Final answer:
The internal tissue of a brachiopod is called the mantle. It has setae for movement and attachment, and the pallium produces the pedicle for attachment to the seafloor.
Step-by-step explanation:
The internal tissue of a brachiopod is called the mantle. The mantle is a thin layer of tissue that surrounds the brachiopod's body and is responsible for secreting the shell. It has setae, which are chitinous bristles that anchor in the epidermis and help with movement and attachment. The mantle also contains the pallium, a specialized region that produces the pedicle, a fleshy stalk-like structure used for attachment to the seafloor.