Biology Paper 2 Questions and Answers - Nyeri Mocks 2021 Exams

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INSTRUCTIONS

  • Write your name and index number in spaces provided
  • This paper consists of two sections A and B.
  • Answer all the questions in section A in the spaces provided.
  • In section B, answer questions 6 (compulsory) and either question 7 or 8.
  • Candidates should answer all the questions in English.

SECTION A

  1. The diagram below represents some gaseous exchange structures in humans;
         NM2021 Bio PP2 ET2 Q1
    1. Name the structures labeled. (3mks)
      1. K
      2. L
      3. M
    2. How is the part labeled J suited to its function? (3mks)
    3. What process is used to move air from the structure labeled L into blood capillaries? (1mk)
    4. Give the scientific name of the organism that causes tuberculosis in humans. (1mk)
  2. The figure below shows a germinating seedling
          NM2021 Bio PP2 ET2 Q2
    1. Name the parts labeled (3mks)
      1. A
      2. B
      3. C
    2. Give two important environmental conditions that are necessary for seed germination and state why they are important. (2mks)
    3. The part labeled D was removed from the above seedling three months later. After a few days, the plant became bushy with several lateral branches
      1. What is this phenomenon called (1mk
      2. Why did the removal of the stem tip result in a shorter plant with bushy growth? (1mk)
    4. Which class does this plant belong? (1mk)
  3. A pea plant with round seeds was crossed with a pea plant that had wrinkled seeds. The gene for round seeds is dominant over that for wrinkled seeds. Using letter R to represent the dominant gene, state;
    1. The genotype of parents if the plant with round seeds was heterozygous. (2mks)
    2. The gametes produced by the round and wrinkled seed parents. (2mks)
      • Round seeds
      • Wrinkled seeds
    3. The genotype and phenotype of F1 generation. Show your working. (3mks)
    4. What is a test cross? (1mk)
  4. The diagram below shows the transverse section of a young plant organ
        NM2021 Bio PP2 ET2 Q4diagram
    1.  
      1. Name the plant organ from which the section was obtained. (1mk)
      2. Give two reasons for the above (a) (i) (2mks)
    2. Give the functions of the structures; (3mks)
      1. A
      2. B
      3. C
    3. What type of cell are found in the part labeled D (1mk)
    4. Name the tissue labeled E (1mk)
  5. An experiment was set up as shown in the figure below
    NM2021 Bio PP2 ET2 Q5
    The glucose solution was boiled and cooled before adding yeast. The set up was left to stand for about 30 minutes
    1. Name the process that was being investigated. (1mk)
    2. Why was the glucose solution boiled (1mk)
    3. What was the role of the oil in the boiling tube? (1mk)
    4. What changes occurred in lime water and glucose yeast suspension.(2mks)
    5. Explain your answer in (d) above. (3mks)

SECTION B

  1. A group of students carried out a study of the population growth of flour weevils
     No. of days after introduction of weevils    Approximate present     No. of weevils present 
                    K             L
     0  20  20
     5  20  20
     40  200  300
     60  550  800
     80  560  1300
     100  650  1750
     120  640  1750
     135  650  1740
     150  645  1748
    A group of students carried out a study of the population growth of flour weevils. They put 16 grams of maize flour into two equal boxes K and L respective. They then introduced equal number of weevils into the boxes. The boxes were kept under similar environmental conditions. The weevils were counted at intervals and the results recorded in the table above.
    1. Using a suitable scale, draw two graphs on the same axes from the results in the table. (8mks)
    2. What was the approximate number of weevils present in the two boxes on the 70th day? (2mks)
      1. Number in K;
      2. Number in L;
    3.  
      1. On what day was the population of weevils in K 580? (1mk)
      2. Between which days was the population difference greatest. (1mk)
    4. Account for the shape of graph L between day 5 and day 100. (4mks)
    5. State factors that would make the human species assume the graph curve  above in K. (4mks)
  2. Describe the role of the liver in homeostasis in the human body. (20mks)
  3.  
    1. Describe the adaptive features of insect pollinated flowers. (12mks)
    2. Describe the roles of the following hormones in a mammalian reproductive cycle;
      1. Luteinizing hormone (3mks)
      2. Progesterone hormone (33mks)
      3. Oestrogen (2mks)

MARKING SCHEME

  1.  
    1.  
      1. K - pleural membranes
      2. L - alveolus
      3. M - intercostal muscles
    2.  
      • Has a C-shaped cartilage ring that support it preventing it from collapsing.
      • Has mucus secreting cells on the inner lining which traps fine dust particles and micro-organisms
      • Has hair like structures (cilia) that move the trapped particles and mucus to the pharynx.
      • It is hollow to allow passage of air.
    3. Diffusion
    4. Mycobacterium tuberculosis
  2.  
    1.  
      1. A - epicotyl
      2. B - cotyledon
      3. C - Hypocotyl
    2.  
      1. Oxygen
        • oxidize food substances releasing energy necessary for cell division and growth
      2. Water - -
        • Activate enzyme
        • Hydrolyse/dissolve food substance
        • Soften testa
        • A medium for enzymatic reaction
        • Transport nutrients for developing embryo
        • Favourable/ optimum temperature
        • Activate enzyme during hydrolysis
    3.  
      1. Apical dominance
      2. Removal of apical bud removes source of auxins, low concentration results in growth of lateral buds
        into side branches
    4. Dicotyledonae
  3.  
    1. Rr, rr
      Round seeds - R and r
      Wrinkled seeds r and r (all r)
      NM2021 Bio PP2 ET2 Ans3
    2. A cross between individuals of unknown genotype with a homozygous recessive individual armed at establishing the genotyped of unknown
  4.  
    1.  
      1. Dicotyledon stem
      2.  
        • Ring arrangement of vascular bundles
        • Presence of pith
        • Presence of vascular cambium
    2.  
      1. A - transport organic food substances from site of manufacture
      2. B - generates cells for secondary growth/thickening
      3. C - transports water and mineral salts to all parts of the plant
    3. Chollenchyma/parenchyma;
    4. Sclerenchyma;
  5.  
    1. Anaerobic respiration (fermentation, rej. respiration alone
    2. To expel oxygen out
    3. Prevents entry of air into the mixture
    4. Lime water forms white suspension; glucose yeast suspension rise in temperature
    5. Fermentation occurred producing energy and carbon (IV) oxide, leading to increase in temperature; CO2 makes lime water to form white suspension.
  6.  
    1.   
      NM2021 Bio PP2 ET2 Ans6a
    2.  
      1. K 555
      2. L 1020
    3.  
      1. 86th day
      2. 100-120
    4. Increase in population because there is adequate food; the number of reproducing individuals is increasing waste products have not accumulated to toxic levels
    5.  
      • Diseases
      • Lack of food
      • Death rate equal to birth rate
  7.  
    • Regulation of blood sugar/glucose
      • When level of glucose rises insulin is secreted by the pancreas √
      • Insulin stimulates the liver to convert;\
        • Excess glucose to glycogen √
        • Excess glucose to fats √
        • Excess glucose is oxidized (respired) to release energy √
      • This leads to a drop in blood sugar √
      • When blood sugar level drops below normal, the pancreas releases hormone; √ glucagon which stimulates the liver to;
        • Convert glycogen to glucose √
        • Converts fats and amino acids to glucose
        • Reduces oxidation of glucose
      • This raises the blood sugar level, back normal
    • Deamination
      • Excess amino acids are deaminated by converting the amino group to urea which is eliminated through urine √
    • Detoxification
      • It converts poisonous substances to less harmful compounds √
    • Thermorefulation
      • When body temperatures drop below normal, the liver increases its activities which releases heat to the blood which is distributed throughout the body √
      • When the body temperatures rise above normal, the liver lowers activities √ which generate less heat to the blood hence lowering body temperature
    • Regulation of plasma proteins
      • The liver synthesizes plasma proteins as they are required e.g. albumen fibrinogen √
  8.  
    1. Insect pollinated flowers
      • Flowers have brightly coloured parts e.g. corolla, sepals, florets to attract insects e.g. hibiscus petal.
      • Scented flowers to attract insects
      • Rough sticky pollen grains; stick on bodies or insects
      • Nectary guides that guide insect to the nectarines
      • Stigma sticky for pollen grains to stick
      • Corolla tube specially shaped to enable insect land; to come in contact with anthers and stigma
      • Nectaries at base of ovary that secret nectar to attract insect.
      • Stigma located inside the flower to ensure they get in contact with insect as it searches for nectar.
      • Anther small, attached to filament inside the flower so that insect can brush against them.
    2. Describe the roles of the following hormones in a mammalian reproductive cycle. (8mks)
      1. Luteinizing hormone (3mks)
        • Stimulate corpus luteum to secret progesterone
        • Causes maturation of ovum
        • Cause ovulation
        • Cause remains of graafian Follicle to change into corpus luteum
        • Stimulate maturation of graafian follicle
      2. Progesterone
        • Stimulate thickening of uterus wall/ endometrium/ proliferation
        • Stimulate increased blood supply to the endometrium.
        • Inhibit production of follicle stimulating hormone
      3. Oestrogen
        • Stimulate repair and healing of endometrium which was destroyed during menstruation
        • Stimulate anterior lobe of pituitary gland to produce luteinizing hormone

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