Question

The scientist who first observed bacteria and protozoa is:
a. Antonie van Leeuwenhoek
b. Robert Hooke
c. Mathias Jacob
d. Robert Brown

Answer 1

Hint: Out of numerous lifeforms existing on Earth, the bacterias are the most abundant organisms. These belong to kingdom Monera and are unicellular prokaryotes which can thrive in a wide range of temperatures from extremely cold to hot humid temperatures.

Complete answer: Bacteria are the members of the kingdom Monera which are found almost everywhere. These are the most primitive organisms with a very simple structural organization and most extensive metabolic activity. Protozoa is the division of the kingdom Protista. Protista includes the unicellular eukaryotic organisms but its boundaries are not well defined. These organisms are primarily aquatic and contain a well-defined nucleus and other cell organelles. These are heterotrophic and are mostly parasitic or predators.
Antonie van Leeuwenhoek was the first to develop microscopes which he used for himself only. Under his single-lens microscope, he observed the microscopic organisms, which he called ‘animalcules’ meaning animal-like. These animalcules were the Protista. Through his experiments, he was the first who relatively determined their size. He also documented the microscopic observations of muscle fibers, bacteria, spermatozoa, and red blood cells.
Antonie van Leeuwenhoek was a Dutch scientist who is also called as the father of microbiology and was the first microscopist and microbiologist. He founded his shop and worked as a draper, while running his shop he wanted to see the thread quality more than which was possibly visible through the magnifying glass of that time; due to which he developed his interest in lens making.
Therefore, the correct answer is Option a- Antonie van Leeuwenhoek.

Note: R.H. Whittaker proposed a five-kingdom classification, in which he arranged the organisms into these five kingdoms according to their cell structure, thallus organization, mode of nutrition, reproduction, and phylogenetic relationships.