Final answer:
The theme expressed in the poem about Salva and Nya is that perseverance is essential for survival, underlining the importance of adaptation and endurance in challenging environments.
Step-by-step explanation:
The theme that is expressed in the two-voice poem about Salva and Nya's survival in challenging environments reflects the idea that perseverance is necessary to survive. This theme is supported by the premise that individuals most adapted to their environment are more likely to survive and pass their traits to the next generation. Both Salva and Nya demonstrate resilience and determination in the face of adversity, highlighting that both physical and emotional strength, along with the help of others, are vital aspects of survival. Moreover, the concept of adaptation and natural selection emphasizes that survival often entails more than just the individual's qualities; it involves a combination of favorable traits, environmental challenges, and sometimes, communal support or collaborative efforts. Hence, even though physical and emotional strength, as well as mutual assistance, play roles in survival, the underlying theme centers around the endurance and adaptability as key to withstanding life's difficulties.