Astronomy Quiz Ch. 8 and 30

** According to the theory of plate tectonics,

slow motions within the mantle of the Earth move large sections of the crust around

** According to the fossil record, how old is the oldest evidence of life forms on the surface of the Earth?

about 3.5 billion years** In terms of numbers, the most common life-forms on Earth today are

** One way in which the ozone layer is useful for life forms on the Earth's surface is that it

absorbs ultra-violet light, preventing much of it from reaching the surface

** Which part of the Earth has the greatest density?

core

** In terms of numbers, the most common life-forms on Earth today are

microscopic creatures, too small to see with our eyes

** Scientists now understand that the Earth consists of layers, with the densest materials in the core. What allowed the differentiation of the Earth s layers to happen?

the early Earth was so hot it was like a liquid and heavier elements sank to the middle

** The Drake Equation allows astronomers to estimate

the number of probable civilizations out among the stars with which we might communicate

** From a scientific perspective, which of the following statements about life elsewhere in the universe is best supported by current evidence?

while we have evidence of the building blocks of life elsewhere in the universe, we have no definite evidence about life around other stars at this time