| << Chapter < Page | Chapter >> Page > |
Card 10 / 29:
The first electron micrograph of a virus (tobacco mosaic virus) was produced in 1939. Before that time, how did scientists know that viruses existed if they could not see them? (Hint: Early scientists called viruses “filterable agents.”)
Viruses pass through filters that eliminated all bacteria that were visible in the light microscopes at the time. As the bacteria-free filtrate could still cause infections when given to a healthy organism, this observation demonstrated the existence of very small infectious agents. These agents were later shown to be unrelated to bacteria and were classified as viruses.
| Previous Card | ← Previous Card Button |
| Next Card | → Next Card Button |
| Flip Card | ↑ / ↓ / Return / Space |
Notification Switch
Would you like to follow the 'Biology 9-11 grades' conversation and receive update notifications?
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|