1. Unit C - Biology
Study of Life

2. Early microscopes & lenses
a better understanding of cells and the structure of living things came hand-in-hand with the development of microscope technology
before the 1500s, scientists could only observe what they could see with the naked eye

3. A little history on the microscope
Hans and Zacharias Janssen
Invented the microscope in 1595
2 lens system (ocular lens & objective lens)
Magnifying power of 20x
considered to be a compound microscope because it used more than one lens

4. Robert Hooke 1665 Improvement by adding:
a third lens (beam of light through a water filled flask)
A light to illuminate the objects

5. Robert Hooke
Hooke observed a cross-section of cork, which he thought was non-living
observing that it was full of empty air chambers, he called these tiny chambers “cells” (latin for: small compartment)
these chambers turned out to be the remnants of living cells

6. Antoni Van Leeuwenhoek
Leeuwenhoek’s microscope only had a single lens – called a simple microscope
the lenses were of much higher quality, and allowed him to magnify objects up to 250X
the first person to observe the movement of living single- celled organisms (such as bacteria, sperm, unicellular protozoa etc)

7. Labeling the Microscope
Eyepiece
Body tube
Coarse adjustment knob
Fine adjustment knob
Revolving Nosepiece
Arm
Objective lenses
Stage
Stage clips
Base
Diaphragm
Light Source

8. Use your textbook to define the function of the microscope parts
Eyepiece or Ocular
Coarse adjustment knob
Fine adjustment knob
Revolving nosepiece
Objective lenses
Stage
Stage clips
Diaphragm
Lamp or Mirror
Arm
Base

9. How to focus a microscope
Ensure that the low power lens is in position
Watch from the side as you use the coarse adjustment knob to lower the lens until it is as close as possible to the stage.
Look through the eyepiece while using the coarse adjustment knob to move the lens upward
Once the image appears almost sharp, use the fine adjustment knob to finish focusing

10. High Power focusing
Move the objective upward with the coarse adjustment knob enough to revolve the high power objective lens into position.
Watch from the side as you lower it close to the slide
Use only the fine adjustment knob to fine tune the focusing

11. Skills in microscopy Magnification:
how many times larger the image is compared to the original
magnification = (power of the objective lens) x (power of the eyepiece)
eyepiece lens – always 10X
objective lens
low power: 4X
medium power: 10X
high power: 40X

12. Magnification – practice problems
What is the magnification of a microscope with a 10X ocular (eyepiece) lens, and a 10X objective lens?
magnification = (10X)(10X) = 100X
How much more powerful is the magnification on high power compared to low power?
magnification high = (10X)(40X) = 400X
magnification low = (10X)(4X) = 40X
the high powered magnification is 10 times more powerful

13. Field of view
the area that can be seen through the microscope with a particular objective lens
field of view can be described in terms of field diametre or field area
when the lens power increases, field of view decreases

14. Field of view
the field diameter on low power can be measured by placing a ruler under the microscope
the field diameter on high power can be calculated using this formula:
high-power field diameter = low-power magnification
low-power field diameter high-power magnification

15. Field of view – practice problems
The image to the right is the view through low power. What is the field diameter of this microscope?
29 mm
What is the field diameter on high power?
2.9mm
How many times smaller is the field diameter on high power as on low power?
one tenth

16. Scale
a comparison between the size of a drawing and the actual size of the object
to calculate it, compare the diameter of the circle in the drawing with the diameter of the field of view you calculated previously
e.g. a drawing with a diameter of 90mm done from low power would roughly have a scale of 90mm:29mm or 3:1.

17. Actual size
once you know the field diameter, you can estimate an object’s size by noting how much of the field of view it occupies
this can be done by estimating how many times across the object would fit
e.g. if it would fit 10 times across, it takes up 1/10th of the field of view
e.g. if the field of view is 29mm and a cell takes up about 1/3 of the field of view, it’s actual size is about 10mm

18. Actual size – practice problem
our field of view on high power was found to be 2.9mm. What is the actual size of this cell, as viewed under high power?
(2.9mm)(1/2)=1.45mm
what is its size in micrometers? (hint: 1 mm = µm)
1.45mm = 1450 µm

19. Distance Units x1012 x109 x106 x103 x102 x101 pm nm µm mm cm dm m
centi
meter
nano
milli
micro
pico
deci
x1012
x109
x106
x103
x102
x101
x100 pm nm µm mm cm dm m

20. Microscope Lab

22. C1.2 Development of cell theory
Brain cells of a rat.

23. When science contradicts belief:
sometimes, despite scientific evidence to the contrary, people find it hard to accept new ideas
as a result, scientific advancement is sometimes slowed
Galileo
imprisoned in 1630s by the Catholic Church for claiming that the Earth revolved around the Sun
the Church took exception to this idea because they believed that since God created man, he should be at the centre of the Universe
despite being correct, Galileo was forced to recount his findings and spent his last years on house arrest
October 31, 1992 – Pope John Paul II issued a papal pardon, 350 years after Galileo’s death

24. Spontaneous Generation
another idea that was believed for hundreds of years despite scientific evidence to the contrary
spontaneous generation is the belief that living things can emerge from non-living matter
widely accepted until the 19th century
people believed there was a life force that caused non-living things to “birth” living things

26. Spontaneous Generation
To the left we have two photos
the first is the imprint of a fossilized plant in a rock
the second is a moldy sandwich
How do we explain these two photos?
the plant:
trapped between the rock and the layers of dirt and sediment above it
as it decomposed, it wore out a pattern in the rock
the sandwich:
microscopic spores of fungus landed on the bread
over time, the fungus spread across the surface of the bread, giving it the moldy appearance

27. Spontaneous Generation
prior to the 19th century, people would have explained these two situations differently
the plant:
they would assume the plant had grown out of the rock
the sandwich:
the sandwich, a non-living thing, would give the mold a life force, allowing it to grow

28. Francisco Redi
set up an experiment to illustrate that maggots, (a living thing) did not grow spontaneously out of raw meat (a non- living thing)
set out two flasks
one with access to air
one without access to air
only the flask open to air (and flies) had evidence of maggots
Redi thought this disproved spontaneous generation, but other scientists said it proved that air was a necessary ingredient in life force

29. John Needham
performed another experiment, and claimed that it proved the existence of life forces
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

30. Lazzaro Spallanzani repeated Needham’s experiment, but in a vacuum
this removed all the air from the flask before it was sealed
no microorganisms appeared
despite this evidence, Needham still maintained this only proved air was an ingredient in life force

31. Louis Pasteur
his experiment in 1864 was finally the decisive proof the scientific community needed to reject spontaneous generation once and for all

32. Louis Pasteur Pasteur set up two flasks, each with the same meat broth
he heated them both to sterilize them and remove the bacteria
the flasks he used had bent necks, so that they were open to the air but protected from dust
initially, neither broth became cloudy with microbial growth

33. In experiment 1, Pasteur broke off the neck of the flask, giving it access to air
In experiment 2, he left the neck intact

34. dust now had access to flask 1, while it got trapped in the neck of flask 2
over time, microorganisms appeared in flask 1, but not in flask 2
this proved that microorganisms are not generated by the broth, but rather carried in the air, and simply too small to see

35. Experimental variables
whenever performing an experiment, a scientist must decided what he or she is testing for
some variables will change from trial to trial, and the results analyzed
some variables will stay the same so the scientist knows that these variables are not the cause of any differences between trials

36. Manipulated variable the variable that is altered between trials
in Pasteur’s experiment, the manipulated variable was whether the flask’s neck was broken or left intact

37. Responding variable
the responding variable is the results of the changes made
in Pasteur’s experiment, the responding variable was the presence of microbial growth

38. Controlled variables
the controls are all the things that could have been changed, but were deliberately kept constant
in Pasteur’s experiment, the controls were:
the temperature and duration of heating
the shape and size of flasks before they were broken
the type of broth
the amount of broth
etc.

39. Variables - Practice problems
In each of the experiments described below, identify the manipulated, responding, and at least two controlled variables:
a science student wants to know if the amount of water given to a plant affects how tall it will grow
a pharmaceutical company wants to know if a new drug is effective in treating migraines
a car company wants to know if the type of brake pads in a car affects stopping distance

40. Robert Brown
with improvements in lens technology came a new understanding of the cell
in 1833, identified the nucleus of the cell as being responsible for controlling cell function

41. Schleiden & Schwann made observations on plant and animal cells
together, proposed that all plant and animals are composed of cells
described cells as the basic unit of life for all organisms

42. Rudolf Virchow Expanded on Schleiden and Schwann’s theories on cells
theorized that all cells arise only from pre-existing cells

43. Summary of cell theory The three points of cell theory are:
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

44. Development in Imaging Technology & Staining
1.3 – 1.4

45. The quality of the image
Three factors affect the quality of an image in microscopy:
magnification
contrast
resolution
Skin cells of a frog

46. Magnification improved with advancements in lens-making
light microscopes used in labs today can now magnify between X

47. Contrast refers to the variation of shadow and colour
it is contrast that allows the human eye to focus on different aspects of the image and to register depth
cells by themselves are mostly colourless
image quality has improved with:
new stains and staining techniques
new methods of illuminating the specimen

48. Contrast a cell with low contrast a cell with high contrast
a cell with phase contrast illumination

50. Resolution
the ability to distinguish between two structures that are very close together
the human eye is capable of resolving objects that are 0.1mm or larger
the higher the resolution of a microscope, the more clearly you can see the magnified image
similar to the resolution capabilities of a digital camera

51. Resolution
the picture on the left has low resolution, and appears pixelated
the picture on the right has a higher resolution and is therefore a clearer image

52. Fluorescent microscopy
fluorescent stains called GFP (green fluorescent protein) are introduced to the specimen
different cell structures absorb stains in different amounts
the specimen is subjected to UV light
depending on the type of dye, the cell glows either yellow, orange or green
unlike conventional staining, GFP does not kill the cell, and allows for observation of living specimens

53. Brightfield microscopes
light passes through the specimen
fixing and staining process kills the specimen
you can’t view living tissues
limited resoloution
you can’t get any higher resolution than 0.2µm

54. Confocal technology uses lasers and computers to focus the light
the later reflects off the object and back to the eyepiece
you see a thin section with high resolution
computer software can be used to build up a 3D image
fluorescent stains work better with confocal microscopes because they eliminate the blurriness of the reflected light

55. Confocal technology
traditional optical microscope
confocal microscope

56. 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, EMs use magnetic fields to focus the image
Canadian invention

57. Transmission Electron Microscope (TEM)
electrons pass through the specimen
100X better magnification and resolution than light microscope
difficult to produce 3D images
specimens are fixed and stained, so living specimens cannot be observed

58. Scanning Electron Microscope (SEM)
good for observing surface features of specimens
the specimen is fixed, and coated in gold
the electrons reflect off the gold and produce a 3D image
2X better image quality than the TEM
uses computes to move the specimen and view it from different angles
new SEMs permit the use of live material

59. Eye of a Fruit Fly

60. Pollen

61. Salt

62. Gene mapping
with new imaging techniques comes new possibilities for research at the cellular level
gene mapping refers to decoding of a species’ genome
an organism’s genome refers to all the information contained within its DNA
in 2001, the Human Genome Project published a complete map of the entire human genome

63. Gene mapping
could help us understand where cancer and other diseases come from and how to treat them more effectively
also allows us to create new varieties of plants
ethical arguments arise about the dangers of genetically modified food

64. Cell communication
cells are open systems, meaning they must interact with their environment to survive
hormones are chemicals produced in one part of your body that act on a different part
for example, the hormone adrenaline is produced in your brain, but acts all over your body in times of stress or excitement
hormones and other transmitter chemicals form part of your cells’ communication system

65. Cell communication
receptors on the surface of the cells allow transmitters to attach to the cell and carry out their function
only transmitters with the correct shape can dock at a particular receptor
similar to a lock and key method

66. Cell communication
certain viruses and bacteria can trick the cells by mimicking the shape of a harmless molecule
in order for your immune system to fight off invaders, it must first identify them, based on the markers on their cell membranes

67. Cell communication
better understanding of cell communication allows scientists and research companies to:
diagnose diseases carried by viruses and bacteria
diagnose diseases of the immune system
make more targeted, and more effective medications