BIO 103 University of Maryland global campus chemistry worksheet

A cell is the smallest unit of a living thing. A living thing, like

you, is called an organism. Thus, cells are the basic building

blocks of all organisms.

In multicellular organisms, several cells of one particular kind

interconnect with each other and perform shared functions to

form tissues (for example, muscle tissue, connective tissue,

and nervous tissue); several tissues combine to form an organ

(for example, stomach, heart, or brain); and several organs

make up an organ system (such as the digestive system,

circulatory system, or nervous system). Several systems

functioning together form an organism (such as an elephant,

for example).

There are many types of cells, and all are grouped into one of

two broad categories: prokaryotic and eukaryotic. Animal cells,

plant cells, fungal cells, and protist cells are classified as

eukaryotic, whereas bacteria and archaea cells are classified

as prokaryotic.

Microscopy

A microscope is an instrument that magnifies an object.

Light Microscopes

The optics of the lenses of a light microscope changes the

orientation of the image.

Most student microscopes are classified as light microscopes

(Figure 2a). Visible light both passes through and is bent by

the lens system to enable the user to see the specimen.

A second type of microscope used in laboratories is the

dissecting microscope (Figure 2b). These microscopes have a

lower magnification (20 to 80 times the object size) than light

microscopes and can provide a three-dimensional view of the

specimen. Thick objects can be examined with many

components in focus at the same time. These microscopes are

designed to give a magnified and clear view of tissue structure

as well as the anatomy of the whole organism.

Electron Microscopes