The sun gets closer to the earth
The Pros are that Doctors can help prevent certain diseases, help cure certain cancer, and help treatments get stronger.
The Cons is that someone people die from these injections, get an infection making a bigger disease, and or being cured but having killer side affects.
It will work in saliva of animals
The answer would be mitochondria.
Generating heat requires energy, and energy is produced with mitochondria.
When continents broke apart from Pangaea lots of different species got separated to different parts of the world. The animals and other living things had to have learned how to adapt to the different climates or they would die and go extinct.