What is the main function of an animal's digestive system?

The main function of an animal's digestive system is breaking down food and absorbing nutrients. This process begins with the intake of food, which is mechanically and chemically broken down into smaller components. Enzymes play a crucial role in this breakdown, as they facilitate the digestion of proteins, fats, and carbohydrates. Once food is broken down into absorbable units like amino acids, simple sugars, and fatty acids, these nutrients are transported into the bloodstream through the walls of the intestines. This allows the body to utilize the nutrients for energy, growth, and cell repair.

In contrast, the other options refer to different biological systems or functions. Producing hormones for growth pertains to the endocrine system and involves glands that release hormones affecting various physiological activities. Regulating body temperature is primarily managed by the integumentary and nervous systems, which help maintain homeostasis. Finally, transporting oxygen in the blood is the key function of the circulatory system, particularly involving red blood cells and hemoglobin. Each of these systems serves distinct roles, highlighting the specialized function of the digestive system in nutrient processing and absorption.