🌍 FIRST LIFE ON EARTH: THE ALGAE STORY
PAGE 1 OF 5, THE EARLY OCEAN
DEEP TIME
THE WORLD 3.5 BILLION YEARS AGO
Before any plant, before any animal, before almost any life at all, the entire Earth was covered in ocean. Beneath those waves, in the mud and shallow sunlit waters, lived the tiniest creatures that would change everything: cyanobacteria. Single-celled blue-green algae.
FIRST
EVIDENCE
🪨 Stromatolites: layered rock formations built by algae over 1 billion years
🔍 Visible in 3.5 billion-year-old rocks from Australia
🔍 Visible in 3.5 billion-year-old rocks from Australia
WHAT THEY ARE
🔬 Cyanobacteria: photosynthetic bacteria
🌊 Found today in oceans, lakes, and soil worldwide
🌊 Found today in oceans, lakes, and soil worldwide
PAGE 2 OF 5, THE OXYGEN REVOLUTION
TRANSFORMATION
CYANOBACTERIA MADE OXYGEN
Cyanobacteria discovered photosynthesis, the ability to trap the sun's energy and use it to break apart water molecules. Oxygen was left over as waste. For 2 billion years, these algae pumped oxygen into the oceans and slowly into the atmosphere. They were terraforming Earth.
OXYGEN!
SCALE
📏 One cyanobacterium: 1–10 micrometres
🌍 Billions form mats metres thick
🌍 Billions form mats metres thick
TIMELINE
🕐 3.5 billion years ago: first algae
📅 2.4 billion years ago: oxygen crisis
📅 2.4 billion years ago: oxygen crisis
REACTION
💨 Oxygen began filling the atmosphere
🌍 Slow change: took 2 billion years
🌍 Slow change: took 2 billion years
PAGE 3 OF 5, THE MASS EXTINCTION
BEFORE
🧬 Anaerobic bacteria ruled the world
💀 They could NOT tolerate oxygen
💀 They could NOT tolerate oxygen
OXYGEN CRISIS
⚡ Oxygen was POISON to ancient life
🌊 99% of species died in 2.4 billion years ago
🌊 99% of species died in 2.4 billion years ago
THE SURVIVORS
LIFE ADAPTS AND THRIVES
But oxygen did NOT remain poisonous, it became FUEL. New bacteria evolved to use oxygen for energy. From this moment, life became more powerful and complex. The first eukaryotes appeared, cells with nuclei and organelles. This was the moment that made YOU possible.
ALIVE!
PAGE 4 OF 5, FROM ALGAE TO PLANTS
EVOLUTION
OXYGEN ATMOSPHERE FORMS
Over 2 billion years, algae produced enough oxygen to transform the atmosphere. Today, 21% of Earth's air is oxygen, and NONE of it would exist without photosynthesis. Every breath you take is a gift from ancient algae.
BREATHE!
FIRST STEPS
🏛️ Stromatolites prove cyanobacteria
📍 Found on every continent, 3.5 billion years old
📍 Found on every continent, 3.5 billion years old
STEPPING STONE
🧬 Eukaryotes evolved from bacteria
🌍 Oxygen enabled complex life
🌍 Oxygen enabled complex life
WHAT'S NEXT
🔴 Iron oxidised in oceans = rusty rocks
📍 Banded iron formations = oxygen proof
📍 Banded iron formations = oxygen proof
PAGE 5 OF 5, LEGACY OF ALGAE
FOREVER CHANGED
THE MODERN WORLD IS BUILT ON ALGAE
Cyanobacteria didn't just make oxygen. They set the stage for EVERYTHING that came next. Algae evolved into plants. Plants sent roots into soil. Plants made forests. Forests made oceans of oxygen. Oxygen-breathing animals evolved. THEN came fish, dinosaurs, mammals, and finally, YOU. Without algae, Earth would be a silent, sterile ocean.
AMAZING!
TODAY
🌊 Cyanobacteria STILL exist everywhere
💚 Still producing much of Earth's oxygen
💚 Still producing much of Earth's oxygen
REMEMBER
🌍 KEY FACT
Every oxygen molecule in every breath you take came from photosynthesis. Every plant, every animal, every human life depends on the photosynthetic strategy that cyanobacteria invented 3.5 billion years ago.
🌱 Algae → Plants
🌳 Plants → Forests
🌍 Forests → Civilization
🌳 Plants → Forests
🌍 Forests → Civilization
🧠 QUIZ TIME!
FIRST LIFE ON EARTH: THE ALGAE STORY · 5 QUESTIONS
QUESTION 01
What were cyanobacteria and why were they important?
QUESTION 02
What happened 2.4 billion years ago in the "Great Oxidation Event"?
QUESTION 03
How long did it take cyanobacteria to fill Earth's atmosphere with oxygen?
QUESTION 04
What is a stromatolite and what does it tell us?
QUESTION 05
Without cyanobacteria and photosynthesis, which of these would NOT exist?
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