What does extinction refer to in biological terms?

In biological terms, extinction refers specifically to the death of every member of a species or a larger taxonomic group. This means that once a species is declared extinct, there are no remaining individuals alive anywhere on the planet. Extinction signifies a complete loss of that species from the ecosystem, and it has significant implications for biodiversity and ecological balance.

The other choices reflect different concepts related to population dynamics or ecological changes, but they do not address the complete and irreversible loss signified by extinction. For example, a reduction in population size or the disappearance of individuals within a species does not imply that the species itself has entirely vanished; some members may still exist. Similarly, migration to a different habitat involves the movement of individuals to new areas but does not constitute extinction. Therefore, understanding extinction as the total eradication of a species is crucial for studying ecology and conservation efforts.