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Answer all questions in this section

    1. the table below shows the concentration of sodium and iodine ions in pond water and in the cell sap.

      Sodium ion concentration 

      Iodine concentration 

      Pond water 



      Cell sap



      Giving reasons name the process through which each of the ions is taken up by the plants
      1. Sodium ion (2mks)
      2. Iodine ion (2mks)
    2. The lettuce plant was then treated with a chemical substance that inhibits the synthesis of ATP Giving a reason, state which ion was affected by the treatment                    (2mks)
    3. Explain why fresh water fish cannot survive is marine habitat                                 (2mks)
  1. The diagram below represents recycling of nutrients in a certain ecosystem
    1. Name the trophic level represented by Q                                                                   (1mk)
    2. Name the process represented by:                                                                                    (3mks)
    3. Name the organism involved in process II                                                                       (1mk)
    4. What would happen within the ecosystem if all the secondary consumers were eliminated? (3mks)
    1. what is non disjunction     (1mk)
    2. Haemophilia is a sex linked trait
      1. If a normal woman but carrier for haemophilia marries a normal man, work out the phenotype of the offspring using a genetic cross     (3mks)
      2. Name two chromosomal disorders     (2mks)
    3. Other then haemophilia, state any other two sex - linked defect in man                 (2mks)
  1. An experiment was set to investigate the effect of unilateral light on the growth of oat coleoptiles. The diagram in the table represents the experimental set ups the start and the result at the end of experiment.
    1. Account for the reaction in experiment set up A                                                        (3mks)
    2. Explain the purpose of experiment set up B and C                                                    (3mks)
    3. Explain the results in the experiment set D and E                                                      (2mks)
  1. The diagram below represents a transverse section through mammalian skin
    1. Name the structures A and B          (2mks
      1. Explain how the hair in human beings helps in keeping the body warm        (3mks)
      2. Explain other methods by which the skin helps to keep the body warm       (3mks)

Answer question 6 (compulsory) and either question 7 or 8 in the spaces provided.

  1. The table below shows how the width of the stomata and the wind speed can affect the rate of transpiration from a leaf of a plant. The width are measured in micrometers (nm)

    Width of stomata in (nm) 

    Rate of transpiration in gm/M2/ hour 


    In still air

    In wind
















    1. On the same axes plot a graph of rate of transpiration against width of the stomata (8mks
    2. Use your graph to predict the rate of transpiration when the stomata have a width of 8nm
    3. Describe the relationship between the width of stomata and the rate of transpiration in still air (3mks)
    4. Explain why the rate of transpiration in wind differs from rate in still air                 (3mks)
    5. Explain why transpiration is important in plants                                                        (4mks)
  1. Describe the various ways in which seeds and fruits are adapted for dispersal (20mks)
    1. State the possible application of the following plants hormones in agriculture          (8mks)
      1. Auxins
      2. Gibberellins
    2. Explain how each of the following serves as evidence of organic evolution
      1. Fossil records           (3mks)
      2. Comparative antinomy (6mks)
      3. Geographical distribution    (3mks)



      1. Sodium ion
        Diffusion, because it’s uptake occurs according to the concentration gradient:
      2. Iodine ion
        Active transport; its uptake occur against a concentration gradient
    2. Iodine; its uptake depends on energy derived from ATP;
    3. This is because fresh water fish would lose water molecule; to the marine habitat since the marine environment is hypertonic;
    1. Primary consumers;
    2. Predation/feeding;
      1. decomposition/decay/predation;   reJ rotting
      2. Absorption
    3. Decomposers /bacteria/ fungi/ saprophytes;
    4. Primary consumers/ organisms in box 02 will increase in numbers; leading o overgrazing decreasing in number of producers; which lead to reduction in numbers of primary consumers;
    1. Non disjunction is a condition in which chromosome fails to separate at anaphase 1 of meiosis leading to addition or loss of a chromosome:
      1. Parental phenotype: normal man currier woman
        Phenotype: 2 normal females: normal male: hemophilic male:
        All normal female; currier female: normal male: /hemophilic male
      2. Kinefelters, torners and dorn syndrome: any two
    3. Colour blindness and hairy pinna/ nostril/ porcupine skin in males (any one)
    1. The coleoptice tip bends towards light (show positive phototropism) Light causes lateral migration of auxins from the lit side of the shoot to the darker side: high concentration of auxins on the darker side stimulates rapid cell elongation and hence faster growth rate at the darker side
    2. –B and C acts as a control experiments
      B-shows that it is the tip that responds to light
      C-Shows that it is the tip that is the source of growth hormones:
    3. Hormones from the tip do not reach region of cell elongation due to mica blade;
      E -The shoot curves because mica blade does not interfere with the movement of auxins hormones from the region of cell elongation on the side away from the light
    1. A- Cornified layer
      B- Sebaceous gland
      1. Hair raised trapping air between hair and the body air is a bad conductor of heat insulates the body against heat loss:
      2. Vasoconstriction- less flows to the skin less head lost
        -Metabolic rate increase heat production;
        -Shivering un involuntary contraction skeletal muscles to generate heat;    

        SECTION B (40MKS)
    1. Plotting (2mks)
      Scale 2mks)
      Axis labelling(1mk)
      Identify curves (2mks)   reg marks for if origin is missing /upper limit
    2. Rate
      Still; 1.4 per m2 per hour;
      Wind ; 6.0 per m2 per hour
    3. As width of the stomata increases the rate of transpiration increase; Increase in the width of the stomata increases the surface area over which water loss by transpiration occurs; hence increasing the rate of transpiration
    4. In still air the water vapour lost from the plant accumulates in the air surrounding the leaf; thus increasing humidity; which reduces saturation deficit between leaf cells and the atmosphere hence reducing transpiration rates,In wind; the water vapour being from the plant(shoot) is carried away from the surrounding of the plant; increasing the saturation deficit between leaf cells and the surrounding air; thus reduce rates of transpiration;
    5. -Evaporation of water from the leaf surface causes cooling of the plant:
      -Facilitates loss of excess water from the plant excretion;
      -Concentrates mineral salts around the roots facilitating their easy, uptake by diffusion;
      -Facilitates turgidity of plant cells hence support in herbaceous plants;
  1. Describe the various ways in which seeds and fruits are adapted for dispersal
    -Some fruits have dry pericarp/ pods with lines of weakness/softness; which splits open and forcefully dispersing the seeds;
    -Some fruits /seeds being small in size/ light in weight reduce their density and float in air;
    Some seeds/ fruits have hooks so that they may cling to animals bodies for as they pass;
    -Some fruits have thick fibrous walls with air pockets; protecting seeds from absorbing water; enhancing floatation in water, transported to far off places;
    -Some fruits seeds have floating devices / wings /harry parachute; to increase the surface area for buoyancy in air
    -Some seed/ coat testa are resistant to enzymatic digestion in animal’s digestion system
    -Seed /coat impermeable to water; to allow seed to remain viable for a long period;
    -Some fruits being succulent heshilly; to attract animals to feed on them;
    -Fruits being brightly colopured; to attract animals to feed on them;
    1. Auxins
      -Promote cell division/elongation/influence tropical movements;
      -Promote fruit formation/parthenocarphy
      -Promote formation of abscission layer bring leaf full;
      -Causes apical dominance
      -Promotes growth adventitious roots and lateral branches
      -IAA and cytokinins induce formation of callus tissue during healing of wounds
    2. Gibberellins/giberelic acid
      -Promotes cell division/elongation in dwarf vanities,
      - parthenocarpy initiale fruit formation
      -Promotes formation of side branch end dormancy in buds:
      -In hibit growth of adventitious roots
      -Activates enzymes during germination break dormancy
      -Affects leaf expansion and shape/ retard lead abscission;
    3. Fossil records /paleontology
      Fossils are remains of organisms that became preserved in naturally occurring materials many years ago; They show morphological charges of organisms over a long period of time (max 3)
      Callparative anatomy;
      Organisms have common embryonic origin; but structures become modified differently to perform different functions; those are called homologous structures other have different embryous origin but structures become modified and adapt in the same environments thus perform similar functions such structures are called analogous structures; others have become reduced in size dug to disuse in the environment; these are called vestigial structures (max 6)
      Geographical distribution
      Presents continents are thought to have been one large land mess (pangea); as a result of continental drift; isolation occurred bringing about different patterns of evolution; of related organisms e.g. llamcis in the amazon resemble the camel;
      Acc ;Jaguars ,panthecs with their counter parts etc (max 3)


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