Final answer:
Diffusion is a biological process where substances like oxygen, nutrients, and wastes move across cell membranes from areas of high to low concentration, essential for gas exchange, nutrient absorption, and waste removal.
Step-by-step explanation:
Diffusion is a key process in biological systems where molecules spread from an area of higher concentration to an area of lower concentration. Here are three examples where diffusion occurs:
- Gas exchange in the lungs: Oxygen diffuses from the air in the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled.
- Nutrient absorption: Nutrients from digested food passively diffuse through the intestinal walls into the bloodstream.
- Cellular waste removal: Waste products like urea diffuse from cells into the blood for removal by the kidneys.
Diffusion through thin cell membranes is remarkably efficient and vital for cellular respiration and passive transport.