Introduction:
Sven chose a canary as his pet for the space station because canaries are resistant to the absence of gravity. This choice offers several advantages in the unique environment of a space station.

Explanation:
1. Canary's Adaptability:
Canaries, as small birds, are known for their adaptability to different environments. They have been kept as pets for centuries and have proven to be resilient in various conditions. Their ability to survive and thrive in harsh environments makes them suitable for the challenges of living in a space station.

2. Resistance to the Absence of Gravity:
Canaries are resistant to the absence of gravity, which is a crucial factor in space environments. The absence of gravity can have adverse effects on the human body, such as muscle and bone loss. While canaries are not immune to these effects, they are better equipped to handle the physical challenges of zero gravity compared to larger animals or humans.

3. Canary's Respiratory System:
Canaries have a unique respiratory system that is highly efficient. They have a high metabolic rate and can extract more oxygen from the air compared to larger animals. This makes them less dependent on a constant supply of fresh air, which may be limited in a closed space station environment. Their ability to survive with lower oxygen levels makes them a suitable choice for space exploration.

4. Canary's Sensitivity to Gas Leaks:
Although not directly mentioned in the question, it is worth noting that canaries have historically been used in coal mines as early warning systems for gas leaks. Canaries are highly sensitive to the presence of toxic gases such as carbon monoxide. If there is a gas leak in the space station, the canary's behavior would change, indicating the potential danger to the astronauts. This sensitivity adds an additional layer of safety to the space station.

Conclusion:
Sven chose a canary as his pet for the space station because canaries are resistant to the absence of gravity, adaptable to different environments, have an efficient respiratory system, and can potentially detect gas leaks. These qualities make canaries a suitable choice for the unique challenges of living in a space station.