UNIT
1
The cell
THE SCIENTISTS
BEHIND CELL THEORY
Biology and Geology 4. Secondary Education
UNIT
1
The scientists behind cell theory
R. Hooke
A. van
Leeuwenhoek
1665
1673
Robert Brown
1831
J.E. Purkinje
1837
BEFORE CELL THEORY
R. Virchow
1855
G. Mendel
1860
Schleiden and Schwann
1839
PROPOSING CELL THEORY
Ramón y Cajal
1888
AFTER CELL THEORY
Sutton, Boveri and Morgan
1910
Watson and Crick
1975
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Biology and Geology 4. Secondary Education
L. Margulis
1981
UNIT
1
The scientists behind cell theory
ROBERT HOOKE (1635-1703)
• Hooke was born in Freshwater, England.
• A prominent scientist, he was one of the
founders of the Royal Society of London.
• He is best known for his work in physics.
He developed Hooke’s law of elasticity.
• In 1665, while analysing a sheet of cork
with a simple microscope, Hooke observed
that it was made up of small, honeycomblike compartments. He called them cells,
from the Latin word for “small room.”
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The scientists behind cell theory
ANTONIE VAN LEEUWENHOEK (1632 – 1723)
• Leeuwenhoek was born in Delft,
Netherlands.
• He was a cloth merchant and
haberdasher.
• Leeuwenhoek’s interest in optics
stemmed from his desire to improve the
magnifying glasses he used to count
the threads in cloth.
• He made his own magnifying glasses
and eventually crafted one of the first
microscopes.
• He made a simple microscope with
which he became the first scientist to
observe certain cells, such as bacteria,
protozoa and red blood cells.
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The scientists behind cell theory
ROBERT BROWN (1773-1858)
• He was born in Montrose, Scotland.
• A leading botanist, Brown carried out a
significant study of the flora of Australia on
an expedition of naturalists and discovered
1,200 new species.
• He discovered the nucleus of eukaryotic
cells.
• While studying the leaves of different
types of plants, he became the first
scientist to observe and describe the cell
nucleus and to affirm that it was present in
all cells.
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The scientists behind cell theory
JOHANNES EVANGELISTA PURKINJE (1787-1869)
• He was born in Libochovice, Bohemia (now in the
Czech Republic).
• After studying medicine, he worked in the fields
of anatomy, physiology and botany.
• He was the first scientist to use a microtome to
slice thin tissue sections in order to observe
them with a microscope.
• In 1837, he discovered Purkinje cells, large
nerve cells with many branching dendrites found
in the cerebellum.
• In 1839, he discovered Purkinje fibres, tissues
found in the heart that conduct electrical
impulses to the ventricles.
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The scientists behind cell theory
MATTHIAS JAKOB SCHLEIDEN (1804-1881)
• He was born in Hamburg, Germany.
• He studied law but gave it up to
pursue botany.
• His research focused on studying
plants with microscopes.
• He determined that all plants are
composed of cells and that they grow as
a result of the generation of new cells
from the nucleus.
• His findings, along with those of
Theodor Schwann, form the first
principle of cell theory.
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The scientists behind cell theory
THEODOR SCHWANN (1810-1882)
• He was born in Neuss, Germany.
• He studied medicine and was particularly
influential in the fields of physiology, anatomy
and histology.
• He researched digestive processes,
fermentation and muscular contraction and
classified the tissues in the body.
• He also discovered Schwann cells, which
generate the myelin sheath that covers the
axons of neurons.
• Building on Schleiden’s theory, he argued
that animal tissues were also composed of
cells.
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The scientists behind cell theory
RUDOLF VIRCHOW (1821-1902)
• He was born in Schivelbein, Germany.
• He studied medicine, specialising in
pathology (the study of diseases).
• He was nominated for the Nobel Prize in
Physiology or Medicine in 1901 and 1902.
• He discovered thrombosis, improved
autopsy techniques and studied a number of
diseases.
• He observed that diseases arose not in
organs, but in their cells.
• This led him to identify the principle of cell
theory that holds that all cells come from preexisting cells (Omnis cellula e cellula).
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The scientists behind cell theory
GREGOR MENDEL (1822-1884)
• He was born in Heinzendorf, Austria.
• Mendel was an Augustinian friar at the
Augustinian abbey in Brno and was
ordained a priest in 1847.
• Working in the monastery garden, he
carried out experiments on plant
hybridisation by crossing different types of
pea plants.
• From his experiments with peas, he
deduced Mendel’s Laws of Inheritance, the
foundation of modern genetics.
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SANTIAGO RAMÓN Y CAJAL
• He was born in Navarre, Spain.
• He studied medicine in Zaragoza and
served as a medical officer in Cuba’s Ten
Years’ War from 1873 to 1876.
• Ramón y Cajal held professorships in
histology and anatomy at a number of
Spanish universities.
• In 1888, he discovered that neurons
were individual cells and analysed the
processes that connect them, studying
grey matter, a main component of the
nervous system.
• He was awarded the Nobel Prize in
Physiology or Medicine in 1906.
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W. SUTTON,T. BOVERI and T.H. MORGAN
• Walter Sutton (New York, 1877-1916) and
Theodor Boveri (Germany, 1862-1915)
developed the “Chromosome Theory of
Inheritance.”
• They demonstrated that alleles are inherited
through chromosomes. They also studied
cellular reproduction, mitosis and meiosis.
Walter Sutton
Theodor Boveri
• Their theory did not gain full acceptance until
1915, when it was corroborated by Thomas
Hunt Morgan’s work with the fruit fly, Drosophila
melanogaster.
• In 1933, Morgan was awarded the Nobel Prize
in Physiology or Medicine for demonstrating that
chromosomes contain the genes responsible for
the inheritance of characteristics.
Thomas Hunt
Morgan
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The scientists behind cell theory
JAMES WATSON (1928) and FRANCIS CRICK (1916 – 2004)
• James Watson (Chicago, USA, 1928)
studied biology in Indiana and earned his
doctorate in zoology.
• Francis Crick (Northampton, England,
1916 – 2004) studied physics in London.
After World War II, he focused on biology
research.
• In 1951, the two scientists began working
together, combining their knowledge.
• Building on Rosalin Franklin’s work with
X-rays and DNA, Watson and Crick
determined the double helical structure of
DNA.
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The scientists behind cell theory
LYNN MARGULIS (1938-2011)
• She was born in Chicago, USA.
• She entered university when she was 16,
graduating with a degree in biology at age 20.
• She is best known for her work in cell biology
and genetics.
• Her research involved the significance of
bacteria in evolution.
• Her theory that eukaryotic cells originated from
symbioses between prokaryotic cells gained
acceptance in 1981.
• The “Serial endosymbiotic theory” was central
to our understanding of the evolution of life.
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