On animals as carbon sinks or carbon sources
Ancient scholars have explored the wonders of nature and the cycle of carbon, which is quite doubtful: Animals, are carbon sinks or carbon sources? This is an important issue related to the creation of heaven and earth and the balance of ecology.

The life of animals, their diet, respiration, and metabolism are all closely related to the flow of carbon. Animals depend on food for survival, and what they eat contains more carbon. If they eat plants and trees, they ingest carbon sequestered by photosynthesis. Meat eaters also indirectly obtain carbon from other animals.

As for respiration, animals inhale oxygen and exhale carbon dioxide. This carbon dioxide is also a carbon-containing waste gas. Every day, thousands of animals emit a considerable amount of carbon. This shows that animals are one end of the carbon source.

However, there are other theories. When an animal dies, its remains are either humus or buried deep in the ground. In the remains, carbon gradually accumulates, changes over time, or becomes a fossil fuel or a part of soil organic carbon. This process is actually the fixation of carbon, just like animals in an invisible way, contributing to the accumulation of carbon.

Furthermore, some aquatic animals, such as shellfish, coral, etc., have shells composed of calcium carbonate. As they grow, carbon is taken from water bodies to help form their shells. This is also one way of carbon fixation and can be regarded as a carbon sink.

In summary, animals are both carbon sources and carbon sinks in the carbon cycle. Their respiration and metabolism are the release of carbon, showing the sign of carbon sources; and the decay and formation of shells are the fixation of carbon, showing the appearance of carbon sinks. To understand the exact position of animals in the carbon cycle, we must carefully observe the whole picture of the ecosystem and comprehensively consider various factors to obtain its true meaning.