This is part of the PowerPoint that covers section 2.1 in the Cambridge Pre-U Biology course. The full PowerPoint covers the following topics: evidence for the single origin of life, endosymbiosis, multicellular advantages. It can be purchased from here: https://sellfy.com/p/eRWP/

1. MAKING SENSE OF
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2. Copyright © 2017 Henry Exham
• These are some of the most
fundamental questions that have
troubled scientists and philosophers
for centuries.
• In this presentation we will be able
to look at plenty of evidence to
explain how life started.
• However, the more science discovers
the harder it has become to clearly
define what life is.
2
What is
Life?
How did
it start?

3. MAKING SENSE OFMAKING SENSE OF
Evidence for single origin of life
Endosymbiosis
Multicellular advantages
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4. Copyright © 2017 Henry Exham
a) Describe the evidence for a single origin of life in terms of
conservation of key biochemical mechanisms including the
genetic code and the ubiquitin/proteasome mechanism.
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5. Copyright © 2017 Henry Exham
• Before a man called Charles Darwin came
along most people believed that humans
were special and separate from the other
creatures on the earth.
• They believed God created all life
independently.
• This 1837 sketch from Darwin in one of his
notebooks shows his idea of the tree of life.
The idea that all life is connected and one
species can turn into another.
• This was the first time someone had
proposed that humans were not created
specially but had just evolved from an
earlier primate.
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6. Copyright © 2017 Henry Exham
• We have now created a very detailed and extensive tree
of life. It can be browsed and downloaded for free:
https://tree.opentreeoflife.org
• Other interactive resources to investigate the tree can be
found here:
– http://www.onezoom.org/
– http://itol.embl.de/
– http://www.wellcometreeoflife.org/interactive/
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7. Copyright © 2017 Henry Exham
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• We now know that Darwin was right and we will look at the evidence over the next
few slides.
• We know that actually all life on Earth is descended from one common ancestor:
LUCA (the Last Universal Common Ancestor)
LUCA
By Own work - Adl, Sina M.; Simpson, Alastair G. B.; et al. (2006). "Toward AutomaticReconstruction of a Highly Resolved Tree of Life". Science 311 (5765): 1283–1287.
DOI:10.1126/science.1123061. PMID 16513982.Ciccarelli, F. D.; Doerks, T; Von Mering, C; Creevey, CJ; Snel, B; Bork, P (2012). "The Revised Classificationof Eukaryotes". J.
Eukaryot. Microbiol. 59 (5): 429–493., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=5497511

8. Copyright © 2017 Henry Exham
• There are various pieces of evidence that we will
look at that point to the idea of LUCA.
1. The universality of the genetic code.
2. The conservation of key molecules
3. Protein degradation
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9. Copyright © 2017 Henry Exham
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presentation visit
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10. This PowerPoint is protected under copyright.
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Copyright © 2017 Henry Exham
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