The giant squid beak is a great example of a gradient structure in biology. To prevent it from breaking it needs to be stiff in some places and bendy in others. These different properties are created using different ratios of the same components. Imagine having to use the same ingredients to make a main meal and a dessert.
Textile designers often create gradients using colour but can also create gradients through structure.
Biology can teach us how gradient structures create multiple properties with the same materials.
The Humboldt squid (Dosidicus gigas) features a very stiff tip, perfect for attacking prey and a more flexible end which makes it easier for the beak to attach to its soft body.
The squid's beak is made from a mixture of chitin, protein, pigment, and water. All four of these elements are found across the entire beak but in different ratios. This results in a gradual change in properties from stiff at the tip of the beak to more flexible where it interfaces with the body.
The squid’s beak is a gradient structure because it is composed of the same substances (just in different ratios) and the positioning of these is what creates the gradual change in properties.