The major classes of vertebrates are Cyclostomata, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. The general characteristics of these phyla are given below:
Cyclostomata
- The body is slender, rounded, and eel-like.
- They are aquatic.
- Their skin is naked meaning no scales are present.
- Fish-like in form.
- True jaws are absent.
- Paired appendages are lacking.
- Gills are the respiratory organs.
- Example: Petromyzon (lamprey).
Chondrichthyes
- All are marine species.
- Their skeleton is cartilaginous.
- Their skin contains placoid scales.
- On both sides of the head, 5-7 pairs of gills are present.
- The body is streamlined so that it can move faster in the water.
- The tail is heterocercal.
- No operculum is present.
- Example: Scoliodon, Swordfish, etc.
Osteichthyes
- They are mostly freshwater fish.
- Their skin contains cycloid, ctenoid, or ganoid scales. Some of them has no scales.
- Four pairs of gills are present on both sides of the body.
- Gills are covered with bony operculum.
- The skeleton is bony; not cartilaginous like Chondrichthyes.
- Gills are the primary respiratory organs.
- The digestive system is complete.
- Fertilization is external.
- Example: Labeo rohita, Tenualosa ilisha, Ompok pabda, Mystus tengara, Mystus cavasius, Anabas testudineus, Puntius ticto, etc.
Amphibia
- Amphibians can breathe under water through their skin.
- They can breathe on land through their lungs.
- They lay eggs in the water.
- The eggs hatch into larvae containing gills and tails. During metamorphosis gills and tail degenerate and lungs develop.
- They are cold-blooded animals.
- Their skin is soft and moist as they contain numerous glands on the skin.
- The digestive system is complete.
- Example: Frog, Toad, Salamander, Newt, Indian Bull Frog(Hoplobatrachus tigerinus or Rana tigrina), Asian Common Toad (Duttaphrynus melanostictus or Bufo melanostictus) etc.
Reptilia
- The skin is dry and contains scales as an exoskeleton.
- They move by crawling.
- They have two forelimbs and two hindlimbs except for snakes.
- Each limb contains five claws.
- The digestive system is complete.
- They lay eggs. Fertilization is internal.
- They are the first fully terrestrial animals.
- Example: Lizard, Snake, Crocodile, etc.
Aves
- The body is covered with feathers.
- Feather is their unique character.
- Two forelimbs and two hindlimbs are present. Forelimbs are modified into wings.
- They have air sacs around their lungs which help them in flight.
- The digestive system is complete.
- They have crop in their digestive system where the food is temporarily stored.
- They are warm-blooded.
- Their heart is four-chambered.
- Their bones are light, strong, delicate, and laced with air cavities.
- Example: Columba livia (Pigeon), Crow, etc.
Mammalia
- Their body is covered with hairs.
- They have two forelimbs and two hindlimbs.
- Female mammals have mammary glands which produce milk.
- They are warm-blooded animals.
- Their heart is four-chambered.
- Their teeth are heterodont.
- All mammals give birth to the child.
- Example: Cavia porcellus (Guinea pig), Royal Bengal Tiger, etc.
Md Ekram Hossain Bhuiyan is a passionate student currently pursuing his studies at Jagannath University in Dhaka. He is a zoology major and his love for animals, nature, and wildlife is evident in his academic pursuits. Ekram is a curious and adventurous individual who always seeks to learn more about the world around him. His passion for animals began at a young age, and he has since dedicated himself to studying the behavior, anatomy, and habitats of various species.
He finds peace in being surrounded by the beauty of nature and observing the creatures that call it home. He believes that it is important to protect and preserve the natural world for future generations.
As a student of zoology, Ekram is dedicated to expanding his knowledge of the subject. He is a hardworking individual who strives for excellence in his studies and is always eager to take on new challenges. Ekram is a driven and compassionate individual who is dedicated to his studies and his passion for animals, nature, and wildlife.