Conditions for Life on Earth Flashcards
Give the key stages of life in developmental order
- The earth is formed
- The crust and core is formed
- The first oceans form
- The first life appears (archaea acidophiles)
- Oxygen begins to accumulate in the atmosphere
- The first animals evolve
- The first animals with backbones (fish) evolve
- The first land plants evolve
- The first land animals with backbones evolve
- The first dinosaurs evolve
- The dinosaurs go extinct
- Modern humans evolved
How and where did early life on earth evolve?
- 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)
What are the early conditions ON Earth that allowed life to develop?
- Presence of liquid water
- Solar insolation
- Atmospheric gases
- Suitable temperature range
5 features creating suitable life conditions
Mass
Distance from Sun
Axis of Rotation
Speed of Rotation
Magnetic field
Why is liquid water an essential condition for the development of life?
- Transport in organisms
- Temperature regulation
- Aquatic habitats
- Anomalous expansion on freezing
- High specific heat capacity
- Solvent
- Absorbs UV light
Why is it important for liquid water to be a solvent in the development of life?
- water is the ‘general physiological solvent’
- most chemical reactions require reactants to be dissolved in it
Why are aquatic habitats important?
- provides places for marine organisms to live
- seas, lakes, marshes, rivers, oceans
How does the distance from the Sun affect conditions for life on Earth?
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
Why is liquid water essential for transport within organisms?
- essential component in blood/sap
- moves dissolved substances EG sugars, amino acids, waste products, gases, mineral nutrients
Why is the absorption of UV radiation essential for the development of life?
- 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
How does liquid water affect temperature regulation?
- evaporation of water absorbs heat
- so temperatures decline
How does mass affect the conditions for life on Earth?
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
How does the high specific heat capacity of liquid water affect the development of life?
- cools and warms over a large temperature range
- reduces extremes and distributes heat
- moderates the rate and size of temperature changes
What is the anomalous expansion on freezing when water is liquid?
- water = most dense at 4 degrees
- anything below this temperature floats, which stops convection currents that could have cooled the whole water body
- the ice crust forming insulates the water underneath
- only water does this
Why is a suitable temperature range an essential condition in the development of early life?
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
Why is solar insolation an essential condition for the development of early life?
- 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
How does the axis of rotation affect the conditions for life on Earth?
Axis creates seasonal change = prevents temperature extremes and gives more equal temp distribution
Why are atmospheric gases an essential component for the development of early life?
CO2 - insulates
- drives photosynthesis and synthesis of carbs, proteins, lipids
Nitrogen - protein synthesis
What environmental changes has life on Earth created?
- Atmospheric oxygen
- Biogeochemical cycles
- Carbon sequestration
- Transpiration
How has atmospheric oxygen changed since life has developed?
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
How does the speed of rotation affect conditions for life on Earth?
Creates day/night cycle (24h) = minimise excessive heating or cooling
Reduces temp extremes - warmer when facing sun, cooler when not. Prevents scorching and freezing
How did carbon sequestration happen when early life developed?
- 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
How did early life influence the change of biogeochemical cycles?
- 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
How has life on earth influenced transpiration?
- 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
