Question

Scientists estimate that the Earth formed some 4.6 billion years ago with the first forms of life appearing around 3.5 billion years ago. These first forms of life were simple prokaryotes. Later, the first photosynethic organisms resulted in more _____________ in the atmosphere. This allowed for more higher level organisms to appear on Earth.

Answer 1

Answer:

in your book only in answer book

Answer 2

Answer:

oxygen

Explanation:

As the first photosynthetic organisms were chemoautotrophs they utilised sunlight  and released oxygen which is suitable for higher organisms.