The actions of internal organs are regulated by the part of the brain called the

Abird flies by moving its wings up and down. which two systems are most directly responsible for the movement of a bird's wings? a. skeletal and muscular systems b. respiratory and muscular systems c. skeletal and digestive systems d. respiratory and digestive systems

Which animal receives the greatest amount of the original energy found in the producers

What tissue type has polarity and is avascular? what tissue type has polarity and is avascular? a. muscle b. connective tissue c. nervous tissue d. epithelium