Final answer:
The early viral studies utilized adenovirus, which is a non-enveloped virus causing respiratory illnesses. This virus types are robust and significant in understanding virology and treating viral diseases.
Step-by-step explanation:
Early viral studies were conducted with the adenovirus, a non-enveloped animal virus known to cause respiratory illnesses in humans. The adenovirus utilizes glycoprotein spikes that protrude from its capsomeres to latch onto host cells.
This virus, along with other non-enveloped viruses such as the poliovirus, papillomavirus, and hepatitis A virus, demonstrates a robust nature which allows them to survive harsh conditions. These studies have contributed significantly to our understanding of virology and the development of treatments and vaccines for various viral diseases.