(a) Aristotle (384-322 B.C) proposed that the origin of life is spontaneous generation. Spontaneous is the concept that living things arise from non-living material.

(b) Carl Linnaeus (1707-1778), a Swedish doctor and Botanist, who is also called the Father of Taxonomy. Proposed the development of hierarchical system of classification of nature. The Linnaean system is important because it has led to the use of binomial nomenclature to identify organisms.

(c) Louis Pasteur (1822-1895), a French Chemist and Microbiologist, known from his discoveries of the principles of vaccination, microbial fermentation and pasteurization.

(d) Robert Koch (1843-1910) was the German Bacteriologist who discovered the bacteria that causes anthrax, septicemia, tuberculosis and cholera.

(e) Gregor Mendel (1822-1884) was Austrian Botanist, teacher and Augustinian prelate, became regarded as the Father of genetics. He discovered the basic principles of heredity and laid the mathematical foundation of the science of genetics.