What, do you think, would happen if we had no backbone? Our backbone not only supports our body, but also enables us to walk erectly. Without a backbone, vertebrates in general would not be able to survive in nature.
However, as we have already seen, not all animals have backbones. Then, how do they survive? Internal and external skeletons help an animal to survive without a backbone. Some invertebrates have internal skeletons that support and protect their internal tissues. These skeletons are made up of different materials. Sponges have a framework of silica or other substances that stiffen their bodies. Others have external skeletons in the form of shells. Invertebrates belonging to the molluscs group have shells made of calcium carbonate, while those that are anthropods have external skeletons made up of a substance called chitin.
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