Conditions for Life on Earth

Question 1

Timeline: 4+ billion years ago

Answer 1

Earth formed in habitable zone of the solar system

Iron + nickel core spins and creates magnetosphere

Early atmosphere forms - high in greenhouse gases

Question 2

Timeline: 3+ billion years ago

Answer 2

Water vapour condenses

Microscopic life

Question 3

Timeline: 2+ billion years ago

Answer 3

Cyanobacteria in Ocean

Increase in oxygen levels causes mass extinction

Question 4

Timeline: 1.2 billion - 200 million years ago

Answer 4

multicellular organisms

plants/land animals/insects

Question 5

Timeline: Today

Answer 5

21% oxygen

complex and diverse life

Question 6

4 Key conditions that allowed early life to develop

Answer 6

Atmosphere
Magnetosphere
Distance from Sun
Insolation
Orbital Behaviours

Question 7

How has the position in the solar system allowed for development of life on Earth?

Answer 7

Controls temperature
Correct distance from Sun for liquid water
Temperature is perfect for photosynthesis

Question 8

How do living organisms affect the cycling of water?

Answer 8

Transpiration - roots uptake water from soil and release it via water vapour

Interception - trees prevent water from reaching the ground

Animals drink the water

Infiltration - water soaks through soil

Used in photosynthesis

Question 9

What other ways have living things changed conditions on Earth?

Answer 9

The carbon cycle (combustion of fossil fuels)
The nitrogen cycle
Photosynthesis (added oxygen to atmosphere)
Respiration
Carbon sequestrian - natural carbon capture

Question 10

Outline the importance of cyanobacteria and later photosynthetic organisms

Answer 10

Excreted so much oxygen it created a surplus

Broke down CO2

Stromatolites - rock like structures covered in cyanobacteria - contribute massively to the Earth’s supply of oxygen

Some organisms adapted to the oxygen and used it to create proteins to become multicellular

Question 11

How have CO2 levels changed?

Answer 11

decrease - 0.04%

Question 12

What has caused the decrease in CO2 levels?

Answer 12

Photosynthesis

Question 13

Where is most carbon now found?

Answer 13

In living things - carbohydrates

In soil - decomposition

Question 14

What is the magnetosphere?

Answer 14

The region around a planet within the planet’s magnetic field

Question 15

How does the magnetosphere work?

Answer 15

Molten iron and nickel outer core spins - generating a magnetic field around earth

Question 16

What does the magnetosphere protect the earth from?

Answer 16

Solar winds - blow atmosphere away
Cosmic radiation - cause cancer

Question 17

Why is water important for the development of life?

Answer 17

Universal solvent

Transporter of nutrients

Used in photosynthesis

Provides habitats

Anomalous expansion - expands when frozen

High specific heat capacity - absorbs large amounts of energy with minor temp change and releases with minor temp change - moderates temperature

Question 18

Why was the composition of the early atmosphere so important for the development of life?

Answer 18

Mostly greenhouse gases

Enhanced greenhouse effect helped warm the earth

Question 19

How does the Earth’s rotation around the Sun allow for the development of life on earth?

Answer 19

controls year length

controls frequency of the seasons

Question 20

How does the Earth’s tilt on its axis allow for the development of life on earth?

Answer 20

controls seasons
hibernation
migration
dictates life cycles

Question 21

How does the Earth’s rotation on its axis allow for the development of life on earth?

Answer 21

24 hour cycle
controls day length
controls temperature (night and day)
creates only small gaps in photosynthesis