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MANGU HIGH SCHOOL 2021 FORM FOUR PAPER 3 MARKING SCHEME

b)          A berry / Hesperidium;

c)          i) Animal Dispersal

ii)        –          Succulent endocarp / juicy endocarp;

–           Seeds resistant to digestions ;

–           Scented ;

–           Bright coloured exocarp;

d)          i) Animal

ii) -Fleshy/ juicy pericarp to attract the animal

–     Brightly coloured epicarp to attract the animal

–     Indigestible seed coats to avoid digestion by enzymes

2. I (a) (i) epigeal

            (ii) – cotyledons are above the ground

      (b) (i) – positive hydrotropism in roots

            – positive phototropism in shoot.

      (ii) Positive phototropism

       Light causes lateral migration of auxins away from the light side, towards the darker side;

      high auxin concentration stimulates growth in the shoot; thus the cells on darker side grew and elongated faster than the cells on the illuminated side; causing the curvature towards light;

      (iii)  Provides yield energy required by the cell for various functions;

       Positive hydrotropism.

      Water causes auxins to migrate towards the side with water / moisture, auxin, are positively hydrotropic; low auxin concentration stimulates growth in roots, auxin high concentration inhibit growth in roots; the cells on the side away from the water grow and elongated faster; leading to curvature towards water.

(ii) Phototropism enables plants (shoot) to obtain optimum light for photosynthesis.

      Hydrotropism by roots enables plants to absorb water and mineral salts for metabolic processes.

II   (a) plate 6 – stamen plate 7 – pistil

(b) (i) dioecium

      (ii) facilitates pollination leading to variation within the species and increase in hybrid vigour.

(c)(i) wind pollination

       (ii) Small incospicuous bracts; that are dull coloured

(d) (i) cross pollination.

      (ii) – male and female parts occur in different plants.

      – the plant pollen grains are sterile to the stigma of the same plant.

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