The person is called a wildlife biologist.
A layer of greenhouse gases – primarily water vapor, and including much smaller amounts of carbon dioxide, methane and nitrous oxide – acts as a thermal blanket for the Earth, absorbing heat and warming the surface to a life-supporting average of 59 degrees Fahrenheit (15 degrees Celsius).
Answer: how much mass is in a certain amount of space
Explanation: density is g/mL; therefore it’s the mass (g) in a certain amount of space (mL)