What does ‘extinction’ refer to in the context of species?

In the context of species, extinction refers to a situation where a species no longer exists anywhere on Earth. This can happen due to various factors, including habitat loss, climate change, overexploitation, and invasive species, among others. Once a species goes extinct, it means that all its members have died out, and there are no remaining individuals to reproduce or maintain the population.

The other choices focus on different concepts related to species but do not accurately define extinction. For instance, the idea of a species adapting to environmental changes addresses resilience and survival rather than extinction. Being confined to a specific area refers to endemic species, which may still be thriving, and while this can pose a risk for extinction, it itself is not synonymous with it. A species that is thriving in its habitat indicates a healthy population and sustainability, which contrasts sharply with the concept of extinction. Therefore, the correct answer highlights the definitive and grave outcome of extinction—total disappearance of a species from the planet.