[Campbell Biology P.924] Based on Figure 40.4 and the accompanying text, explain how the exc... | Practice Question

Based on Figure 40.4 and the accompanying text, explain how the exchange of materials in complex animals can be described as both "internal" and "external."

  • A: External exchange occurs directly between cells and the environment, while internal exchange is between body systems.
  • B: External exchange involves the entry of substances from the environment into the body (e.g., oxygen in lungs, food in gut) and the exit of wastes from the body to the environment (e.g., carbon dioxide from lungs, metabolic waste from kidneys). Internal exchange then refers to the transport and distribution of these substances within the body's internal fluids (circulatory and interstitial fluid) and their final exchange between these fluids and individual body cells.
  • C: Internal exchange only refers to processes within individual cells, and external exchange is limited to the skin surface.
  • D: Complex animals only perform internal exchange, as they are too large for direct external exchange.

Explanation

External exchange in complex animals refers to the processes where substances are taken in from the external environment e.g., oxygen via lungs, food via the digestive system and wastes are expelled to the external environment e.g., carbon dioxide from lungs, metabolic waste from kidneys . These processes occur at specialized internal surfaces that have openings to the outside. Internal exchange, on the other hand, involves the transport of these substances within the body's internal fluids blood and interstitial fluid and the subsequent exchange between these fluids and the individual cells of the body, ensuring all cells have access to necessary resources and can dispose of wastes.