What Is the Difference Between Vertebrates and Invertebrates?

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The primary difference between vertebrates and invertebrates is the presence of a backbone or spinal column, which vertebrates have and invertebrates do not. Examples of vertebrates are humans, dogs, cats and birds. Examples of invertebrates are flatworms, mollusks, sea urchins and insects.

Vertebrates have a well-developed internal skeleton, an outer covering of protective cellular skin, an advanced nervous system and a highly developed brain. On the other hand, invertebrates are heterotrophic and multicellular, have no cell walls and have no backbone. The characteristics that differentiate vertebrates from their counterparts are their backbones, vertebrae and notochords.

Vertebrates are typically large in size because they have a versatile support system that enables them to develop more quickly. Invertebrates are mostly small and slow in movement. They do not have effective ways to support a big physique or the muscles needed to power a large body. Vertebrates are classified into five different groups: mammals, amphibians, fish, birds and reptiles. Invertebrates are classified into 30 phyla.

Because vertebrates all belong to the same phylum, they all share several traits that are characteristic of phylum Chordata in general. These include a complete digestive system, a closed blood system, bilateral symmetry, a ventral heart and a tail at some point in their development. All chordates have endoskeletons, but there are some that lack backbones, called invertebrate chordates. Some classes of vertebrates include birds, mammals, jawless and armored fish, reptiles and amphibians.

Only two percent of animal species are vertebrates, and the remaining 98 percent are invertebrates. Both live in a vast array of habitats, but vertebrates are more capable of adapting to all habitats, including land, air and sea. Vertebrates have a well-developed nervous system that enables them to react swiftly to environmental changes, but invertebrates have simple nervous systems that allows them to behave by instinct.