Heterotrophic organisms obtain energy and materials by consuming other organisms or organic matter, breaking down complex substances into simpler ones that can be used for maintenance, growth, and reproduction.

Energy is necessary to maintain vital functions such as circulation, respiration, and cellular repair, even when we are not actively engaged in physical activity.

Excretion ensures that harmful waste materials are efficiently removed from the body, helping to maintain homeostasis and prevent the accumulation of toxins that could disrupt cellular function and overall health.

Examples include carbon dioxide produced during cellular respiration, nitrogenous wastes from protein metabolism, and other metabolic by-products that can accumulate and harm cells if not removed.

The transportation system in multi-cellular organisms facilitates the movement of waste from individual cells to the specialized excretory tissues for disposal.