Wednesday, October 28, 2020

2017 March | HSE +1 Exam | Botany - ANSWERS

2017 MARCH (+1) 

1. b) F. Skoog

2. b) (i) and (iv)

  • Algae help in CO2 fixation by photosynthesis.
  • Increase level of oxygen.
  • Primary producers of ocean.
  • Used as food etc.
4. Nitrogenase enzyme/Mo-Fe protein & leg-haemoglobin.

5. In C3 plants some O2 bind to RuBisCO. Hence CO2 fixation is decreased. Here RuBP binds with O2 to form one molecule of phosphoglycerate and phosphoglycolate. This pathway is called photorespiration. In this pathway, there is no synthesis of sugars, ATP and NADPH. Hence photorespiration is a wasteful process. Rather it causes the release of CO2 by using ATP.

6. Agricultural applications of ethylene:
  • Influences horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot seedlings.
  • Promotes senescence and abscission of plant organs especially of leaves and flowers.
  • Promotes fruit ripening.
  • Breaks seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers.
  • Promotes rapid internode/petiole elongation in deep water rice plants. It helps leaves/upper parts of the shoot to remain above water.
7. Blackman's law of limiting factors: 
“If a biochemical process is affected by more than one factor, its rate is determined by the factor nearest to its minimal value: it is the factor which directly affects the process if its quantity is changed.”

    Factors which influence the rate of photosynthesis in plants:
  • Internal (plant) factors: The number, size, age and orientation of leaves, mesophyll cells and chloroplasts, internal CO2 concentration and amount of chlorophyll.
  • External factors: Sunlight, temperature, CO2 concentration and water.
8. This is the only way water and solutes can enter the vascular cylinder.

9. a) iv) Inflorescence
    b) Actinomorphic: Here, a flower can be divided into 2 equal radial halves in any radial plane passing through centre.
        Zygomorphic: Here, a flower can be divided into two similar halves only in one particular vertical plane.

10. a) Cork cambium
b) In dicot stems, cells of cambium present between primary xylem & primary phloem is intrafascicular cambium. a continuous ring of cambium is formed.

In dicot root, vascular cambium is completely secondary in origin. It originates from the tissue just below the phloem bundles, a portion of pericycle tissue above the protoxylem forming a complete and continuous wavy ring and later become circular.

11. a) Lysosome.
      b) Rough endoplasmic reticulum (RER): 
Bear ribosomes on their surface. RER is frequently observed in the cells actively involved in protein synthesis and secretion. They extend to the outer membrane of the nucleus.

Smooth endoplasmic reticulum (SER):
Ribosomes are absent. SER is the major site for synthesis of lipid. In animal cells lipid-like steroidal hormones are synthesized in SER.

12. Anaphase:

    Two events of anaphase:
  • Centromere of each chromosome divides longitudinally resulting in the formation of two daughter chromatids.
  • As the spindle fibres contract, the chromatids move from the equator to the opposite poles.
13. a) Cytoplasm.
      b) A – glucose 6-phosphate 
          B – fructose 6-phosphate 
          C – fructose 1, 6-diphosphate
          D – 1, 3-bisphosphoglyceric acid (DPGA) 
          E – 2 phosphoglyceric acid 
          F – Phosphoenol pyruvic acid


a) Hans Krebs
b) Diagrammatic sketch of Krebs’ cycle.

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