Introduction to the Cell Theory Robert Hooke 1665

Introduction to the Cell Theory

Robert Hooke, 1665 • English born scientist and inventor. • The first person to describe cells.

Robert Hooke developed this microscope and illumination device that was considered one of the best microscopes of his time.

Robert Hooke observed cork from the bark of a cork tree. He thought the cork looked like little boxes. He names them cells which means “little rooms” in Latin.

Robert Hooke wrote a bestseller of his time called Micrographia. This book detailed the observations he made with his illuminated microscope device.

Anton Van Leeuwenhoek Dutch Merchant that used a microscope to examine pond scum. He saw small organisms that he called animalcules, which means “little animals”. Today we call these singlecelled organisms protists.

Leeuwenhoek was the first person to see bacteria. He also discovered that the yeast that makes bread rise is a single-celled organism.

Almost 200 years passed before scientists concluded that cells are present in all living things. • In 1838, Matthias Schleiden concluded that all plant parts were made of cells. • In 1839, Theodor Schwann concluded that all animal tissues were made of cells. • in 1858, Rudolf Virchow stated that all cells could form only from other cells.

The Cell Theory • All organisms are made of one or more cells. • The cell is the basic unit of all living things. • All cells come from existing cells.

Introduction to the Microscope §Care §Parts §Focusing

• • • Always carry with 2 hands Only use lens paper for cleaning Do not force knobs Always store covered Keep objects clear of desk and cords

Eyepiece Body Tube Revolving Nosepiece Objective Lens Stage Clips Diaphragm Light Arm Stage Coarse Focus Fine Focus Base

• Place the Slide on the Microscope • Use Stage Clips • Click Nosepiece to the lowest (shortest) setting • Look into the Eyepiece • Use the Coarse Focus

• • Follow steps to focus using low power Click the nosepiece to the longest objective Do NOT use the Coarse Focusing Knob Use the Fine Focus Knob to bring the slide What can you find on your slide?

To calculate the power of magnification, multiply the power of the ocular lens by the power of the objective. What are the powers of magnification for each of the objectives we have on our microscopes? Fill in the table on your worksheet.

Comparing Powers of Magnification We can see better details with higher the powers of magnification, but we cannot see as much of the image. Which of these images would be viewed at a higher power of magnification?