Answer:
Girls have two X chromosomes and boys have chromosomes (XY).
Explanation:
Girls have two X chromosomes (XX), and boys have one X and one Y chromosome (XY). Whether a baby will be a boy or a girl is determined at the time of conception.
Answer:
Cellular respiration that proceeds in the absence of oxygen is anaerobic respiration. Cellular respiration that proceeds in the presence of oxygen is aerobic respiration. Anaerobic respiration evolved prior to aerobic respiration.
Answer:
pacemaker cells.
Explanation:
Cardiac muscle tissue works to keep your heart pumping through involuntary movements. This is one feature that differentiates it from skeletal muscle tissue, which you can control. It does this through specialized cells called pacemaker cells.
