Even the cell membrane is like the cell wall its flexible and lets certain things in and certain things out.
The Cỉculatory system is an organ system that permits blood to everywhere in the body and transport nutrients, oxygen, carbon dioxide, ...to help fighting diseases ,.... The main parts of the Circulatory system are heart , lungs , veins , vessels, arteries,...
Only animals in the same <u>species</u> can always breed and have fertile offspring.
Although animals in the same genus<em> can </em>breed, their offspring are usually infertile.
