Only the strongest animals survive
Stem cells are what allow planaria to grow and regenerate as the stem cells can change into any of the cells that make up the planaria.
Exhaled air has more carbon dioxide because the blood contains some carbon dioxide (a waste product) that is transferred to the air in the lungs, which is then exhaled. The result is that the exhaled air contains less oxygen and more carbon dioxide than the inhaled air. The air in the lungs also becomes humidified with water before it is exhaled.
<span>(</span><span>A. specialized cells that perform specific functions)</span><span>
</span>
