Question

Scientists agree that the early Earth, before 2.4 billion years ago, contained only trace quantities of oxygen and that the oceans were

full of dissolved iron, Data collected point toward oxygen poor, iron-rich conditions for 90% of Earth's history, with oxygen and
hydrogen sulfide present and found mostly to the surface layers and along the margins of the oceans, Scientist also agree that most
Life forms evolved initially in marine habitats. How did the marine environment change to help foster the evolution of so many life
forms?
A)
With the advent of photosynthesis, oxygen began to build up in the oceans.
B)
Volcanic lava added oxygen to Earth's crust and is dissolved in ocean
water
C)
Oxygen was the by-product of the chemical decomposition of early
Lithospheric rocks
Anaerobic cellular respiration of prokaryotes produced dissolved oxygen in
D)
the oceans
Submit

Answer 1

C

Step-by-step explanation:

Answer 2

The correct answer is: A) With the advent of photosynthesis, oxygen began to build up in the oceans.

Photosynthesis, a process used by green plants, algae, and some bacteria to convert sunlight into chemical energy, produces oxygen as a byproduct.

The passage states that the early Earth had little oxygen and abundant dissolved iron. This indicates an anoxic (oxygen-depleted) environment.

It then mentions the evolution of life forms in marine habitats, suggesting a connection between the changing environment and the emergence of life.

The key point is the introduction of photosynthesis. Photosynthesis releases oxygen as a byproduct, gradually altering the composition of the atmosphere and oceans.

While other options mention oxygen sources (volcanic lava, rock decomposition, anaerobic respiration), these are unlikely to have contributed significantly to the widespread oxygenation of the oceans necessary for the evolution of diverse life forms.

Therefore, the increase in oxygen caused by photosynthesis is the most likely explanation for the dramatic change in the marine environment that helped foster the evolution of so many life forms.