- Sexual reproduction is a kind of reproduction
- The reproductive system is used for sexual reproduction
- Hence, the reproductive system is used for reproduction

- Producing offspring ensures the continuation of a species
- Reproduction produces offspring
- So, reproduction ensures the continuation of a plant or animal species

- The reproductive system is used for reproduction
- Reproduction ensures the continuation of a plant or animal species
- So, the reproductive system is used for continuing the species

- The reproductive system is used for continuing the species
- If something is used for a performing a process, then performing that process is a function of that something
- So, a function of the reproductive system is continuing the species

So, a function of the reproductive system is continuing the species
Q: Which body system's primary function is the continuation of the species?
Context:
- If something is used for a performing a process, then performing that process is a function of that something 
- Sexual reproduction is a kind of reproduction 
- Producing offspring ensures the continuation of a species 
- Reproduction produces offspring 
- The reproductive system is used for sexual reproduction