Flatworms absorb oxygen by diffusion mechanism through their
skin to the cells in their bodies. Since flatworms do not have a circulatory system,
their bodies' cells are positioned close to the skin to ease the uptake of
oxygen from surrounding fluids or water.
Genetic variation is important because a population has a better chance of surviving and flourishing than a population with limited genetic variation. Genetic diversity also decreases the occurrence of unfavorable inherited traits.
Blood needs to flow faster around the body in order to supply the muscles with oxygen for respiration
