Tag: oviparous and viviparous

The cell is the structural unit of life. Unicellular organisms are made up of one cell that performs all the functions and thus, called as a single-celled organism.

The animals who posses a proper notochord are known as vertebrates whereas the organisms who do not have a proper notochord are known as invertebrates.

The vertebral column is a supportive structure derived from the notochord. It is more commonly called the backbone or the spine. Animals that do not possess or develop a vertebral column or backbone are commonly called invertebrates. They include crabs, snails, lobsters, octopuses, sea urchins, worms, etc.

Vertebrates are the animals that possess a dorsal hollow nerve cord, pharyngeal gill slits, and a notochord at some stage of their lives. Human beings are mammals that possess all three of these characteristics and are hence vertebrates.

In nonchordates, heart is present on dorsal side of the body whereas in chordates heart is present on ventral side of the body.

• Invertebrates do not have a notochord, their heart is present on the dorsal side. They are less evolved animals, 
• whereas vertebrates have notochords, their heart is on the ventral side and they are highly evolved animals.

Vertebrates are animals that possess a notochord, a dorsal hollow nerve cord and pharyngeal gill slits at some stage of their lives. They might possess these characteristics during the initial stages of their lives and lose them later on or they might develop these features later in their lives.

Most of the hemichordates are free living but animals like Rhabdopleura are sedentary. They tend to live with solid attachments.

• Vertebrates have a backbone with a spinal cord, whereas invertebrates do not.
  
• The diversity is exceptionally high among the invertebrates compared to vertebrates.
  
• Vertebrates are always bilaterally symmetrical, while invertebrates could show either bilateral or radial symmetry.
  
• Vertebrates are usually large-bodied and move fast compared to invertebrates.
• Vertebrates have a closed blood system, a well-developed brain, either gills or lungs for respiration, and a complex and sophisticated nervous system, whereas those are primitive in invertebrates. Therefore, it concerns that vertebrates have many specializations to extract the best out of the environment compared to invertebrates.
• Despite all these changes, someone could draw a point that invertebrates are more adaptive due to their simplicity, whereas vertebrates do not have good adaptability in comparison because of the specialization. However, I would like to quote a popular quote to finish that in evolution specialization paralyzes and ultra specialization kills the viability of taxons.