Abi - 10 centaurus
Vertebrates are
animals with an internal backbone or spinal column. There are over 85,000
species of vertebrate animals such as amphibians, birds, fish, mammals and
reptiles. Most large land animals are vertebrates. Even large sea animals, such
as the whale, are vertebrates. However, only about 5% of all animal species are
vertebrates. The remaining 95% of animals are invertebrates that don’t have an
internal backbone.
Fifty thousand
species might seem like a lot. Compared to the invertebrates, there are not
that many species of vertebrates. One reason is that vertebrates are usually
larger than invertebrates. They need more space. Another reason is that, even
though they are more advanced, there are many limitations on the environments
that are available to them.
The defining
characteristic of all vertebrates is the vertebral column or backbone. This
vertebral column is a strong series of bones extending through the core of the
body. Near the front end of the backbone is the mouth, with the anus opening near
the back end of the backbone. In vertebrates with a tail, the vertebral column
extends beyond the anus to the end of the tail. Above the backbone is the
spinal cord, a major component of the nervous system. Below the backbone is the
gastrointestinal or digestive tract.
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