Prentice Hall - Science Explorer - Cells and Heredity
Chapter 1- Cell structure and Function
Section 1- Discovering Cells
Questions - Comment - Key Words -
Connections
Cells
Microscope
The Cell theory
Magnification
Main Ideas; Visuals + Predictions
An overview of Cells * Cells are the basic units of structure and function in living things. Cells: The basic unit of structure and function in living things.
Cells and Structure * The structures of living things are determined by the amazing variety of ways in which cells are put together. ex: A high tree consists of cells arranged to form a high trunk and leafy branches. A red newt’s cells form a body with a head and four legs.
Cells and Function * An organism's functions are the processes that enable it to stay alive and reproduce. (Cells involve these functions as well) ex:oxygen, getting rid of wastes, obtaining food, and growing.
Many and Small
* This picture shows the cells of your skin. There are many cells but they are too small to see in the naked eye.
First Observations of Cells * The invention of the microscope made it possible for people to discover and learn about cells. Microscope: An instrument that makes small objects look larger.
The Microscope: Improvements over time
* This image is a timeline about the evolution of microscopes.
Development of the Cell Theory
Schleiden, Schwann, and Virchow
* Schleiden, Schwann, and Virchow, were scientists who made the conclusion that plants and animals are all made up of cells.
*This images shows the relation between plant and animal cells.
What the Cell Theory Says * Schleiden, Schwann, Virchow, and other scientists helped develop the cell theory.The cell theory: is a widely accepted explanation of the relationship between cells and living things. The cell theory states the following:
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.
Light and Electron Microscopes
Magnification and Lenses
* The first property, magnification: is the ability to make things look larger than they are. The lenses in light microscopes magnify an object by bending the light that passes through them.
Compound Microscope Magnification
* Compound microscopes use more than one lens. Light passes through a specimen and then through two lenses. The first lens, near the specimen, magnifies the object. Then a second lens, near the eye, further magnifies the enlarged image. The total magnification of the microscope is equal to the magnifications of the two lenses multiplied together.
ex: if the first lens magnifies it to 10 and the second lens magnifies it to 40. The total magnification is 10 X 40= 400.
Resolution *The ability to clearly distinguish the individual parts of an object is called resolution. Resolution is another term for the sharpness of an image. ex: A microscope improves the resolution as seen in the figure below.
Electron Microscopes* Electron microscopes use a beam of electrons instead of light to produce a magnified image. Electron microscopes can obtain pictures of extremely small objects and the resolution is also much better than other microscopes.
ex: An electron microscope is better both in magnification and resolution, as seen in the figure below.