Final answer:
Antoni van Leeuwenhoek called "animalcules" are what we now know as bacteria and protozoa, first observed by him in the 1670s using his pioneering microscopes.
Step-by-step explanation:
The microorganisms Antoni van Leeuwenhoek called "animalcules" we would recognize today as bacteria and protozoa. In the 1670s, Leeuwenhoek used his simple but powerful microscopes to observe single-celled organisms in rain water and scrape samples from his teeth, which he termed "animalcules." These observations provided the first evidence of microbial life which includes both bacteria and protozoa. It is also noteworthy that Leeuwenhoek is often credited with the discovery of circular bacteria, spiral bacteria, and rod-shaped bacteria through his early use of microscope technology.