Chapter 1- Tree Of Life Flashcards
Define theory
An explanation for a general class of phenomena or observations
The discovery of the cell
In 1665 Robert Huck use a crude microscope to examine the structure of court from an oak tree. The instrument magnified objects up to 30 times their normal size and allowed him to see something extraordinary, he observed small pore like compartments that were invisible to the naked eye. These became known as cells.
Further observations of the cell
Soon after Hooke, Anton van Leeuwenhoek succeeded in developing much more powerful microscopes, with these instruments he inspected samples of pond water and made the first observation of single-celled organisms like the Paramecium
Smallest organism
Bacteria, which consist of a single cell and are 200 nm wide
Definition of a cell
A highly organized compartment that is bounded by thin flexible structure called a plasma membrane and that contains concentrated chemicals in an aqueous solution
The components of scientific theories
The first describes a pattern in the natural world, while the second identifies a mechanism or process that is responsible for creating that pattern
Who added the process component of the cell theory?
Rudolph Virchow in 1858
The complete cell theory
All organisms are made of cells, and all cells come from pre-existing cells
Define hypothesis
A proposed explanation
Spontaneous generation
The belief that organisms arose spontaneously under certain conditions
The difference between theory and hypothesis
Theories refer to proposed explanations for broad patterns in nature and hypotheses refer to explanations for more tightly focused questions
Prediction
Something that can be measured and that must be correct if the hypothesis is valid
Louis Pasteur’s idea
He wanted to determine whether microorganisms could arise spontaneously in a nutrient broth or whether they appear only when a broth is exposed to a source of pre-existing cells.
Louis Pasteur’s experiment
He created to treatment groups: a broth that was not exposed to a source of pre-existing cells and he brought that was. Both treatments were identical in every respect but one. Both used glass flasks filled with the same amount of nutrient broth and both were boiled for the same amount of time to kill any existing organisms. But one had a straight neck exposed to preexisting cells after sterilization (the straight neck allowed pre-existing cells like bacteria and fungi that cling to dust particles in the air to drop into the nutrient broth) and one had a swan neck (this allowed water to condense in the crook of the neck after boiling and this pool of water would trap any bacteria or fungi that entered in on dust particles, thereby making it isolated from any pre-existing cells).
Pasteur’s results
His data suggested that the spontaneous generation hypothesis was incorrect and that all cells came from pre-existing cells. His experiment was enough to prove to other biologists the validity of this.
