Biology Paper 2 Questions and Answers - Mwakican Joint Pre Mock Examination 2021

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
   
   
   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]
      A –
      B –
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]
      
      1. __________________________________
         __________________________________
      2. __________________________________
         __________________________________
5. The diagram below represents a plant in the division Byrophyta:
   
   
   1. Name the parts labeled [5 Marks]
      U
      W
      X
      Y
      Z
   2. Name one function of part labeled. [3 Marks]
      X
      Y
      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 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]
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. U – Thallus
      W – Rhizoids
      X – Antheridia
      Y – Archegonia
      Z – Capsule
   2. X – Produce male gamete
      Y – Produce female gamete
      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.
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. 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.
    2.    
       • 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
12. Adaptation of Epidermis
    
    1.    
       • 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.