Laboratory Tools & Techniques

The Biology Laboratory•Scientific investigations are based on observations and measurements.

•Biologists use a wide variety of tools to aid in their investigations. Some include:–Microscopes –Thermometers–Scales

• Proper safety procedures are also essential in the laboratory at all times.

Early Discoveries in Biology• The invention of the microscope had an enormous influence on the development of biology as a science. • Anton van Leeuwenhoek, a Dutch lens maker, is considered the first person to have built a simple microscope. • With his invention, the first single-lens microscope, van Leeuwenhoek was able to magnify the image of tiny objects more than 270 times their normal size.

Anton van Leeuwenhoek

Early Discoveries in Biology

• In 1665, Robert Hooke, an English physicist, made a compound light microscope using two lenses.

• With this device, he observed the inside structure of a thin piece of cork and called the spaces he saw "cells."

Early Discoveries in Biology

In the 1800s, scientists in other countries used microscopes to learn much more about

cells.• Robert Brown in Scotland discovered

the central structure in plant cells: the nucleus.

• Two German researchers, Matthias Schleiden (studying plants) and Theodor Schwann (studying animals), concluded that the tissues of all living things are composed of cells.

• This is the basis for the cell theory.

Microscopes in the Laboratory Using a Microscope:• The compound light

microscope uses two lens types, the objective lens and the ocular lens (eyepiece) to magnify the image of a specimen.

• The magnified image seen through the objective lenses is further enlarged by the ocular lens.

• When viewing a specimen, one should begin with the low-power objective, first using the coarse-adjustment knob to focus and then the fine-adjustment knob.

• Further study of specimen details can then be done by using the high-power objective and the fine-adjustment knob only.

• The area seen while looking through a microscope is called the field of view. The actual diameter of the field being viewed decreases as you switch from low power to high power.

Parts of the Compound Light Microscope & Their Functions

Base – Supports microscopeArm – used to carry microscopeBody tube – holds objective lens & eyepieceStage – platform for slide (specimen) in which light passes

throughClips – holds slide in positionNosepiece – holds objective lensesCoarse adjustment - Larger knob used for rough-focusing with

low-power objectiveFine adjustment - Smaller knob used for focusing with the

high-power objectiveLamp or mirror - Directs light to the specimen (on the stage)Diaphragm - Controls the amount of light reaching the

specimenObjective lenses - Lenses mounted on the nosepieceOcular lens - Lens at the top of the body tube, or eyepiece

Microscopes in the Laboratory http://www.biology.ualberta.ca/facilities/multimedia/uploads/intro-biology/microscope.html

The wet mount technique is used to prepare a biological specimen for viewing under a microscope.

Many specimens, such as tissue samples or tiny organisms, need to be studied with a microscope by first preparing a wet mount and applying a stain.

Electron Microscopes• Many cell parts and

structures are not visible with a compound light microscope.

• University and professional laboratories use electron microscopes to magnify images more than 250,000 times.

Transmission Electron Microscope

Scanning Electron Microscope

Taking MeasurementsAs part of their scientific investigations, researchers take a variety of measurements.

One or more of the following factors may be measured while conducting an experiment: length, volume, temperature, and mass.

A centimeter ruler is used to measure length.

Graduated cylinders are used to measure the volume of a liquid; measurements arein milliliters (mL).

Some important readings on the Celsius and Fahrenheit

thermometers are shown for comparison.

FYI:Always read the volume of liquid at the bottom of the meniscus (not at the top of the curve)

Chemicals & Safety ProceduresOne of the most important things to do before you go to work in a lab is: Be prepared. Study the assigned investigation before you come to class. When in the laboratory, maintain a clean, open work area that is free of everything except those materials needed for the investigation.

Chemical Indicators and Reagents

Chemical Stains such as iodine and methyl blue are used in preparation of microscope slides.

Chemical indicators are used to test for the presence of certain substances.

Chemical Indicators and ReagentsLitmus paper is an indicator used to determine whether a solution is acidic or basic. Blue litmus turns red in an acid. Red litmus turns blue in a base.

pH paper has an indicator soaked into the paper that changes to one of many colors based upon the actual pH of the solution.

Bromthymol blue is an indicator that turns a solution yellow in the presence of carbon dioxide.

Benedict solution tests for the presence of simple sugars. When heated, it turns from blue to yellow, green, or brick red, depending on the amount of sugar present.

Lugol solution, or iodine solution, tests for the presence of starch. In its presence, it turns from dark red to blue-black.

Biuret solution, which is colorless, turns violet in the presence of protein.

Handling Chemicals Safely• Do not handle

chemicals or equipment unless you are told by your teacher to do so.

• Never eat or drink in the laboratory.

• Read the label on every container before you use it.

• Wear protective clothing and keep chemical stains off counters and other materials.

• Tie back long hair and remove all dangling jewelry.

• Wear safety goggles!

Other Laboratory Procedures• Chromatography is a

method used for separating and analyzing mixtures of complex chemical substances.

• The mixture to be separated is placed on a material such as chromatography or filter paper.

• A solvent is added, which begins to move through the material.

• Different substances in the mixture will move along with the solvent at different rates, causing them to be separated and allowing them to be studied.

• The resulting pattern of bands shows the different substances that were originally mixed together.

Gel electrophoresis is used to separate molecules that have

different charges; the smaller DNA fragments move farthest from the

wells.

• Electrophoresis is a technique used to separate molecules that have different electrical charges.

• An electric current is run through a material, usually a gel, in which the mixture has been placed.

• Different substances move at different rates in the electrical field.

Centrifugation• Centrifugation is the method used to separate materials of different densities from one another.

• The original liquid mixture is placed in a test tube, which is spun around in a centrifuge.

• The heaviest particles settle to the bottom; the least-dense material forms a layer on the top.

Putting it all Together• Observations and data collected during scientific research needs to analyzed to see what they mean.•The data may be organized and represented in a variety of ways.•When the data is finally interpreted, the results may be that the hypothesis was correct,•Or•It can lead to a revision of the original explanation, the development of a new hypothesis, and the design of a new experiment!