The Origin of Earth's Atmosphere

Question 1

When was the Earth/ solar system formed?

Answer 1

4.55 billion years ago

Question 2

What is the contracting rotating cloud of gas also known as that formed the solar system?

Answer 2

Solar nebular

Question 3

What is the solar nebular mainly made of?

Answer 3

Hydrogen and some helium

Question 4

What was in the middle of the solar nebular as it rotated and contracted?

Answer 4

mass and metal concentrated in the middle

Question 5

What was earths surface likely to be like for the first 0.5 Ga

Answer 5

very hot, partcially molten, lots of meteorite bombardment, radioactbie decay

Question 6

Why is venus inhospitable (4 reasons)

Answer 6

strong greenhouse effect
temp hot enough to melt lead
thick suphuric clouds reflecting solar radiation and trapping CO2
no oceans so CO2 was never dissolved

Question 7

why is mars inhospitable (3 reasons)

Answer 7

too cold for advanced lifeforms
very thin atmosphere
distance from the sun

Question 8

What is Stanley Miller and Harold Urey’s theory to how life on earth started?

Answer 8

They trapped H2O CH4 NH3 and H2 in a flask and subjected the gas to eletrical charge, this lead to a soup of organic molecules at the bottom of the flask, the soup wasn’t allive but generated amino acids which are the building blocks of protiens.

Question 9

What was the theory of how life on earth started (comets)?

Answer 9

Biological precursor molecules were carried to earth on comets

Question 10

What was the theory of how life on earth started (vents)?

Answer 10

Oceanic hydrothermal vents in the deep ocean was where the origin of life began where bacteria do not rely on photosynthesis.

Question 11

What are the three theories of how life on earth started?

Answer 11

Comets brought pre-bacteria
began in hydrothermal vents in the deep ocean
Stanley miller and harold urey

Question 12

When did stanley miller and harold urey come up with there theory of how life on earth began?

Answer 12

1953

Question 13

Which two scientists came up with the organic soup theory

Answer 13

stanley miller and harold urey

Question 14

what caused oxygen levels on earth to rise over time

Answer 14

photosyntesis in plants and algae and other biological activity led to a rapid increases of atmospheric oxygen

Question 15

when did atmospheric O2 reach apprecible conditions

Answer 15

2Ga ago

Question 16

How do we know atmospheric oxygen levels rose

Answer 16

BIFS - Banded Iron Formations

Question 17

What are BIFS

Answer 17

silica rich rocks with alternating thin layers of sivler green or red sediments reflecting alternation of oxygen rich or oxygen poor conitions

Question 18

what were the key steps from the second atmosphere to the modern atmosphere

Answer 18

1. creation of life
2. origin of oxygen producing bacteria
3. colonization of the planet by plants

Question 19

when did the ozone layer form

Answer 19

2Ga - rise in atmospheric oxygen led to hte formation of the oxone layer

Question 20

why is the ozone layer so important in the evoulution of life on earth

Answer 20

protects life on earth from harmful UV radiation therefore life from the deep ocean could move into the uppermost layer

Question 21

what is photosynthesis

Answer 21

green plants use light energy to convert H2o and Co2 into O2 and energy rich organic compounds (carbohydrates) that are stored in plants

Question 22

what are carbohydrates made of (photosyntesis)

Answer 22

glucose C6H12o6