Answer:
Less oxygen. Less life.
Explanation:
Plants make up most of our oxygen here on earth, because of the carbon cycle and photosynthesis. They take carbon dioxide, and turn it into oxygen. And not only that, but some animals live in trees to protect themselves from birds and other animals.
An Organ. Why does the answer need to be 20 characters long?
The immune system.
The immune system acts as a defense system of the body. It fights against bacteria, viruses and any other disease causing pathogens. Some chemicals can weaken the immune system and make them vulnerable.