The movement of oxygen from an area of high concentration to an area of low concentration is an example of:

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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

Label the offspring chromosomes a1, a2, b1, or b2. circle any mutation chromosomes.