1. The origin of the first cells on Earth is still not fully known, but they likely arose through natural processes from non-living matter around 3.8 billion years ago. 2. Early atmospheric conditions and lightning may have produced simple organic molecules, while hydrothermal vents could have provided energy for assembling polymers. 3. The development of cell membranes around 1.9 billion years ago was a major advance, allowing compartmentalization within lipid vesicles.

1. 1.6. The origin of cells
Miltiadis-Spyridon Kitsos
Platon IB Diploma
https://endosymbiotichypothesis.files.wordpress.com/2010/09/1471-2105-9-393-1-l.jpg

2. The official IB Diploma Biology guide
Essential idea: There is an unbroken chain of life from the first cells on Earth to all cells in organisms
alive today.
https://ibpublishing.ibo.org/server2/rest/app/tsm.xql?doc=d_4_biolo_gui_1402_1_e&part=8
&chapter=1

3. Spontaneous generation is the formation of living organisms from non living matter
Ancient Greek Theophrastus c. 371 – c. 287 BC reported that
Silphium had sprung out of soil without being planted before.
An example of spontaneous generation?
Aristotle c. 384 – c. 322 BC wrote about insects being
formed from the dew, or from the hair, flesh of faeces of
animals.
How does passive observation affects our judgment? Why these
ideas persisted for so many years?
Swiss botanist Paracelsus (1493-1541)
believed in the spontaneous generation of
mice, frogs and eels from decaying matter.
http://www.nndb.com/p
eople/563/000107242/t
heophrastus-1-sized.jpg
http://www.missouriplants.com/Yellowo
pp/Silphium_integrifolium_plant.jpg
https://upload.wikimedia.org/
wikipedia/commons/a/ae/Ari
stotle_Altemps_Inv8575.jpg
https://youtu.be/WNByRghR6sw
https://upload.wikimedia.org/wikipedi
a/commons/8/8b/Wenceslas_Hollar_-
_Paracelsus_(State_2).jpg
http://brothersofthebook.com/wp-content/uploads/2011/06/Thinker-Silhouette-of-statue.gif

4. Refutation of the theory of spontaneous generation
Francesco Redi (1626-1697) using a
controlled experiment showed that maggots
may not develop in pieces of meat not
exposed to air
As our knowledge and understanding on microbiology and sexual reproduction improved more
evidence accumulated showing the the theory of spontaneous generation was wrong
The era of active experimentation
Similarly Lazzaro Spallanzani
demonstrated that organism may
develop only in broths exposed to air.
https://upload.wikimedia.org/wikipedia/c
ommons/a/af/Francesco_Redi,_founder_of_experi
mental_biology.jpg https://d2gne97vdumgn3.cloudfront.net/api/file/GlBtsNx8SQi8AweaCFdJ
https://d2gne97vdumgn3.cloudfro
nt.net/api/file/GlBtsNx8SQi8AweaC
FdJ
http://images.slideplayer.com/15/4509174/slides/slide_12.jpg

5. Evidence from Pasteur’s experiments that spontaneous generation of cells and
organisms does not now occur on Earth.
The swan-neck flasks experiments – experimental refutation of the theory of spontaneous
generation
http://a2.files.biography.com/image/upload/
c_fit,cs_srgb,dpr_1.0,h_1200,q_80,w_1200/
MTE5NTU2MzE2MzM5NTM3NDE5.jpg
Louis Pasteur (1822-1895), famous French scientist, known for his
discoveries in the field of microbiology and immunology. He contacted
a series of experiments that contributed to the final refutation of the
theory of spontaneous generation.
1. Glass flasks were filled with nutrient broth.
2. Neck of flasks were bent using flame to form the
so called swan necks. Broth was sterilized by
boiling.
http://s.hswstatic.com/gif/scientific-method-9.jpg
http://blog.cmog.org/wp-content/uploads/2016/07/1_6-768x435.png
http://blog.cmog.org/wp-content/uploads/2016/07/pasteur-bottle-
400x267.jpg
Hypothesis: Life will not arise spontaneously in broths isolated from
open air.

6. Evidence from Pasteur’s experiments that spontaneous generation of cells and
organisms does not now occur on Earth.
The swan-neck flasks experiments – experimental refutation of the theory of spontaneous
generation
3. Swan neck flasks were left to sit undisturbed for several days.
No signs of microbial growth were detected.
http://s.hswstatic.com/gif/scientific-method-9.jpg
http://amoebamike.wordpress.com/200
9/10/06/spontaneous-generation-a-
brief-history-of-disproving-it
4. In second treatment neck of flasks was broken. After several
days broth was discolored and cloudy, indicating the
development of bacteria.
http://amoebamike.wordpress.com/200
9/10/06/spontaneous-generation-a-
brief-history-of-disproving-it
Conclusion: Spontaneous generation is refuted since microbes
may not grow spontaneously in isolated broths. A source of
contamination is always needed.

7. Use the tutorials to learn about Pasteur’s
experiment.
Evidence from Pasteur’s experiments that spontaneous generation of cells and
organisms does not now occur on Earth.
http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html
Repeat Pasteur’s experiment and
see the results for yourself.
http://biologyjunction.com/pasteur_experiment.ht
m
http://www.sumanasinc.com/webcontent/animations/content/scientifi
cmethod.html
Slide from

8. According to the cell theory, every cell comes from a pre-existing cell
while eukaryotes undergo mitosis and, those that reproduce
sexually, produce gametes via meiosis
Thus, there is a continuity of life from the ancestral cells to the
existing cells
Male gamete
Female gamete
Fertilization
and
Development
of the zygote
Meiotic division and gamete formation
Mitotic divisions
Prokaryotic cells are divided through binary fission,
https://upload.wikimedia.org/wikipedia/co
mmons/thumb/0/02/Binary_Fission_2.svg/5
12px-Binary_Fission_2.svg.png

9. https://i.ytimg.com/vi/FzcTgrxMzZk/maxresdefaul
t.jpg
There is not enough evidence to propose a natural
mechanism on how cells may be produced by simpler
subunits.
We also accept that cells come from pre-existing cells because..

10. There is no example of cell increase at any organizational
level without cell division of pre-existing cells.
https://youtu.be/Q6ucKWIIFmg
We also accept that cells come from pre-existing cells because..

11. We also accept that cells come from pre-existing cells because..
Viruses are produced via the combination of simpler
macromolecules but they are non-cellular structures
https://youtu.be/Rpj0emEGShQ

12. Origin of the first cell
The first cells must have arisen from non-living material
Lets step back into time…

13. Having traced the origin of the first cells back into time we still have a big question mark:
How did the first cells arise?
Plausible hypotheses:
(a) Cells have an extraterrestrial origin
(b) First cells may have arisen from non living material
Here are some evidence supporting the idea that the complex structure of cells went through
a series of evolutionary steps of increasing complexity.
Origin of the first cell
The first cells must have arisen from non-living material

14. The first atmosphere was formed by outgassing of gases
trapped in the interior of the early Earth, a process which
still goes on today through volcanic eruptions.
3.8 billion years ago the earth's atmosphere was a reducing mixture of nitrogen (N2), methane (CH4),
water vapor (H2O), and possibly ammonia (NH3)
It is believed that solar radiation and lightning
discharges into the reducing gas mixture produced
natural organic compounds
Stage 1: Formation of important organic molecules
Origin of the first cell
The first cells must have arisen from non-living material
http://www.universetoday.com/wp-content/uploads/2009/06/archaean-
580x327.jpg
http://www.universetoday.com/wp-content/uploads/2009/06/archaean-580x327.jpg

15. The Miller-Urey experiments
The first cells must have arisen from non-living material
Stanley Miller and Harold Urey contacted an experiment, that replicated the conditions in
the primitive atmosphere. Water vapor passed through a mixture of methane (CH4),
hydrogen and ammonia (NH3). Electrical discharges were used to simulate lightning.
The atmosphere was cooled and the vapor was condensed. Resulting water was checked for
organic compounds. Different organic compounds (e.g., amino acids) were produced.
https://en.wikipedia.org/wiki/File:Miller-Urey_experiment_-
_Work_by_the_C3BC_consortium,_licensed_under_CC-BY-3.0.webm
https://upload.wikimedia.org/wikipedia/commons/thumb/5/54/Miller-Urey_experiment-
en.svg/2000px-Miller-Urey_experiment-en.svg.png

16. The Miller-Urey experiments
The first cells must have arisen from non-living material
Stanley Miller and Harold Urey developed a device which would replicate the conditions in
the primitive atmosphere. Water vapor passed through a mixture of methane (CH4),
hydrogen and ammonia (NH3). Electrical discharges were used to simulate lightning.
The atmosphere was cooled and the vapor was condensed. Resulting water was checked for
organic compounds. Different organic compounds (e.g., amino acids) were produced.
https://en.wikipedia.org/wiki/File:Miller-Urey_experiment_-
_Work_by_the_C3BC_consortium,_licensed_under_CC-BY-3.0.webm
https://upload.wikimedia.org/wikipedia/commons/thumb/5/54/Miller-Urey_experiment-
en.svg/2000px-Miller-Urey_experiment-en.svg.png

17. The first atmosphere was formed by outgassing of
gases trapped in the interior of the early Earth, which
still goes on today in volcanoes.
1.9 billion years ago the earth's atmosphere was a reducing
mixture of nitrogen (N2), methane (CH4), water vapor (H2O),
and possibly ammonia (NH3)
Solar radiation and lightning discharges into the reducing
gas mixture are believed by the consensus of evolutionists
to have produced natural organic compounds
Polymerization of carbon compounds
The first cells must have arisen from non-living material
Deep sea vents: Areas in the deep sea floor
where gushing hot water comes out along
with reducing chemicals such as iron sulfate.
These chemical may have provided the energy
for the assembly of simpler carbon
compounds Into polymers.
https://youtu.be/rTR6gGDWcJk
Read more
Meet Luca, the Ancestor of All Living Things
http://www.nytimes.com/2016/07/26/science/last-universal-
ancestor.html?_r=0
We’ve been wrong about the origins of life for 90 years
http://qz.com/761430/weve-been-wrong-about-the-origins-of-life-for-90-
years/

18. The first atmosphere was formed by outgassing of
gases trapped in the interior of the early Earth, which
still goes on today in volcanoes.
1.9 billion years ago the earth's atmosphere was a reducing
mixture of nitrogen (N2), methane (CH4), water vapor (H2O),
and possibly ammonia (NH3)
Solar radiation and lightning discharges into the reducing
gas mixture are believed by the consensus of evolutionists
to have produced natural organic compounds
Deep sea vents: Areas in the deep sea floor
where gushing hot water comes out along
with reducing chemicals such as iron sulfate.
These chemical may have provided the energy
for the assembly of simpler carbon
compounds Into polymers
https://youtu.be/rTR6gGDWcJk
Read more
Meet Luca, the Ancestor of All Living Things
http://www.nytimes.com/2016/07/26/science/last-universal-
ancestor.html?_r=0
We’ve been wrong about the origins of life for 90 years
http://qz.com/761430/weve-been-wrong-about-the-origins-of-life-for-90-
years/
Polymerization of carbon compounds
The first cells must have arisen from non-living material

19. Remember what we discussed about phospholipid chemistry? Phospholipids are
amphipathic molecules with a natural tendency to build bilayers. Experiments have
demonstrated the ability of these phospholipid bilayers to form vesicles which then, may
engulf and isolate other molecules.
The formation of membranes was a giant step in the evolution of the cells since it allowed
the isolation of environments and internal chemistry.
Stage 3: Formation of membranes
The first cells must have arisen from non-living material
Read more
The early evolution of lipid membranes and the three domains of life
http://www.nature.com/nrmicro/journal/v10/n7/index.html
Jonathan Lombard, Purificación López-García and David Moreira, The early
evolution of lipid membranes and the three domains of life, NATURE REVIEWS |
MICROBIOLOGYVOLUME 10 | JULY 2012 | 507

20. Remember what we discussed about phospholipid chemistry? Phospholipids are
amphipathic molecules with a natural tendency to build bilayers. Experiments have
demonstrated the ability of these phospholipid bilayers to form vesicles which then, may
engulf and isolate other molecules.
The formation of membranes was a giant step in the evolution of the cells since it allowed
the isolation of environments and internal chemistry.
Stage 3: Formation of membranes
The first cells must have arisen from non-living material
Read more
The early evolution of lipid membranes and the three domains of life
http://www.nature.com/nrmicro/journal/v10/n7/index.html
Jonathan Lombard, Purificación López-García and David Moreira, The early
evolution of lipid membranes and the three domains of life, NATURE REVIEWS |
MICROBIOLOGYVOLUME 10 | JULY 2012 | 507

21. RNA (ribonucleic acid) may have been the first genetic material since
it has diverse properties.
• May store information
• Self-replication (non-enzymatic in certain cases)
• Acts as a catalyst
Stage 4: Developing inheritance
The first cells must have arisen from non-living material
http://biology-
forums.com/gallery/195549_23_08_14_12_26_47.jpeg
https://youtu.be/VYQQD0KNOis
This hypothesis that RNA could be the first genetic
material is called the RNA world hypothesis.
Read more
The RNA world hypothesis
http://www.nature.com/scitable/content/the-rna-world-10239
https://youtu.be/jfq5-i8xoIU

22. RNA (ribonucleic acid) may have been the first genetic material since
it has diverse properties.
• May store information
• Self-replication (non-enzymatic in certain cases)
• Acts as a catalyst
Stage 4: Developing inheritance
The first cells must have arisen from non-living material
http://biology-
forums.com/gallery/195549_23_08_14_12_26_47.jpeg
https://youtu.be/VYQQD0KNOis
This hypothesis that RNA could be the first genetic
material is called the RNA world hypothesis.
Read more
The RNA world hypothesis
http://www.nature.com/scitable/content/the-rna-world-10239
https://youtu.be/jfq5-i8xoIU

23. Endosymbiosis in eukaryotes
The origin of eukaryotic cells can be explained by the endosymbiotic theory.
Eukaryotes appeared approximately 2 billion years
ago, that is, 2.3 million years after bacteria.
The appearance of eukaryota coincides with an
increase of oxygen in the atmosphere (2%) which
yielded enough energy for membrane development,
increase in size and compartmentalization. https://home.cc.umanitoba.ca/~frist/PLNT3140/l01/evolutionary_timeline.png
The endosymbiotic theory
The endosymbiotic theory claims that mitochondria
evolved from small aerobic prokaryotes who were
respiring aerobically (using oxygen) and were
“shallowed" by larger anaerobic bacteria.
The small aerobic bacteria were not destroyed. On the
contrary, a mutualistic relationship (win-win) has
developed between the two cells and this provided an
evolutionary advantage.
The small aerobic bacterium evolved to be a
mitochondrion. Aerobic prokaryoye

24. Endosymbiosis in eukaryotes
The origin of eukaryotic cells can be explained by the endosymbiotic theory.
Photosynthetic prokaryote
Similarly chloroplasts evolved from small aerobic
prokaryotes who were photosynthesizing (producing
oxygen) and were “shallowed" by larger anaerobic
bacteria. Again a mutualistic relationship developed
and the small photosynthetic bacterium evolved to be
the chloroplast.
https://highered.mheducation.com/sites/9834092339/student
_view0/chapter4/animation_-_endosymbiosis.html
Evidence for the symbiotic theory
Resemblance of mitochondria and chloroplasts, with
bacteria:
• Mitochondria and chloroplasts are produced by
division of pre-existing mitochondria and
chloroplasts.
• Have their own 70s ribosomes, resembling the
bacterial 70s ribosomes.
• Have their own genes, which may transcribe,
produce mRNA and translate to produce own
proteins.
• Their DNA is circular resembling that of the
prokaryotes.

25. The first synthetic cell
Daniel Gibson and his colleagues at the J. Craig Venter Institute in Rockville,
Maryland, synthesized the genome of the bacterium Mycoplasma mycoides,
consisting of about 1.1 million base pairs.
Having assembled the genome inside a yeast cell, they transplanted it into a cell
from a closely related species, Mycoplasma capricolum.
After the newly made cell divided, the cells of the bacterial colony that formed
contained only proteins characteristic of M. mycoides
http://www.nature.com/news/2010/100520/full/news.2010.253.html http://www.nature.com/news/2007/070628/full/news070625-9.html
Read more

26. http://www.stepsinbiology.com