urmom

What are the five layers of Earth's atmosphere (from lowest to highest)?

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Which layer of the atmosphere is closest to Earth?

Troposphere

What happens in the troposphere?

Weather occurs (clouds, rain, storms). It contains most of the atmosphere's air.

How does temperature change in the troposphere?

Temperature decreases as altitude increases.

What is the average rate that temperature decreases in the troposphere?

About 6.5°C per 1,000 meters (about 3.5°F per 1,000 feet).

What is the chemical composition of the troposphere?

Mostly nitrogen (78%) and oxygen (21%), plus small amounts of water vapor and other gases.

What is special about the stratosphere?

It contains the ozone layer, which absorbs harmful UV radiation.

How does temperature change in the stratosphere?

Temperature increases as altitude increases.

What happens in the mesosphere?

Meteors burn up in this layer.

How does temperature change in the mesosphere?

Temperature decreases as altitude increases (coldest layer).

What happens in the thermosphere?

Auroras occur in this layer.

How does temperature change in the thermosphere?

Temperature increases greatly as altitude increases due to absorption of solar radiation.

What is the exosphere?

The outermost layer of the atmosphere where particles are very spread out and satellites orbit.

What gases are most common in the exosphere?

Mostly hydrogen and helium.

Which layer is the densest?

Troposphere

What is the oxygen cycle?

The continuous movement of oxygen between the atmosphere, living organisms, water, and land.

Why is oxygen important for living organisms?

Oxygen is needed for cellular respiration to release energy from food.

What process adds oxygen to the atmosphere?

Photosynthesis.

How does photosynthesis contribute to the oxygen cycle?

Plants use carbon dioxide and sunlight to make glucose and release oxygen.

What process uses oxygen in the oxygen cycle?

Cellular respiration.

How does cellular respiration contribute to the oxygen cycle?

Organisms use oxygen to break down glucose for energy and release carbon dioxide.

How does the oxygen cycle support life on Earth?

It keeps oxygen and carbon dioxide levels balanced for respiration and photosynthesis.

What role do plants play in the nitrogen cycle?

Plants absorb nitrogen from the soil and use it to build proteins and other molecules.

Why can't plants use nitrogen directly from the air?

Atmospheric nitrogen (N₂) cannot be used directly by plants.

In what form do plants absorb nitrogen?

As nitrates (NO₃⁻) and ammonium (NH₄⁺).

How does nitrogen become usable for plants?

Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia, which is changed into nitrates.

What do plants use nitrogen for?

To make proteins, enzymes, chlorophyll, and DNA.

How do plants help move nitrogen through the ecosystem?

Animals eat plants to get nitrogen, and decomposers return nitrogen to the soil.

Why are plants important to the nitrogen cycle?

They move nitrogen from the soil into the food web.

How does air temperature change as distance from the ground increases in the troposphere?

Temperature decreases as altitude increases.

What is an example of temperature change with altitude?

If it is 15°C at sea level, it would be about 8.5°C at 1,000 meters.

Why does air temperature decrease with altitude in the troposphere?

The ground heats the air above it, so air farther from the ground is cooler.

Does temperature always decrease as altitude increases?

No. In the stratosphere and thermosphere, temperature increases with altitude.