Definitions / Explanation : Analogous organs & Vestigial or rudimentary organs
They have almost similar appearance and perform the same function but these develop in totally different groups and are totally different in their basic structure and developmental origin e.g. Wings of butterfly (chitinous), bird (feathered), Pterodactyle and bat (skin fold) serve the same purpose of uplifting the body in air but differ in structure.
$=$ They are the useless remnants of structures or organs which might have been large and functional in the ancestors.
- Vermiform appendix in man, nictitaing membrane, auricular muscles vestigial tail in vertebrates, wisdom teeth, mammary glands in males and body hair are some of its examples.
Definitions / Explanation : Recapitulation theory or Biogenetic law & Palaeontology
$A$ : $A$ single large mutation called saltation can produce new species.
$R$ : Mutations are directional
Contribution of scientist : Hugo de Vries, Hardy - Weinberg and Ernest Haeckel.
Definitions / Explanation : Homology & Adaptive radiation or divergent evolution
Given below are four statements $(A-D)$ each with one or two blanks. Select the option which correctly fills up the blanks in two statements. Statements :
$(A)$ Wings of butterfly and birds look alike andare the results of ___$(i)$___ evolution.
$(B)$ Miller showed that $CH_4 , H_2 , NH_3$ and ___$(i)$___ when exposed to electric discharge in a flaskresulted in formation of ___$(ii)$___ .
$(C)$ Vermiform appendix is a ___$(i)$___ organ and an ___$(ii)$___ evidence of evolution.
$(D)$ According to Darwin evolution took placedue to ___$(i)$___ and ___$(ii)$___ of the fittest.