Substrate

The video tutorial explains the concept of 'substrate' across different scientific fields. In material science, a substrate is the surface on which a coating is applied. In biochemistry, it refers to the substance on which an enzyme acts. In biological science, a substrate is the material found at the bottom of a body of water, such as silt and stones on a riverbed.

Describe the characteristics of a substrate found at the bottom of a body of water.

List examples of materials that can be considered substrates in a riverbed.