Unit C: Topic 1

UNIT C TOPIC 1:

Microscope functions:

The base - supports the microscope

Ocular lens - magnifies the image produced by the objective lens

Objective lens - captures and refracts the light reflected from the specimen

Revolving nosepiece - holds two or more objective lenses which can be easily turned to switch between lenses

Light source - shines light on the specimen

Diaphragm - Controls how much light enters the microscope

Stage - where the specimen is placed for observation

Stage clips - holds the slides in place

Tube - supports the eyepiece and lenses

Calculations and Formulas:

Magnification formula - power of the objective lens (4x, 10x, 40x) and multiply by the eyepiece (usually 10x)

Field diameter formula - low power field diameter      =   medium power mag.

                                   medium power field diameter       low power mag.

Scale calculation formula - drawing diameter : field diameter

Estimate the size of specimens - field diameter

                    number of specimens that can fit along the diameter 

Mm and micrometer conversions - 1 mm = 1000 um (multiply mm by 1000)

Contrast: The ability to see the difference between two things based on how they absorb and reflect light.

Resolution: The ability to distinguish differences between images or specimens that appear very similar.

SEM and TEM microscopes:

SEM - 3D image, not a very high magnification, can view a large specimen

TEM - can see inside of cells, has extreme magnification, hard to make slides

Spontaneous generation:

SCIENTISTS

Redi - Claimed that spontaneous generation is false and it's is just from flies laying eggs

Needham - Disagree with Redi and started an experiment where he heated a flask of gravy to kill the bacteria and then sealed it. After a few days he noticed organisms forming in the gravy and he thought that he proved Redi wrong but there was a flaw within his experiment. Needham did not let the gravy come to a boil, therefor not all bacteria was killed

Spallanzani - Redid Needham's experiment. He did two experiments, one where he heated the gravy to a boil and left the top open, and the other he heated it to a boil and sealed it with a cork. The first experiment had a lot of living things and bacteria within it while the second one was completely normal and proved that Needham messed up his experiment

Louis Pasteur - Disproved the theory of spontaneous generation by creating an experiment. He did the same thing that Spallanzani did but instead he added a S shaped neck to the bottle. This neck allowed for fresh air to enter, but any microorganisms contained in the air would get stuck. With air entering the flask, no organisms were found in the broth but after they broke the neck off and after a few days, there were in fact microorganisms in the broth. This proved that the cause for mold or other organisms is caused by the bacteria in the air.

Development of cell theory:

1st. Janssens brothers - Invention of the compound microscope (20x)

2nd. Hooke - discovered plant cells and came up with the word ‘cell’

3rd. VanLeeuwenhoek - created the first microscope with 250x power

4th. Redi - proved that maggots were fly eggs and disapproved the spontaneous generation

5th. Needham - discovered bacteria and tried to prove redi wrong

6th. Spallanzani - proved that Needham has a flaw in his experiment

7th. Pasteur - Proved that organisms in the air are needed for other organisms to grow

8th. Brown - Identified the nucleus

9th. Schleiden -  Observed that all plants are made up of cells

10th. Schwaan - Observed that all animals are made up of cells

11th. Virchow - Observed that cells came from other cells (cell division)