Conditions for life on Earth
1. Earth life supporting features
Earth is the only planet in our solar system with know life, there are a number of unique features to Earth that allow life to survive.
1. Insolation: Just the Right Amount of Sunshine
Not too hot, not too cold: Earth receives just the right amount of solar energy (insolation) to keep temperatures within a livable range.
Planetary thermostat: Albedo (Earth’s reflectivity), the atmosphere, and heat absorption help regulate this energy, preventing extremes.
2. Atmosphere: Earth’s Protective Bubble
Gravity kept it close: Earth’s mass created a gravitational pull strong enough to hold onto its atmosphere.
Gases for life: Early atmosphere provided essential gases like carbon dioxide, methane, and nitrogen — vital for early organisms.
Liquid water? Check. The right mix of atmospheric pressure and temperature meant water could stay in its life-giving liquid form.
3. Distance from the Sun: Our Solar Sweet Spot
Goldilocks zone: Earth’s distance from the Sun is just right — far enough to avoid scorching, close enough to prevent freezing.
This perfect positioning supports stable conditions that life needs to grow and thrive.
Radiation protection: The molten iron core powers a magnetic field — Earth’s magnetosphere — that deflects harmful solar radiation.
Without it, solar winds could strip away our protective atmosphere
4. Magnetic Shield: Earth's Invisible Armor
Daily rhythms: Earth’s rotation gives us day and night.
Seasonal changes: Its tilted axis and orbit around the Sun create seasons — key for ecological cycles and biodiversity.
5. Movement: A Planet on the Move
2. Early Earth
How old is the Earth?
How did the Earth form?
Earths layers
Early atmosphere
4.6 billion years old
Earth formed around the same time as the rest of the solar system from a cloud of dust and gas swirling around the young Sun.
Cosmic collisions: Tiny particles stuck together to form larger rocks, which eventually smashed together to build a growing proto-Earth.
Planet-building heat: These violent impacts, along with radioactive decay and pressure, made early Earth incredibly hot.
Molten chaos: At first, the planet was mostly molten rock, a fiery, churning ball with no oceans or solid crust.
Dense material sinks: As Earth cooled, denser materials (like iron and nickel) sank to the centre to form the core.
Lighter materials floated: This created the mantle and crust — the rocky outer layer where life would eventually begin.
Volcanic breath: Gases like nitrogen, water vapor, carbon dioxide, ammonia, and methane were released by intense volcanic activity.
No oxygen yet! The air was toxic to modern life, and there was no ozone layer — meaning lots of harmful UV radiation.
First oceans
As the planet cooled...
Water vapor condensed into rain.
Rain filled low-lying areas, forming the first oceans.
These oceans became the starting point for early life.
3.How life changed Earth
Increased Oxygen
The first oxygen was made by photosynthetic cyanobacteria (photoautotrophs) in ancient oceans.
Later, algae and plants joined in, producing oxygen as a by-product of photosynthesis.
Over time, oxygen built up in the atmosphere
Decreased carbon dioxide
Early photoautotrophs (organisms that make their own food from light) absorbed carbon dioxide (CO₂) during photosynthesis.
This helped cool the planet over time by reducing greenhouse gases.
Some carbon also got locked in rocks and fossil fuels, taken out of circulation for millions of years.
Recap - Photosynthesis equation
Carbon dioxide + Water -------> Glucose + Oxygen
light
In the stratosphere, oxygen molecules reacted with ultraviolet (UV) light to form the ozone layer.
This layer shields Earth’s surface from harmful UV rays, making land life possible.
Ozone layer
Biogeochemical Cycles
Waste not, want not: Life became part of biogeochemical cycles such as carbon, nitrogen and phsopherous
organisms, keep resources flowing and prevent waste build-up and resource shortages
Without these cycles, Earth’s systems would become unbalanced and unlivable.
4.Monitoring the past
Ways of monitoring climate change
1. Historic data: Past records based on a lack of technology
Why is historical data not very accurate or representative?
Lack of data in many areas
Limited co-ordination between researchers
Lack of sophisticated equipment for accurate measurements
Limited reliability of data from most time periods
Reliance on proxy data e.g. pollen analysis and dendrochronology
Improved methods for data collection
Use of electronic monitoring equipment
Collection of long term data sets
Collaboration between researchers
Why is monitoring climate change difficult?
Often a time delay between cause and effect
Natural fluctuations have always occured
Difficult to know what has been directly caused by human activities
Climate systems are interconnected e.g. hydrosphere and atmosphere
Changes occur over a range of time and spacial scales
Positive and negative feedback systems
Reliance on proxy data
2. Proxy data: Indirect measurements of past climate, used when direct data has not been taken
Dendrochronology
Use of tree ring growth to show past temperatures, rainfall, carbon dioxide levels and light intensity
May be impacted by wild fires or disease
Important to gather overlapping data from lots of trees for accuracy
Pollen grain analysis
Pollen grain presence in sediment indicate past climatic conditions by correlating the conditions that plant need to grow
Pollen only preserved in wat environments such as bogs
Only shows partial records as some plants don't produce much or any pollen
Pollen can be dispersed for from the plant location giving an inaccurate representation
Ice core analysis (requires modern technology)
Ice cores are drilled from Antarctica and Greenland
Annual snowfall accumulates into ice layers, air bubbles get trapped in these layers
The air in the ice is representative of the atmosphere when it got trapped
Levels of carbon dioxide in bubbles indicate atmospheric temperature (more carbon dioxide = warmer temperature as it is a greenhouse gas)
Ratios of oxygen 18 to oxygen 16 also indicate temperature
Higher oxygen 18 ratio = warmer climate (heavier that oxygen 16 so will only evaporate and precipitate in warmer climates)
3. Satellites: Sensors carried by satellites collect data of climate factors
Satellite benefits
Allows continuous moniotring
Covers large areas quickly and cheaply
Gives access to inaccessible areas
minimal disturbance of habitats
Low labour intensity
Altimetry - Measures changes in ice levels by recording time taken for radar pulse to hit target and come back
LiDAR (light detection and ranging) - Emits a laser that gets reflected back and measures the time taken, can also be used to estimate ice mass
GRACE (gravity recovery and climate experiment) - Maps variations in Earths gravitational field caused by changes in mass
4. Other climate monitoring methods: Use of modern technology to monitor and predict impacts of climate change
Aircraft data collection - Similar to satellites but don't monitor continuously
Computer modelling - Feed data and see if it can predict a future outcome, can model a range of outcomes and be shared electronically but only shows predictions
ARGO floats - Can monitor deep oceanic currents, ocean salinity and ocean temperatures
Buoys - Can monitor surface currents, ocean salinity and ocean temperature