CHAPTER 2

Section 2

EARLY MICROSCOPES

1500s – 1st microscope was made

Mid 1600s – Antonie van Leeuwenhoek Made a simple microscope with a tiny glass bead

for a lens

Could magnify objects 270 times

The object was 270 times larger than its actual size

MODERN MICROSCOPES

Depending on how many lenses a microscope contains it is called simple or compound

Simple: like a magnifying lens – it has only one lens

The image is enlarged and directs light toward your eye

The change in size of the object is the magnification

Not all microscopes have the same magnification

MODERN MICROSCOPES The microscope most commonly used in life

science is the compound microscope

Compound microscope: 2 sets of lenses Eyepiece lens Objective lens

Eyepiece lenses – can be one or two of these Two eyepieces: the object is 3-D

One eyepiece: The object is not 3-D

Objective lens Typically 2-4 moveable objective lenses with different

magnifications

MAGNIFICATION

Two pieces of information needed to determine magnification

1st determine the magnification of the eyepiece – typically 10x magnification

Objective lenses – the magnification will be on the lens Example 10x

Total magnification: (10) x (10) 100x magnification

ELECTRON MICROSCOPE

If the object is too small to be seen with a light or compound microscope then an electron microscope must be used Instead of using lenses, a magnetic field in a

vacuum is used to direct a beam of electrons

Types of electron microscopes1. Scanning electron microscope

Produce a 3-D image

2. Transmission electron microscope Produce a 2-D image of a thinly sliced specimen

CELL THEORY

Cells were not discovered until the microscope was improved

1665 – Robert Hooke cut a thin slice of a cork and called the small boxes he observed under the microscope cells

1830s – Matthias Schleiden used a microscope to study plants and concluded that they are made of cells

CELL THEORY

Theodor Schwann concluded that all animals are made of cells He combined his idea with Schleiden’s and they

concluded that all living things are made of cells

Rudolf Virchow hypothesized that all cells divide to form new cells Every cell comes from a cell that already existed

CELL THEORY

1. All organisms are made up of one or more cells

All organisms can be one cell or many cells like most plants and animals

2. The cell is the basic unit of organization in organisms

Even in complex organisms, the cell is the basic unit of structure and function

3. All cells come from cells Most cells can divide to form two new, identical

cells