Changing Atmosphere

The Evolution of the Atmosphere

Tuesday 2nd March 2021

The Earth's Atmosphere

Last lesson with Mr. Brown you looked at the early atmosphere of the Earth.

You discussed which gases were found in the early ages of the Earth and how this compares to gases on other planets.

The early atmosphere was mostly made up of carbon dioxide. But, over time the composition of the Earth's atmosphere changed.

Today we will be looking at how the atmosphere on Earth has changed over time, to life as we know it today.

Open Ended

What were to blame in the Earth's early atmosphere for the high concentration of CO₂? (HINT: they're a type of natural disaster!)

Multiple Select

Which two modern planets is the early atmosphere of Earth often compared to?

• mars

• pluto

• venus

• mercury

Today's Atmosphere!

The atmosphere as we know it today is mostly made up of nitrogen and oxygen.

There is also a small amount of argon and a tiny amount of carbon dioxide.

Youtube Video

GCSE Chemistry - Evolution of the Atmosphere #52 - YouTube

This video will describe and explain some of the changes that have occurred over time.

Once you have watched it, you will need to answer some questions based on the video :)

Fill in the Blank

Around 2.7 billion years ago, _____ began to appear. These microorganisms could carry out photosynthesis.

Fill in the Blank

As the algae began to photosynthesise, the amount of carbon dioxide in the atmosphere declined and ______ increased. This allowed for more complex life to evolve.

Open Ended

There were three examples in the video of places where carbon dioxide was 'trapped'. Name as many as you can!

Where did the CO₂ go??

The carbon dioxide didn't just disappear... so where did it go?

1. When the Earth began to cool it got trapped in our oceans.

2. Used up in photosynthesis by algae and plants.

3. Trapped in sedimentary rock like limestone

- limestone is made of calcium carbonate (CaCO₃)

4. Formation of crude oil/gas.

- dead plants/organism decompose and get compressed into crude oil/gas.

Open Ended

Which factor do YOU think was the biggest contributor to the changing of the Earth's atmosphere and why?

Multiple Select

How confident do you feel with describing how the Earth's atmosphere changed?

• I need some practice to be more confident with this topic

• I think I've got it - I could do with some practice

• I know what I'm doing