7.3 & 7.4 The Earth's Atmosphere In The Past/Life On Earth Flashcards
What was the earth covered in in its first billion years?
Volcanoes
Name 3 things that volcanoes release
- carbon dioxide
- water vapour
- nitrogen
How were the oceans formed?
As the earth cooled down, most of the water vapour released by volcanoes condensed to form the oceans
What gases were in the early atmosphere?
- carbon dioxide
* water vapour
What other gases did scientists believe were in the early atmosphere?
- nitrogen
- methane
- ammonia
Where did most of the earths carbon dioxide, nitrogen and water vapour in the early atmosphere come from?
It was released by volcanoes
What developed over the 2nd and 3rd billion years of the earth?
Bacteria, algae and plants
Why did the amount of carbon dioxide in the air decrease after about 2 billion years of the earths formation?
It was absorbed by the plants for photosynthesis which released oxygen
What produced the oxygen in the atmosphere?
Photosynthesis from the plants
Where did the first plants probably evolve from?
Simple organisms like plankton and algae in ancient oceans
Why are we not sure about how life began?
There are lots of theories but no proof or evidence for any of them
How long ago do scientists believe the earth was formed?
4.5 billion years ago
What was the Miller-Urey experiment?
An experiment based on what scientists at that time thought was in the early atmosphere
What mixture of substances were used in the Miller-Urey experiment?
- water
- ammonia
- methane
- hydrogen
What did Miller and Urey add to their experiment (not a gas) and why? What did this cause?
They gave the gases a high voltage spark to simulate lightning
This caused the elements to react together
What did Miller and Urey find after a week of their experiment?
Amino acids had been formed
What are amino acids?
The building blocks for proteins
Name a substance that had not been made in the Miller-Urey experiment
•oxygen was not made
What is the primordial soup theory?
The organic molecules formed a primordial soup. The amino acids in this mixture combined to make proteins from which life began
What is the Murchinson meteorite theory?
Fragments of meteors contain amino acids, which shows that molecules capable of starting life may have arrived from outer space. The Murchinson meteorite landed in 1969 in Australia, weighing 100kg
Amino acids are made from the elements carbon, hydrogen, oxygen and nitrogen. Suggest why Miller and Urey used a mixture of water, ammonia, methane and hydrogen in their experiment.
They all contain the elements need to make amino acids •water contains hydrogen and oxygen •ammonia contains nitrogen and hydrogen •methane contains carbon and hydrogen •hydrogen is hydrogen
