Growth in Humans and Animals



Growth in Humans and Animals

  1. Growth in multicellular organism such as humans and animals is an irreversible process which involve the increase in quantitive parameters such as size (height or length),body mass,volume and number of cells.
  2. Parameters for the growth of humans: body size,height and length
  3. Parameters for the growth of animals: body mass,fresh mass and dry mass

Growth in insects:

  1. Organism with exoskeleton such as insects,crabs and prawns undergo growth by either complete metamorphosis or incomplete metamorphosis
  2. In development of exoskeletal organisms, metamorphosis is a developement process from larval stage to adult stage
  3. During development stage, organism undergoes a moulting process known as ecdysis
  4. In complete metamorphosis, the growth of organisms involves four stages starts from egg to larva,larva to pupa and pupa to adult.
  5. In incomplete metamorphosis, the growth of organisms only involves three stages starts from egg to larva and from larva to adult
Sigmoid growth curve of an organism:
Phase Explanation
A (lag phase)
  • Slow growth rate
  • Little or no cell division
B (exponential phase)
  • Growth rate at the fastest
  • Cell division and cell elongation are active
  • The size of organisms increase rapidly
C (slow growth phase)
  • Steady growth rate
  • Limited by growth factor such as food shortage
D (stationary phase)
  • Form a plateau
  • The growth rate is zero
  • The organism reached maturity
  • Cell division occurs to replace the dead cells
E (death phase)
  • The organism undergoes ageing and death
Growth curve of insects:


  • Insects have a hard exoskeleton made of chitin
  • In order to growth in size, insects must undergo a moulting process known as ecdysis
  • The horizontal lines show zero growth periods known as instars
  • During ecdysis:
  1.    I: An insect breathes in a lot of air to expand the body
  2. II: The old exoskeleton breaks
  3. III: The insect expands by breathing in more air, before the new exoskeleton hardens
  4. IV: Ecdysis is repeated several times until the adult phase