What does the term 'extinct' refer to in biology?

The term 'extinct' in biology specifically refers to a species that has completely disappeared from Earth, meaning that there are no living individuals remaining of that species. When a species becomes extinct, it no longer exists in any form, whether in the wild or in captivity. This can occur due to various factors such as habitat loss, climate change, competition with other species, or human activities. Understanding extinction is crucial in studying biodiversity and conservation efforts, as it highlights the fragility of ecosystems and the dire consequences of environmental changes.

In contrast, a species that is endangered but still exists continues to have surviving members, while adaptations to new environments describe how species evolve over time to survive in changing conditions. Evolution itself is a broader process that involves changes in a species over generations, rather than a definitive state like extinction.