Earth's biosphere extends from Earth's surface into the atmosphere to an altitude of approximately ________ kilometers.

• 4

• 40

• 400

• 4,000

• 40,000

How long after Earth formed did it take for oxygen to accumulate in the atmosphere?

• .5 billion

• 1 billion

• 2.0 billion

• 2.5 billion

What parameter is not important in affecting the amount of solar radiation received by Earth from the sun?

• earths spin

• earths tilt

• earths orbit

• earths atmospheric composition

When is Earth closest to the Sun?

• during the northern hemisphere summer solistice

• during the northen hemisphere equinox

• during the northern hempishere winter solstice

The solid, inorganic portion of the Earth system is known as the ________.

• earth

• lithosphere

• hydrosphere

• atmosphere

The Earth is one of ________ planets in the solar system.

• four

• eight

• twenty

• nine

Earth is ________.

• one of the biggest planets

• one of the largest planets

• the smallest planet

• one of the inner planets

The universe is thought to be on the order of ________ billion years old.

• 0.4

• 4.0

• 14.0

• 140

The formation of our solar system occurred ________.

• about 50 million years ago

• about 5 billion years ago

• 14 billion years ago

• 50 billion years ago

Which of the following planets is not considered to be within the potential habitable zone around the sun:

• earth

• mercury

• venus

• mars