Difference between Vertebrates and Invertebrates | Vertebrates vs Invertebrates

 Vertebrates and invertebrates are two major categories of animals. The main difference between the two is the presence or absence of a backbone. 

Vertebrates have a backbone or a spinal column that runs along their back. This backbone is made up of a series of small bones called vertebrae, which are interconnected by joints and cartilage.

In contrast, invertebrates do not have a backbone or a spinal column. Instead, they have a soft body that is supported by an exoskeleton or a hydrostatic skeleton. Some invertebrates, such as insects and crustaceans, have an exoskeleton made of chitin. Others, such as jellyfish and worms, have a hydrostatic skeleton that is supported by water pressure.

Vertebrates and invertebrates also differ in terms of their complexity and diversity. Vertebrates are generally more complex and diverse than invertebrates, with a wider range of body sizes, shapes, and functions. This is due in part to the evolution of the vertebrate brain and nervous system, which has allowed for greater complexity and adaptability.

Vertebrata: Notochord is replaced by vertebral column and internal skeleton. They are bilaterally symmetrical, triploblastic, coelomic and segmented having paired gill pouches. Vertebrates are grouped into five classes. 

1. Pisces: These are commonly called as “fishes”, exclusively aquatic. Body is streamlined and a tail for locomotion. Gills for respiration, heart is two chambered, cold blooded, skin is covered with scales, plates. They are cold-blooded animals. Skeleton of bone ( Rohu) / cartilage( Shark). They lay eggs. 

Ex. Lion Fish, Dog Fish

2. Amphibians: These are commonly called as “Amphibians” because they can live on land and in water”. Body is streamlined and a webbed foot/ foot for locomotion. Gills or lungs or skin for respiration, heart is three chambered, cold blooded, skin is lack of scales, plates. They are cold-blooded animals. They lay eggs. 

Ex. Rana, Hyla

3. Reptilia: These are commonly called as “Reptilians”. A lung for respiration, heart is three chambered (Crocodile heart is four chambered), skin have scales. They are cold-blooded animals. They lay eggs.

 Ex. Snakes, Turtles

4. Aves :These are commonly called as “Birds”. A lung for respiration, heart is four chambered, fore limbs are modified for flight, skin has feathers. They are warm-blooded animals. They lay eggs. 

Ex. Ostrich (Flightless Bird), Pigeon, Sparrow

5. Mammalia: These are commonly called as “animals with mammary glands for producing milk to nourish their young ones”. A lung for respiration, heart is four chambered, skin has hairs, sweat or oil glands. They are warm-blooded animals. They lay eggs (Platypus, Echidna), give birth to young ones poorly developed (Kangaroo) & give birth to developed 76 young ones (Human beings). 

Ex. Lion, Whale, Bat

Invertebrates includes Porifera, Coelenterata, Platyhelminthes , Nematoda, Annelida, Arthropoda, Mollusca and Echinodermata.

1. Porifera: The word Porifera” means organisms with holes”. The canal system helps in circulating water, food, oxygen. They are non-motile with cellular level of organization and mainly marine organisms with hard outer coat called as Skeleton. They are commonly called as Sponges. 

Ex. Spongilla, Sycon

2. Coelenterata: The word Coelenterata” means organisms with body cavity calledCoelenteron” . They are radially symmetrical, Diploblastic ( two layers of cells), commonly called as Cnidarians ( Stinging cells for protection are present in the body). 

Ex. Hydra, Sea Anemone 

3. Platyhelminthes: The word Platyhelminthes means organisms with flatworms ( dorsocentrally flattened)”.They are bilaterally symmetrical Triploblastic ( three layers of 74 cells ), either free-living or parasitic. No true Coelom is present - Acoelomates. 

Ex. Planaria( Free living) , Tape worm( Parasitic)

4. Nematoda: The word Nematoda “means organisms with roundworms”. They are bilaterally symmetrical Triploblastic ( three layers of cells ), familiar with parasitic worms. The false Coelom is called as Pseudocoelome. 

Ex. Ascaris, Wuchereria (Filarial worm causes elephantiasis)

 5.Annelida: The word Annelida “ means organisms with metameric-segmented”. They are bilaterally symmetrical Triploblastic(three layers of cells) with closed circulatory system, familiar with earth worms. The Coelom is called as true Coelom. 

Ex. Neris, Earth worm, Leech 

6. Arthropoda: The word Arthropoda “means organisms with jointed legs” They are bilaterally symmetrical Triploblastic(three layers of cells ), familiar with cockroaches. The Coelom is blood filled called as Haemo Coelom. 

Ex. Prawn, Scorpion, Housefly 

 7. Mollusca: The word Mollusca “means organisms with soft body” They are bilaterally symmetrical, Triploblastic(three layers of cells), familiar with Octopus, Pila. Foot is for moving, kidney like organ for excretion, with open circulatory system.

 Ex. Unio, chiton

8. Echinodermata: The word Echinodermata “means organisms with spiny skinned”. Exoskeleton is with calcium carbonate. They are radially symmetrical Triploblastic ( three layers of cells ) with coelomic cavity, familiar with Star fish. They are exclusively free-living marine animals. 

Ex. Sea Cucumber, Feather Star 

Despite these differences, both vertebrates and invertebrates play important roles in the ecosystem and are essential for maintaining a healthy balance in nature. They are also fascinating and diverse groups of animals that continue to captivate scientists and nature lovers alike.