Hint: They are found in freshwater and ocean environments like caves, deep-sea habitats, and thermal springs and vents. Also, present in different shapes and have different behavioral habitats. They have a heart of two-chambers.
-Bony fishes belong to the classes Sarcopterygii (lobe-finned fishes) and Actinopterygii (ray-finned fishes) in the subphylum Vertebrata.
-It includes a large number of living fishes usually the world’s sport and commercial fishers.
-Due to the presence of a Bony endoskeleton, fishes are called Bony fishes, having a streamlined body and mouth is generally terminal.
-They have usually four pairs of gills, which is covered by the operculum on each side, having cycloid/ctenoid scales all over the skin. Air bladder helps in buoyancy.
-Bony fishes are dioecious animals, Usually have two-chambered hearts, and are cold-blooded. Externally fertilized, development is direct and is oviparous.
Marine fishes - Exocoetus (Flying fish), and Hippocampus (Sea horse)
Freshwater fishes – Labeo (Rohu), Catla (Katla), and Clarias (Magur)
Aquarium fishes – Betta (Fighting fish), and Pterophyllum (Angelfish).
Reptiles - having three-chambered heart i.e. two atria and one partially divided ventricle. The ventricle is not divided completely therefore it causes the mixing of oxygenated and deoxygenated blood.
-All the reptiles have three-chambered hearts except 23 living species of crocodiles having four-chambered hearts like birds and mammals i.e. two atria and two ventricles.
Sponges - They are mostly marines and some found in freshwater also having a cellular grade of organization.
-Rotifers have Choanocytes or collar cells.
Mammals - give birth to young ones. Hence, they are viviparous except the Ornithorhynchus (platypus) which lay eggs. Hence they are oviparous.
So, the correct answer is, “All bony fishes have four pairs of gills and an operculum on each side”.
-A series of bones that are present in Bony fishes is called an operculum, helps in facial support, and covers the gills.
-Many Bony fishes have five pairs of gills although some lost over the course of evolution.
-In two classes the Bony fishes are divided - ray-finned fish and lobe-finned fish.