Section: Gas Exchange in Multicellular Organisms

Question: Where are the structures involved in gas exchange located?

Answer: Organs for gas exchange have evolved differently in various organisms, yet they all have a common function: exchanging gas molecules between cells and the external environment

Support: 21.1 Variation in Gas Exchange Systems

Organs for gas exchange have evolved differently in various organisms, yet they all have a common function: exchanging gas molecules between cells and the external environment

Small multicellular animals, such as planarians, obtain oxygen and give off carbon dioxide directly through their body surfaces

The respiratory organs found in many animals that live in water are called gills

Gills provide these water dwellers with a large respiratory surface

Water contains dissolved oxygen, but only in small amounts

To satisfy the need for oxygen in a fish, for example, water must constantly pass over the gill surfaces

Gills are highly efficient gas exchange organs

The filaments of gills are made up of thin disklike structures lined up parallel with the direction of water movement

Support: 21.8 Structure of the Urinary System

Nitrogen is removed from these nutrients when they converted to carbohydrates or fats

Cells of the tubule wall selectively remove substances from the surrounding capillaries that were left in the plasma after filtration or returned by reabsorption

Some topics in this essay:
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