Question
Ozone layer depletion, since the 1970s, is primarily attributed to:
The correct answer is
chlorofluorocarbons
Ozone Depletion Cause Identified
The ozone layer protects Earth by absorbing harmful UV radiation. Its depletion, particularly noticeable since the 1970s, involves a significant reduction in ozone concentration in the stratosphere.
Primary Cause: Chlorofluorocarbons (CFCs)
The primary factor driving ozone layer depletion is the release of chlorofluorocarbons (CFCs). These chemicals were widely used as refrigerants, propellants, and solvents.
How CFCs Deplete Ozone
- CFCs ascend to the stratosphere.
- Here, UV radiation breaks them down, releasing chlorine atoms ($Cl$).
- Chlorine atoms act as catalysts in a destructive cycle, breaking down ozone molecules ($O_3$) rapidly. Key steps include:
- $Cl + O_3 \rightarrow ClO + O_2$
- $ClO + O \rightarrow Cl + O_2$ (where $O$ is an oxygen atom)
- This cycle allows a small amount of chlorine to destroy a large amount of ozone.
Evaluating Other Factors
- Carbon dioxide ($CO_2$) primarily contributes to global warming, not direct ozone depletion.
- Global warming is a separate issue concerning increased global temperatures.
- UV radiation is essential for breaking down CFCs in the stratosphere but is not the *cause* of depletion itself; it's the radiation we need protection from.
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Important Questions from Abiotic factors
- Species that co-occur in space and time tend to be similar to each other in traits such as tolerance to heat or to drought. This is most likely because of _________.
- A researcher carried out an experiment to study how daylength and temperature influence diapause in a moth species. He placed larvae in one of four treatment conditions for 2 weeks, with 30 larvae in each condition. The treatments involved two temperatures ($18\text{ }^\circ\text{C}$ or $27\text{ }^\circ\text{C}$) and two lighting conditions (12h:12h Light:Dark (LD) or complete darkness (DD)). At the end of the experiment, he counted the number of larvae that had entered diapause and those that had not. The data are shown below.Which one or more of the following conclusions can he reasonably make from these findings?
Condition Larvae in diapause Larvae NOT in diapause Treatment 1 $27\text{ }^\circ\text{C}$, 12:12 LD 2 28 Treatment 2 $18\text{ }^\circ\text{C}$, 12:12 LD 7 23 Treatment 3 $27\text{ }^\circ\text{C}$, DD 12 18 Treatment 4 $18\text{ }^\circ\text{C}$, DD 29 1 - Terrestrial plants conduct gas exchange through stomata. Having only few stomata on the leaf surface is a common adaptation to which one of the following conditions?
- Some air-breathing marine vertebrates such as whales, seals and marine turtles possess adaptations for long, deep dives. Which one or more of the following is/are examples of such adaptations?
- Which one or more of the following is/are greenhouse gas(es)?
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