Biology Paper 2 Form 3 Questions and Answers - End Term 2 Exams 2021

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Biology Paper 2 Form 3 End Term 2 Exams 2021 with Marking Schemes

INSTRUCTIONS TO CANDIDATES:

  • Write your name,and admission in the spaces provided above.
  • This paper consists of TWO sections A and B
  • Answer ALL the questions in section A in the spaces provided
  • In section B, answer Question 6 (Compulsory) and either Question 7 or 8 in the spaces provided.

SECTION A (40 MARKS)

Answer all questions in this section

  1. The diagram below represents a nitrogen cycle.
    biop2endterm2q1
    1. Name the groups of organism represented by J. (1mrk)
    2. Name the process represented by R,P,M and N. (4mrks)
      R: .......................................................................................
      P: .......................................................................................
      M: ......................................................................................
      N: ......................................................................................
    3. Name one process represented by T. (1mrk)
    4.  
      1. Name a structure in roots involved in process M. (1mrk)
      2. State one adaptation of the structure named in d (i) above to its function. (1mrk)
  2. The following diagram shows a cell at a certain stage of cell division.
    biop2endterm2q2
    1. Name the type and stage of cell division. (1mrk)
      Type..................................................................
      Stage.................................................................
    2.  
      1. Give one reason for your answer in (a) above. (1mrk)
      2. What is the significance of the process shown in the diagram above in relation to the behavior of chromosomes? (1mrk)
    3. What is the general name of organs where the above process occurs? (1mk)
    4. Name the part labeled; (2mrks)
      C ..........................................................................
      F ...........................................................................
    5. State the significance of part labeled A in relation to the process shown above ?. (1mrk)
    6. Name one cell in plants which is haploid (1mrk)
  3. In an experiment to analyze a 200cm3 sample of air was treated with pyrogallic acid. This reduced its volume to 168cm3. Potassium hydroxide was then added and the volume of gas reduced further to 160cm3
    1. What was the role of pyrogallic acid? (1mrk)
    2. What was the role of potassium hydroxide? (1mrk)
    3. Calculate the percentage of oxygen and percentage of carbon (iv) oxide in the sample.(2mrks)
    4. Suggest the likely biological source of carbon (iv)oxide gas. (1mrk)
    5. State the behavior of external intercostal muscles during exhalation. (1mk)
    6. Explain why smokers are more prone to respiratory tract infections than the non- smokers (2mks)
  4. The diagram below represents two process underwent by a plant cell.
    biop2endterm2q4
    1. Identify process X...................................................................................................... (1mrk)
    2. Name the state of the cell after undergoing process; (2mrks)
      1. X.................................................................................
      2. Z ..................................................................................
    3. Name the substance which is found in parts labelled; (2mrks)
      1. P..................................................................................
      2. Y ...............................................................................
    4. Name parts labelled M and Q. (2mrks) M...................................................................... Q...................................................................... (e) Name the cell organelle which is usually referred to as “ cell’s kitchen”. (1mrk) 
  5.  
    1. Name two substances transported in blood plasma. (2mrks)
    2. Wanjiru is blood group A.
      1. Name an antibody found in her blood plasma. (1mrk)
      2. Name an antigen found in her red blood cell. (1mrk)
      3. Name the blood groups she can donate to; (2mrks)
        Blood groups-
        ____________
        ____________
    3. What is meant by the term allergy? (1mrk)
    4. Name one substance that can cause allergy. (1mrk)

 

SECTION B (40 MARKS)

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

  1. Two herbivorous mammal species were introduced into an ecosystem at the same time and in equal numbers. The graph below represents their populations during the first seven years. Study the graph and answer the questions that follow.
    biop2endterm2q6
    1.  
      1. Which species has a better competitive ability? (1mrk)
      2. Give a reason for your answer. (1mrk)
    2. Account for the shape of the curve for spicies A between;
      1. One year and three years. (3mrks)
      2. 4 years and eight years. (3mrks)
    3. A natural predator of species A was introduced into the ecosystem. With a reason, state how the population of each species would be affected? (4mrks)
    4. State four other biotic factors of the ecosystem which affects organisms distribution in their habitat other than the one illustrated in the above graph. (4mrks)
    5. Name the instruments used to measure the following;
      1. Light intensity......................................................................................................... (1mrk)
      2. Light penetration in water..................................................................................... (1mrk)
      3. Speed of wind........................................................................................................ (1mrk)
      4. Atmospheric pressure............................................................................................ (1mrk)
  2. Describe how human male reproductive system is adapted to its functions (20 marks)
  3. Describe how seeds and fruits are adapted to different modes of dispersal. (20marks)

Marking Scheme

  1.  
    1. Plants /Autotrophs ; (1mrk)
    2. R - Denitrification ; (1mrk)
      P - Feeding /Nutrition ; (1mrk)
      M - Absorption ; (1mrk)
      N - Decay/decomposition
    3. Fixation by lightning/ Biological fixation (1mrk)
    4.  
      1. Nodules; (1mrk)
      2. They harbour Rhizobium bacteria which convert atmospheric nitrogen into ammonia, which is used by leguminous plants to form nitrogen containing organic compounds/proteins; (1mrk)
  2.  
    1. Type; meiosis I. stage; prophase I
    2.  
      1. - Pairing of homologous chromosomes (synapsis);
        - Crossing over has occurred /chiasma formation;Mark the first answer only
      2. It allows for the exchange of the genes and hence variation in the species; (1mrk)
    3. Gonads (1mrk)
    4. C - Chromatid (1mrk)
      F - bivalent /paire homologous chromosomes; (1mrk)
    5. A - forms spindle fibres; /forms the opposite poles in relation to the equator of the cell; (1mrk)
    6. Haploid cell in plants -/synergids/ antipodal cells/ eggs cell in embryo sac;rej pollen grain(1mrk)
  3.  
    1. To absorb oxygen; (1mrk)
    2. To absorb carbon (IV) oxide; (1mrk)
    3. Oxygen; 200 - 168 =32cm3
      32  x 100 =16%; (1mrk)
      200

      Carbon (IV)oxide: 168 - 160 = 8cm3
      8 x 100 = 4%; (1mrk)
      200
    4. Exhaled air;
    5. External intercostal muscles relax ; (1mrk)
    6. Cigarette smoke inhibits action of cilia in the respiratory tract resulting to accumulation of dust particles, bacteria and mucus; bacteria invade cells of mucous membrane thus causing diseases /respiratory tract infections (2mrks)
  4.  
    1. Plasmolysis; (1mrk)
    2. X – Plasmolysed (Flaccids); (1mrk)
      Z – Turgid; (1mrk)
    3. P– Sap/cell sap; (1mrk)
      Y – Hypotonic solution; (1mrk)
    4. Name the part labeled M and Q
      M - Cell wall; (1mrk)
      Q – Cell membrane; (1mrk) 
    5. Chloroplast; (1mrk) 
  5.  
    1. Carbon (IV) oxide ;/Oxygen/ urea/Food substances/ Ions;
      Any 2 - (2mrks)
    2.  
      1. b; (1mrk)
      2. A; (1mrk)
      3. A; AB; (2mrks)
    3. A hypersensitive reaction to an antigen by the body/over reaction by the body to certain foreign substances introduced into it or exposed to it;
    4. - Drugs such as penicillin, chloroquine, aspirin;
      - Dust;
      - Pollen grains;
      - Certain foods such as meat eaten/amino- acids;mark the first substance stated

SECTION B

  1.  
    1.  
      1. Species A; (1mrk)
      2. The rate of growth (multiplication) of species A is higher than that of B; (1mrk)
    2.  
      1. Population increased exponentially (rapidly); due to high number of reproducing individuals; and suitable environmental conditions(such as food , space, resources not limiting e.tc.); (3mrks)
      2. Population becomes constant; because of shortage of resources like food and space; and birth rate equals death rate; (3mrks)
    3. Species A would decrease; due to predation; while the population of species B would increase; due to less competition for food with species A/ more resources or food available; (4mrks)
    4.  
      1. Predation; (1mrk)
      2. Parasitism; (1mrk)
      3. Symbiosis; (1mrk)
      4. Saprophytism; (1mrk)
    5.  
      1. Photographic light meter; (1mrk)
      2. Sacchi disc; (1mrk)
      3. Anemometer; (1mrk)
      4. Barometer; (1mrk)
  2. Describe how human male reproductive system is adapted to its functions 
    • The testes found/ hang outside the body; to provide a cooler environment for sperm production;
    • Seminiferous tubules; consist of actively diving cell; which give rise to/ produce sperms; 
    • Epididymis; is highly coiled; to store sperms; Sperm duct / vas deferens ; connect the epididymis to the urethra;
    • Seminal vesicle; provides an alkaline fluid which contains nutrients for spermatozoa;
    • Prostate gland; produce alkaline secretion to neutralize the vaginal fluids; also to activates the sperms; 
    • Cowper’s gland; produce fluid to neutralize the acidity along the urethra; 
    • Urethra used for the expulsion of urine to the exterior; 
    • Penis is made up of spongy tissue/ muscles and blood vessels filled with blood; to enable vessels filled with blood to enable it penetrate during coitus;
  3. Wind dispersal;
    • Small and light; to float in air/blown by air; Have wings; to increase buoyancy;
    • Have hairs/parachute shaped; to increase buoyancy in air.
    • Animal dispersal;
    • Are succulent; to attract animals;
    • Scented; to attract animals.
    • Have small and hard seeds resistant to digestive enzymes;to prevent digestion once swallowed; Have 
    • hooks; to attach to fur/hair of animals;
    • Brightly coloured; to attract animals;
    • Water dispersal;
    • Water proof epicarp; to prevent entry of water or soaking;
    • Fibrous mesocarp; with air spaces to increase buoyancy in water;
    • Self-explosive mechanism;
    • Have lines of weakness; where they break to release seeds;
    • Have rings of pores; through which seeds are released;
      Max 20 marks
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