The document summarizes key developments in cell theory from 1665 to 1880. Robert Hooke first observed cells in 1665 and they were named after rooms in cathedrals. In 1839, Schleiden and Schwann developed cell theory, stating that all living things are composed of cells. Rudolf Virchow later extended this in 1855 by proposing that all cells come from pre-existing cells, known as the biogenic law. This challenged the idea of spontaneous generation. By 1880, Weissman introduced the idea that present-day cells can trace their ancestry back to early ancestral cells.

1. Biology and Human Concerns
Notes – 10/02/09
Cell Theory
1665 – Robert Hooke
Reported to the Royal Society of London in his observation of “cells” in a
piece of cork. Cells named after the areas where people lived in cathedrals.
1839 – Theodor Schwann together with Matthias Schleiden, developed the cell
theory in 1839 which identified as the fundamental particles of plants and
animals.
M.J. Schleiden and Theodor Schwann’s conclusions were expressed in the
principle of cell theory: “All living things are composed of living cells”.
1855 – Rudolf Virchow proposed an important extension of cell theory that “All
living cells arise from pre-existing cells. (“Omnis cellula e celula”)
-This statement has become what is known as “Biogenic law”.
-This idea that all cells (and life for that matter) arose from pre-existing cells flew
in the face of current doctrine. It impoied that there were no spontaneous
creation of cells from non-living matter.
-Pasteur disproved the widely held belief
-1880 August Weissment introduces important corollary to the biogenic law which
was: “that cells living today can trace their ancestry back to ancient times” ex.
There must be a common ancestral cell
A Tour of the Cell
-How we study cells: Microscopes provide windows to the world of the cell
-Light microscopes force light up through the specimen through a series of
lenses. Limitation = thin/small enough organism so that light can travel
through.
-Electron microscopes make images with a beam of electrons that travel
through the organism. Specimen surface needs to be covered with heavy
metal so the electron flow is stopped, image shows, internal parts of cells
become visible.