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What are the two major groups of animals?
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Animal
The fallow deer (Dama dama) has been introduced in many areas ever since the Neolithic Period.
The two major groups of animals are vertebrates and invertebrates.1
These groups are primarily distinguished by the presence or absence of a backbone:
- Vertebrates: These animals possess a vertebral column, or backbone. They are also characterized by a distinct head with a differentiated brain, a central nervous system, and a muscular system with bilaterally paired masses.123
- Invertebrates: These animals lack a vertebral column. They represent more than 90 percent of all living animal species and include a vast array of organisms such as insects, mollusks, and crustaceans. Unlike vertebrates, which are contained within a single phylum (Chordata), invertebrates are distributed across more than 30 different phyla.2