1.3 Early Evolution On Planet Earth

The Hadean Eon- encompasses the earliest period of Earth's history, lasting from the formation of the Earth approximately 4.6 billion years ago until around 4 billion years ago, characterized by a hot, molten surface and the formation of the first solid crust. Led to possibility of protocells.

The Archean Eon-


Snowballs Earth- Valcano’s poked through ice, releasing heat that melted all of the ice.


  1. Bacteria (Procaryotic)- 3.8 BYA

  2. Archaea 3.7 BYA- strives in harsh environment

  3. Beginning of anaerobic bacterial photosthesis 3.2

  4. Eukaryotes 2.7 BYA - the emergence of eukaryotic cells, leading to greater complexity in life forms.



-Prokaryotes are simpler, unicellular organisms without a nucleus or membrane-bound organelles, while eukaryotes are more complex, with a true nucleus and organelles, and can be unicellular or multicellular.


Prokaryote VS Eukaryote (memorize)


All extant cells:

-Enclosed by a membrane

-store hereditary information in DNA

-replicate DNA by using the same basic mechanism

-use RNA for transcription of DNA

-translate RNA into protein via tRNA & ribosomes

-use proteins as catalysts

-use ATP (adenosine triphosphate) for free energy


Deep Dive into Photosynthesis

-There was no oxygen (no source). Oxygen highly reactive

-Development of oxygenic or non-cyclic photosynthesis led to the slow process of oxygen being present.

-Oxygen didn’t accumulate until 2.2 BYA (Leads to the first mass instinction.)

-Aerobic respiration became dominant form of metabolism against bacteria.



-6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂. (This happens in the chloroplast)


The Ediacaran fauna: 600-540 MYA

-First most ancient complex organisms on Earth


The Cambrian Explosion:

-Over 100 different phyla compared to 30+ now

-Created predator/prey relationships

The missing link: How did we get from ocean to land?

-Tiktaalik