Chapter 2: Biology as a Science
2-2: Biology: The Study of Life
Biology: The Study of Life

Biology is the science that seeks to _____________________________________
________________________________________________

Biology advances by observing the world, asking questions, and forming
hypotheses that can be tested by experiment

A ___________________________________ is anyone who uses the scientific
method to study living things
Branches of Biology

Contains many branches, or divisions
o Examples:

______________________________________

______________________________________

______________________________________

______________________________________
Questions at the Molecular Level

Molecular biologists may study the basic ________________________________
________________ of life

Molecular geneticists investigate the workings of ________________, the
molecule that controls heredity and directs all the activities of the cell

Other researchers might study the effects of drugs on molecules in cells in order
to understand why entire organisms react to those drugs as they do
Questions at the Cellular Level

_________________________________________________ might study the way
normal cells become cancer cells when exposed to radiation or to the chemicals
found in cigarette smoke

Might try to explain how a single cell divides and changes to form all the cell
types in an adult organism

Other cell biologists might study how cells communicate with nearby cells
Questions at the Multicellular Level

Goes beyond ________________________________________________

Study changes in ___________________________________________________
Questions at the Population Level

Interested in _______________________________________________________
that make up populations and how these populations interact with their
environment
Questions at the Global Level

Takes a more worldwide view of biology and are concerned with organisms and
their environment on a _____________________________________

Biologists are both studying and trying to preserve the wonderful things that are
alive on planet Earth – not just for their own use, but for the use of those who will
live on this planet after us
Tools of a Biologist

Use a wide variety of tools
o ___________________________________________
o ________________________________
o ________________________________

To study small organisms, researchers have developed several kinds of
____________________________________

Microscopes are instruments that produce larger-than-life images, pictures,
or even videotapes
The Compound Light Microscope

Most commonly used microscope

Make it possible to observe many kinds of cells and small organisms while
_________________________________________________

To view –
o Object is placed on a microscope slide and covered with a cover slip
o It is then placed on the stage of the microscope so that light passes through
it into the lenses of the microscope

Lens at the bottom = ______________________________________

Lens at the top = ___________________________________

Because both lenses are used to form an image, it is properly known as a
____________________________________________________________
Limits of Resolution

There are limits to what can be seen with the compound light microscope

As the magnification is increased, more and more detail can be seen – up to a
certain point

Beyond this point, called the __________________________________________,
objects get blurry and detail is lost

For standard light microscopes, the limit of resolution is about
______________________________________
Using a Compound Light Microscope

Many specimens are ______________________________ before they are
observed under a microscope

Stains are used to color ______________________________________________
to make them clearly visible

Because many stains kill living cells, special types of light microscopes that do
not require staining are used to observe __________________________________
___________________________

Each uses a different property of light rays to improve the clarity of the image
o Phase contrast microscope
o Dark field microscope
o Nomarski microscope
Electron Microscopes

In the 1920s physicists in Germany realized that electromagnets could bend
streams of __________________________________

They used these electromagnets to build electron microscopes

The limit of resolution of electron microscopes is about _____________________
finer than the light microscope

________________________________________________________________ –
shine a beam of electrons at a sample and then magnify the image onto a
fluorescent screen and the bottom of the microscope

________________________________________________________________ –
beam of electrons scans back and forth across the surface of a specimen; electrons
that bounce off the specimen are picked up by detectors that provide the
information to form an image on a television screen
Limitations of Electron Microscopes

Extremely useful but do have serious drawbacks

Specimens must be placed inside a ___________________________ and cut into
very thin slices

Specimens must be completely ___________________________ before they are
placed in the vacuum

Living cells ____________________________________________________ in
the electron microscope – they are killed by the sample-preparation processes
Probe Microscopes

Developed in the ___________________

Do not use lenses to produce images

Trace the surfaces of a sample with a fine tip known as a probe

Have revolutionized the study of ______________________________ and have
even made it possible to observe ______________________________________

Specimens do NOT need to be placed in a vacuum
Laboratory Techniques of a Biologist

In addition to staining, the following techniques are also used in the laboratory
o _______________________________________
o _______________________________________
o _______________________________________
Centrifugation

Involves placing cells in a _____________________________ to break them
apart
o Cell fractionation

The broken bits of cells are then placed in a liquid in a tube

The tube is inserted into a centrifuge, which is a device that can spin the tube up
to ___________________________________________

While spinning, the cell parts begin to separate – with the heaviest parts setting
near the bottom of the tube

A scientist can then remove the specific part of the cell to be studied by selecting
the appropriate layer
Micromanipulation

Another technique to remove parts of a cell is called _______________________
______________________________, which is a form of micromanipulation
o Special tools that are so small they can be used only by looking through a
microscope are used to dissect, remove, insert, or otherwise manipulate
specific parts of a cell
Cell Cultures

Sometimes scientists want to study a particular kind of cell but to do so they need
__________________________________________________________________

To obtain a cell culture, a single cell is placed in a dish that contains the nutrients
the cell needs

The cell is allowed to _________________________________ so that in time an
entire population is grown from that single original cell