AP BIOLOGY

Detailed explanation-1: -Using single-lensed microscopes of his own design and make, van Leeuwenhoek was the first to observe and to experiment with microbes, which he originally referred to as dierkens, diertgens or diertjes (Dutch for “small animals” [translated into English as animalcules, from Latin animalculum = “tiny animal"]).

Detailed explanation-2: -Leeuwenhoek is universally acknowledged as the father of microbiology. He discovered both protists and bacteria [1]. More than being the first to see this unimagined world of ‘animalcules’, he was the first even to think of looking-certainly, the first with the power to see.

Detailed explanation-3: -Answer and Explanation: “Animalcule” is an old term for microorganisms.

Detailed explanation-4: -Using his handcrafted microscopes, he was the first to observe and describe microorganisms, which he originally referred to as animalcules (from Latin animalculum = “tiny animal").