The Conditions for Life on Earth Flashcards
How does the mass of the Earth create suitable conditions for life?
Mass of Earth is great enough to prevent most gases from escaping into space. This atmosphere included the elements essential for life: carbon, hydrogen, nitrogen and oxygen. They were present in compounds such as ammonia, methane and carbon dioxide.
Atmospheric pressure is high enough to prevent all liquid water from boiling. Water is vital for living organisms - general physiological solvent in which most biological reactions take place (important in transport and temp regulation).
How does the Earth’s distance from the Sun create suitable conditions for life?
Light emitted from Sun, and distance from Sun, create temperatures suitable for life.
Being too close or too far away from the Sun would prevent liquid water form being present.
Time taken for Sun to rotate on it’s axis produces day/night cycle that’s fast enough to minimise excessive heating/cooling.
How does the axis of rotation of the Earth produce suitable conditions for life?
It is at an angle to its orbit around the Sun which produces seasonal variations in conditions as the Earth orbits the Sun.
How does the Earth’s speed of rotation create suitable conditions for life?
The temp of the Earth’s surfaces rise when exposed to sunlight and falls when not.
24-hour period of rotation of Earth around its axis reduces temp extremes.
How does the Earth’s magnetic field create suitable conditions for life?
Molten layers beneath the crust produce the Earth’s magnetic field that deflects the ‘solar wind’ and prevents biologically damaging radiation reaching the Earth’s surface.
How did the presence of liquid water allow life to develop?
Solvent water - most chemical reactions in living organisms involve reactants that are dissolved in water.
Transport within organisms - water is the solvent in blood and sap where it transports dissolved gases, sugars, amino acids, mineral nutrients & waste products.
Temperature control - the evaporation of water absorbs heat, causing temperatures to decline.
Anomalous expansion on freezing - water is most dense at 4C so water that is cooler that this floats, stopping convection currents that may have cooled the whole water body.
HIgh specific heat capacity - water warms up and cools down slowly, helps to moderate the rate and size of temp changes.
Aquatic habitats - oceans, lakes, rivers, marshes, etc.
Absorption of UV radiation - protected living organisms in oceans before ozone layer developed which absorbs UV light into stratosphere.
How did temperature range allow life to develop?
Most areas of the Earth have temperatures between 0C and 35C, so most areas are warm enough to have liquid water but not hot enough to denature proteins.
How did atmospheric gases allow life to develop?
Carbon dioxide for photosynthesis and the synthesis of carbohydrates, proteins, and lipids.
Nitrogen for protein synthesis.
How did solar insolation allow life to develop?
Sunlight provides the energy for photosynthesis.
Heat produced by the absorption of sunlight provides the energy that drives the water cycle and warms the Earth’s surface and the oceans.
The amount of sunlight that is absorbed by the Earth’s surface depends upon the albedo of the surface.
The composition of the atmosphere controls the amount of infrared energy that is absorbed and converted to heat.
How has life on Earth caused atmospheric oxygen levels to change?
As some Archeae developed the ability to photosynthesis and release oxygen, the atmospheric oxygen levels increased.
As life began to form, animals began to respire, taking in oxygen, and plants began to photosynthesise, releasing oxygen.
How has life on Earth caused carbon sequestration?
CO2 is a greenhouse gas that helps retain heat energy in the atmosphere.
Photosynthetic organisms absorbed CO2, some of which was stored in geological sediments such as carbonate rocks and fossil fuels.
Reduction in CO2 levels = prevents long-term temperature rise.
How does life on Earth aid in cause biogeochemical cycles?
Greater variety of organisms evolved = interconnected biological processes developed, which produced biogeochemical cycles.
Meant that relatively small amounts of some nutrient elements could support life over long periods of time without the resources becoming depleted.
How does life on Earth cause transpiration?
Once plants had evolved and colonised the land, transpiration returned water vapour to the atmosphere and increased the amount of rainfall in other areas, making the growth of even more plant life possible.
What are some new analytical techniques that have been developed to be used to estimate past climate?
Radioisotope composition can be used to date samples such as the ratio of carbon-12 to carbon-14.
The ratio of oxygen-18 to oxygen-16 can be used to estimate past temperatures.
The composition of past atmosphere can be analysed from air bubbles collected from ice cores.
The ratio of magnesium to calcium in calcite deposits can be used to estimate the temperature - more magnesium is incorporated at higher temperatures.
