What is most likely consequence if a group of living organisms is unable to adapt to changing conditions within the Earth system

If a group of living organisms is unable to adapt to changing conditions with the earth's system, it shall face extinction.

Explanation:

As time goes by, the earth's systems keep changing, either negatively or positively.

If the earth's temperature decreases then living organisms shall adapt to surviving in cold conditions, they shall for instance grow heavy fur cover on their skin to cover them from the cold.

Those that fail to adapt to the cold conditions shall face extinction by being overpowered by cold related complications.