Final answer:
Diffusion is essential for the exchange of nutrients and waste products, particularly oxygen entry into the bloodstream and carbon dioxide exit into the alveoli from the blood. While not directly involved in the digestion process, it assists in nutrient transport post-digestion. In larger organisms, specialized structures complement diffusion to maintain efficient gas exchange.
Step-by-step explanation:
Diffusion is pivotal for several physiological processes in living organisms. It is the dominant mechanism that facilitates the exchange of nutrients and waste products between the blood and tissue and between the air and blood in the lungs. For instance, oxygen must diffuse from the lungs into the bloodstream to be delivered to cells for respiration, and likewise, carbon dioxide, a metabolic waste gas, must diffuse from the blood into the alveoli of the lungs to be exhaled.
Answering the student's query:
- a. Allows organisms to break down and process food during digestion: While not directly involved in digestion, diffusion is essential for transporting the digested nutrients from the digestive system into the bloodstream.
- b. Allows oxygen to leave the lungs and enter the bloodstream: This is a primary function of diffusion in the respiratory system, key for gas exchange to sustain cellular respiration.
- c. Allows carbon dioxide to exit the blood into the alveoli: The expulsion of carbon dioxide from the bloodstream into the lungs for exhalation is another critical role of diffusion, maintaining the acid-base balance in the body.
Diffusion is also a slow, passive transport process that is sufficient only for small organisms or those with highly flattened bodies for gas exchange. Larger organisms have evolved specialized respiratory tissues, such as gills and lungs, to facilitate this process across larger distances and maintain efficient uptake and release of gases.