What Are Vertebrates? Definitions, Groups & Real-Life Examples
Animals that have skeletons and backbones are called vertebrates. There are different kinds of vertebrates that fall under various classes. These include humans, mammals, birds, amphibians, reptiles, and fish.
Before we proceed to vertebrate characteristics, note that Vertebrata falls under phylum Chordata. Other sub-phyla are – Cephalochordata and Urochordata.
Characteristics of Vertebrates
Thinking what are the basic features of vertebrates? Read below to know more about it.
There is a distinct similarity in the anatomy of vertebrates with the presence of a vertebral column, gastrointestinal tract, and spinal cord.
Notochord develops into a vertebral column, and the vertebrae are present on the dorsal side.
Presence of the central nervous system is a crucial identifier. Nerve tube of the spinal cord in the anterior part expands into the brain.
Jaws are present in some vertebrates. Order of vertebrates includes jawless species.
Internal skeleton aids in the distribution of different muscle attachment nodes.
Fun Fact!
Even though different types of vertebrates across the world include approximately 65,000 species, it does not amount to more than 3% of animals on the face of Earth. Hence most animal species in our world are actually invertebrates!
What is the Classification of Vertebrates?
Find out more about the classification of vertebrates with examples.
Class – Mammalia
Mammals have a four-chambered heart and warm blood. Usually, they give birth to their offspring, but exceptions like Echidna can also be found, which reproduce by laying eggs. The habitation of such vertebrates is varied.
Mammary glands are present for feeding the younger ones. Mammals have functional limbs and external pinna. Fertilization in these vertebrates is usually internal. Examples – kangaroo, dolphin, whale, platypus.
Class – Aves
Birds fall under this class of vertebra. The distinctive feature of Aves is the feather-covered body and forelimbs that evolved as wings for flight. An exception in this regard is Ostrich, which cannot fly.
Bones have air cavities, and additional chambers can be found in the digestive tract. Example – vulture, pigeon, crow, etc.
Class – Reptilia
The body of reptiles is covered by scutes or scales, and in some instances, the epidermal scales can be cast-off as well. There is no external pinna and the tympanum performs the auditory functions. Reptiles have three-chambered hearts, except crocodiles, which it is four-chambered. As opposed to other vertebrates, reptiles are cold-blooded animals. Examples – tortoise, turtle, crocodile, snake, etc.
Class – Amphibia
Amphibians are both terrestrial and aquatic animals. The tympanum acts as the ear, and the body is covered by moist skin without scales. Cloaca acts as a common opening to the reproductive tract, urinary tract, and alimentary canal. Respiration is through both lungs and gills, and the heart is three-chambered. Examples – salamander, tree-frog, toad, etc.
Class – Pisces
This class includes fish with scales all over the body. These vertebrates are oviparous, and respiration takes place only through gills. Fish have two-chambered hearts, and the skeleton is made entirely of cartilage. Exception being sharks with a skeleton made up of both cartilage and bone.
Test Your Knowledge
Vertebrates are of five kinds. Which of the following does not fall under vertebrate?
Birds
Mammals
Reptiles
Arthropods
Ans. (d) Arthropods
Which of the following vertebrates is not considered as a mammal, even though other characteristics of vertebrates are present?
Sloth
Armadillo
Whale
Shark
Ans. (d) Shark
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Vertebrates are those organisms that have skeletons, a bone structure, and a backbone. There are various types of vertebrates and they fall under various classes, some vertebrates are humans, birds, amphibians, mammals, fish, and reptiles. Vertebrata comes under the phylum Chordata. Other subcategories are - Cephalochordata and Urochordata.
The concept of vertebrates is taught in schools much earlier, however, the properties and characteristics of vertebrates are studied in depth in class 11 biology. Vertebrates are mainly discussed in the NCERT book in chapter 4 animal kingdom, chapter 21 control, and coordination, chapter seven structural organization in animals. These chapters are prescribed by the Central Board of secondary education and are taught in schools that follow the curriculum set by the CBSE. Properties and characteristics of vertebrates are extremely important in the sense that it carries significant weightage in the examinations. Students who are aspiring to go into the medical field will have to give NEET which is the national eligibility cum entrance test. The basis for NEET is the study of biology physics and chemistry of classes 11 and 12 and therefore students should first clear their bases which are taught in class 11 NCERT books.
Key Concepts That are Important to Study in Relation to Vertebrates-
4.1.1 Levels of Organisation
4.1.2 Symmetry
4.1.3 Diploblastic and Triploblastic Organisation
4.1.4 Coelom
4.1.5 Segmentation
4.1.6 Notochord
4.2 CLASSIFICATION OF ANIMALS
4.2.1 Phylum – Porifera
4.2.2 Phylum – Coelenterata (Cnidaria
4.2.3 Phylum – Ctenophora
4.2.4 Phylum – Platyhelminthes
4.2.5 Phylum – Aschelminthes
4.2.6 Phylum – Annelida
4.2.7 Phylum – Arthropoda
4.2.8 Phylum – Mollusca
4.2.9 Phylum – Echinodermata
4.2.10 Phylum – Hemichordata
4.2.11 Phylum – Chordata
4.2.11.1 Class – Cyclostomata
4.2.11.2 Class – Chondrichthyes
4.2.11.3 Class – Osteichthyes
4.2.11.4 Class – Amphibia
4.2.11.5 Class – Reptilia
4.2.11.6 Class – Aves
4.2.11.7 Class – Mammalia
FAQs on Vertebrates: Classification, Characteristics & Key Facts
1. What are vertebrates? Please provide some common examples.
Vertebrates are animals belonging to the subphylum Vertebrata, under the phylum Chordata. The defining characteristic of a vertebrate is the presence of a vertebral column or backbone, which is a segmented series of bones that protects the spinal cord. This internal skeleton, or endoskeleton, provides structural support and allows for greater mobility and size. Common examples of vertebrates include fish, frogs, snakes, eagles, dogs, and humans.
2. What are the key characteristics that define an animal as a vertebrate?
All vertebrates share several key characteristics that are aligned with the CBSE/NCERT syllabus for the 2025-26 session. These include:
Notochord: Presence of a notochord during the embryonic stage, which gets replaced by a cartilaginous or bony vertebral column in most adults.
Dorsal Hollow Nerve Cord: A single, hollow nerve cord that runs along the back (dorsal side), which develops into the brain and spinal cord.
Paired Pharyngeal Gill Slits: These are present at some stage of life. In aquatic vertebrates like fish, they function in respiration, while in terrestrial vertebrates, they are modified for other functions.
Post-Anal Tail: A tail that extends beyond the anus is present at some point in their life cycle.
Ventral Heart: A heart with two, three, or four chambers, located on the ventral (front) side of the body.
3. How are vertebrates classified? List the major divisions and classes.
The subphylum Vertebrata is broadly divided into two main divisions based on the presence or absence of jaws:
Agnatha (Jawless Vertebrates): This division includes primitive fish-like animals that lack jaws. It has one living class: Cyclostomata (e.g., Lamprey, Hagfish).
Gnathostomata (Jawed Vertebrates): This division includes all vertebrates that possess jaws. It is further divided into two superclasses:
1. Pisces (Fishes):
Class Chondrichthyes (Cartilaginous fishes, e.g., Sharks, Rays)
Class Osteichthyes (Bony fishes, e.g., Rohu, Tuna)
2. Tetrapoda (Four-limbed vertebrates):
Class Amphibia (e.g., Frogs, Salamanders)
Class Reptilia (e.g., Snakes, Lizards, Crocodiles)
Class Aves (Birds, e.g., Pigeons, Ostriches)
Class Mammalia (e.g., Humans, Whales, Kangaroos)
4. What is the fundamental difference between vertebrates and invertebrates?
The fundamental difference is the presence of a vertebral column (backbone) in vertebrates, which is completely absent in invertebrates. This single feature leads to other significant distinctions:
Skeleton: Vertebrates possess an endoskeleton (internal skeleton) made of bone or cartilage, while many invertebrates have an exoskeleton (external skeleton) or are soft-bodied.
Nervous System: Vertebrates have a highly developed dorsal, hollow nervous system with a brain protected by a cranium (skull). Invertebrates have a simpler, often ventral, solid nervous system.
Body Size: The supportive endoskeleton allows vertebrates to achieve much larger body sizes compared to most invertebrates.
5. Are all chordates considered vertebrates? Explain why or why not.
No, all chordates are not vertebrates. This is a common point of confusion. The phylum Chordata is divided into three subphyla: Urochordata, Cephalochordata, and Vertebrata. While all three groups share the primary chordate features (notochord, dorsal hollow nerve cord), only the members of subphylum Vertebrata have their notochord replaced by a true vertebral column. Therefore, all vertebrates are chordates, but not all chordates (like Urochordates and Cephalochordates) are vertebrates.
6. What is the evolutionary importance of the endoskeleton in vertebrates?
The evolution of an endoskeleton provided vertebrates with several significant advantages. Primarily, it offers a strong, flexible internal framework that supports the body and protects vital organs like the brain (cranium) and spinal cord (vertebral column). Unlike an exoskeleton, which must be shed for growth, an endoskeleton grows along with the animal, allowing for continuous development and the attainment of a much larger body size. This framework also provides efficient attachment points for muscles, enabling complex and powerful movements.
7. On what key adaptive features is the classification of Tetrapoda (Amphibia, Reptilia, Aves, Mammalia) based?
The classification of Tetrapods into its four classes is based on major evolutionary adaptations, primarily related to their transition from water to land. Key features include:
Method of Respiration: Gills in larval amphibians versus exclusive reliance on lungs in reptiles, birds, and mammals.
Reproduction: External fertilisation and aquatic eggs in most amphibians, versus internal fertilisation and the development of the amniotic egg in reptiles, birds, and mammals, which allowed reproduction on land.
Thermoregulation: Amphibians and reptiles are generally cold-blooded (poikilothermic), while birds and mammals are warm-blooded (homeothermic), maintaining a constant internal body temperature.
Integument (Skin): Moist, glandular skin in amphibians; dry, scaly skin in reptiles; feathers in birds; and hair/fur and mammary glands in mammals.
8. Explain the difference between cartilaginous fish (Chondrichthyes) and bony fish (Osteichthyes).
The primary difference lies in their skeletal composition. Chondrichthyes, like sharks and rays, have an endoskeleton made entirely of cartilage. In contrast, Osteichthyes, like tuna and carp, have a skeleton made primarily of bone. Other key differences include the presence of an operculum (gill cover) in bony fish, which is absent in cartilaginous fish (who have visible gill slits), and the type of scales on their body.
