Answer:
plasma membrane
Explanation:
The plasma membrane is also known as the cell membrane. It is the boundary between the internal components of a cell and its external surroundings. It controls the entry and exit of substances into or out of the cell and thus, facilitates the exchange of substances between the cells and their external environment.
The first step in designing an experiment is the form a testable question.
Answer:
Flatworms and cnidarians
Explanation:
In simple organisms, such as cnidarians and flatworms, every cell in the body is close to the external environment. Their cells are kept moist so that gases diffuse quickly via direct diffusion. Flatworms are small, literally flat worms, which 'breathe' through diffusion across the outer membrane
The pulmonary vein differ from the other veins in the body because it carries oxygenated blood whereas other veins carried deoxygenated blood
Which means that the pulmonary vein carried out the blood to the entire body as a source for metabolism
hope this helps
