Lesson 3: Tools Used in Biology
Video Lesson:
Lesson Objective:
At the end of this section, the student will be able to:
- identify the major tools of biologists
- describe the functions of the identified biologist tools
Biologists use various tools in the laboratory and field for scientific investigations. These tools are essential for measuring, observing, and culturing microorganisms. Here’s an overview of some of the primary tools used by biologists:
Laboratory Tools of Biologist
1.Hand Lens
A hand lens, also known as a magnifying glass, provides higher magnification than the naked eye. It consists of a convex lens fixed within a circular metallic loop and is attached to a handle. The main function of a hand lens is to provide an enlarged image of the object placed under it. However, it is not sufficient to observe the detailed structure of cells, for which microscopes are needed.
2. Microscope
One of the most important tools for biologists, a microscope magnifies small objects, making them visible to the human eye. It is used to observe the shape of bacteria, fungi, parasites, and other microorganisms. There are several types of microscopes:
- Light Microscope: Uses a beam of light to view specimens. There are two main types:
- Simple Light Microscope: Consists of a single lens.
- Compound Light Microscope: Consists of two or more glass lenses and can magnify the image of an object up to 2000x. A compound light microscope with a single eyepiece is called monocular, while one with two eyepieces is called binocular.
- Electron Microscope: Uses a beam of electrons and electromagnets to magnify the image of an object. It provides higher magnification than light microscopes, making it possible to observe extremely small microorganisms such as viruses. Types of Electron Microscopes:
- Transmission Electron Microscope (TEM): Provides high-resolution images of the internal structure of specimens
- Scanning Electron Microscope (SEM): Produces detailed 3D images of the surface of specimens.
The parts and function of the light microscope
Eyepiece (Ocular Lens) The eyepiece is the part at the top of the microscope that you look through. It is also called the ocular. The standard magnification is 10x, but eyepieces with magnifications ranging from 5x to 30x are available.
Objective Lenses
Objective lenses are the primary lenses that provide the initial magnification of the specimen. They come in a range of magnifications, typically from 4x to 100x, allowing for various levels of detail to be observed. These lenses are mounted on a rotating nosepiece, enabling the user to easily switch between different magnifications depending on the requirements of the observation.
Types and Functions the Objective Lenses
- Scanning Objective (4x): The lowest magnification lens, ideal for getting an overview of the specimen and locating areas of interest. It provides a wide field of view, making it easier to find and center the sample.
- Low Power Objective (10x): This lens is used for a more detailed view of the specimen, often employed for examining larger structures and getting a closer look at areas identified with the scanning objective.
- High Power Objective (40x): Provides a much higher level of detail, suitable for examining the fine details of the specimen’s structure. This lens is used for detailed observations of cells, tissues, and microorganisms.
- Oil Immersion Objective (100x): The highest magnification lens, often used with a special oil to increase resolution by reducing light refraction. This lens is crucial for observing very small structures such as bacteria and fine cellular details.
Arm The arm connects all the components of the microscope and provides support, ensuring the microscope can be used properly. It also serves as a handle for carrying the microscope.
Body Tube The body tube connects the eyepiece to the objective lenses, ensuring proper alignment of the optical components.
Nosepiece The nosepiece is a rotating mount that holds multiple objective lenses. It allows you to change the magnification by rotating different objective lenses into position.
Adjustment Knobs The adjustment knobs are used to focus the microscope. There are two types: fine adjustment knobs and coarse adjustment knobs.
- Fine Adjustment Knob: Regulates the distance between the specimen and the objective lens to achieve sharp focus. It moves the stage minimally for precise focusing.
- Coarse Adjustment Knob: Brings the specimen into general focus by moving the stage more significantly. It is used to quickly capture the approximate focus.
Stage The stage is the platform where the specimen slide is placed for viewing. It often has clips to hold the slide in place.
Stage Clips Stage clips secure the specimen slide on the stage, preventing it from moving accidentally.
Aperture The aperture is a hole in the microscope stage through which light from the illuminator passes to reach the specimen.
Microscopic Illuminator The illuminator is the light source located at the base of the microscope. It provides illumination instead of a mirror, capturing light from an external source, typically at a low voltage of around 100V.
Condensers Condensers are lenses located under the stage that collect and focus light from the illuminator onto the specimen. They ensure clear, sharp images, especially at high magnifications of 400x and above.
Diaphragm (Iris) The diaphragm, also known as the iris, is found under the stage and controls the amount of light that reaches the specimen. It is adjustable, allowing you to regulate light intensity and the size of the light beam.
Base The base is the bottom part of the microscope. It supports the entire microscope and houses the illuminator.
The important function of microscope is magnification and resolution.
- Magnification is the number of times larger an image is, than the real size of the object.
- Resolution can be defined as the ability to distinguish between two separate points.
Figure 3.4.: Electron Microscope
Most microscopes have multiple powerful lenses that allow viewers to inspect specimens at magnifications exceeding 100 times their actual size. Modern biology would not exist without the microscope, and these instruments are indispensable for the daily work of most biologists. Due to their importance and high cost, it is crucial to understand the functions of all microscope components and handle the device properly before using it in the laboratory.
When observing a specimen under a light microscope, light rays are focused onto the specimen placed on a microscope slide. This light, transmitted through the specimen, is then focused by two sets of lenses: the eyepiece (ocular) lens and the objective lenses. The image is enlarged by both sets of lenses. The total magnification of a compound light microscope is the product of the magnifications of the eyepiece and the objective lens. For example, with a 10x eyepiece and a 40x objective lens, the total magnification is 400x.
Total magnification=Magnification power of eyepiece lens×Magnification power of objective lens
| Eye lens magnification | Objective lens magnification | Total lens magnification |
| X5 | X4 | X20 |
| X10 | X10 | X100 |
| X15 | X40 | X600 |
Handling and using a light microscope
Using a light microscope requires careful handling to ensure accurate observations and maintain the instrument’s longevity. By following proper procedures for both usage and storage, you can enhance your microscopy experience while preserving the microscope’s functionality. Below are essential guidelines for handling and using a light microscope effectively:
- Handling the Microscope: Start by carefully removing the microscope from its storage cabinet, ensuring a firm grip on the arm and supporting its base to prevent any mishandling.
- Preparing the Slide: Before placing the slide on the stage, ensure it is clean and dry. Position the slide so that the area of interest is centered over the stage hole for optimal viewing.
- Focusing and Magnification: Begin focusing on low power (4X objective) to locate your specimen, then adjust to higher magnifications as needed. Use the coarse and fine-focusing knobs for precise clarity.
- Using Immersion Oil: Utilize immersion oil exclusively with the 100X objective (oil immersion lens), applying a single drop and focusing by moving the lens and specimen apart.
- Lens Care and Maintenance: Always avoid touching the lens surfaces with fingers or any object to prevent damage or contamination.
- Cleaning and Storage: After use, clean the lenses using lens paper and alcohol. Ensure the microscope is stored correctly with the 4X objective over the stage, the stage lowered, and the light turned off. Return the microscope to its designated cabinet, placing the oculars towards the back and properly wrapping the cord for storage.
By adhering to these guidelines, you can effectively handle and use a light microscope while maintaining its optimal performance and lifespan.
Glass slides and cover slips:
Microscope Slides:
These are rectangular, flat glass pieces that act as a platform for specimens being examined under the microscope. They come in standard sizes (typically 25 x 75 mm) and thicknesses (1-1.2 mm) and can be frosted or plain. Frosted slides allow for labeling with a pencil or marker.
Usage:
- A small drop of the specimen is placed on the slide.
- The specimen may need to be stained to highlight specific structures.
Cover Slips:
These are small, thin glass sheets (usually 20 x 20 mm or 22 x 22 mm) placed over the specimen on the microscope slide. Cover slips serve multiple purposes:
- Protection: They shield the specimen from contamination, dust, and physical damage.
- Moisture Retention: By sealing the specimen, they prevent it from drying out during observation.
- Enhanced Viewing: They flatten the specimen, allowing for clearer and more detailed observation under the microscope. The even surface ensures uniform thickness, improving focus and image quality.
- Support for Staining: When staining, cover slips help to evenly distribute the stain and minimize evaporation, ensuring consistent results.
Preparation:
- Place a small drop of the specimen on the slide.
- Gently lower the cover slip at an angle to avoid air bubbles, which can interfere with viewing.
Types of Cover Slips:
- Square and Circular: Available in various sizes to accommodate different specimen types and slide sizes.
- Plastic vs. Glass: While glass cover slips are more commonly used for their clarity and durability, plastic cover slips are sometimes preferred for specific applications, such as when using certain staining techniques or with delicate specimens.
Autoclave:
Autoclave: is the equipment used to sterilize (kill micro-organisms) different biological samples. An autoclave sterilizes contaminated materials including culture media, and bacterial spores by exposing them to high temperatures and highly pressurized steam.
An autoclave is a critical tool for sterilization in any biological laboratory. It uses a combination of high pressure and steam to effectively kill all microorganisms, including bacteria, viruses, fungi, and spores.
The process involves placing items to be sterilized inside the autoclave chamber, sealing it, and then raising the temperature to about 121 degrees Celsius at a pressure of around 15 pounds per square inch for a designated period, usually about 15-20 minutes. This ensures that all potentially harmful microorganisms are destroyed, providing a clean and safe environment for your biological samples, culture media, and equipment.
Autoclaves come in various sizes, from small bench-top models to large, industrial-sized units.
Culturing is the procedure used to grow microorganisms in a controlled environment. Many microorganisms reproduce very quickly. Culturing of micro-organisms also have important function like in medicine (Penicillin) and for food (beverage) preparation. Wine and beer making uses culturing on a large scale, as it does in cheese making, bio-fuel production, and many other endeavors.
There are many ways of killing microorganisms, including chemical disinfectants, flame, dry or wet heat, ultraviolet light, and ionizing radiation such as X-rays or gamma rays. The problem is, some bacteria form spores, which are resistant to chemical disinfectants, including bleach. In these situations, it is very important to use autoclaving which kill microorganisms as well as their spores.
Incubator
Incubators are essential for cultivating microorganisms, cells, and tissues. They maintain a controlled environment with precise temperature, humidity, and CO2 levels to support optimal growth conditions. For instance, a typical incubator for bacterial cultures might be set at 37 degrees Celsius, mimicking the human body temperature to encourage bacterial growth.
Some advanced models also feature shaking capabilities to keep cultures well-mixed, and programmable settings to simulate different environmental conditions. Incubators are used in various applications, including microbial culture, cell culture, and even hatching eggs in research involving embryology.
Petri dishes
Petri dishes are shallow, cylindrical glass or plastic dishes with lids that are widely used to culture microorganisms. They are usually filled with agar, a gelatinous substance derived from seaweed that provides nutrients and a solid surface for microorganisms to grow on. To prepare a Petri dish, you pour liquid agar into the dish and let it solidify. Once solid, you can inoculate the surface with microorganisms using a sterile technique. Petri dishes are crucial for isolating and identifying microbial species, testing antibiotic sensitivity, and conducting various microbiological experiments.
Culture tubes
Culture tubes, also known as test tubes, are cylindrical glass or plastic tubes used to grow and maintain microbial cultures in both liquid (broth) and solid (agar) media. They come in various sizes and can be sealed with caps to prevent contamination. Before use, culture tubes are sterilized, typically in an autoclave, to ensure no unwanted microorganisms interfere with your experiments. In a laboratory setting, these tubes are used for tasks such as culturing bacteria, yeast, or other microorganisms, as well as for storing small samples.
Flasks:
Flasks are versatile glass containers with a flat bottom and a narrow neck, making them ideal for mixing solutions and growing microorganisms. There are several types of flasks used in biology labs:
- Erlenmeyer Flasks: These have a conical shape and are great for mixing by swirling without spilling.
- Volumetric Flasks: Used for precise measurement of liquid volumes.
- Florence Flasks: Also known as boiling flasks, these have a round body and long neck, suitable for boiling liquids.
Flasks are essential for preparing culture media, storing solutions, and conducting chemical reactions.
Balance
A balance, or scale, is used to measure the mass of substances accurately. There are two main types of balances used in labs:
- Analytical Balances: Highly precise, capable of measuring very small masses with a high degree of accuracy, often down to micrograms.
- Top-loading Balances: Less precise but suitable for larger masses.
Balances are crucial for preparing accurate solutions and reagents, ensuring experimental consistency and reliability.
Dropper:
Droppers, also known as pipettes or eye droppers, consist of a glass or plastic tube with a small opening at one end and a rubber bulb at the other. They are used to add liquids in very small, controlled amounts, which is essential for tasks requiring precise measurement and transfer of reagents or samples.
Tongs
Laboratory tongs are used to handle hot or hazardous materials safely. They come in various shapes and sizes to handle different types of equipment, such as beakers, flasks, and crucibles, without direct contact, thereby protecting you from burns or contamination.
Dissecting Tool Kit
A dissecting tool kit contains various instruments needed for dissection and examination of specimens. Typical tools include:
- Scalpel: For making precise cuts.
- Forceps: For holding and manipulating tissues.
- Scissors: For cutting through tougher tissues.
- Pins: For holding the specimen in place.
These tools allow for detailed study of the internal structures of organisms, helping you understand their anatomy and function.
Dissecting pan
A dissecting pan, often lined with a wax or rubber surface, holds specimens securely during dissection. It provides a stable, clean, and organized area to work on, ensuring that the specimen stays in place and is easy to manipulate.
Crucible
Crucibles are small containers made of ceramic or metal that can withstand extremely high temperatures. They are used to heat, melt, or burn substances in various chemical reactions. Crucibles are essential for tasks like ashing samples, which involves burning organic material to leave a residue of inorganic ash for further analysis.
Beaker
Beakers are cylindrical glass or plastic containers used for stirring, mixing, and heating liquids. They come in various sizes, typically with graduations for approximate measurement. Beakers are versatile and used in numerous laboratory procedures, from simple mixing to complex titrations.
Hotplate
A hotplate provides a controlled source of heat for heating solutions, preparing agar culture media, or conducting chemical reactions. Many hotplates also have magnetic stirrer capabilities, which can help keep solutions well-mixed while they are being heated.
PH Meter
A pH meter is an electronic device that measures the acidity or basicity (pH) of a substance, providing a numerical value. It consists of a probe that you immerse in the solution, and a digital display shows the pH reading. pH meters are essential for ensuring that experimental conditions are within the desired pH range.
Thermometer
Thermometers measure the temperature of substances, ensuring that experimental conditions are maintained accurately. They come in various types, including digital, mercury, and alcohol thermometers, each suitable for different temperature ranges and precision requirements.
Forceps
Forceps are tweezer-like instruments used to handle small objects or tissues delicately. They come in various shapes and sizes, such as:
- Straight Forceps: For general use.
- Curved Forceps: For accessing hard-to-reach areas.
- Fine-tip Forceps: For delicate manipulations.
Spatula
Spatulas are used for scraping, transferring, or applying powders and pastes. They come in various shapes and sizes to handle different substances and tasks in the lab.
Wash Bottles
Wash bottles are squeezable plastic containers with a spout, used to rinse glassware and other lab equipment. They are typically filled with distilled water or other cleaning solutions, allowing you to control the flow and pressure by squeezing the bottle.
Bunsen burner or alcohol burner
A Bunsen burner is a small gas burner used to heat substances during laboratory experiments. It produces a single, open flame that can be adjusted to different temperatures, making it ideal for sterilizing equipment, heating chemicals, and performing flame tests.
Field Tools
In addition to laboratory tools, biologists frequently rely on field tools to study organisms in their natural habitats. These tools are designed to facilitate the collection, observation, and analysis of specimens in the field, providing invaluable data for ecological and environmental research. Field tools must be portable, durable, and efficient to support the diverse and dynamic nature of fieldwork. Here, we’ll explore some of the primary tools used by biologists in the field.
Insect Nets Insect nets are specialized tools for collecting insects. They consist of a net bag made from cloth or fine mesh, which is attached to a circular wire loop. This loop is then secured to a wooden or metal pole, providing a handle for ease of use. Insect nets are designed to be lightweight and maneuverable, allowing you to catch insects without harming them. They are ideal for field studies and ecological research, enabling the capture and study of various insect species in their natural environments.
Fishing Nets Fishing nets are essential tools for catching fish and other aquatic organisms. These nets are constructed from fibers woven into a grid-like structure, forming a mesh. Fishing nets come in various forms, including those designed to trap fish, known as fish traps. The mesh size and type of thread used can vary depending on the target species and fishing method. Fishing nets are versatile and can be used in both freshwater and marine environments, playing a crucial role in the study and management of aquatic life. They help biologists monitor fish populations, study behavior, and collect samples for further analysis.
General Laboratory Safety Rules
Safety in the laboratory is crucial to prevent harm or danger. It involves recognizing and controlling hazards to maintain an acceptable level of risk. Before engaging in any laboratory activities, observe these essential safety rules:
- Work Carefully: Exercise caution during all laboratory procedures.
- Address Minor Issues: Address minor problems promptly to prevent them from escalating.
- Maintain Safety Awareness: Keep safety at the forefront of all activities.
Important General Laboratory Safety Rules:
- Follow Instructions: Familiarize yourself with the entire laboratory procedure before starting. Understand the use of all equipment.
- Know Safety Equipment Locations: Locate and be proficient in using safety equipment like fire extinguishers and first-aid kits. Regularly inspect and ensure their functionality. Familiarize yourself with laboratory safety signs.
- Proper Attire(Wear Personal Protective Equipment(PPE)): Wear protective clothing such as laboratory coats, safety goggles, gloves, hearing protection, long pants, and long-sleeved shirts. Use leather shoes or boots that fully cover your feet (no sandals). When handling toxic chemicals, wear a disposable respirator mask as appropriate for the experiment.
- No Eating or Drinking: Eating, drinking, or storing food and beverages is strictly prohibited in the laboratory, especially near experimental materials.
- Avoid Chemical Exposure: Never taste or smell chemicals. Label all containers properly and read labels before use to prevent accidents.
- Handle Chemicals Responsibly: Do not mix chemicals randomly. Improper mixing can lead to explosions, fires, or toxic gas releases.
- Clean and Dispose Properly: Begin and end each session by cleaning glassware, chemicals, and equipment. Dispose of waste materials according to laboratory guidelines.
- Chemical Handling: Wear appropriate protective gear when handling toxic chemicals. Prevent direct contact with skin.
- Emergency Procedures: Know how to respond to accidents, such as chemical spills or burns. Rinse burns with cold tap water immediately.
- Maintain Chemical Hygiene: Ensure all chemical containers are properly labeled and securely closed when not in use.
These guidelines and signs are essential for maintaining a safe laboratory environment, promoting both personal safety and effective scientific work