Question

If a keystone species disappears from an ecosystem, no other species will be able to fill its ecological niche

Answer 1

The species department on it are not able to survive and they too disappear and slowly whole food chain gets effected and all the species in the world also gets extincted.

Answer 2

When some animals (and plants) encounter the impacts of climate change in their environment, they respond by changing behavior and moving to a cooler area, modifying their physical bodies to better deal with the heat, or altering the timing of certain activities to match changes in the seasons