(a) Name three parameters that can be used to measuring growth.(3m) (b) State the limitation in the use of the above parameters in the measurement of growth in organisms. (6mks) (c) Describe the structural adaptations of the insect’s tracheal system to its functions (14mks)

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(a) Name three parameters that can be used to measuring growth.(3m)
  • Length, mass/ weight (dry), volume (3mks)
b) Limitation in measuring growth (6mks)
  • Difficulty in choosing the right growth parameter
  • The use of a singe growth parameter does not take into account growth in other directions
  • Molume cannot be used for those organisms with irregular shape
  • Mass of an organism is usually affected by variation in the fluid content of the organism
  • Use of dry mass involved killing the organism
  • The use of mass or size may be inaccurate because? different parts of an organism at different times
  • Irregularities in the growth of an organism due to fluctuation in the environment / diet

(c) Structural adaptation of the insect tracheal system
  • Spiracle; are openings through which gases (O2 and CO2) enter or exit the tracheal system
  • Valves; on the spiracle control the opening and closing of spiracle;
  • Hairs on the spindle; traps dust / foreign particles and prevent entry into the tracheal system;
  • Trachea is mechanically strengthened with rings of cartilage; to prevent collapse / keep trachea open.
  • Air sacs; to act as air reservoirs air storage especially for very active insects
  • Trachea highly branched into tracheole: to increase the surface area for gaseous exchange
  • Tracheoles are thin walled’ to reduce diffusion distance for gases / rapid exchange of gases
  • Tracheoles contains a fluid; which absorbs oxygen thus facilitating diffusion into the tissues; (16mks) (14 max)

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