How does the ozone layer protect living organisms, and what are the main causes of ozone depletion?

How does the ozone layer protect living organisms, and what are the main causes of ozone depletion?

• A. The ozone layer absorbs most UV-B radiation, protecting living organisms; depletion is mainly caused by human-made ozone-depleting substances like CFCs and halons that release chlorine and bromine in the stratosphere.
• B. The ozone layer absorbs UV-A radiation; depletion is caused by water vapor.
• C. The ozone layer shields infrared radiation; depletion from methane.
• D. The ozone layer is not essential for life; there is no depletion.

Answer: (A)

The essential idea is that the ozone layer acts as a shield, absorbing most of the sun’s ultraviolet-B radiation and thereby reducing the amount of harmful UV that reaches living organisms. This protection helps prevent DNA damage that can lead to skin cancer, cataracts, and harm to ecosystems such as phytoplankton at the base of food chains. The main cause of ozone depletion is human-made ozone-depleting substances, like chlorofluorocarbons (CFCs) and halons, which release chlorine and bromine in the stratosphere. These halogen atoms participate in catalytic cycles that destroy ozone molecules, thinning the layer over time. Natural factors can influence ozone levels, but the dominant driver of the long-term decline has been these human-made chemicals.

The essential idea is that the ozone layer acts as a shield, absorbing most of the sun’s ultraviolet-B radiation and thereby reducing the amount of harmful UV that reaches living organisms. This protection helps prevent DNA damage that can lead to skin cancer, cataracts, and harm to ecosystems such as phytoplankton at the base of food chains. The main cause of ozone depletion is human-made ozone-depleting substances, like chlorofluorocarbons (CFCs) and halons, which release chlorine and bromine in the stratosphere. These halogen atoms participate in catalytic cycles that destroy ozone molecules, thinning the layer over time. Natural factors can influence ozone levels, but the dominant driver of the long-term decline has been these human-made chemicals.