IGCSE Marine section 3.4

  The syllabus states :

The students should be able to identify and describe the main characteristic features used to place marine vertebrates into groups within the animal kingdom, with reference to mammals, birds, reptiles and fish

state examples of each group of marine vertebrates

(a) mammals (cetaceans, pinnipeds, sirenians) 

(b) birds (pelagic birds, shorebirds) 

(c) reptiles (sea snakes, turtles) 

(d) fish (cartilaginous and bony)

Identify and state the functions of the main external features of fish

(a) operculum, as a gill cover 

 (b) scales, for protection 

(c) dorsal, pelvic, pectoral, anal, caudal fins, for control of pitching, rolling and yawing, directional changes and forward thrust 

 (d) lateral line, to detect vibration 

(e) nares, to detect chemicals

My notes for the chapter is here:

The IGCSE syllabus here focuses on Sharks, fish, reptiles, birds and mammals.

The external features of fish is iportant to memorise and work with for the exam prep.