Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below:
Assertion (A): Earth is the only planet known to have life.
Reason (R): Earth has an atmosphere which is a mixture of Oxygen, Nitrogen and Carbon dioxide.
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
Understanding the Assertion and Reason: Life on Earth and its Atmosphere
Let's carefully examine the given Assertion (A) and Reason (R) regarding life on Earth and its atmosphere.
Analysis of Assertion (A)
Assertion (A): Earth is the only planet known to have life.
Currently, based on scientific observation and exploration, Earth is indeed the only celestial body where the existence of life has been confirmed. While scientists are actively searching for evidence of past or present life on other planets (like Mars) or moons (like Europa or Enceladus), and the universe is vast, as of now, Earth holds the unique status of being the only known planet with life. Therefore, Assertion (A) is considered correct based on our current knowledge.
Analysis of Reason (R)
Reason (R): Earth has an atmosphere which is a mixture of Oxygen, Nitrogen and Carbon dioxide.
Earth's atmosphere is primarily composed of Nitrogen (around 78%), Oxygen (around 21%), Argon (around 0.9%), and trace amounts of other gases, including Carbon dioxide (around 0.04%). So, the statement that Earth's atmosphere is a mixture of Oxygen, Nitrogen, and Carbon dioxide is factually correct. These are indeed major components (along with Nitrogen being dominant). Therefore, Reason (R) is correct.
Analyzing the Relationship between (A) and (R)
Now we need to determine if Reason (R) is the correct explanation for Assertion (A). Earth's atmosphere, with its specific composition including Oxygen, Nitrogen, and Carbon dioxide, is certainly crucial for the life that exists on Earth. Oxygen is vital for aerobic respiration. Carbon dioxide is essential for photosynthesis, which forms the base of most food chains. Nitrogen is a key element in proteins and nucleic acids. However, is this specific atmospheric mixture the *only* reason, or the *correct* explanation, for Earth being the only planet known to have life?
Life on Earth depends on a multitude of factors working together, not just the atmospheric composition alone. Some other critical factors include:
- The presence of liquid water.
- A suitable temperature range.
- A stable climate over long periods.
- A protective magnetic field shielding from harmful solar radiation.
- The right distance from the Sun (Goldilocks zone).
- The presence of necessary elements and nutrients.
While the atmosphere mentioned in Reason (R) is a necessary condition for life as we know it on Earth, it is not sufficient on its own, nor is it the sole correct explanation for Earth being the only known planet with life. Other planets might have some atmospheric components, but lack other crucial conditions. Hence, Reason (R) is a correct statement about Earth's atmosphere, but it does not fully and correctly explain why Earth is the only planet known to have life.
Evaluating the Options
Based on our analysis:
- Assertion (A) is correct.
- Reason (R) is correct.
- Reason (R) is not the correct explanation for Assertion (A).
Let's match this with the given options:
- Both (A) and (R) are correct and (R) is the correct explanation of (A). (Incorrect, R is not the correct explanation)
- Both (A) and (R) are correct but (R) is not the correct explanation of (A). (This matches our analysis)
- (A) is correct but (R) is not correct. (Incorrect, R is correct)
- (A) is not correct but (R) is correct. (Incorrect, A is correct)
Therefore, the most appropriate answer is the one stating that both Assertion (A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).
Revision Table: Assertion and Reason on Earth and Life
| Statement | Assessment | Explanation |
|---|---|---|
| Assertion (A): Earth is the only planet known to have life. | Correct | Based on current scientific knowledge and observation. |
| Reason (R): Earth has an atmosphere which is a mixture of Oxygen, Nitrogen and Carbon dioxide. | Correct | These are major components of Earth's atmosphere. |
| Is (R) the correct explanation for (A)? | No | Atmosphere is a necessary factor for life on Earth, but not the sole or complete explanation. Many other factors like water, temperature, distance from Sun, etc., are also essential. |
Additional Information: Factors for Life and Earth's Habitability
The question touches upon the conditions necessary for life, particularly on Earth. The search for life beyond Earth (astrobiology) focuses on identifying environments that could support life as we know it, often referred to as habitable zones.
Key factors contributing to Earth's habitability include:
- Liquid Water: Water is essential as a solvent for biological processes. Earth's temperature range allows water to exist in liquid form.
- Atmosphere: Provides gases necessary for biological processes (like O$_2$, CO$_2$, N$_2$), helps regulate temperature through the greenhouse effect, and offers some protection from small meteoroids. However, its specific composition is often a result of life itself (e.g., high Oxygen levels are produced by photosynthetic organisms).
- Energy Source: Primarily the Sun provides energy for photosynthesis and warmth.
- Nutrients: Availability of essential elements like carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, etc., that can be cycled and incorporated into living organisms.
- Stable Environment: Factors like a steady energy output from the star, a magnetic field to deflect harmful charged particles (solar wind), and a relatively stable orbit contribute to long-term habitability.
While Earth's atmosphere is a vital component of its habitable environment, stating it as the *sole* reason or *correct explanation* for Earth being the only known planet with life overlooks the complex interplay of these multiple factors. The presence of oxygen-rich atmosphere itself is a strong indicator *of* life (photosynthesis), rather than just a prerequisite.
Important Questions from Assertion and Reason
Given below are two statements:
Statement I: Arithmetic Progression is a sequence in which the addition of any two consecutive terms is a constant.
Statement II: In a Geometric Progression, the ratio of any term to its preceding term is a constant.
In the light of the above statements, choose the most appropriate answer from the options given below.
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The filament in an electric bulb does not burn up although its temperature is about 2700°C when it glows.
Reason (R): Bulb filament is made of tungsten.
In the light of the above statements, choose the most appropriate answer from the options given below.
Given below are two statements: one is labeled as Assertion (A) and the other is labeled as Reason (R).
Assertion (A): Diamond is used for cutting glass.
Reason (R): Diamond has a high refractive index.
Choose the most appropriate answer:
Given below are two statements: one is labeled as Assertion (A) and the other is labeled as Reason (R)
Assertion (A): Copper is used to make electrical wires.
Reason (R): Copper has very low electrical resistance.
In the light of the above statements, choose the correct answer from the options given below.
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Mercury is the second farthest planet from the Sun.
Reason (R): Mercury is the smallest planet in the entire solar system.
In the light of the above statements, choose the most appropriate answer from the options given below:
