Biology Paper 2 Questions and Answers - Asumbi Girls High School KCSE Mock 2021

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  • Answer all the questions in Section A in the spaces provided.
  • In section B answer question 6 Compulsory and Either Question 7 or 8


  1. The quantity of urine passed per day was established in five mammals A, B, C, D, and E of the same species in the natural habitats. The results are ash shown in the following diagram;
    1. Which of the above mammals is likely to be excreting urine very high in ammonia? Explain (2mks)
    2. Which of the five mammals was likely to be living in a desert? Explain (2mks)
    3. State two structural differences expected in the nephron of mammals A and D. (2mks)
    4. Name two physiological mechanisms used in mammal D to regulate its salt and water balance in the body. (2mks)
    1. State the function of the following parts of mammalian ear;
      1. Tympanic membrane (1mk)
      2. Pinna (1mk)
      3. Ear ossicles (1mk)
    2. Give two defects of mammalian eye (2mks)
    3. The diagram below show how the iris and pupil of a human eye appear under different
      1. Name the structures labeled X and Y (2mks)
      2. State the condition that lead to the change in appearance shown in the diagram labeled B
  3. A biologists carried out a study to investigate the growth of a certain species of herbivorous fish and the factors influencing plant and animal life in four lakes A,B,C and D. The lakes were located in the same geographical area.
    Two of the lakes A and B were found to contain hard water due to the presence of high content of calcium salts. The mean body length of 2 year old fish, amount of plant use and invertebrates biomass in each lake were determined. The data was shown in the table below;
    Lakes  Means of fish
    body length (m)
    Type of
    Amount of
    plant life 
     Invertebrate biomass g/cm3
    insects snails  crabs  worms 
    A  31.2  Hard  1050  11  300  10 180
    B  38.6  Hard  950 72  100  9 90
    C 18.4 Soft  1.2  79  0  2 20
    D 16.3 Soft 0.5  99  0  1  10

    1. Describe the procedure that may have been used to determine the mean body length of the fish. (4mks)
    2. What are the likely reasons for the difference in mean body length of the fish living in lakes A and D (2mks)
    3. Explain why primary producers have a higher biomass than primary consumers. (2mks)
  4. In an experiment to investigate a factor affecting photosynthesis a potted plant which had been kept in the dark overnight was treated as shown in the diagram below and exposed to light.
    1. why was the potted plant kept in the dark overnight? (1mk)
    2. Which factor was being investigated in the experiment? (1mk)
      1. Which test did the students perform to confirm photosynthesis in the leaves labeled P and
      2. State the results obtained in the leaves labeled P and Q.
      3. Explain the results obtained in the leaves labelled P and Q
      4. What was the purpose of the leaf Q in the experiment? (1mk)
  5. The diagram below shows samples of blood obtained from two different persons A and B
    1. What genetic disorder is person B suffering from? (1mk)
    2. State one advantage and one disadvantage of the disorder exhibited in person A. (2mks)
    3. Work out the genotype and phenotypes of the resulting offspring of a marriage between person A and B. Show your working (5mks)


  1. The data below represents levels of progesterone hormone produced in a female’s body within a period of 34 days. Study the data and use it to answer the questions that follow
    NB: The days were counted from the 1st day that menstruation was noticed.
     Day Progesterone hormone concentration in arbitrary units 
    1 6
    2  5
    3  3
    4  2
    5  1
    6  1
    8  1
    10 2
    12 4
    14 7
    16 8
    20 9
    22 10
    24 10
    26 10
    28 10
    30 11
    32 11
    34 11

    1. Plot a graph of progesterone concentration against time using a suitable scale. (6mks)
    2. Account for the progesterone levels in the blood between
      1. Day 1 - day 5 (2mks)
      2. Day 14 – day 20 (2mks)
      3. Day 28 – day 35 (2mks)
    3. Name two structures that produce progesterone in females . (3mks)
    4. Suggest the process that usually takes place at day 14. (1mk)
    5. Suggest two other hormones that were in high concentration in the body of the female between day 10 – 15 . Give reasons for your answer. (4mks)
  2. Describe how water moves from the soil to the leaves in a tree. (20mks)
    1. Describe the process of carbohydrates digestion in human beings. (12mks)
    2. Describe the flow of energy from the sun through the different trophic levels in an Ecosystem (8mks)

Marking Scheme

    1. C; Ammonia is very toxic and highly soluble hence requires a lot of water for dilution;
      producing large amount of dilute urine; Max 2
    2. D; There is a shortage of water hence excrete little amount of using to conserve water; 2 mks
       A  D
      Short loop of Henle 
      Many and large sized glomeruli
      Long loop of Henle;
      Few and small sized glomeruli;
      2x1= 2mks
      • Uses metabolic water;
      • Reduced level of sweating; 2x1= 2mks
      1. Tympanic membrane
        • Receives sound waves (from the air); and vibrates;
        • To transmit them to the ear ossicles/ maleus/ stripes; Rej hammer, anvil and stirrup 2x1=2mks
      2. Pinna
        • Collects sound wave
        • Concentrates sound waves and directs it to the auditory meatus/ ear canal; 2x1=2mks
      3. Ear ossicles
        • Amplify/transmit sound vibrations; from the tymphanic membrane to the inner ear/venestra ovalis/oval window;
    2. Two defects of mammalian eye
      • Short- sightedness/myopia;
      • Astigmatism;
      • Long-sightedness/hypermetropia;
      • Squintedness;
      • Oldsight(presbyopia);
      • Mark the first two 2x1=2mks)
    1. Fish were caught, age determined; 2 years old retained; length measured and recorded. This was done repeatedly until a large number were measured; the total length divided by number of fish; (4mks)
    2. Lake A has hard water with more calcium than Lake D necessary for bone formation;
      Fish in A grow faster and greater bone length than fish in Lake D;
      Lake A has more food which fish eat than lake D;
      Max – 2mks
    3. Receives light energy directly from the sun; and energy is lost from one trophic level to the
      Next; 2x1= 2mks
    1. To destarch /remove starch from the leaf; Acc plant (1mk)
    2. Carbon (IV) oxide; Acc Co2 Rej if (iv) in small letter (1mk)
      1. (Test for) starch; Rej Iodine test (1mk)
      2. P- Retained the colour of iodine solution/Brown/yellow; (1mk)
        Q Turned blue –black; (1mk)
      3. P- Did not photosynthesis/No starch was formed because sodium hydroxide pellets absorbed Carbon (IV) oxide; (1mk)
        Q- Photosynthesis /starch was formed because Carbon (IV) oxide was in the flask; (1mk)
    4. Control (experiment); (1mk)
    1. Sickle cell anemia; (1mk)
    2. Advantage – individuals having this trait hardly/rarely suffer from malaria;
      Disadvantage - Suffocation due to insufficient supply of oxygen during strenuous activity;
      2x1= 2mks
    3. Parental phenotypes sickle cell trait
      1. Day 1 - day 5
        Level of progesterone was going down; causing the shedding of the endometrium; (2mks)
      2. Day 14 – day 28
        Level of progesterone increasing rapidly; this occur after menstruation to cause healing of the cells of the uterus; (2mks)
      3. Day 28 – day 35
        Level of progesterone increases further; this is because implantation has taken place and progesterone is required to maintain pregnancy; (2mks)
    3. Production of progesterone after 28th day increases due to release of egg and formation of Corpus luteum; in preparation for conception; and also to maintain pregnancy; (3mks)
    4. Ovulation; (1mk)
    5. Oestrogen and luteinizing hormone
      Oestrogen; – to stimulate repair and healing of the endometrium/wall of the uterus stimulates the anterior lobe of pituitary gland to produce the luteinizing hormone; (2 mks)
      Luteinising hormone;- stimulates ovulation; (2 mks)
    • Water exists as a thin film in the soil between soil particles;
    • The concentration of cell sap of root hair cells is greater than that of the surrounding solution in the soil;
    • Thus drawing water molecules across the (cell wall and) membrane into the root hair cells; by osmosis;
    • Water drawn into the root hair cells dilutes the cell sap/making it less concentrated than that in the adjacent cortex cells of the root;
      (Due to the osmotic gradient)water moves from the root hair cell into the cortex cell; Then from cell to cell (by osmosis);
    • Across the endodermis by active transport; into the xylem vessels; (of the root)
    • Then conducts the water up the xylem (vessels) of the stem;
    • Into the xylem of the leaves;
    • Water is pushed rises up by root pressure;
      (in the xylem vessels) water rises by capillarity; cohesive; and adhesive forces;
    • Water moves as a continuous /an interrupted water column in the xylem (vessels) up the tree to the leaves;
    • As water vaporizes from the spongy mesophyll cells, their cell sap becomes more concentrated than adjacent cells;
    • This increases the osmotic pressure of the spongy mesophyll cells;
    • As a result water flows into the cell from other surrounding cells, which in turn takes in water from xylem vessels within the leaf veins;
    • This creates a pull/ sunction force/ transpiration pull;
    • That pulls a stream of water from xylem vessels in the stem and roots;
    • The transpiration pull maintains continuous column of water from the roots;
    • Total points 23 Max 20
  8. Carbohydrates digestion in human being
    1. In the mouth; food is chewed; to increase surface area of enzyme activity;
      • (Saliva contains) salivary amylase ptyalin; saliva (mixes with food and) provides an alkaline medium; for amylase/ptyalin (enzyme);
      • Salivary amylase acts on starch and converts it to maltose;
      • In the duodenum; food is mixed with bile; and pancreatic juice;
      • Bile provides alkaline medium; for activity of duodenal enzymes; ACC. correct example of enzyme.
      • ACC .Sodium hydrogen carbonate for bile Rej Sodium bicarbonate
      • And neutralizes acidic chime /food from stomach;
        (Pancreatic juice contains) pancreatic amylase; which converts starch to maltose; Acc Amylose for starch
      • In the ileum; epithelial cells in the ileum secretes succus eutericus/intestinal juices; which contains invertase/sucrase; which acts on sucrose and converts it to fructose and glucose;
      • Lactase; which acts on lactose and converts it to glucose and galactose; Maltase; which acts on maltose and converts it to glucose;
        Total 23 Max 12 mks
      • Energy from the sun is trapped by chlorophyll in green plants; which occupy the 1st trophic
      • Level producers; and used during photosynthesis; food /carbohydrates are made; Energy in form of food goes to the herbivores /primary consumers which feed on green plants; which occupy the 2nd trophic level; in the herbivore/primary consumers food/carbohydrate is digested; absorbed and assimilated; when carnivores/ secondary consumers; feed on herbivores energy floes to them / to the 3rd trophic level; Tertiary consumers feed on carnivores; etc. plants, herbivores, carnivores die; material/energy flows to the decomposers;
        Total 14 max 8

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