The Study of Biology Lecture 1

Biology explores life from the global to the microscopic scale. The science of biology reaches from the global scale of the entire planet down to the microscopic world of cells and molecules. The biosphere is what scientists call the entire plant Earth. An ecosystem is the community of living things in an area, along with the non-living features of the environment that support the living community. Community of living things are made up from its individual parts, the organism. Organisms are made up from microscopic parts called cells. And finally cells themselves are made up from parts called molecules, which are made of atoms.

Spontaneous Generation vs. Biogenisis For many years people thought that living things arose from non-living matter. In 1668, Francesco Redi, an Italian physician proposed that living things only arise from other living things. Redi formed a hypothesis and set out to test it.

Needham’s Test of Redi’s Findings In the mid 1700’s, John Needham, an English Scientist, termed the word animalcules. Needham claimed that spontaneous generation could occur under the right conditions. “These little animals,” he inferred, “Can only have come from juice of the gravy.” An Italian scholar, Lazzaro Spallanzani, thought that Needham had not heated his samples enough and decided to improve upon Needham’s experiment. Spallanzani concluded that non-living gravy did not produce living things. The microorganisms in the unsealed jar were offspring of microorganisms that had entered the jar through the air. This experiment and Redi’s work supported the hypothesis that new organisms are produced only by existing organisms.

Spallanzani (Italian scholar)

Pasteur’s Test of Spontaneous Generation Well into the 1800’s, some scientist continued to support the spontaneous generation hypothesis. Some of them argued that air was a necessary factor of generating life because air contained the “Life force” needed to produce new life. In 1864, an engineous French scientist, Louis Pasteur, designed a flask that remained opened to air but denied microorganisms entry. Pasteur changed biology for ever as he began to uncover the very nature of infectious diseases, showing that they were the result of microorganisms entering the bodies of the victims.

Louis Pasteur (French scientist)

How a Theory Develops In science, the word theory applies to a well tested explanation that unifies a broad range of observations.

The End