Conditions for Life on Earth

• 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

• 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)

• Presence of liquid water • Solar insolation • Atmospheric gases • Suitable temperature range

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

• Transport in organisms • Temperature regulation • Aquatic habitats • Anomalous expansion on freezing • High specific heat capacity • Solvent • Absorbs UV light

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

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

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

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

• 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

• evaporation of water absorbs heat • so temperatures decline

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

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

• 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

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

• 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

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

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

• Atmospheric oxygen • Biogeochemical cycles • Carbon sequestration • Transpiration

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

Creates day/night cycle (24h) = minimise excessive heating or cooling Reduces temp extremes - warmer when facing sun, cooler when not. Prevents scorching and freezing

• 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

• 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

• 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