Correct Option
The correct option is 2 and 3 only.
Explanation
The Earth's atmosphere is composed of various gases that play critical roles in sustaining life and regulating the environment. While some gases like Oxygen are universally essential for aerobic life, others like Ozone exhibit different properties and impacts depending on their altitude within the atmosphere.
Statement-wise Analysis
- Statement 1 is Incorrect: Ozone is not harmful at higher atmospheric levels; it is essential there. In the upper atmosphere (Stratosphere), ozone forms a layer that shields the Earth from harmful ultraviolet (UV) radiation. It is at the ground level (Troposphere) that ozone is considered a secondary pollutant and is harmful to human health and vegetation.
- Statement 2 is Correct: Oxygen (O2) is a fundamental requirement for aerobic respiration, the metabolic process by which most living organisms generate energy. It is a vital component of the atmosphere for the survival of aerobic life forms.
- Statement 3 is Correct: The ozone layer located in the stratosphere performs a crucial protective function. It absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, preventing it from reaching the Earth's surface where it can cause skin cancer, cataracts, and ecological damage.
Key Takeaway
Ozone exhibits a dual nature: it acts as a protective shield in the Stratosphere ("Good Ozone") but functions as a harmful pollutant and greenhouse gas in the Troposphere ("Bad Ozone").