7.3 & 7.4 The Earth's Atmosphere In The Past/Life On Earth Flashcards Preview

GCSE Chemistry 1.7 Our Changing Planet > 7.3 & 7.4 The Earth's Atmosphere In The Past/Life On Earth > Flashcards

Flashcards in 7.3 & 7.4 The Earth's Atmosphere In The Past/Life On Earth Deck (21)
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What was the earth covered in in its first billion years?



Name 3 things that volcanoes release

•carbon dioxide
•water vapour


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?



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?



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