What is meant by the following terms? Give an example in each case.
(i) Homologous structures.
(ii) Analogous structures.
(iii) Vestigial structures.
Answer:
(i) Homologous structures.
-Structures that have common basic plan and have a common embryonic origin and are modified to perform different functions.
Examples: vertebrate forelimb/pretadactyl limb, beaks of bird, mouth parts in insects.
(ii) Analogous structures.
-Structures with different structural plan and different embryonic origin but evolve to perform similar functions.
Example: wings of insect, wings of bird.
(iii) Vestigial structures.
-Structures that are greatly reduced in size and therefore cease to function.
Examples : human appendix, kiwi (flightless bird) with reduced wings, vestigial wings in flies, human hair,presence of hind limbs in python,reduced pelvic girdle in whale.
-Structures that have common basic plan and have a common embryonic origin and are modified to perform different functions.
Examples: vertebrate forelimb/pretadactyl limb, beaks of bird, mouth parts in insects.
(ii) Analogous structures.
-Structures with different structural plan and different embryonic origin but evolve to perform similar functions.
Example: wings of insect, wings of bird.
(iii) Vestigial structures.
-Structures that are greatly reduced in size and therefore cease to function.
Examples : human appendix, kiwi (flightless bird) with reduced wings, vestigial wings in flies, human hair,presence of hind limbs in python,reduced pelvic girdle in whale.
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