- These are also called bony fishes because of bony endoskeleton.
- The body is streamlined. Mouth is usually terminal.
- There are four pairs of gills which are covered by operculum on each side.
- The skin is covered with cycloid/ctenoid scales.
- Air bladder is present which helps in buoyancy.
- The heart is two-chambered. They are cold-blooded animals.
Reproduction: These are dioecious animals. Fertilization is usually external and development is direct. Most of the bony fishes are oviparous.
Examples from Marine Habitat: Exocoetus (Flying fish), Hippocampus (Sea horse)
Examples from Freshwater Habitat: Labeo (Rohu), Catla (Katla), Clarias (Magur) Aquarium Betta (Fighting fish), Pterophyllum (Angel fish).
- The amphibians can live both in aquatic and terrestrial habitats. They need water for fertilization.
- Two pairs of limbs are present in most of the amphibians.
- Body is divided into head and trunk. Tail can be present in some of them.
- The skin is moist and scales are absent.
- Eyelids are present on the eyes. A tympanum represents the ear.
- There is a common chamber, called cloaca, in which the alimentary canal, urinary tract and reproductive tract open.
- Respiration is by gills, lungs and through skin.
- There are three chambers in the heart (two auricles and one ventricle).
- These are cold-blooded animals, which means they cannot regulate their body temperature rather their body temperature depends on ambient temperature.
Reproduction: These are dioecious animals. Fertilization is external and development can be direct or indirect. These are oviparous animals.
Common Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).
- These animals show creeping or crawling mode of locomotion. Most of them are terrestrial animals.
- The body is covered by dry and cornified skin, epidermal scales (scutes).
- Tympanum represents ear.
- Limbs are in two pairs, when present.
- Three-chambered heart is present in most of the reptiles. Crocodiles have four-chambered heart.
- These are cold-blooded animals.
Reproduction: These are dioecious animals. Fertilization is internal and development is direct. These are oviparous animals.
Common Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).
- Presence of feathers and wings are the characteristic features of Aves.
- The forelimbs are modified into wings.
- The hind limbs usually have scales and are modified for walking, swimming or clasping the tree branches.
- Skin is dry without glands, but oil gland is present at the base of the tail. Beaks are present.
The endoskeleton is composed of bones. Long bones are pneumatic, i.e. are hollow with air cavities. Air cavities in the long bones help in weight reduction and this is an important flight adaptation. Crop and gizzard are the additional chambers in the digestive tract.
There are four chambers in the heart. They are warm-blooded (homoiothermous) animals. Respiration is by lungs, and air sacs (connected to lungs) supplement respiration.
Reproduction: These are dioecious animals. Fertilization is internal and development is direct. They are oviparous animals.
Common Examples: Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture).
- Presence of mammary glands is the most unique feature of these animals.
- The young ones are nourished with milk from the mammary glands.
- Hairs are present on the skin and external ears are present.
- Different types of teeth are present in the jaw.
- The two pairs of limbs are adapted for walking, running, climbing, burrowing, swimming or flying.
There are four chambers in the heart. They are warm-blooded animals, which means they can control their body temperature and do not depend on environment for that. Respiration is by lungs.
They are dioecious animals. Fertilization is internal and development is direct. Most of them are viviparous.
Oviparous Mammals: Ornithorhynchus (Platypus)
Viviparous Mammals: Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca(Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion).
4 Classes of Tetrapoda:
- Amphibia: Capable of living on both land and water but need water for some stages of the life cycle. Respiration is through lungs, skin and gills. These are cold-blooded animals.
- Reptilia: Creeping or crawling mode of locomotion. The skin is hard with scale like structures. These are cold-blooded animals.
- Aves: Pneumatic bones, feathers and wings are the important flight adaptations. Forelimbs are modified into wings. These are warm-blooded animals.
- Mammalia: Milk is produced by the mammary glands in females and is utilised for nourishing the young ones. Hairs are present on the skin. External ears are present. These are warm-blooded animals.