Biology Paper 1 - 2021 KCSE Prediction Questions and Answers Set 1

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Instruction to Candidates

  1. Answer all questions
  2. All questions must be written in English


  1. State the functions of each of the following organelles: (2mks)
    1. Plasma membrane
    2. Ribosome
    1. State two ways by which leaves of plants are adapted to gaseous exchange. (2mks)
    2. Name the structure from which the above process occurs.                                               (1mk)
  3. How do identical and fraternal twins arise?
    1. Identical          (2mks)
    2. Fraternal (1mk)
  4. State three reasons why it is important for plants to lose water to the atmosphere. (3mks)
  5. What is meant by destarching a leaf? (1mk)
  6. State two ways in which sunlight increases the rate of transpiration. (2mks)
  7. List two features of flowers that attract insect pollinators. (2mks)
  8. State three activities in human digestive system that depend on respiration.       (3 mks)                                                                    
  1. In the table below, indicate the deficiency diseases caused by lack of given nutrients in man. (2mks)


    Deficiency disease



    Vitamin A

    1. Give two ways in which red blood cells are adapted to carry out their functions.         (2mks)
    2. Name chemical forms in which carbon IV oxide is transported in the human body.     (2mks)
  1. Name any two divisions of the kingdom plantae.          (2mks)
    1. Name the hormone produced in human body when one takes in a large amount of water. (1mk)
    2. What disease results from the inadequate production of the hormone in 12(a) above?   (1mk)
    1. A cow in a paddock was found to be infected with ticks. State the trophic level occupied by the        (2mks)
      1. Cow
      2. Tick
    2. Give one disadvantage of using pesticide to eliminate the ticks. (1mk)
    3. Write a food chain arising from the above feeding relationship                                   (1 mk)
  1. State two roles of water in germinating seeds?          (2mks)
    1. State two limitations of fossil records as an evidence for organic evolution theory. (2mks)
    2. State an idea that led to the formulation of Lamarck’s theory of evolution.                   (1mk)
  1. Explain what happens to red blood cells placed in distilled water for 20 minutes. (3 mks)
    1. Write the base sequence of M RNA that would be coded from the DNA strand shown below. 
    2. How many nitrogenous bases code for a single amino acid?                                            (1mk)
  1. Why are animal cells put in isotonic solution when performing an experiment?          (2mks)
  2. Study the diagram below
    1. Suggest the aim of the experiment. (1mk)
    2. Account for the results observed at the end of the experiment. (2mks)
  1. Explain why a camel has a longer nephron than a whale. (3 mks)
  1. State role of the following bacteria in the nitrogen cycle. (3mks)
    1. Nitrosomonas
    2. Nitrobacter
    3. Azotobacter
  1. Explain the importance of each of the following during digestion in man.
    1. teeth (1mk)
    2. Saliva .(1mk)
    1. Distinguish between prokaryotic and eukaryotic cells.                                                          (2mks)
    2. Name one kingdom with:
      1. Prokaryotic cells (1mk)
      2. Eukaryotic cells(1mk)
  1. What would blood gain on passing through each of the following organs:
    1. The lungs(1mk)
    2. Active muscles(1mk)
  1. How do sunken stomata lower the rate of transpiration? (2 mks)               
  1. State two adaptations of fruits dispersed by wind. (2mks)
    1. Describe two ways how white blood cells fight against infection.                   (2mks)               
    2. State the function of blood platelets       (1mk)
  1. Calculate the diameter of the cells in micro-metre( µm) given that the diameter of the field of view is 3mm and that they are 10 cells across the field of view, the total magnification was x100. (3mks)
    1. Apart from AIDs, name one diseases of the reproductive system in man that is caused by viruses. (1mk)
    2. State one way by which HIV/AIDs is transmitted from mother to child.                                   (1mk)
    1. Below is a diagram of a specialized cell:
      1. Name parts        (2mks)

      2. What is the role of part D?            (1mk)
    2. State two roles of progesterone. (3mks)













    1. Control movement of materials in and out of the cell;
      Enclose the cell contents
    2. Site of protein synthesis;
      • Presence of stomata to allow passage of gases;
      • Presence of intercellular spaces/air passages to allow free circulation of air;
      • Thin to allow easy diffusion of gases;
      • Flattened shape to offer large surface area of air to reach cells;
      • Moist inner surface of cells to allow easy diffusion of gases;
      • Exposure to air to allow easy diffusion of gases; Mark only first two.
    2. Stomata
    1. Identical – a fertilized ovum divided into two; and develops into two separate embryos;
    2. Fraternal – two different ova are fertilized;(by different sperms)
  2. -Cools the plant cells
    - Provide mechanism through which mineral salts and water are transported in plants cell
    - Removal of excess water from the plants.
    - Maintain turgor of cells
  1. Process by which the leaf is made devoid of starch; (by keeping it in dark (about 48 hours); so that all starch present is used up.)
  1. -By increasing internal leaf temperature thus high rate of evaporation of water from the leaf;
    -By increasing the size of stomata opening aperture hence large surface area for water loss;
  1. -brightly colored petals;
    -Sweet scented
    - nectar from nectaries (nectaries glands); Mark only first two
  1. - Absorption of digested food materials
    - Secretion of digested enzymes/hormones/mucus
    - Contraction and relaxation of smooth muscles of alimentary canal to bring about peristalsis
    - Chewing/mastication(movement of jaw muscles)
  1. iron-anaemia, Vit A-Night blindness/poor night vision
    1. -lack of nucleus increasing the surface area of haemoglobin package;
      -Small in size to squeeze in the small capillaries;
      -Numerous/many to increase surface for efficient transport of oxygen;
      -Biconcave to increase the surface area for oxygen to diffuse in; Mark only first two.
    2. – Weak carbonic acid;
      - Hydrogen carbonate;
      - Carbaminohaemoglobin
  1. – Bryophyta;
    1. Antidiuretic hormone (ADH)/ Vasopresin;
    2. Diabetes insipidus; rej. Water diabetes
      1. Primary consumer;
      2. Secondary consumer;
    2. -Pollutes environment;
      - kill non-targeted organisms Mark first one
    3. grass/plants   →    cow     →    tick      
    • Hydrolysis of stored food;
    • Acts as a solvent for hydrolysed foods;
    • Medium of transport;
    • Activation of enzymes for hydrolysed foods;
    • Medium for enzymatic reactions;
    • Soften seed coat to allow plumule and radical to come out; 
      Mark only first two
    1. Desctruction of fossils by geological activities;
      Distortion of information due to sedimentation;
      Missing record/linkss;       only first two
    2. – the theory of need;
      - the theory of use and disuse;
      - acquired traits can be inherited;
  1. Red blood cells draw in water by osmosis. They swell/enlarge and the cell membrane Bursts ( by a process called haemolysis)
    2. Three;
  1. To maintain osmotic pressure of the cells in the tissue; to as to obtain accurate results.
    To avoid the cell gaining or loosing water;which can inaccurate resu;lts
    1. - To investigate products of (aerobic) respiration
      -To investigate the gas produced during respiration
      Reject anaerobic respiration
    2. – Lime water form white precipitate; to show that carbon IV oxide is produced;
      - blue cobalt II chloride turns pink; due to the presence of water produced when food burns
      Mark the two points independently
  1. A camel is a desert animal, a larger nephron increases the surface area; for reabsorption of water; to conserve it; while a whale is an aquatic animals (hence does not need to conserve water)
    1. Converts Ammonia to nitrites;
    2. Converts nitrites to nitrates;
    3. Fix nitrogen into ammonia which is then converted to nitrates;
    1. Cut /chew/crush/grind food to increase surface area for digestion;/easy swallowing.
    2. -Contain water which is a medium for chemical reactions; / acts as a solvent.
      -Contain salivary amylase/ptyalin which digests starch to maltose.
      -contain mucus/mucin to lubricate food material Any first one.
    1. Prokaryotic – nuclear materials not membrane bound (naked;)
      Eukaryotic – nuclear bound by membrane; NB-Use sentence connector i.e. use of while for student to score)
      1. Monera;
      2. Protoctista/plantae/animalia/fungi;
    1. The lungs – oxygen;
    2. Active muscles carbon IV oxide;/ lactic acid.
  4. Water vapour accumulates in the pits/depression; lowering the water vapour concentration gradient thus lowering the rate of water loss from the leaves.
  5. -Are small and light to be carried easily by wind;
    -Develop wing-like extensions to increase surface area for increased buoyancy in the air;
    -Have hair like structures or floss to increase buoyancy in the air; (only first two).
    1. -By engulfing and digesting pathogens;
      -By secretion of antibodies; which destroy pathogens and their products.
    2. blood clotting to stop further bleeding
    1. Hepatitis B;
    2. – Breast feeding;
      -Through placenta;
      1. A – Axon;
        D – myelin sheath;
      2. insulate the axon;
    2. -growth of mammary glands
      -Inhibit FSH;
      -Inhibit prolactin release
      Inhibits contraction of myometrium; Only first two
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