Describe one similarity and one difference between the term era and period. Please help soon

Compare the composition of the moon's surface with the composition of the earth's surface.

What makes a dominant allele different from a recessive allele

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