Biology Paper 1 Questions and Answers - KCSE 2021 Past Papers

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Answer all the questions in the spaces provided.

  1. Explain why it is necessary for plants to have their leaves spread out. (2 marks)
  2. The diagram below represents the transverse section through a young dicotyledonous stem and a structure, F, obtained from the same section.
    23 zxaxa
      1. Identify the part labelled E. (1 mark)
      2. State the function of the part labelled E. (1 mark)
      1. Label the part Z, on the section from which structure E was obtained. (1 mark)
      2. State two ways in which structure E is structurally adapted to its functions. (2 marks)
  3. State two ways in which herbaceous plants obtain their mechanical support. (2 marks)
    1. Name the proteinous substance that makes up the exoskeleton of members of Phylum Arthropoda. (1 mark)
    2. State two functions of the exoskeleton. (2 marks)
    3. State one disadvantage of the exoskeleton to members of Phylum Arthropoda (1 mark)
  5. Explain how each of the following structures adapt the fish to movement in water.
    1. Swim bladder (1 mark)
    2. head (1 mark)
  6. The diagram below represents the anterior view of a mammalian vertebra.
    ererer adada
      1. Identify the vertebra. (1 mark)
      2. Name the region of the vertebral column where the vertebra was obtained from. (1 mark)
    2. Name the part labelled G. (1 mark)
    3. Name the bone in the mammalian endoskeleton that articulates with the vertebra at the part labelled L. (1 mark)
  7. The word equation below shows a process that takes place in a certain living organism
    Lactose + Water Arrow Substance J + Galactose K
    1. Name process K.   (1 mark)
    2. State the importance of substance J in the living cells.  (1 mark)
  8. The setup below was used to demonstrate products of exhalation in grasshopers. The setup was left undisturbed for 48 hours and observations made.
      1. State the observation made in the test tubre.     ( 1 mark)
      2. Account for the observation made in 8(a) (i)   (2 marks)
    2. Explain the observation made in the test tube if similar setup included young growing plants in the jar containing grasshoppers at the beginning of the experiment.   ( 2 marks)
  9. State the difference between glycolysis and Kreb's cycle based on the following:
    1. Where they occur (1 mark)
    2. Amount of energy produced (1 mark)
    1. Distinguish between gaseous exchange and respiration. (2 marks)
    2. Explain the importance of algae in a pond(2 marks)
  11. State two advantages of an insect undergoing a complete metamorphosis process. (2 marks)
  12. Complete the table below, outlining the differences between members of Class Diplopoda and Chilopoda based on the characteristics given. (3 marks)
     Characteristic Diplopoda Chilopoda
    Body shape     
    Body segmentation    
    Number of legs per segment    
    1. State two reasons why the snake is classified as a reptile. (2 marks)
    2. Name the structure which enables Paramecium to move. (1 mark)
  14. The diagram below represents an apparatus used to collect specimens for study.
    1. Identify the apparatus. (1 mark)
    2. State why it is advisable to have the apparatus illustrated above made of glass. (1 mark)
    1. State two activities that take place in the ovule of a flowering plant during fertilisation. (2 marks)
    2. State two functions of the seminal fluid in reproduction. (2 marks)
    3. Name the hormone that stimulates the contraction of muscles of the uterine wall during birth (1 mark)
    1. Giving an example in each case, state the difference between internal and external fertilisation. (2 marks)
    2. State the agent of pollination in a maize plant. (1 mark)
  17. Identify the response and receptor from the following list of sensory structures and processes:
    • salivary gland
    • smell of fried eggs
    • olfactory cells 
    • salivation.
      1. Response (1 mark)
      2. Receptor (1 mark)
  18. Explain how the knowledge of apical dominance is applied in agriculture, (2 marks)
    1. Explain why the population of people with sickle-cell anaemia is higher in malaria-prone arcas. (2 marks)
    2. Explain why it is not advisable to put a patient on a drip of distilled water for rehydration (3 marks)
  20. In an experiment, the stem of a plant was cut above the soil surface and a thin, transparent tube inserted immediately as shown below.KCSE2021P1BioQ20
    1. Name the process ny which mineral salts are absorbed from the soil.   (1 mark)
    2. Account for the observation made at the end of the experiment.    ( 3 marks)
  21. In an experiment. live termites were placed at the junction between two interconnected chambers, L and M as shown below. Chmaber L contained dry cotton wool and was covered by a transparent lid. Chamber M contained moist cotton wool and was covered with an opaque lid.
    1. State the likely observation m at the end of the experiment.  ( 1mark)
    2. Explain two factors responsible for the observation in 21 (a) (i)
  22. State one function of each pf the following parts of the mammalian movable joints:
    1. Synovial membrane  ( 2 marks)
    2. Ligaments   ( 1 mark)
  23. A form of dwarfism called Achondroplasia is caused by a dorminant gene (D) located on body chromosomes. Individuals who are homozygous (DD) for the condition do not survive. Those who are homozygous (dd) are of normal height, while heterozygous (Dd) are dwarfs. If two dwarfs married, work out the likely survival chances of their offspring.    (4 marks)
  24. Explain the difference in Basal Metabollic Rate (BMR) between a 55-year-old man and his 8-year-old grandson.           ( 3 marks)
  25. The illustration below represents a plant learners collected and drew during a field study.
    With a reason, state the Diviison and Class to which the plant belongs:
    1. Division:......( 1 mark)
      Reason .... ( 1 mark)
    2. Class: ...........( 1 mark)
      Reason: ........(1 mark)


  1. To expose the leaves (or increase the surface area exposed) to light/ carbon (IV) oxide/moisture/water; for maximum manufacture of food/ photosynthesis;
    (2 marks)
      1. Cambium (tissue);     (1 mark)
      2. For secondary growth (increase in the girth) of the plant;      (1 mark)
        • Elongated, hollow and firmly connected to one another forming a composite material/for strength;
        • Lignified walls for strength;pits to allow for passage of materials;
        • Narrow to enhance capillarity;
        • Hollow for passage of materials;   (2 marks)
    • Twinning around other plants/surfaces;
    • Turgor pressure of the living cells;
    • Use of tendrils;    (2 marks)
    1. Chitin;     (1 mark)
      • (Hardened to) support/protect inner, delicate tissues;
      • Water-proof to prevent (excessive) water-loss/desiccation;
      • For muscle attachment;
      • For movement;       (2 marks)
    3. Hinders/limits (smooth/continuous) growth;      (1 mark)
    1. Provides the fish with buoyancy/adjust its vertical position in relation to depth in water (when inflated or deflated);    (1 mark)
    2. Pointed, streamlined, reducing resistance as it move/cuts through the water easily/has mucous/slimy substance that reduces friction, enhancing movement;        (1 mark)
      1. Thoracic (vertebra);    (1 mark)
      2. Thoracic region;   (1 mark)
    2. Neural spine;    (1 mark)
    3. Rib (bone);   (1 mark)
    1. Condensation;   (1 mark)
      • Provides energy (during respiration);
      • Are building units for larger/complex carbohydrates;    (1 mark)
      1. Lime water turned milky/forms a white precipitate/turbid;   (1 mark)
      2. Grasshoppers exhale carbon (IV) oxide; which forms a white precipitate with lime water;   (2 marks)
    2. Rate of formation of the precipitate will be slower/no white precipitate will form in the test tube; (part of) the carbon (IV) oxide (produced by grasshoppers) is used up by the growing plants to make food/photosynthesize);   (2 marks)
     Glycolysis  Kreb's cycle
     a) In the cytoplasm  a) In the matrix of the mitochondria;
     b) Yields less energy (about 2 molecules of ATP)  b) Yields more energy (about 38 ATP molecules)
    (2 marks)
    1. Gaseous exchange involves passage of respiratory gases (oxygen/carbon (IV) oxide) across respiratory surfaces; while respiration is the chemical breakdown/oxidation of substrates/food substances in the living cells (to release heat/energy, carbon (IV) oxide and water);   (2 marks)
      • Releases oxygen into the water for use by other organisms (during the day while photosynthesizing);
      • Utilizes the CO2 produced during respiration of other organisms in the pond reducing the acidity in the water/pond.
      • Used as food by other organisms in the pond;n  (2 marks)
    • Survives harsh environmental/climatic conditions and predators;
    • Feeds on a variety of food;     (2 marks)
     Diplopoda  Chilopoda
     Cylindrical  (Dorso-ventrally) flattened;
     More segments (range from 25-100)  Fewer segments (between 15-21);
     Two pairs of legs per segment  One pair per segment;
    (3 marks)
  13.  .
      • Body covered with scales;
      • Ectothermic;
      • Lay eggs;
      • Poikilothermic;   (2 marks)
    2. Cilia/cilium;   (1 mark)
    1. Specimen bottle;   (1 mark)
    2. To be able to see through it/glass is transparent hence some features on the specimen can be seen/studied directly when the specimen is in the bottle; OWTTE      (1 mark)
      • Tube nucleus disintegrates;
      • One of the male nuclei fuses with the egg cell nucleus; (forming a diploid zygote which develops into an embryo);
      • The other male nucleus fuses with the polar nucleus to form a triploid nucleus;      (2 marks)
      • Neutralizes the spermatozoa;
      • It's alkaline, neutralizing the vaginal fluids;
      • Activates sperms;   (2 marks)
    3. Oxytocin hormone;
      • External fertilization occurs in amphibians/fish;
        The females lay eggs (in water) the males shed sperms on the eggs to fertilize them externally;
      • Internal fertilization occurs in mammals; the eggs develop within the females' body (uterus) till parturition;      (2 marks)
    2. Wind (pollination);  (1 mark)
    1. Salivation;     (1 mark)
    2. Olfactory cells;     (1 mark)
  18. (Farmers) prune fruit/horticultural crops; encouraging sprouting of branches, leading to increased yields;    (2 marks)
    1. Individuals with sickle-cell traits do not succumb to malarial attacks; hence over time, they reproduce/give rise to more individuals with similar traits in such regions;  (2 marks)
    2. Distilled water is hypotonic compared to the (individual patient's) internal body fluids; by osmosis; the cells would take in distilled water, swell and burst/haemolyse (leading to death/more damage;   (3 marks)
    1. Active transport/diffusion;     (1 mark)
    2. Water was seen to have risen in the capillary tube; due to the root pressure in the (roots of the stump); the water molecules in the (thin) capillary tube formed a continuous stream due to cohesive forces between the water molecules/adhesive forces between water molecule and the tube;    (3 marks)
    1.  The termites will have moved to chamber M;  (1 mark)
    2. The termites were attracted to:
      • the humid/moist conditions in chamber M;
      • the darkness in chamber M (as a result of the opaque cover/ lid);       (2 marks)
    1. Secretes the synovial fluid (which lubricates the joints);     (1 mark)
    2. Provides attachment of muscles to the bone;    (1 mark)
    (4 marks)
  23. The 8-year-old grandson has a higher BMR compared to the 55-year-old man; the son is more active/has actively dividing cells; hence a higher rate of BMR to generate the necessary energy/replenish the lost heat (since the son has a higher surface area to volume ratio exposed for heat loss); OWTTE
    (3 marks)
    1. Division: Spermatophyta;    (1 mark)
      Reason: Presence of flowers/roots/leaves/differentiated plant body;    (1 mark)
    2. Class: Dicotyledonae;   (1 mark)
      Reason: Net-veined leaves/broad leaves/tap root system/ petiole/ presence of flower;  (1 mark)
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