7.1 The Discovery of Cells
Chapter 7
A View of A Cell
Pages 171 - 174
Eggs are giant cells.
Some are more giant than others.
This is a replica of the egg from an
Elephant Bird Egg Aepyornis maximus
It became extinct around 400 years
ago. They were found on Madagascar,
Africa.
This egg is 15 times the bulk of an
Ostrich egg and is believed to be the
largest egg that has ever existed.
The brown egg is a chicken egg.
The tiny white one is a hummingbird,
the smallest bird that lives on our
planet today.
Egghead
A man poses with
the alleged largest
egg in the world
during a photocall in
central London. The
egg was laid in the
early 17th century,
by the now extinct
Great Elephant Bird
of Madagascar.
(AFP/Shaun Curry)
This was what we believe the elephant bird looked
like!
They had eggs, up to three feet in circumference.
They were the eggs of a bird that would later come
to be known as the Elephant Bird, or Vouron Patra
(Aepyornis maximus). The eggs that the Elephant
Bird laid were larger than the largest dinosaur eggs,
and, in fact, I have heard that some mathmeticiantypes somewhere have calculated that they were as
large as a structurally functional egg could possibly
be...the largest single cells to have ever existed on
Earth.
The flightless bird grew to around ten or eleven feet
tall, and is estimated to have weighed up to 1100
pounds. By comparison, a BIG Ostrich will go eight
feet and 300 pounds. Only the largest of the New
Zealand Moas were taller, some reaching thirteen
feet, but they weren't as massively built.
All were extinct by 1700.
The History of the Cell Theory
• Cells are the basic unit of living organisms
Light microscopes
• Anton van Leeuwenhoek used a simple
microscope in the 1600’s
• Compound light microscopes use series of
lenses to magnify objects up to 1500 times
• In our classroom, 40X, 100X, 400X
Anton van Leeuwenhoek
(1632-1723)
• Dutch microscopist who was
born and died in Delft, the
Netherlands.
• He was the finest lens
grinder of his time.
• He made his own microscopes.
• He was the first to observe
sperm, bacteria, and red
blood cells.
• His observations laid the
foundations for the sciences
of bacteriology and
microbiology.
• Called the protists he saw
”wee beaties”.
Anton van Leeuwenhoek
(1632-1723)
•
Leeuwenhoek made over 500 "microscopes," but fewer
than ten have survived to the present day.
•
Most of Leeuwenhoek's instruments were really
powerful magnifying glasses, not compound
microscopes of the type used today.
•
A drawing of one of Leeuwenhoek's "microscopes" is
shown at the right.
•
Compared to modern microscopes, it is an extremely
simple device, using only one lens, mounted in a tiny
hole in the brass plate that makes up the body of the
instrument.
•
The specimen was mounted on the sharp point that
sticks up in front of the lens, and its position and
focus could be adjusted by turning the two screws.
•
The entire instrument was only 3-4 inches long, and
had to be held up close to the eye; it required good
lighting and a lot of patience to use.
Mirror
Fine adjustment knob
Course adjustment knob
Eye piece
Nose piece
Objective lenses
Stage clips
Stage
Diaphragm
The Cell Theory
• Robert Hooke used a compound light
microscope to look at cork
• He gave box like structures the name cells
because it reminded him of the rooms
monks lived in at the monastery
Robert Hooke (1635-1703)
• There are no known pictures of
Robert Hooke.
• Some say his name is not as well
known today because he did not get
along with Sir Isaac Newton.
• An experimental scientist from the
seventeenth century.
• He studied physics and astronomy,
chemistry, biology, and geology, to
architecture and naval technology.
• He worked with or corresponded
with scientists as diverse as
Christian Huygens, Antony van
Leeuwenhoek, Christopher Wren,
Robert Boyle, and Isaac Newton.
Robert Hooke (1635-1703)
• Some of his accomplishments include:
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the universal joint,
the iris diaphragm,
an early prototype of the respirator;
invented the anchor escapement
the balance spring, which made more accurate
clocks possible;
served as Chief Surveyor and helped rebuild
London after the Great Fire of 1666;
worked out the correct theory of combustion
devised an equation describing elasticity that
is still used today ("Hooke's Law")
assisted Robert Boyle in studying the physics
of gases
invented or improved meteorological
instruments such as the barometer,
anemometer, and hygrometer
he made important contributions to biology
and to paleontology.
• Hooke's reputation in biology is from his
book Micrographia, published in 1665.
The Cell Theory
• In the 1830’s two German scientists made
some cell observations.
• Matthias Schleiden studied plants.
• Theodor Schwann studied animals.
Matthias Schleiden (1804-1881)
•
•
•
•
German botanist
Master microscopist
studied primarily cells in plants.
He observed that all plants seemed to
be made of cells.
• Schleiden observed various cell
activities such as protoplasmic
streaming.
• Schleiden also found that certain
fungi live on or within the roots of
some plants.
• This relationship between fungi and
plants, called mycorrhiza ("fungi
roots"), has since been shown to be
very common and extremely beneficial
to both organisms.
Theodor Schwann (1810 -1882)
•
In 1839 Schwann proposed that all organisms
are made of cells.
•
Together with Matthias Schleiden he
formulated the cell theory of life.
•
Schwann also discovered the cells, now known as
Schwann cells, that form a sheath surrounding
nerve axons.
•
He conducted experiments that helped disprove
the theory of spontaneous generation.
•
He was the person who came up with the word
“metabolism” to define the chemical changes
that take place in cells.
•
He demonstrated that yeast organisms cause
fermentation of sugar solutions.
•
I remember that Schwann is the animal part of
this duo because “Schwann” sounds like ”swan”.
Teddy Bear Swan
Schwan sounds like swan which is an animal
The Cell Theory
• Both Schleiden & Schwann came up with
the ideas that we now know as the cell
theory.
Cell Theory
1. All organisms are composed of one or
more cells
Unicellular organism
Multi-cellular organisms
The Cell Theory
• 2. The cell is the basic unit of structure
and organization of organisms.
• The same type of cells make tissue
• The same type of tissue make an organ
• The organs doing the same type of job
make an organ system
• Many organ systems make an organism
Cell Theory
2.
The cell is the basic
unit of organization
within an organismThe cell is the
simplest part of any
living thing.
Cell Theory
3. All cells come from preexisting cells
Electron Microscopes
• Electron microscopes can magnify more
than 150,000 times actual size
• Developed in the 1930’s
• Uses a beam of electrons instead of light
Electron Microscopes
• Specimens must be examined in a
vacuum because the electrons can collide
with air particles
• Two types; SEM scanning & TEM
transmission
SEM scanning
• Scanning shows 3-d image of the outside
TEM transmission
• Transmission shows what the inside looks
like
Soil microbe
Leaf cutter ant eye
Leaf cutter ant head with jaw
Fly’s head
SEM (Scanning Electron Microscope) image of a white blood cell, platelet and red
blood cell. White blood cells or leucocytes (far right) fight infection by producing
antibodies or devouring invading bacteria. Red blood cells or erythrocytes (far left)
carry oxygen from the lungs to the rest of the body. Platelets (middle) are cell
fragments that play a role in the ability of blood to clot.
Two Basic Cell Types
• Two Groups of cells ~ Those with membrane
bound organelles and those without membranes
around organelles.
• Prokaryotes
• Pro = first ,like prototype
• Most bacteria are prokaryotes
• Eukaryotes
• Eu = true, more advanced
• Some unicellular and all multicellular are
eukaryotes