Why didn't people know about germs or microbes before the mid-1800s?

How does the molecular clock work? a. it analyzes the brain functionality of two different species.b. it examines and compares the physical characteristics of two different species.c. it illustrates relationships between two different species.d. it compares the number of mutations that exist in the dna of two different species.

The similarities of organisms in which two areas numbered above provide the best evidence for common ancestry between organisms in both locations?

Which of the following is an eon in the time scale? phanerozoic proterozoic archean all of the above