Biology Paper 2 Questions And Answers - Form 4 Term 2 Opener 2021

Instructions to candidates:

• Answer All Questions in the Spaces Provided

SECTION A

1. The diagram shows two types of cells placed in a certain solution. Study them and answer questions that follow
            
   
   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.
            
   
   1. Name the chemical compound labeled X and state its function. [2 Marks]
      Compound –
      Function –
   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;
             
   
   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:
            
   
   1. Name the parts labeled [5 Marks]
      
      1. U
      2. W
      3. X
      4. Y
      5. Z
   2. Name one function of part labeled. [3 Marks]
      
      1. X
      2. Y
      3. Z
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

10. 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 miligrams
    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]
11.  
    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]
12.  
    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.  
   1. Osmosis
   2. Flaccid; crenated
2.  
   1. glucose
   2. Photosynthesis
   3. Light, chlorophyl
3.  
   1. To absorb CO₂ produced
   2. Provides fovourable temperature
   3. H₂O rises in the capillary tube; to occupy space after O₂ is used up
   4. Use a dead organism or do not include X.
4.  
   1.  
      1. Arthropoda;
      2. Arachnida
   2.  
      1.  
         • segmented body
         • Jointed appendages;
         • Exoskeleton
      2.  
         • 4 Pairs legs;
         • Head and thorax fused to form cephalothorax
5.  
   1.  
      1. U – Thallus
      2. W – Rhizoids
      3. X – Antheridia
      4. Y – Archegonia
      5. Z – Capsule
   2.  
      1. X – Produce male gamete
      2. Y – Produce female gamete
      3. Z – Produce spores
6.  
   1.  
      1. Apical dominance
      2. Development of more branches required for increased harvest. E.g. tea & coffee.
   2.  
      • 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.

   3. the cotyledon is pushed above the soil by rapid elongation of the hypocotyl and they function as photosynthetic organs till the establishment of the seedling.

7.  
   1. long loop of henle
      Few & small glomeruli
   2. Nephritis
8.  
   
9. 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;
10.  
    1.  
       
    2.  
       1. Weight of embryo increases steadily; cell under division; new protoplasm is synthesized; hence increase in weight;
       2. 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
11.  
    1. mammalian heart adaptation to its functions
       • 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
    2. 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.
12.  
    1. Adaptation of the 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;
         Hairly 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.