| 
 Protochordates:- 
 Balanoglossus: Tornaria larva Ascidia: Retrogressive metamorphosis  | 
Amphioxus
| 
 Agnatha:- 
 Petromyzon  | 
Ammocoete larva
| 
 Gnathostomata 
 Scoliodon 
  | 
Economic importance of Fishes
| 
 Amphibia 
 Reptilia 
  | 
Poisonous & Non-poisonous snakes
Poison apparatus
| 
 Aves 
 Mammals 
  | 
Hair and its development