Pollen grains can be preserved as fossil because

Options

A. they vary from species to species
B. they have a wide variety of architecture.
C. their wall is made up of sporopollenin
D. they exhibit a fascinating array of patterns and design

Answer

**Step-by-Step Solution:**

1. **Understanding Pollen Grains**: Pollen grains are the male gametophytes of seed plants and are crucial for reproduction. They consist of two layers: an outer layer and an inner layer.

2. **Layers of Pollen Grains**: The outer layer of pollen grains is known as the exine, while the inner layer is called the intine. The exine is particularly important for preservation.

3. **Composition of Exine**: The exine is primarily made up of a substance called sporopollenin. This compound is known for its exceptional durability and resistance to degradation.

4. **Resistance of Sporopollenin**: Sporopollenin is considered the most resistant organic material known. It can withstand extreme conditions, including high temperatures and harsh chemical environments (strong acids and alkalis).

5. **Degradation Resistance**: One of the most significant properties of sporopollenin is that it cannot be broken down by enzymes. This means that even after long periods, pollen grains can remain intact and preserved.

6. **Conclusion**: Due to the presence of sporopollenin in the exine, pollen grains can be preserved as fossils. This durability allows them to survive through geological time, making them valuable for paleobotanical studies.

**Final Answer**: Pollen grains can be preserved as fossils because they have a tough outer layer made of sporopollenin, which is resistant to degradation by enzymes and can withstand extreme environmental conditions.

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