Answer: Unusual sounds or noises, sights,smells or odors, appearances or behaviors are often
the first sign of an emergency.
Bystander roles in an emergency may include giving first aid, calling 9-1-1 or the designated emergency number, or getting equipment
( for example: A first aid kit).
Explanation:
This could be the different times you did the experiment
A biological system is a complex network of biologically relevant entities. ... Examples of biological systems at the macro scale are populations of organisms. On the organ and tissue scale in mammals and other animals, examples include the circulatory system, the respiratory system, and the nervous system. source: google