BIOLOGY PAPER 1

1.      
   1. What is meant by the term wilting? (1 mark)
   2. Explain how an increase in temperature affects the rate of active transport. (2 marks)
2. The diagram below represents a cell as seen under an electron microscope.
   
   1. Based on the diagram, state whether it represents an animal cell or a plant cell. (1 mark)
   2. Give two reasons for your answer in 2(a) above. (2 marks)
   3. Why is the palisade layer a tissue? (1 mark)
3.    
   1. State two external features found in the clas Mammalia only. (2 marks)
   2. Name the taxonomic unit that comes immediately after a phylum in classification. (1 mark)
4.    
   1. State two roles of mucus in the stomach. (2 marks)
   2. Explain how age determines a person's energy requirements (2 marks)
5. Describe how turgor pressure builds up (3 marks)
6. Using a microscope, a student counted 55 cells across a field of view whose diameter was 6000μm. Calculate the average length of the cells. Show your working. (2 marks)
7. Explain how the following forces contribute to the movement of water up the xylem vessels: (2 marks)
   1. cohesion;
   2. adhesion.
8. Construct a step in a dichotomous key using two leaves one with a serrated and the other with a smooth margin. (2 marks)
9. State one way in which each of the following is structurally adapted to its function:
   1. neurone; (2 marks)
   2. mitochondrion (2 marks)
10. How are lenticels adapted for gaseous exchange? (2 marks)
11. State the advantage of possessing blood group AB. (1 mark)
12.    
    1. A student collected an organism and observed the following features: simple eyes, four pair of legs and two body parts.
       1. State the class to which the organism belongs. (1 mark)
       2. Give an example of an organism in this class. (1 mark)
    2. Name the kingdom to which plasmodium belongs. (1 mark)
13. State two characteristics of living organisms that are specific to plants. (2 marks)
14. Name the three end products of anaerobic respiration in plants. (3 marks)
15. State two reasons why accumulation of lactic acid leads to an increase in heart beat. (2 marks)
16. Name three mechanisms that ensure cross pollination takes place in flowering plants. (3 marks)
17. Name the flower part that produces gametes. (1 mark)
18. How is the human sperm cell structurally specialised? (2 marks)
19. State three factors in seeds that cause dormancy. (3 marks)
20. Explain the theory of evolution by natural selection. (2 marks)
21.    
    1. Explain the role of continental drift in evolution (3 marks)
    2. What is meant by the term organic evolution?
22. The diagram below illustrates a response by a certain plant.
    
    1. Name the type of response (1 mark)
    2. Explain how the response illustrated above occurs (3 marks)
23. The diagram below illustrates a defect in the eye
    
    Explain how the defect illustrated above can be corrected. (2 marks)
24. Explain three protective functions of mammalian blood. (3 marks)
25. State one adaptation of xylem vessels to their function. (2 marks)
26.    
    1. What is meant by the term sex linked genes? (1 mark)
    2. Name two sex linked traits in human beings. (2 marks)
27.    
    1. State two differences between complete and incomplete metarmorphosis. (2 marks)
    2. State the importance of moulting to an insect. (1 mark)
28.    
    1. State two features of a ball and socket joint (2 marks)
    2. Name the bone that allows the head to:
       
       1. nod; ...................................
       2. turn side ways ................................... (2 marks)
29. State two functions of pelvic girdle in mammals. (2 marks)
30. State two ways in which osmosis is significant to plants (2 marks)

MARKING SCHEME

1.      
   1. Is when the rate of water loss is more than the rate of absorption and the plant droops; (1 mark)
   2. The rate of active transport increases with increase intemperature up to the optimum temperature; 1 mark
      Further increase in temperature slows down the rate of active transport until it stops because it denatures enzymes; 1 mark
2.    
   1. Animal cell; 1 mark
   2.    
      • Has cell membrane only/has no cell wall;
      • Has numerous small vacuoles;
      • Has central nucleus; Max. 2 marks
   3. Consists of many similar cells performing the same function; 1 mark
3.    
   1. Have mammary glands; have external ears/pinna;
      Body covered with fur/hair; Max. 2 marks
   2. Class; 1 mark
4.    
   1. Lubrication; Protection; 2 marks
   2. Young people are more active; requiring more energy;/
      Older people are less active; requiring less energy; 2 marks
5. As the cell gains water by osmosis; the sap/cellvacuole enlarges; pushing the cytoplasm outwards; exerting pressure on the cell wall; Any 3 (3 marks)
6. 6000(μm)
   55 (cells) ; 109μm; 2 marks
7.    
   1. Water molecules cling to each other maintaining a continuous column of water/preventing the break of water column; 1 mark
   2. Water molecules cling to the sides of the xylem vessel walls; 1 mark
8.    
   1. Leaf with serrated margin  -- go to 2;
   2. Leaf with smooth margin  -- go to --; 2 marks
9.    
   1. Presence of myelin sheath for insulation/increases transmission; Axon for transmission of impulses;
      Large cell body controls activites of cell; Nerve endings/dendrites receives impulses from receptors cells;
      Node of Ranvier speeds up impulse transmission.
   2. Inner membrane highly folded/cristae to increase S A for attachment of (respiratory) enzymes. 4 marks
10. Cells loosely arranged;  to facilitate air circulation;
    Cells have moist surfaces;  to dissolve respiratory gases; 2 marks
11. Can receive blood from any donor/ universal recepient; 1 mark
12.    
    1.    
       1. Arachnida; 1 mark
       2. Spider/scorpion/tick/mite; 1 mark
    2. Protoctista/protista; 1 mark
13. Autotrophic nutrition; show alternation of generation;
    Limited movement;
    Limited excretory products/unspecialized respiratory structures;
    Localised growth; 2 marks
14. Alcohol/ethanol; Carbon (IV) oxide; Energy/Adenosine Triphosphate; 3 marks
15.    
    • To increase supply of oxygen to the tissues;
    • The oxygen is used to oxidize lactic acid (to carbon (IV) oxide, water and energy); 2 marks
16. Protogyny; protandry; Dioecious; Dichogamy;
    Self sterility/incompatibility;   Heterostyly;
    Presence of structures/substances to attract agents of pollination; Max.  3 marks
17. Ovary /Anther; 1 mark
18.    
    • Acrosome/Lysosome contain enzyme to digest membrane of the ovum;
    • Numerous mitochondria to provide energy for movement;
    • Long tail for faster movement; Max.   2 marks
19.    
    • Embryo not fully developed;
    • Chemical inhibitors/presence of abscisic acid;
    • Hard/impermeable testa/seed coat;
    • Low hormones/low enzymes concentration; Max. 3 marks
20. Genetically acquired beneficial characteristics which occur spontaneously; are perpetuated through reproduction; 2 marks
21.    
    1. Continents existed as one large Landmass/Pangea/Laurasian and Gondwana Land;
       Present continents drifted from it leading to isolation of organisms;  organisms in each continent evolved along different lines hence emergence of new species; 3 marks
    2. Emergence of new life/species/organisms from preexisting simple forms, gradually over a long period of time, to present complex forms; 1 mark
22.    
    1. Thigmotropism/Haptotropism; 1 mark
    2. Part of the tendril in contact with support causes migration of auxins to the opposite side;
       leading to faster cell division/growth on the side not in contact with the support;
       This causes the tendril to curl around the support; 3 marks
23. Use of biconcave/concave lens/divergent lens; to diverge the rays and make image be focussed on the retina; 2 marks
24.    
    • Contains antibodies that defend the body from foreign antigens;
    • Has white blood cells that produce antibodies/while blood cells engulf antigens;
    • Has platelets that initiate blood clotting to prevent excessive bleeding at an open wound/ prevent entry of pathogens; 3 marks
25.    
    • Thin and long to allow for capillarity;
    • Walls lignified to strengthen the stem/to prevent collapse of vessels;
    • Have bordered pits to allow for exchange of materials; Max. 2 marks
26.    
    1. Genes inherited along with the sex chromosomes; 1 mark
    2. Haemophilia;  hairy ears/pinna/nose; colour blindness/red green; blue-green colour blindness;
       Muscular diastrophy; baldness 2 marks
27.    
    1. Complete metamorphosis - eggs hatch into larvae while in incomplete metamorphosis hatch into nymphs which resemble the adult;
       Complete metamorphosis has four stages; egg, larvae, pupa and adult while an incomplete metamorphosis has three stages; egg,nymph and adult. 2 marks
    2. To allow for growth of the insect; 1 mark
28.    
    1. Ligaments; synovial fluid; synovial membrane;   articular cartilage;
       synovial capsule; a bone with rounded head fitting into a cavity of  another bone; Max.   2 marks
    2. (i)Atlas; (ii) Axis allows movement in all planes; 2 marks
29.    
    • Form joints with the legs to make walking possible; 1 mark
    • Provide large surface area for attachment of muscles; 1 mark
    • Offers support (to the body weight)
30. Absorption of water;   support;
    Opening and closing of stomata;
    Feeding in insectivorous/plants;