C1.0 Flashcards
what did Robert Hooke do?
improved on the Janssen’s design by:
1) adding a third lens
2) adding a light to illuminate the objects
what did Antoni van Leeuwenhoek do?
first person to discover the movement of living single-called organisms
microscope only had a single lens (simple microscope)
high quality lenses which allowed him to magnify objects up to 250X
what is magnification?
how many times larger the image is compared to the original
what is field of view?
the area that can be seen through the microscope with a particular objective lens
what is scale?
a comparison between the size of a drawing and the actual size of the object
what did galileo do?
imprisoned in 1630’s by the Catholic Church for claiming that the earth revolved around the sun
what is spontaneous generation?
the belief that living things can emerge from non living matter
Francisco Redi
Set up an experiment to illustrate that maggots did not grow spontaneously out of raw meat.
he set out two flasks:
1) one with access to air
2) one without access to air
only the flask open to air ( & flies ) had evidence of maggots
• proved that air was a necessary ingredient in life force
John Needham
boiled chicken broth ( to kill bacteria ) & put it in a sealed flask. found that microorganisms still appeared
* likely because broth wasn’t heated for long enough or at a high enough temperature
Lazzaro Spallanzani
repeated Needham’s experiment, but in a vacuum. which removed all of the air from the flask. no microorganisms appeared
• only proved that air was an ingredient in life force
Louis Pasteur
his experiment was finally the decisive proof the scientific community needed to reject spontaneous generation once & for all.
he heated them both to sterilize them
the flasks had bent necks so they were open to air but protected from dust
I’m experiment 1 : Pasteur broke off the neck of the flask giving it access to air
In experiment 2 : he left the neck intact
overtime, microorganisms appeared in flask 1 but not flask 2
• this proved that microorganisms are not generated but the broth, but rather carried in the air & simply too small to see
what did the Janssen brothers do?
Hans & Zacharias
invented the first miscroscope (1595)
considered to be a compound microscope because it used more than one lens
what is a manipulated variable?
the variable that is altered between trials
what is the responding variable?
the results of the changes made
what is the controlled variables?
all the things that could have been changed, but were deliberately kept constant
Robert brown
identified the nucleus of the cell as being responsible for controlling cell function
Schleiden & Schwann
proposed that all plants and animals are composed of cells.
described cells as the basic unit of life for all organisms
Rudolf Virchow
theorized that all cells arise only from pre-existing cells
Summary of cell theory
- all living things are made up of one or more cells and the materials produced by these cells
- all life functions take place in cells, making them the smallest unit of life
- all cells are produced from pre-existing cells through the process of cell division also called mitosis
what are the factors affecting the quality of an image in microscopy?
- magnification
- contrast ( variation of shadow & colour )
- resolution ( ability to distinguish between two structures that are very close together )
fluorescent microscopy
- fluorescent stains called GFP ( green fluorescent protein ) are introduced to the specimen
- specimen is subjected to UV light
- depending on the type of dye, the cell glows either yellow, orange or green
- allows for observation of living specimens
types of microscopy
- brightfield microscopes
- confocal technology
- electron microscopy
- transmission electron microscope
- scanning electron microscope
Brightfield microscopes
- light passes through the specimen
- fixing and staining process kills the specimen
- you can’t view living tissues
- limited resolution
- you can’t get any higher resolution than 0.2 µm
Confocal technology
- uses lasers and computers to focus the light
- you see a thin section with a high resolution
- Computer software can be used to build up a 3-D image
- fluorescent stains work better with confocal microscopes because they eliminate the blurriness of the reflected light
Electron microscopy
- uses a fine beam of electrons instead of light
- The electrons pass through different materials at different rates due to differences in density
- instead of lenses, EM’s use magnetic fields to focus the image
transmission electron microscope
- electrons pass through the specimen
- difficult to produce 3D images
- specimens are fixed and stained so living specimens cannot be observed
scanning electron microscope
- good for observing surface features of specimens
- the specimens is fixed and coated in gold
- produce a 3D image
- uses computer to move the specimen and view it from different angles
- permit the use of live material
gene mapping
decoding of a species’ genome ( which refers to all the info contained within its DNA )
also allows us to create new varieties of plants
what are hormones?
they are chemicals produced in one part of your body that act on a different part
what are receptors?
on the surface of cells allow transmitters to attach to the cell and carry out their function
