Write down AT LEAST the things in green Title the next page in your notes: Cell Theory Write down AT LEAST the things in green

Take Action! Look at the back of your hand… What do you see? Write down 1-2 observations. Now look at the same spot using a hand lens… What do you see now? Photo credit: OroGold school

Think You actually have about 100,000 cells per square centimeter of skin. That’s a lot of cells! But how do we know they are there? Photo Credit: Samuel Markings, FineArt, University of Utah,

Write This was taken with a close-up camera Microscope technology had to be invented before we could discover cells. This was taken with a scanning electron microscope This was taken with a high-power light microscope Photo Credit: Samuel Markings, FineArt, University of Utah,

Create Make this timeline in your notes: 100 1250 1590 1660 1674 1830s 1855 1933 1965 1981

Brief History 100 Romans begin blowing glass They discovered that curved glass made things look bigger. Probably a teenage boy trying to burn ants…

Brief History 1250 Lenses help people see better These simple “microscopes” had a magnification power of about 6x to 10x. One common item that people loved to look at were fleas. Magnifiers were sometimes called “flea glasses.”

Brief History 1590 First compound microscope Hans Janssen, a Dutch spectacle maker, created the first compound microscope by fixing two lenses far apart in a tube. He discovered that he could see VERY tiny things. The tube would focus by sliding longer and shorter.

Active Learning: Janssen’s microscope was adjustable, and could focus on slightly larger or smaller things by changing how far apart the lenses were. Use your own hand-lenses, put one hand lens on something on your paper. Then place a second lens on top of it and slowly lift up the second one. What happens to the thing under the lenses? Remember: to learn something new, you have to actively form pictures in your mind, and attach new information to something you already know.

Brief History 1660 Light microscope shows cells Robert Hooke, an English scientist, first observed cells from cork bark through a light microscope he created. He thought the cork looked like little rooms, or “cells.” He had no idea what cells were or what they did. This is his drawing of cork cells 1660 Light microscope shows cells

Active Learning: Remember: to learn something new, you have to actively form pictures in your mind, and attach new information to something you already know. Study the diagram of Hooke’s microscope. Why do you think he had an oil lamp and a water flask? What do you already know about light?

Brief History 1674 Single-celled organisms described Anton vanLeeuwenhoek, a Dutch fabric merchant, began fiddling with ways to see the threads of his fabrics better. He put lenses together in a tiny 4 inch microscope then used it to look at other things, such as pond water and the scum from his teeth! He called these little moving creatures “animalcules.” 1674 Single-celled organisms described

Brief History 1830s All living things are made of cells For the past century, scientists had been trying to figure out what made something “alive.” Mathias Schleiden declared that all plant tissues are composed of cells. Theodor Schwann concluded that all animal tissues are composed of cells too. They worked together to form a new theory in biology: CELL THEORY Schleiden Schwann 1830s All living things are made of cells

Brief History 1855 Cells come from existing cells There was still one question about cell theory that had to be answered: Where do cells come from? With the help of some powerful microscopes, Rudolph Virchow proved that cells come from other cells. They simply make copies of themselves then divide in half. 1855 Cells come from existing cells

Brief History 1933 First electron microscope Ernst Ruska, a German engineer, developed a way to use an electromagnet to focus electrons into a wave, like a light wave but much shorter. This meant that we could now see things which were smaller than a light wave. This is a nerve cell.

Brief History of Microscopes 1965 Scanning electron microscope Scientists in England and Japan worked together to create a microscope that shows how electrons bounce off of an object. These electrons created an image that was super-detailed and almost like 3-D.

Active Learning Use your prior knowledge of light and color and electrons. Why are ALL photos taken through an electron microscope only black and white?

Brief History of Microscopes With the invention of the tunneling electron microscope, we could actually see INSIDE of individual cells. We could see the structures of the stuff inside and started to guess at what they did… What questions do YOU have about cells? 1981 Tunneling electron microscope This is a mitochondrion. It is a tiny part of a single cell. Not only can we see that the mitochondria are there, we can see the folded membranes inside of the mitochondrion. Awesome!

Big Ideas of Cell Theory 1- All living things are made of one or more cells. 2- The cell is the basic building block of life. 3- Cells come from existing cells. (write this in your notes and put a cloud around it)