A Walk through Time: The Cell

What is a Cell? Cells are the structural and functional units of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multi-cellular, or have many cells—an estimated 100,000,000,000,000 cells! Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Even more amazing is that each cell stores its own set of instructions for carrying out each of these activities.

The Microscope—Improvements Over Time The discovery of cells would not have been possible without the microscope. Microscopes have been improved in many ways over the last 400 years. 1590—Hans Janssen and his son Zacharias were Dutch eyeglass makers. They made the first compound microscope. It was a simple tube with a lens on each end. The Microscope—Improvements Over Time

Robert Hooke In 1660, an Englishman, Hooke, improved upon the compound microscope made by Anton van Leeuwehnhoek. Hooke’s microscope added a stand and had oil for a flame to light the specimen. He first observed a cork, and called the structures that he observed “cells,” because they looked like a line of prison cells. First compound light microscope.

Anton van Leeuwenhoek Van Leeuwenhoek was a Dutchman that worked with magnifying lenses. He was making microscopes before Hooke, But, it was his discovery in 1683 that gave him the name of Father of Microbiology. He was the first person to see many one-celled organisms. He gave the first detailed descriptions of bacteria, protozoa, red blood cells and capillary circulation. He created over 400 different types of microscopes.

1886 Modern Compound Light Microscope invented by three German scientists. It magnified specimens up to 1,000 times. Ernst Abbe Carl Zeiss

1931 German physicist, Ruska, created the first electron microscope 1931 German physicist, Ruska, created the first electron microscope. It makes images by sending electrons through a thinly sliced specimen. It can magnify up to 500,000 times. Ernst Ruska 1965 The first three-dimensional microscope is used that sends a beam of electrons over the surface of a microscope. It can magnify up to 150,000 times. It was developed by Prof. Sir Charles Oakley and Gary Stewart of Great Britain. 1931 Electron Microscope 1965 - Scanning Electron Microscope Gerd Binnig and Heinrich Rohrer invented the scanning tunneling microscope that gives three-dimensional images of objects down to the atomic level. Binnig and Rohrer won the Nobel Prize in Physics in 1986. The powerful scanning tunneling microscope is the strongest microscope to date. Three-dimensional image of a flower.

Early Contributions to the Understanding of a Cell Because of the developments and improvements of the microscope, the following scientists were able to contribute to the discovery and understanding of the cell, thus developing The Cell Theory.

Antonie van Leeuwenhoek Robert Hooke 1663: The first person to see cells. He was looking at cork and noted that he saw "a great many boxes.” 1674: Observed living cells in pond water, which he called “animalcules.” Antonie van Leeuwenhoek

Matthias Schleiden 1837: A German botanist who observed that the tissues of plants contained cells. He recognized the importance of the cell’s nucleus. He recognized that the cell is the basic unit of structure and organization in organisms. Co-founder of the Cell Theory along with Theodor Schwann and Rudolf Virchow.

Theodor Schwann 1837: A German zoologist who observed that the tissues of animals had cells. After meeting with Schleiden, he discovered that all living organism are comprised of cells or cell parts. He studied the nervous system and discovered the Schwann cells. And, he coined the term “metabolism.” Co-founder of the Cell Theory along with Matthias Schleiden and Rudolf Virchow.

Rudolf Virchow 1857: A German pathologist, and anthropologist widely credited for his advancements in public health. Known as the "father of pathology." He reported that every living thing is comprised of vital units, known as cells. He also predicted that cells come from other cells. His scientific contribution to The Cell Theory explained the effects of disease on the body. He also developed a standard method of autopsy procedure. Co-founder of the Cell Theory along with Matthias Schleiden and Theodor Schwann.

The Cell Theory 1. All cells arise from pre- existing cells. 2. The cell is the basic unit of structure and function. It is the smallest unit that can perform life functions. 3. Every living organism is made of one or more cells. Why is it called a theory and not a fact?

What Is A Theory? As used in science, "theory" does not mean the same thing as it does in everyday life. A theory is not a guess, hunch, or speculation. It is much more. A theory is built upon one or more hypotheses and upon evidence. The word "built" is essential, for a theory contains reasoning and logical connections based on the hypotheses and evidence. Scientists, world-wide, classify data and observations so that others in the scientific community can validate their findings. Newton’s Theory of Gravity Newton’s Theory of the Motion of Planets Einstein’s Theory of Relativity Germ Theory of Disease Cell Theory Theory of the Motion of Land Masses (Plate Tectonics)