c9 composition and evolution of the earths atmosphere

Question 1

what are the % of gases in the atmosphere

Answer 1

80% nitrogen
20% oxygen
+ small amounts of co2/water vapour

Question 2

the reasons of increased oxygen and what evolved

Answer 2

algae + plants produce oxygen in photosynthesis
plants evolved over the next bil years
animals evolved as rising o2 levels

Question 3

when did algae start producing oxygen

Answer 3

2.7 mil years ago

Question 4

how did co2 decrease in the atmosphere

Answer 4

algae + plants reduced co2 by photosynethis
co2 dissolved in oceans- producing sediments-reduced co2
formation of fossil fuels

Question 5

how has volcanic activity helped early atmosphere and forming oceans

Answer 5

eruptions produced many gases causing water vapour condensing forming oceans

Question 6

describe earths ealry atmosphere

Answer 6

covered in volcanoes
about 4.6 mil years ago
mainly co2
similar to mars/Venus