K.C.S.E Biology Q & A - MODEL 2004PP1QN14

K.C.S.E Biology Q & A - MODEL 2004PP1QN14

 What is meant by the following terms? Give an example in each case.
i) Homologous structures
ii) Example
iii) Vestigial structures Example 

answers

​(i) Have a common ( embryonic) origin modified to perform different  functions; vertebrae  for limb/ pentadactyl limb
Example
Vertebrate fore limb/ pretadactyl limb; acc beaks of birds ( fee of birds/ mouthparts in insects.
(ii) Have different (embryonic) origins ( but have evolved) to perform similar functions.
(iii) Are greatly reduced in size and therefore caused to function
   Acc. Third  digit of wing of bird
Halteres in flies
Presence of hind limb  ( buds) in python
Human ear muscles
Example
Human appendix / kiwi ( flightless bird) with reduced  wings/ vestigial wings in flies human  hair/ presence  of hind limbs in python; reduced pelvic girdle  of whale.