Early evolution on earth

Fermi’s paradox

The high probability that extraterrestrial life exists on earth and the total lack of evidence or contact

The great filter

Advanced life is rare because there’s an evolutionary or technological step that is impassable. Either we’ve already survived it, or it’s coming in the future.

Limitations of time and space

Interstellar communication is limited by the speed of light and the vastness of space. Civilizations may rise and die at different times, missing each other’s windows.

What led to the oxygen revolution

Protocells, Bacteria, archaea, photosynthetic bacteria, first eukaryotes, oxygen revolution

Snowball Earth

Rise in oxygen opposed greenhouse gases like CO2 and methane and led to cooling of the Earth. 3 cycles of freezing and warming occurred

Endosymbiotic theory

Organelles started as a symbiotic relationship between cells of varying types that ultimately resulted in engulfing one of the organisms into the other

Asgard archaea

Genetic sequencing showed that all eukaryotic organisms likely evolved from the ancestors of these archaea. Found in hydrothermal vents

Protocells

PRE-cells that evolved into early bacteria-like prokaryotic cells

Cyanobacteria

Photosynthetic bacteria that do not release oxygen. Also make up stromatolites

Eukaryotic cells

membrane-bounded organelles; can be single cells or multicellular organisms

Prokaryotic cells

(both bacteria and archaea) – no membrane-bound organelles (although there is structure); single-celled organisms