{ Discovering Cells Coulter

 Cells are the basic units of structure and function in living things.  Cells and structure: structures of living things are determined by the amazing variety of ways in which cells are put together. (tree/dog)  Cells and function: the processes that enable it to stay alive and reproduce.  Many and small: human skin cells, one square centimeter of your skin’s surface contains more than 100,000 cells. An overview of cells

 The invention of the microscope made it possible for people to discover and learn about cells.  Microscope-is an instrument that makes small objects look larger.  Some do this by using lenses (like eye glasses) to focus light.  Simple microscope- one lens  Complex microscope- more than one lens First Observation of Cells

 1663 Hooke used his microscope to observe the structure of a thin slice of cork  He thought what he saw looked like small rooms, so he called them cells.  He described what he observed; “these pores, or cells, were not very deep, but consisted of a great many little boxes…”  He was amazed about how many cells there were, he estimated that in 1 cubic centimeter there were 1,200,000,000 cells “almost incredible” Robert Hooke

 Looked at drops of lake water, scrapings from teeth and gums, and water from rain gutters.  Was surprised to find a variety of one-celled organisms.  Noted that many moved, he called them animalcules (little animals) Anton van Leeuwenhoek

 Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.  In 1839, Schleiden concluded that all plants are made of cells.  In 1840, Schwann concluded that all animals are also made up of cells  This huge discover did not explain where cells came from.  In 1855, Virchow proposed new cells formed only from cells that already exist. Development of the cell theory

 Is a widely accepted explanation of the relationship between cells and living things  All living things are composed of cells  Cells are the basic units of structure and function in living things  All cells are produced from other cells The Cell Theory

 The lenses in light microscopes magnify an object by bending the light that passes through them.  Observe a hand lens  What do you notice?  Lens is curved, thicker in the middle. A lens with this curved shape is called a convex lens.  Light passes through the sides and the lens bends inward. When this light hits the eye, the eye sees the object as larger than it really is. Magnification of Lenses

 Uses more than one lens.  Total magnification of the lens is equal to two lenses multiplied together.  Example: first lens makes object 10 times larger. The second lens makes the object 40 times larger.  10x40=400 Compound microscope

 The ability to clearly distinguish the individual parts of an object is called resolution  sharpness, of an image Resolution

 Electron microscopes use a beam of electrons instead of light to produce a magnified image.  Electrons are tiny particles that are smaller than atoms.  Can see smaller images than those of light microscopes.  Resolution is much better than light microscopes. Electron microscope

 Problem: How can you build a compound microscope?  Materials:  2 dual magnifying glasses, each with one high- power and one low-power lens  Metric ruler  Black construction paper  tape Build a microscope

 Work with a partner. Using only you eyes, examine words in a book. Then use the high-power lens to examine the same words. In your notebook write your observations.  Hold the high-power lens about 5 to 6 cm above the words in the book. When you look at the words through the lens, they will look blurry.  Keep the high-power lens about 5-6cm above the words. Hold the low-power lens above the high- power lens. Write your observations.  Move the low-power lens up and down until the image is in focus and upside down. Build a microscope

 One the image is in focus, experiment with raising and lowering both lenses. Your goal is to produce the highest magnification while keeping the image in clear focus.  When the image is in focus at the position of highest magnification, have your lab partner measure and record the distance between the book and the high- power lens. Your lab partner should also measure and record the distance between the two lenses.  Write a description of how the magnified words viewed through two lenses compares with the words seen without magnification. Build a microscope

 Based on what you learned in part 1, work with a partner to build your own microscope.  Sketch your design in lab report.  Test your microscope by examining a chosen living and non-living organism from outside. Write down observations. Draw to the best of your ability what you see. Build a microscope