Unit 3 - Learning Target 3 Flowchart

2.5 BILLION YEARS AGO

Cyanobacteria evolve to be able to do photosynthesis

A waste product of photosynthesis is oxygen, so the level of carbon dioxide decreased in the atmosphere and the amount of oxygen increased.

Oxygen was toxic to many early life forms because of how it destroys internal cell biochemistry, so most life went extinct.

Some single-celled life forms evolved that could bind oxygen to protect themselves from damage, This process is called cellular respiration.

As a result, there was a huge increase in the number and types of living things that can now live in an oxygen environment on Earth.