The appearance of fossils would the the answer.
Although there has been some scientific debate about what fossil strata should mark the beginning of this period, the "International Geological Congress" determined that the Cambrian period was approximately 543 million years ago of which the first appearance in the fossil record of worms that made horizontal burrows was discovered.
Answer:
Explained
Explanation:
The first thing that the etiologist can do is try and culture bacteria from the tissue samples in the lab. And then study about the bacterium's properties and characterstics that are leading to causing diseases in the humans.
The doughnut because it contains carbohydrates
oak tree DNA is much longer than that in human and the number of chromosomes also differ
