The Earth's Population (In Mid-2009) Was About __________ People

Q28: The Earth's atmosphere acts as a blanket,

Q29: Oceans cover _ percent of the Earth's

Q30: The central portion of the Earth, called

Q31: Earth's core consists mostly of _.<br>A) iron

Q32: Imagine that a system has been perturbed

Q34: Earth's surface systems are ultimately powered by

Q35: Gradualism states that:<br>A) the Earth is uniform

Q36: A _ _ occurs when a small

Q37: The _ is a mixture of gases,

Q38: The core is:<br>A) the least dense layer