Question

In the early days of germ theory, contagious diseases were thought to be caused by fungi or bacteria. In the 1890s, Dmitri

Ivanovski filtered extracts from diseased tobacco plants and discovered that the disease could be transmitted to new plants

through the filtrate. He concluded that the disease was caused by particles smaller than bacteria: the tobacco mosaic virus.

Which best explains how Ivanovski's work led to a change in the germ theory?

He tried to promote his hypothesis as a law.

He used a new experimental method to test his hypothesis.

He used a more powerful bacterial strain than other scientists had.

He obtained results that confirmed what other scientists were thinking

Answer 1

The work of Ivanovski resulted in a change in the germ theory as he used a novel experimental approach to test his hypothesis. According to the germ theory, the diseases are caused by microbes. Before the 1890s, it was considered that communicable diseases are caused by microbes like fungi and bacteria, as viruses were not familiar at that time.

The work of Ivanovski on the tobacco plant was the one that led to the discovery of the prevalence of viruses. Ivanovski was able to get to the conclusions as he used a new experimental method to examine his hypothesis.