The answer is spicules. These
sharp-pointed structures are formed from calcium carbonate skeleton of
the organisms. They can also be formed from silica. They can be big (megascleres),
or microscopic (microscleres). Also dependent on the number of axis on the spicules, they are classified as monoaxon,
triaxon or polyaxon.
Sponges have spicules, small spiky elements, in their bodies, made out of different minerals in different sponge species that serve as protection against predators. Since sponges have no organized tissues, just layers of cells, these spicules stand between two layers of sponge cells.
The sun gets its energy from the process of nuclear fusion. This process occurs in the sun's core or interior, where temperature and pressure are extremely high. During most of the sun's life, energy comes from the fusion of hydrogen nuclei
