What are the conditions essential for effective respiration?

The conditions essential for effective respiration are:
1. Presence of thin and permeable respiratory surface thin and permeable respiratory surfaces.
2. Rich supply of blood to the respiratory surface.
3. Passage for bringing oxygen to the respiratory surface and removing CO₂ through the same passage.
4. Moist respiratory surface.
5. Presence of a circulatory system.
 6. Presence of a respiratory pigment to carry out the respiratory gases (CO₂ and O₂) .