Sec. 4- Tools and Procedures

• Metric system-decimal system of measurement whose units are based on certain physical standards– Scaled on multiples of ten

Length Mass Volume Temperature

1 m= 100 cm 1 kg= 1000 g 1 L= 1000 mL 0 deg Cel= freezing pt of water

1 m= 1000 mm 1 g= 1000 mg 1 L= 1000 cm3 100 deg C= boiling pt of water

100 m= 1 km 1000 kg= 1 metric ton

Microscope• What is the most widely used tool in

biology?– Microscope

• What is a microscope used for?– View object too small to be seen with the

naked eye.• How does a microscope enlarge an object?

– By magnification with lenses• What is magnification?

– It is a microscope’s power to increase an object’s apparent size.

Light Microscope• This microscope uses a beam of light (sun or light

bulb) to pass through a series of lenses to produce an enlarged image.– Can use it on dead or alive organisms– Can magnify the object a 1000 times

• 2 lenses used in the light microscope– 1. Objective lens – closest to the specimen

being viewed. Usually 3 objectives.– 2. Eyepiece (ocular lens) – closest to the eye

• How is magnification figured in a microscope?– Eyepiece magnification X Objective

magnification

Electron Microscope• An electron microscope works by beam of

electrons being shot onto the specimen, which enlarges the object as an image.

• You cannot observe living organisms with this microscope.

• 2 main types of electron microscopes

– 1. Transmission electron microscope (TEM) – uses an extremely thin sliced specimen.

• It magnifies all the way up to 2 million times.

2. Scanning electron microscope (SEM) – scans the surface of an object through the use of an electron beam. The object is prepared by covering the object with a thin layer of gold and platinum spray. The image produce is a 3-D image.

• It magnifies the image 50,000 to 100,000 times.

• Copies can be printed off from the image.

• It costs between $30,000 – $80,000

Microscope Parts• 1. Field- area seen through the

eyepiece.• 2. Eyepiece or Ocular lens• 3. Course focus- used first when

focusing• 4. Fine focus- to fine focus the object.• 5. Low power- field is larges and least magnified.• 6. High power- field is smallest and

most magnified.

• 7. Diaphragm- regulates amount of light allowed in.

• 8. Objective- adjustable lenses.

• 9. Resolution- the clarity of the field.

• 10. Micron- microscope’s unit of measurement.

• Light Microscope is limited to about 1,000 X.