Conditions for Life on Earth

Question 1

Give the key stages of life in developmental order

Answer 1

1. The earth is formed
2. The crust and core is formed
3. The first oceans form
4. The first life appears (archaea acidophiles)
5. Oxygen begins to accumulate in the atmosphere
6. The first animals evolve
7. The first animals with backbones (fish) evolve
8. The first land plants evolve
9. The first land animals with backbones evolve
10. The first dinosaurs evolve
11. The dinosaurs go extinct
12. Modern humans evolved

Question 2

How and where did early life on earth evolve?

Answer 2

• The first life evolved around 3 billion years ago around hydrothermal vents.
• The vents provided heat from the earth’s core and rich mix of chemicals meant that biological processes could occur
• single celled organisms, archaea - they are acidophiles (thrive in acid conditions)

Question 3

What are the early conditions ON Earth that allowed life to develop?

Answer 3

1. Presence of liquid water
2. Solar insolation
3. Atmospheric gases
4. Suitable temperature range

Question 4

5 features creating suitable life conditions

Answer 4

Mass
Distance from Sun
Axis of Rotation
Speed of Rotation
Magnetic field

Question 5

Why is liquid water an essential condition for the development of life?

Answer 5

1. Transport in organisms
2. Temperature regulation
3. Aquatic habitats
4. Anomalous expansion on freezing
5. High specific heat capacity
6. Solvent
7. Absorbs UV light

Question 6

Why is it important for liquid water to be a solvent in the development of life?

Answer 6

• water is the ‘general physiological solvent’
• most chemical reactions require reactants to be dissolved in it

Question 7

Why are aquatic habitats important?

Answer 7

• provides places for marine organisms to live
• seas, lakes, marshes, rivers, oceans

Question 8

How does the distance from the Sun affect conditions for life on Earth?

Answer 8

Goldilocks zone = just right, not too hot, not too cold.

Light & energy levels = Good for liquid water

Speed of rotation at this distance is fast enough to prevent excessive heating/cooling

Question 9

Why is liquid water essential for transport within organisms?

Answer 9

• essential component in blood/sap
• moves dissolved substances EG sugars, amino acids, waste products, gases, mineral nutrients

Question 10

Why is the absorption of UV radiation essential for the development of life?

Answer 10

• before ozone layer formed to absorb UV in the stratosphere, liquid water in the oceans absorbed harmful UV which made them suitable for life
• therefore life evolved there first as it was protected and everything stemmed from that

Question 11

How does liquid water affect temperature regulation?

Answer 11

• evaporation of water absorbs heat
• so temperatures decline

Question 12

How does mass affect the conditions for life on Earth?

Answer 12

Big mass = influences gravity, preventing gases escaping into space, forms atmosphere

Essential gases - N, C, O, H

N and CO2 insulate the Earth, keeping warm. Enzymes is good. O is for respiration

Good gravity = maintains correct atmospheric pressure for liquid water because prevents evaporation. Uses of water: temp regulation, transport and chemical reactions essential for life

Question 13

How does the high specific heat capacity of liquid water affect the development of life?

Answer 13

• cools and warms over a large temperature range
• reduces extremes and distributes heat
• moderates the rate and size of temperature changes

Question 14

What is the anomalous expansion on freezing when water is liquid?

Answer 14

• water = most dense at 4 degrees
• anything below this temperature floats, which stops convection currents that could have cooled the whole water body

Question 15

Why is a suitable temperature range an essential condition in the development of early life?

Answer 15

0-35 degrees is a liveable condition - not extreme
- warm enough to have liquid water
- not too hot that it denatures enzymes
- not to cold to immobilise enzymes

This temperature range is also enough to drive evaporation, which powers the water cycle
- water cycle regulates the conditions within the atmosphere which is also essential for life

Question 16

Why is solar insolation an essential condition for the development of early life?

Answer 16

• provides energy for photosynthesis
• heat produced by absorption of sunlight warms the surface and oceans - life can live
• drives the water cycle
• albedo determines how much heat is absorbed/reflected (reflected sunlight heat the atmosphere)
  - high albedo = lots reflected, surface temp cooler
  - low albedo = less reflected, heats surface.
• provides light to see by

Question 17

How does the axis of rotation affect the conditions for life on Earth?

Answer 17

Axis creates seasonal change = prevents temperature extremes and gives more equal temp distribution

Question 18

Why are atmospheric gases an essential component for the development of early life?

Answer 18

CO2 - insulates
- drives photosynthesis and synthesis of carbs, proteins, lipids

Nitrogen - protein synthesis

Question 19

What environmental changes has life on Earth created?

Answer 19

1. Atmospheric oxygen
2. Biogeochemical cycles
3. Carbon sequestration
4. Transpiration

Question 20

How has atmospheric oxygen changed since life has developed?

Answer 20

OCEANS - 2.7 billion years ago = archaea began to photosynthesise. This released oxygen
- the oxygen produced reacted with the iron in the oceans for millions of years
(iron was extremely abundant)
- when all the iron had reacted, excess dissolved oxygen built up in ocean
- eventually was released into the atmosphere - concentration rises about 2.45 billion years ago

ATMOSPHERE - now in the atmosphere, oxygen absorbs UV light
- produces dynamic equilibrium of reactions involving O3, O2 and O
- absorption of UV makes life possible
- build up lasted until 540 million years ago - PROTERZOIC EON

• many archaea/bacteria died out but complex organisms EG animals/plants evolved

Question 21

How does the speed of rotation affect conditions for life on Earth?

Answer 21

Creates day/night cycle (24h) = minimise excessive heating or cooling

Reduces temp extremes - warmer when facing sun, cooler when not. Prevents scorching and freezing

Question 22

How did carbon sequestration happen when early life developed?

Answer 22

• CO2 = greenhouse gas. helps retain heat energy in atmosphere

photoautotrophs developed - they photosynthesise and absorb CO2.
- carbon gets locked away in geological sediments EG carbonate rocks and fossil fuels.
- because the CO2 levels are lower, this prevents long term temperature rise despite the brightness of the sun increasing 10% every billion years

Question 23

How did early life influence the change of biogeochemical cycles?

Answer 23

• greater variety of organisms evolved - inter-connected biological processes develop, producing biogeochemical cycles
• basically everything gets recycles
• therefore smaller amounts of nutrient elements are needed to sustain life over a long period of time without depletion

Question 24

How has life on earth influenced transpiration?

Answer 24

• plants evolve and colonise land
• transpiration returns water vapour to the atmosphere which increases rainfall in other areas and can make new plants grow, which build up the stream