Chapter 2: Biology As a Science

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

oExamples:

______

______

______

______

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 –

oObject is placed on a microscope slide and covered with a cover slip

oIt 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

oPhase contrast microscope

oDark field microscope

oNomarski 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

oCell 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

oSpecial 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