Small organisms, like a amoeba's, have large surface area : volume ratios which means the exchange can take place by diffusion through the cell wall, the same as any other single celled organsism.
Gas exchange occurs in the alveoli in the respiratory system. The thin-walled structures allow diffusion of gases into and out of the capillaries.
During the stage of photosynthesis, the exchange of gases occur in the leaves.
Amoebas carry out respiration through diffusion. Oxygen from the surrounding water can pass through the cell membrane and into the cell, while carbon dioxide produced during metabolism can diffuse out of the cell. This process allows for the exchange of gases necessary for cellular respiration to occur in amoebas.
The gas occurs by simple diffusion through the cells.
the blood vessel which allows gas exchange to occur is the capillaries
The respiratory system's role in energy metabolism lies is to allow the exchange of gases to take place in the lungs and tissue cells. Oxygen is needed for certain metabolic reactions to occur and for the production of energy.
In any living organism that needs to breath, the only thing consistently required for life is the presence of moist membranes. The movement of oxygen and carbon dioxide across the membranes between the environment and the respiratory surface occurs by diffusion. Respiratory surfaces are generally thin and, since living animal cells must be wet in order to maintain their plasma membranes, these respiratory surfaces must be moist.
Gas exchange does not occur in the respiratory tract, it occurs in the alveoli.
Lungs
hydra has no specialized respiratory organs and exchanges of gases take place via simple diffusion from surface lining of the enteron on so in this way the surface lining of enteron acts as an efficient respiratory surface
it occurs through the heart
Amoeba reproduces by binary fission .