the large sized starch molecules from crossing;
    3. Explain what would happen to a red blood cell when placed in distilled water and left to stand for the same duration as for the experiment above.                                                                       (3 marks)
      The cell sap is hypertonic to the solution / distilled water; hence water molecules moved into the cell by osmosis; making the cell to swell and eventually burst;
    4. Define cell physiology.                                                                                                      (1 mark)
      It is the study of the functions of cell structures;
  1. In a plant breeding research, a certain plant species was developed and found to be normally green in colour. A recessive gene for colour (g) causes these plants to be white in the homozygous state. In this state, the gene is lethal causing white plants to die at an early age soon after germination. In the heterozygous state, these plants are pale green in colour and grow to maturity.
    1. Suggest a reason for the early death of the plants with homozygous recessive genes.   (1 marks)
      They lack chlorophyll therefore cannot carry out photosynthesis( to manufacture food);
      As soon as their food reserves (in the Endosperm / cotyledon) are depleted, they die;
    2. A normal green plant was crossed with a pale green plant; work out the genotypes of the F1 generation. Show your working.                       (4 marks)
      5bqsnss
      Accept a relevant Punnet square as follows,
      Parental phenotypes; Parental genotypes; Gametes;
      Followed by the Punnet square below
       

      G

      g

      G

      GG

      Gg

      G

      GG

      Gg

    3. Seeds from the heterozygous plants were planted. The plant breeders allowed the resulting plants to self-pollinate. Work out the phenotypic ratio of the plants that would grow to become mature.(2 marks)
      5ccqsadczv
    4. Give an explanation for the occurrence of the pale green colour in heterozygous plants.        (1 mark)
      Pale green is due to incomplete dominance;
      Acc Blending and co-dominance; 

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

  1. A group of students carried out a study to estimate the population of grasshoppers in their school compound. The table below shows the number of grasshoppers that were collected from eight sites within the school compound.

    Site

    1

    2

    3

    4

    5

    6

    7

    8

    Number of grasshoppers

    280

    50

    190

    220

    85

    300

    175

    30

    1.  
      1. Construct a bar graph to represent the number of grasshoppers collected from each site.                        (6 marks) 
      2. In a related exercise, students caught 240 grasshoppers, marked them with ink and then released them. After five days, they caught 160 grasshoppers and found that 40 were marked. Work out the estimated population of grasshoppers in the school compound.                                              (3 marks)
        Total population = First captured X Second captured            ;
        Marked Recaptured
        240 X 160 ;
                 40
        =960 grasshoppers ;
    2.  
      1. Identify the method described in (a)(ii) above.                                                                        (1 mark)
        Capture recapture method ; / Capture – mark – release – recapture method;
      2. Identify the instrument the students might have used to get the grasshoppers.              (1 mark)
        Sweep net ; Specimen bottles;
      3. State three factors that would influence the results in the method above.                                 (3 marks)
        -Predation;
        -Availability of food;
        -Diseases;
        -Competition;
    3. Outline the adaptable observations the students would make on the grasshopper regarding;
      1. Locomotion.          (2 marks)
        Six jointed legs for walking;
        Well developed muscular hind legs for jumping / hopping ;
        Wings for flight;
      2. Protection.                                                                                                                         (2 marks)
        Body colour resemble the background colour of environment /Camouflage for difficult identification by predators;
        Spikes on Tibia of hind limbs for scaring away predators;
      3. Feeding.                                                                                                                           (2 marks)
        Maxillae with maxillary pulps for holding and directing food into mouth;
        Mandibles for cutting and crushing food ;
        Labium and Labrum for closing the mouth while food is being chewed;
  1.  
    1. Name the tissues in flowering plants responsible for secondary thickening (2 marks).
      -Vascular cambium;
      -Cork cambium;
    2. Describe an experiment you would carry out to demonstrate the region of growth in the root of a bean seedling.                       (8 marks).
      - Select a germinating bean seedling with a (straight) radicle;
      -Using a ruler, fine thread and an indelible ink, mark the radicle at equal intervals of 2mm;
      -Pin the seedling firmly onto a cork and place it in a boiling tube lined with wet filter paper;
      -Leave the set up undisturbed for five days;
      -Examine / observe the ink marks at the end of the experiment;
      -Measure the distance between successive ink marks;
      -Record your observations;
      -Compare with original ink marks and conclude;
    3. Explain the role of growth hormones in metamorphosis of a housefly                           (10 marks).
      -The housefly undergoes complete metamorphosis / egg, larva, pupa and adult;
      -The process of metamorphosisis regulated by moulting stimulating hormone, juvenile hormone and moulting hormone ( Ecdysone);
      -Juvenile hormone secreted by corpus allatum stimulates formation of larval cuticle / retention of larval stages / youthful characteristics / inhibits metamorphosis;
      -The larva feeds a lot and undergoes several moults;
      -Prior to each moult the neurosecretory cells secrete moulting stimulating hormone;
      -Moulting stimulating hormone stimulate prothoracic glands to secrete moulting hormone / ecdysone;
      -Ecdysone stimulates moulting of larva to larva; when the concentration of juvenile hormone is high;
      -When the larva matures, the corpora allatum disintegrates; and secretion of juvenile hormone ceases;
      -Absence of juvenile hormone causes moulting of larva to pupa;
      -The pupa does not produce juvenile hormone; hence allowing metamorphosis into an adult;
  1.  
    1. Process by which nature selects those individuals which are sufficiently well adapted to the environment and allow them to survive; but rejects those that are poorly adapted.(2mks)
    2. Individuals of same species show certain variations; which are caused by genes; and the variations can be passed from parents to their offsprings; through genetic inheritance; some of the variations or characters become more suited to the prevailing environment condition; due to selection pressure or competition; most organisms tend to produce more offsprings that the environment can support; this leads to struggle for existence; among the individual species e.g food, water, shelter, mates; due to stiff competition; individuals that posses characteristics that enable them to have competitive advantage stand a better chance of survival in the struggle; the result is that well adapted individuals survive; and their reproductive age; from where they pass on their desirable genes/ trails to their offsprings; those that are poorly adapted; fail to reach their reproductive age; and hence does not pass over the poor traits to their offsprings; and thus perish to allow the fittest survive.  (Max 18mks)
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