Most plants and animal's body temperatures proceed at a rate depending upon ambient temperature and are therefore very sensitive to rapid climate oscillations like that of the Younger Dryas. As glacial periods approach, growing seasons become shorter and therefore less time for reproduction and less diversity and quantity there will be there will be. Variations in the timing of the seasons changes biological events for animals and plants. They get on a cycle for the colder and warmer weather but once the glacial period starts they can not adjust any longer and are in threat of being damaged.