The correct option is 2 and 3 only.
Explanation
Biological activity is a critical component of exogenic geomorphic processes, specifically weathering and soil formation (pedogenesis). It involves the interaction of flora, fauna, and microorganisms with the parent rock material.
- Statement 1 is Incorrect: Vegetative cover is the primary source of organic matter in the soil, not a barrier to it. Plants contribute organic material through leaf fall, root decay, and the decomposition of dead tissues. This addition of organic matter is essential for soil fertility and structure.
- Statement 2 is Correct: When plants and other organisms die, their remains are decomposed by soil microorganisms (bacteria, fungi, etc.). This decomposition process converts raw organic material into humus, a dark, amorphous organic substance that is vital for soil health.
- Statement 3 is Correct: The process of humification and the metabolic activities of soil bacteria produce various organic acids (such as humic and fulvic acids). These acids react with soil minerals, facilitating chemical weathering and the decomposition of the parent rock material, thereby aiding in soil formation.
Key Takeaway: Biological activity accelerates soil formation by adding organic matter (humus) and producing organic acids that chemically weather minerals.