Ex 1.18 Fill in the gaps with the correct article.

1. An individual bacterium is so small that (with only a few exceptions) it is invisible to ___ naked eye.

2. These minute organisms really are ___ distinct form of life.

3. Other common adaptations contributed to both ___ ubiquity and ___ staying power of these ancient organisms.

4. The minute organisms have no direct analog in ___ macroscopic world.

5. Surprisingly, oxygen can be ___ deadly poison for many others, known as anaerobic bacteria, which have evolved to live in air-free environments.