Final answer:
The ozone layer was not well-developed by 3.5 billion years ago; it formed after free oxygen accumulated in the atmosphere about 2.4 billion years ago, making the statement False.
Step-by-step explanation:
The statement that the Earth's ozone layer was well-developed by 3.5 billion years ago is False.
The free oxygen that began accumulating in Earth's atmosphere about 2.4 billion years ago led to the formation of the ozone layer. This layer, composed of ozone (O3), a molecule with three oxygen atoms, plays a crucial role in protecting the Earth's surface from the Sun's harmful ultraviolet radiation.
The ozone layer allows for the possibility of life on land, as it did back when it first formed, providing a shield that enabled life to move out of the oceans.
The international action against the use of chlorofluorocarbons (CFCs) in the 1980s had a positive impact on reducing the depletion of the ozone, showing that humanity can work together to preserve the conditions necessary for life on Earth.