Question

During an excavation of soil, Pollen. fossils were retrieved from deepest layer of soil. The pollen grains remained as fossils because

• A. The intine of pollen grains is made up of pectin.
• B. Exine has spiny Ornamentation.
• C. The exine of pollen grains is highly resistant to enzyme action.
• D. Pollen grains are asexual reproductive structures.

Answer 1

The Correct Option is C

The preservation of pollen grains as fossils in the deepest soil layer can be explained by analyzing the structural and chemical properties of pollen walls:

Key factors enabling pollen fossilization:

1. Exine composition: The outer wall (exine) of pollen grains contains sporopollenin, one of the most chemically resistant biological compounds known. This complex biopolymer is: - Highly resistant to enzymatic degradation - Stable under extreme temperature and pH conditions - Impervious to most microbial action - Chemically inert against most environmental factors

2. Intine properties: While the inner wall (intine) is pectin-cellulose based (option A), this layer decomposes readily and doesn't contribute to fossil preservation.

3. Ornamentation relevance: While exine may have spiny ornamentation (option B), this feature aids in species identification but doesn't affect preservation potential.

4. Reproductive nature: Pollen grains are sexual reproductive structures (making option D incorrect), but this characteristic doesn't influence fossilization.

Thus, the correct answer is (C) The exine of pollen grains is highly resistant to enzyme action.

Answer 2

Pollen grains remain preserved as fossils primarily because their outer layer (exine) is composed of sporopollenin, one of the most chemically resistant organic compounds known. This allows pollen to withstand microbial degradation, extreme temperatures, and chemical weathering over geological time scales. While the spiny ornamentation (B) may aid in identification, it's the chemical nature of exine that ensures preservation. The intine's pectin composition (A) and pollen being asexual (D) are irrelevant to fossilization.

The correct answer is (C) The exine of pollen grains is highly resistant to enzyme action.