BIOLOGY PAPER 2 - FORM 4 END TERM 1 EXAMS 2020

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Instructions to candidates:

Answer All Questions in the Spaces Provided

  1. The diagram shows two types of cells placed in a certain solution. Study them and answer questions that follow
    haemolysis.PNG
    1. Name the physiological process responsible for the observed results. [1 Mark]
    2. Give the correct biological term used to describe cells A & B. [2 Marks]
  2. The equation below shows a chemical reaction that takes place in plants.
    Carbon (iv) oxide + water                        A + water
    1. Identify substance A. [1 Mark]
    2. Name the process represented by the equation. [1 Mark]
    3. Other than the reactants state two conditions necessary for this reaction. [2 Marks]
  3. The diagram below illustrates an experiment used to determine rate of respiration in a small insect.
    respiration.PNG
    1. Name the chemical compound labeled X and state its function. [2 Marks]
    2. Why is the conical flask placed in a water bath? [1 Mark]
    3. What would happen to the level of coloured water after 5 minutes? Explain: [2 Marks]
    4. How can a control experiment be set? [1 Mark]
  4. In a biology lesson a student collected the animal in the diagram below.
    Use it to answer questions that follow;
    spider.PNG
    1. Name the phylum and class to which the organism belongs
      1. Phylum ______________________________________             [1 Mark]
      2. Class________________________________________             [1 Mark]
    2. Give two reasons for your answer in 1 (i), (ii) above [4 Marks]
  5. The diagram below represents a plant in the division Byrophyta:
    byrophyta.PNG
    1. Name the parts labeled U, W, X, Y and Z [5 Marks]
    2. Name one function of part labeled X, Y and Z [3 Marks]
  6.  
    1. It is observed that when apical bud of a plant is removed, lateral buds sprouts, where as they do not sprout in presence of the apical bud;
      1. What is the biological term used to describe this? [1 Mark]
      2. Give one application of this phenomena in agriculture. [1 Mark]
    2. State four roles of IAA in plant growth and development: [4 Marks]
    3. In epigeal germination the cotyledon is brought above the soil surfaces; Explain [2 Marks]        
  7.  
    1. State 2 structural modifications of nephrons in desert mammals. [2 Marks]
    2. State a kidney disease whose symptom is coloured and turbid urine [1 Mark]
  8. In a biological experiment; a cross was made between a tall pea plant & dwarfs plants; their progeny was selfed and the resulting plants were in a mixture in the ratio of 3:1. Make a biological cross to show these outcomes.             [4 Marks]
  9. Explain geographical distribution as evidence of organic evolution. [2 Marks]

SECTION B

Answer Questions 10 (Compulsory) and either question 11 or 12 in the Spaces Provided

  1. The table below shows the changes observed in the dry weight in milligrams of a barley seedling, its embryo and Endosperm during the first ten days after the onset of germination.
     

    Dry weight in milligrams

    Time (days)

    Embryo

    Endosperm

    Whole seedling

    0

    2

    41

    45

    2

    2

    39

    43

    4

    7

    32

    41

    6

    15

    21

    38

    8

    22

    11

    35

    10

    35

    6

    43


    1. Using a suitable scale and on the same axis, plot a graph of dry weight of embryo, endosperm and whole seedling against time. [8 Marks]
    2. State and account for the changes in dry weight shown by:-
      1. Endosperm [4 Marks]
      2. Embryo [4 Marks]
    3. Explain the role of water during germination [4 Marks]
  1.  
    1. Describe how the mammalian heart is adapted to its function [10 Marks]
    2. How does gaseous exchange take place in terrestrial plants? [10 Marks]
  2.  
    1. How is the Epidermis of a green plant adapted to its function? [6 Marks]
    2. Describe how structural factors affect rate of transpiration in plants [8 Marks]
    3. Describe how xerophytes adapted to minimize water loss in their habitat. [6 Marks]

MARKING SCHEME

  1. (a) Osmosis
    (b) Flaccid; crenated
  1. (a) glucose
    (b) Photosynthesis
    (c)  Light, chlorophyll
  1. (a) To absorb Co2 produced
    (b) Provides favorable temperature
    (c) H2O rises in the capillary tube; to occupy space after O2 is used up
    (d) Use a dead organism or do not include X.
  1. (a) i)  Arthropoda;
    ii) Arachnida
    (b) i)   segmented body
    Jointed appendages;
    Exoskeleton
    ii) 4 Pairs legs;
    Head and thorax fused to form cephalothorax           
  1. (a) U – Thallus
    W – Rhizoids
    X – Antheridia
    Y – Archegonia
    Z – Capsule
    (b) X – Produce male gamete
    Y – Produce female gamete
    Z – Produce spores
  1. (a) i)  Apical dominance
    ii) Development of more branches required for increased harvest. E.g. tea & coffee.
    (b) – Stimulate cell division & cell elongation bading to primary growth
    – Tropic responses
    – Stimulate growth of adventitious roots; from the stem
    – Promotes palheno carpy;
    – Induce formation of callus tissues
    – Induce cell division in Cambrian leading to secondary growth.
  1. (a) long loop of henle
    Few & small glomeruli
    (b) Nephritis
  2.  
    dwarfs progeny.PNG 
  1. The earth was a single land mass; (pangea), it broke into parts that drifted away (continental drift)
    Organisms that were related become separated and evolved differently;
  2.  
    1.  
      graph_of_dry_weight_.jpg
    2. (i) Weight of embryo increases steadily; cell under division; new protoplasm is synthesized; hence increase in weight;
      (ii) Decrease in weight; stored food is hydrolysed; and transported to other regions; for respiration & synthesis of new materials.
    3. – Hydrolysis of stored food
      – Activation of hormones & enzymes
      – Medium for enzyme catalyzed reactions
      – Medium for transport of hydrolyzed food
  1. (a) Gaseous Exchange
    • Takes place in the spongy mesophyl during the day air diffuses in the large air spaces of the spongy mesophyll through stomata;
    • The air dissolves in the thin layer of moisture over the spongy mesophyll cells; carbon dioxide from the air diffuses into the cells (photosynthetic cells) in solution form.
    • Oxygen produced during photosynthesis diffuses out of the cells and out of leaves.
    • At night air diffuses into the large air spaces & into the thin film of moisture over the spongy mesophyll cells
    • Oxygen diffuses into the cells, Carbon(iv)oxide diffuses out of the cells into the air spaces & out of the leaf via stomata.
    • Gaseous exchange also occur through the cuticle epidermis of young leaves; epidermis of root in the soil lenticels.
    • In the lenticels cork cells are loosely packed; gaseous exchange occur between the loosely arranged cells & atmosphere.

    (b) 
    • Has myogenic muscles that contract & relax rhythmically without fatigue
    • Cardiac muscle fibres are interconnected to ensure rapid spread of excitation through the wall of heart ventricle walls thicker than auricle walls & generate high pressure to pump blood over a long distance
    • Has coronary artery that supplies the muscles with oxygen and nutrients and remove wastes from the heart muscles
    • The pericardium surrounds the heart & prevent it from over dilation
    • Has semi-lunar valves that prevent blood in the arteries from flowing back into the ventricles
    • Inner layer of pericardium secretes pericardial fluid that lubricates the heart.
    • Outer layer of heart covered with fat that acts as shock absorber
    • Has Sino arteriole node that acts as pace maker
    • A longitudinal septum separates the heart into two preventing mixing of oxygenated & deoxygenated blood
    1. Adaptation of Epidermis
      • Transparent to allow light to penetrate to the photosynthesis tissues
      • A single layer of cells to reduce distance over which light penetrates
      • Presence of stomata for gaseous exchange
    2. Stomata
      • The higher the number the higher the rate of transpiration and vice versa
      • Location of stomata – rate is high when most are on upper leaf surface.
      • Late is lower when stomata are sunken other than exposed;
      • Some plants reverse the stomata rhythm which reduces rate of transpiration;

      Leaf size and shape
      • When a leaf is blood surface area for evaporation increases which increases rate of transpiration when leaf is narrow rate of transpiration reduces;

      Cuticle
      • when leaf has a thick waxy cuticle rate of transpiration reduces wax in water proof when cuticle is thin and not waxy rate of transpiration increases;

      Hairy leaves

      • Hairs on the leaf surface traps moisture air around the leaf is saturated with water vapour which reduces transpiration.
    3. Adaptation of xerophytes
      • Have leaves that are reduced in size which reduces surface for evaporation;
      • Leaves have waxy cuticle that is thick to reduce evaporation since wax is water proof some leaves are folded to reduce number of stomata exposed to environmental factors.
      • Stomata in them are usually sunken; water vapor accumulates in these depressions preventing further water loss’
      • They have stomata whose number is greatly reduced to reduce rate of evaporation.

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