Question

What protects living things from too much ultraviolet radiation? A) the ozone layer C) nitrogen B) oxygen D) argon

Short answer

The ozone layer (A) protects living things from UV radiation.

Step-by-step solution

Identify the Role of Each Option

First, let's identify the role of each option listed. The ozone layer is known to absorb most of the Sun's harmful ultraviolet (UV) radiation, protecting living organisms. Nitrogen and oxygen are major components of the Earth's atmosphere but are not specifically protective against UV radiation. Argon is a noble gas present in the atmosphere in trace amounts and doesn't play a role in UV protection.

Assess the Function of the Ozone Layer

The ozone layer contains a high concentration of ozone (O3) molecules. These molecules are very effective at absorbing UV-B and UV-C radiation from the Sun, which can be harmful to DNA in living organisms. Without this layer, most living organisms would be exposed to harmful levels of ultraviolet radiation.

Eliminate Incorrect Options

Given the information, we can eliminate options C, B, and D. Nitrogen (C), oxygen (B), and argon (D) are not responsible for protecting living things from UV radiation. They either have no role (argon) or have different roles in the atmosphere.

Choose the Correct Answer

Based on the role that each gas plays in the atmosphere, the clear choice is A) the ozone layer, as it is directly involved in protecting life by absorbing ultraviolet radiation from the Sun.

Key concepts

Ultraviolet Radiation

Ultraviolet (UV) radiation is a type of energy emitted by the Sun. It falls outside the visible light spectrum, so while we can't see it, its effects are felt by living organisms on Earth.
UV radiation is classified into three main types:

• UV-A: This form has the least energy and can cause skin aging and wrinkles.
• UV-B: More energetic and can cause sunburns, skin cancer, and cataracts.
• UV-C: The most energetic and potentially harmful, but it's absorbed by the ozone layer and does not reach the Earth's surface.

All forms of UV radiation can have negative effects on living organisms. For humans, overexposure can damage the skin, eyes, and immune system. Plants and aquatic life can also be affected. To cope with these potential harms, protective measures are essential.

Atmospheric Gases

The Earth's atmosphere is made up of a mixture of gases that envelop our planet. These gases are crucial in many aspects, like supporting life, maintaining temperature, and protecting against space hazards.
The major components of atmospheric gases include:

• Nitrogen (N extsubscript{2}): This makes up about 78% of the atmosphere and is vital for the formation of amino acids in living organisms.
• Oxygen (O extsubscript{2}): Essential for respiration, it comprises about 21% of the atmosphere.
• Argon (Ar): A noble gas present in small amounts, about 0.93%, it is nonreactive and has little effect on life or environmental processes.
• Carbon dioxide (CO extsubscript{2}): Although a trace gas, it is important for photosynthesis and contributes to the greenhouse effect.
• Ozone (O extsubscript{3}): Found in small concentrations, primarily in the stratosphere, and crucial for UV protection.

While most of the atmospheric gases have important roles, not all are directly involved in UV protection, highlighting the unique importance of ozone.

Earth's Atmosphere

The Earth's atmosphere acts as a protective shield, performing many functions essential for life. It extends up to about 480 kilometers above the Earth, with various layers that have distinct roles.
The main atmospheric layers are:

• Troposphere: The lowest layer where weather occurs. It contains the majority of the atmosphere's mass.
• Stratosphere: Above the troposphere, it houses the ozone layer, providing the critical function of absorbing UV radiation.
• Mesosphere: Located above the stratosphere, it protects the Earth by burning up meteors.
• Thermosphere: Here, temperatures rise as it absorbs high-energy radiation.
• Exosphere: The outermost layer, fading into space, where particles can escape into the vacuum.

The interaction between these layers and solar radiation is vital to sustaining life and maintaining environmental stability. The stratosphere's ozone layer stands out for its pivotal role in UV protection.

UV Protection

Protection from ultraviolet radiation is crucial to prevent potential damage to living organisms. The primary protector against harmful UV radiation is the ozone layer, which absorbs a significant amount of UV-B and almost all UV-C radiation before it reaches the surface.
Here's how the ozone layer achieves this protection:

• Ozone molecules (O extsubscript{3}) in the stratosphere react with UV radiation, breaking down the ozone into an oxygen molecule (O extsubscript{2}) and a free oxygen atom (O).
• This process absorbs the energy of the UV radiation, preventing it from reaching the Earth's surface.
• The free oxygen atoms can then recombine with oxygen molecules to reform ozone.

This cycle is notably fragile, subject to changes such as those caused by human activities that release ozone-depleting substances. Because of the ozone layer's vital role, efforts to reduce pollution and repair the ozone hole are crucial for continued UV protection, keeping living beings safe from excessive UV exposure.