MICROSCOPY

Question 1

What is a microscope?

Answer 1

An instrument which enables you to magnify an object hundreds, thousands, or even hundreds of thousands of times

Question 2

By making visible the individual cells which make multicellular organisms , microscopes allow us to do what?

Answer 2

Discover how details of their structures relate to their functions

Question 3

What was the first microscope developed?

Answer 3

Light microscopes (mid 19th century)

Question 4

What is cell theory?

Answer 4

It was first developed by the mid 19th century when scientists had access to microscopes with a high enough level of magnification to see individual cells

Question 5

What are the three rules of cell theory?

Answer 5

• both plant and animal tissue is composed of cells
• cells are the basic units of all life
• cells only develop from existing cells

Question 6

Why is light microscopy important?

Answer 6

• easily available
• relatively cheap
• observes living organisms as well as dead prepared specimens

Question 7

What is the importance of microscopes in the study of living organisms?

Answer 7

We are able to see how their structures relate to their functions in multicellular organisms

Question 8

Why was cell theory not fully developed before the mid-19th century?

Answer 8

Because previous microscopes had worse resolution and magnification

Question 9

What two lenses does a compound light microscope have?

Answer 9

2 lense objective lens near the specimen and an eyepiece lens through which the specimen is viewed

Objective lens produces a magnified image, which is magnified again by the eyepiece lens. This provides grater magnification and lower chromatic aberration than in a simple light microscope

Question 10

What is chromatic aberration?

Answer 10

An effect produced by the refraction of different wavelengths of light, failure to focus

Question 11

Light microscope advantages

Answer 11

• enable observation of living specimens
• easy to use
• relatively inexpensive
• can be easily transported

Question 12

Light microscope disadvantages

Answer 12

• limited resolution means most internal cellular structures cannot be seen

Question 13

What is magnification?

Answer 13

The number of times an image is enlarged compared ton actual object

Question 14

What is resolution?

Answer 14

The ability to distinguish between two separate objects/ points and therefore the ability to see detail

Question 15

What is the advantage of having two lenses?

Answer 15

• objective lens magnifies the specimen
• eyepiece lens magnifies image (from objective lens)
• higher magnification

Question 16

What do we need to think about when interpreting images?

Answer 16

Different planes of section will give different shapes

Question 17

Explain Dry Mount

Answer 17

Solid specimens can be used whole or cut into sections (sectioning)
Specimen is placed on the centre of slide & cover slip
Eg hair pollen dust = whole or muscle tissue or plants are sectioned

Question 18

What is a Wet Mount?

Answer 18

Specimens are suspended in a liquid (water/immersion oil)
Cover slip is placed at an angle eg aquatic animals

Question 19

Describe Squash Slides

Answer 19

Wet Mount is prepared first, then lens tissue is used to press down. Damage to the cover slip can be prevented by squashing the sample between two microscope slides.
Careful so that the cover slip isn’t broken when pressed eg root tip squashes for cell division

Question 20

Describe Smear Slides

Answer 20

Edge of slide used to smear sample
Thin even coating on another slide
Cover slip is placed over sample eg red blood cells