Today im going to talk about cells, the cell theory, and microscopes. The word Microscope is given to the tool used to view objects that are too small to be seen with the naked eye. They make small things look larger using lenses to bend the light. This is called magnification. A simple microscope has 1 lens, but a compound microscope like the one in this picture uses 2 lenses at once to magnify an image. One lens is fixed in the eyepiece. A second lens is chosen from a group of 2 or 3 lenses on the revolving nose piece or the objective lens. Here you can see the eyepiece lens, the objective lens with 3 magnifications to choose from, the slide, the stage, the clips to hold the slide to the stage, the coarse focus, the fine focus, and the light which illuminates the object.
To know the total magnification of an object seen through a compound microscope, the magnification of the 2 individual lenses are multiplied together. For example, if the lower lens magnifies the object 4 times, and eyepiece lens magnifies the object 10 times, the total magnification would be 40 times, or 40X. You can do the same calculation with a magnification of 10 in the lower lens or objective lens. 10 times 10 is 100X. And with an objective lens of 40 your total magnification would be 400X.
The microscopes we just saw focus light through lenses to produce a magnified image. However, other microscopes can produce a more detailed image. This is called resolution, when the image can be seen much more clearly. Here in this picture of microtubules, the conventional microscope image does not have nearly as good a resolution as the STORM microscope image does.
The early scientists used light microscopes, but in the 1930’s scientists developed several types of microscopes which can obtain pictures of objects that are too small to be seen with light microscopes. The small hairs on this spiders body would never be seen under a light microscope. This image was taken from an electron microscope which allows high magnification and better resolution than light microscopes.
Here is another picture from the insect called the flea. This image was taken using an electron microscope.
Here is another image of a butterfly taken using an electron microscope.
3 people made key discoveries in the early study of cells. One of them was Robert Hooke who saw slices of cork under a microscope. Cork is the bark of a tree made of dead cells. Hooke thought they looked like tiny rectangular rooms, so he called them “cells” which means “small rooms.”
Anton discovered the first living things to be seen under a microscope. These were bacteria, which he called “little animals”.
Finally, 3 other men named Schleiden, Schwann, and Virchow came to some conclusions about cells: All plants are made from cells, all animals are made of cells, and all cells come from other cells. Together these 5 men formed the Cell Theory.
The Cell Theory states that 1.) all living things are made of cells. 2.) Cells are the basic unit of structure and function. 3) All cells are produced from other cells.
Because cells are common to all living things, cell can provide clues about the functions that living things perform. And because all cells come from other cells, scientists can study them to learn about growth and reproduction. The Cell Theory holds true for all living things, no matter how big, or how small.
Low and high resolution of an image
Electron microscopes (1930s) use beams of electrons, not light waves, to magnify objects up to 1 million times.
II. First sightings of cells – A. Robert Hooke • 1. 1663, he observed slices of cork under a microscope. They looked like tiny rooms, so he called them “cells.”
– B. Anton van Leeuwenhoek • 1. First person to see living organisms under a microscope (bacteria).
III. Cell Theory – A. 1838: Matthais Schleiden concluded that all plants are made of cells. – B. 1839: Theodor Schwann concluded that all animals are made of cells. – C. 1855: Rudolf Virchow proposed that new cells are formed from existing cells. – D. These observations, and others led to the development of the cell theory:
Cell Theory –1. All living things are made of cells. –2. Cells are the basic unit of structure and function in living things. –3. All cells are produced from other cells.