Question

Earth's atmosphere

1. dates from the early accretionary phase of Earth's history
2. has always been as rich in oxygen as it is now
3. was probably much richer in carbon dioxide (CO2) during early Earth history
4. was probably derived from the evaporation of comets that collided with the Earth
5. lacks any distinct layers and is homogeneous with respect to elevation above the Earth's surface

Answer 1

The Earth's atmosphere was originally rich in carbon dioxide with very little oxygen. Photosynthesis by organisms like cyanobacteria increased the oxygen levels over time, leading to the current oxygen-rich atmosphere and the formation of the ozone layer. The atmosphere is structured into distinct layers, showing that statement 5 is incorrect.

Step-by-step explanation:

The Earth's atmosphere has undergone significant changes since the planet's formation. Initially, the atmosphere formed through the outgassing of volcanic activity and potentially through impacts from comets and asteroids. It contained high levels of carbon dioxide (CO2) and very little oxygen. Overtime, photosynthetic organisms, such as cyanobacteria, began to release oxygen into the atmosphere through the process of photosynthesis.

This dramatically altered the atmospheric composition, leading to an environment rich in oxygen, and eventually, the development of the ozone layer. Hence, the Earth's atmosphere has not always been as rich in oxygen as it is now, and it was actually much richer in carbon dioxide during its early history. Additionally, the atmosphere is structured into distinct layers such as the troposphere, stratosphere, mesosphere, thermosphere, and exosphere, contradicting the idea that it lacks any distinct layers and is homogeneous with respect to elevation above Earth's surface.