Our Amazing Atmosphere

When did oxygen first become a major part of our atmosphere?

• We have always had a large amount of oxygen in our atmosphere.

• Around 2 billion years, after photosynthetic life had evolved.

• After the asteroid hit and wiped out the dinosaurs.

Our daily weather occurs in this layer of the atmosphere.

• thermosphere

• mesosphere

• stratosphere

• troposphere

Air becomes saturated with water vapor when it is cooled to this temperature.

• 32 degrees F.

• the dewpoint

• the freezing point

The hot young Earth was volcanically active. The eruptions released large amounts of ______, which was the main gas in our atmosphere at that time.

• nitrogen

• methane

• carbon dioxide

• water vapor

Gases in our atmosphere help regulate our _____, making it possible for liquid water to exist at the surface,

• air pressure

• humidity

• cloudiness

• temperature

This gas in the stratosphere protects us from harmful ultraviolet solar radiation.

• nitrogen

• oxygen

• ozone

• carbon dioxide

Water vapor can enter our atmosphere by evaporation from lakes, rivers, and the ocean. It can also enter the atmosphere from plants through a process known as ___.

• condensation

• precipitation

• transpiration

Temperature increases as you go higher in the stratosphere because ___ gas is absorbing ultraviolet radiation.

• nitrogen

• oxygen

• ozone

• carbon dioxide

Which gases are important to our weather? Select all that apply.

• oxygen

• water vapor

• nitrogen

• carbon dioxide

When dew forms on the grass in the morning, what is the relative humidity of the air around the grass?

• 0%

• 50%

• 100%

• 110%