• Respiration is the process of releasing energy from glucose molecules, whereas breathing is the physical act of inhaling oxygen and exhaling carbon dioxide.

  Aerobic respiration occurs in the presence of oxygen and involves the complete breakdown of glucose into carbon dioxide and water, releasing energy in the form of ATP. The overall equation for aerobic respiration is: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (ATP)

  Anaerobic respiration occurs in the absence of oxygen and involves the partial breakdown of glucose into lactic acid or ethanol and carbon dioxide, releasing energy. The overall equation for anaerobic respiration in humans is: C6H12O6 → 2C3H6O3 (lactic acid) + energy (ATP)

I) The blood vessel that brings oxygenated blood to the human heart is the pulmonary vein. II) The left atrium receives oxygenated blood from the pulmonary vein. III) Oxygenated blood from the left atrium is pumped into the left ventricle, which then contracts to send the oxygenated blood to all parts of the body through the systemic circulation.

• Emulsification of fats is significant because it breaks down large fat globules into smaller droplets, increasing the surface area available for enzymatic action. This process, usually aided by bile salts produced by the liver and stored in the gallbladder, enhances the efficiency of fat digestion by lipase enzymes, allowing for better absorption of fatty acids and fat-soluble vitamins in the small intestine.

• The small intestine in herbivores is larger than in carnivores primarily because plant matter requires more extensive digestion and absorption. Herbivores typically consume diets rich in complex carbohydrates like cellulose, which require longer processing times and more surface area for absorption. Therefore, a larger small intestine provides ample space for microbial fermentation and absorption of nutrients from plant material.

• A four-chambered heart provides efficient separation of oxygenated and deoxygenated blood, ensuring that oxygen-rich blood is pumped to the body tissues and oxygen-depleted blood is sent to the lungs for reoxygenation. This separation prevents mixing of oxygenated and deoxygenated blood, allowing for a more effective oxygen supply to the body tissues, which is particularly important for sustaining high metabolic rates in warm-blooded animals like mammals and birds.