Why is life not all extinct? what traits or characteristics may have allowed certain species to survive while others perished? what indications of this would you expect to see in the fossil record?

All life is not extinct because of natural selection and evolution. Traits gained depend on the climate. If an animal in a hot climate does not adapt quickly to shed its fur and pass down the traits that species will die out. You would see things in the fossil that could have been the reason why the species went extinct. like a small beaked bird where it needed a big beak to crack the nuts in climate it all depends.