If an animal is having a well developed skeleton system, a backbone then it belongs to vertebrate. Also, size is an important factor to identify vertebrate and invertebrate.
Explanation:
Vertebrates have a well developed skeleton system and backbone. Their skeleton system is made up of bones and cartilage. While, invertebrates don't have any backbone.
Due to lack of backbone or skeleton system, invertebrates are small in size. As there is no proper mechanism to support large body so invertebrates are small in size and also they move very slowly. This is also a major difference in vertebrate and invertebrate.
Another important difference between vertebrate and invertebrate is that body of vertebrate is covered with some structure like hair, feathers, skin, scales or a combination of these.
These features help to distinguish vertebrate from invertebrate by observing them, no need to dissect.
