The document summarizes key concepts in the evolution of life. It discusses early theories of spontaneous generation and the Miller-Urey experiment demonstrating organic molecules can form from inorganic precursors. Modern evolutionary theory developed from Darwin's principles of variation within populations, a struggle for existence, and survival of the fittest. Evidence for evolution includes homologous and vestigial structures, transitional fossils, embryological similarities, and molecular comparisons. Present-day evolution theories have expanded on Darwin's work through ideas like punctuated equilibrium, selfish genes, and the endosymbiotic origin of eukaryotic cells. New species arise through genetic isolation of populations and their gradual differentiation over time. The appearance of human beings is traced from early homin

1. UNIT8:
THEORIGINANDEVOLUTION
OFLIFE

2. INDEX
1. The beginning of life
2. Evolutionary theoriesbefore the20th century
3. Evidence of evolution
4. Present-day theories of evolution
5. The beginning of new species
6. The appearance of human beings
Stanley Miller

3. 1. The beginning of life
Spontaneous generation = life can appear from inanimate objects
WRONGIt was accepted In ancient Egypt and in the Middle Ages

4. Francesco Redi was the first one to prove that spontaneous generation
was FALSE. (17th century) .
He proved that larvae found in rotting meat came from fly eggs.
http://www.phschool.com/atschool/phsciexp/active_art/redi_pasteur_experiment/
In the 19th century Louis Pasteur demonstrated that microorganisms
did not com from spontaneous generation either.

5. Spontaneous
chemical
reactions among
methane,
ammonia,
hydrogen and
water vapor
occurred.
The reactions
were started by
electric charges
from storms,
volcanic
eruptions…
Organic
molecules
appeared
Water vapour
condensed 
primitive seas
were formed.
(primordial
soup)
Coacervates
appeared
Life arose from processes which ocurred in the atmosphere of the primitive Earth.

6. Coacervate:
• stable spherical
structure made
up of organic
molecules.
Coacervates isolated organic molecules
inside themselves.
They also could divide and multiply,
thanks to a nucleic acid.

7. http://www.wiley.com/college/trefil/0470118547/vdl/lab_miller_experi
ment/
They proved that organic molecules could be synthetised from inorganic molecules.
Inorganic compounds
Organic compounds
Electrical currents

8. Current additions to Oparin’s theory:
• The process probably happened in areas with clay or muddy
soil, not in water.
• The first nucleic acid to appear probably would have been
RNA.
Other theories: Theory of panspermia
Life comes from the spores of other microorganisms that were inside meteorites.
Activities 5, 6 and 7 page 145

9. Previously there were only non-
evolutionary theories:
Linnaeus stated that species had
been created separately and
independently by God. They would
be static or unchanging.
Cuvier explained the existence of
fossils from species that had
disappeared as a result of catastrophes
that killed these organisms.

10. Animals developed structures and
organs that they needed to adapt to
their environment.
These new characteristics were
transmitted to their descendants
First hypothesis of evolution were developed:
A. Lamarckism
(Evolutionary theory)
 Theory of inheritance of acquired characteristics
No longer accepted

11. B. Darwinism
• Individuals in a population have differences among them.
• Struggle for existence: There is competition between
new-born individuals for space and food.
• Survival of the fittest: individuals whose variations help
their survival in a certain environment are favoured.
• The surviving individuals produce the next generation, so
that the more favourable variations are transmitted to the
offspring.
Basic principles of Darwinism

13. When Charles Darwin was only 22, he set out on a voyage around the
world, to discover new species and help in the age of exploration. What
was to be a 2 year voyage stretched into 5. The young explorer gathered a
lot of data and based on them he wrote “The origin of Species”.
He discovered 14 different species of
finches in Galapagos Islands, which
were adapted to different types of food.

14. Natural selection
The individuals that have the most
advantageous characteristics
survive and their frequency in the
population increases progressively.
There is a gradual disappearance
of these less favoured traits.
After many generations, significant
changes are produced.

15. Explain the evolution of giraffes
according to
Darwin’s theory of evolution

16. 3. Evidence of evolution
Homologous organs  same structural pattern
but different functions. Proof of divergent
evolution.
Analogous organs  same function although
they have a different evolutionary origin.
Vestigial organs  remains of organs which tend
to disappear because they no longer have a
function

17. Some human vestigial organs
Homologous organs
Analogous organs

18. Fossils show that organisms in the past were different from the
organisms today.
•Slow but clear changes can be observed in these fossils.
•An increase in diversity and complexity can be seen.
•There are fossils with intermediate characteristics which later evolved in different groups.
Archaeopteryx

19. Fossil evidence for evolution

20. Some embryos from different species are similar, which shows that there is a clear
evolutionary relationship between them.
Similarities between embryos are greater within more closely related groups

21. Groups of organisms which were isolated geographically evolved
differently to form new species.

22. Biogeographical evidence for evolution

23. All living beings are made up
of the same type of molecules
(proteins, nucleic acids…)
By comparing the molecular
sequences in different species,
the evolutionary relationship
between them can be
established

24. Page 151 activities 9, 13, 14, 16 and 17

25. 4. Present-day theories of
evolution
New
discoveries
have been
included in
Darwin’s
theory:
Mendel’s laws
Sexual
reproduction,
which
produces
variation in
the offspring
Genetic
recombination,
which happens
during meiosis
mutations

26. Theory of the
selfish gene
(Richard Dawkins)
The unit of evolution is
the gene, not the
population and
competition is between
genes themselves
rather than between
individuals
Theory of
the
punctuated
equilibrium
The process of
evolution has not
always been slow and
gradual
Endosymbiotic
theory
(Lynn Margulis)
Eukaryotic cells
originated from the
fusion of two types of
bacteria.
They had the capacity
to phagocytose other
cells whic became
cellular organelles,
such as mitochondria
and chloroplasts.
https://www.youtube.com/watch?v=3ESXvLHceDc  Endosymbiotic theory
https://www.youtube.com/watch?v=-FQmAnmLZtE

27. Lynn Margulis

28. 5. The origin of new species
Species = set of individuals that can reproduce with each other
and create fertile offspring.
1. Natural selection favours some individuals and prejudices other 
new populations of the same species
2. Genetic isolation of the new population: the members of 2 different
populations in the same species cannot reproduce with the other population.
Possible reasons of genetic
isolation
Geographical barriers:
mountains, a river…
Physiological barriers:
incompatibilities in the
functioning of gametes
Ethological barriers:
new types of behaviour
…

29. 3. Gradual differentiation: after isolation, populations become
more and more different.
2
3 4
1
4. Speciation: over time genetic changes produces
such significant differences that it is no longer
possible for the two populations to produce
fertile offspring.

31. Microevolution
 The process of
evolution that causes
the appearance of
new species.
 Species belonging to
the same genus were
caused by
microevolution.

32. Macroevolution
 The type of evolution
that resulted in large
groups of different
species because of
drastic changes.
 Example: Birds and
mammals evolving
from reptiles.

34. 6. The appearance of human
beings

35. Characteristics
of Hominids
Bipedal
Changes in the
cranium, pelvis,
spine and limbs
Upright position
It improved their
sight and freed
their hands

36. Craniums of
1. Gorilla
2. Australopithecus
3. Homo erectus
4. Neanderthal
5. Steinheim Skull
6. Homo sapiens
Characteristics of
the Homo genus
• Capacity to use
tools
• Opposable thumb
• Developed brain
Opposable thumb
Chronological
appearance of
Homo
Homo habilis
Homo erectus
Homo sapiens

38.  Glossary
 Spontaneous generation
 Coacervate
 Natural selection
 Phlylogenetics
 Speciation