UNIT 2: THE ORIGIN OF
LIFE AND EVOLUTION
Characteristics of Life
1.
2.
3.
4.
5.
6.
7.
Cellular organisation
Reproduction
Growth and Development
Energy
Response to the Environment
Regulation
Evolutionary adaptation
http://study.com/academy/lesson/the-defining-characteristics-of-living-organisms.html
Activity 1: Make your own
quotation about life or living
organisms
1. THE ORIGIN OF LIFE
The Origin of Life Timeline
http://exploringorigins.org/timeline.html
http://www.daniellaberge.com/history/timeline1.htm
The Oparin Hypothesis
Among the explanations for the origin of
life we can mention the theory of the
prebiotic chemical evolution.
 This theory was stated at the beginning of
the 1920s by the biochemist Alexander
Oparin, and it said that the organic
molecules appeared on Earth thanks to
the inorganic compounds that evolved into
the most primitive forms of life.

inorganic molecules (H2,
CH4, NH3…)
organic molecules
(aminoacids, sugars,
nucleic acids…)
This hypothesis suggested the existence of a
primitive atmosphere without oxygen, but
with other gases such as methane, ammonia
or molecular hydrogen, along with steam, a
huge amount of energy related to the
volcanic activity and strong electric storms.
The absence of the ozone layer also
promoted a huge amount of ultraviolet
radiation. That atmosphere favored
chemical reactions among gases and the
formation of organic molecules, that were
accumulated in the primitive oceans
creating what we call the primordial
soup.
Stanley Miller´s experiment
•Stanley
Miller´s experiment reinforced the
hypothesis of the change of inorganic
molecules into simple organic molecules.
•In 1953 Miller simulated the conditions of
Oparin’s primitive atmosphere in the laboratory
and, by using electrodes that generated
electric shocks, he found out that amino acids,
sugars and some precursors of nucleic acids
appeared.
https://www.youtube.com/w
atch?v=iahBQolXQH8

We don’t know how fast or slow has been
the development of those chemical
reactions, but we have found evidence of
life with an age of 3,500 million years.
2. EVOLUTION
It is the change in biological
organisms over successive
generations.
2.1.-Theories about evolution
AGAINST
IN FAVOUR
FIXISM (Until XIX century)
Linneo
LAMARCKISM (1809)
Lamarck
CATASTROPHISM (1822)
Cuvier
DARWINISM (1859)
A. Wallace and C. Darwin
CREATIONISM (1859)
BALDWIN EFFECT (1896)
Baldwin
NEODARWINISM (1930-1940)
T. Dobzhansky
PUNCTUATED EQUILIBRIUM (1972)
S.J. Gould
Lamarck
In 1801, a French naturalist named Jean
Baptiste Pierre Antoine de Monet, Chevalier de
Lamarck proposed a theory of evolution.
We know now that Lamarck´s theory of
evolution is incorrect, but it is interesting from
the point of view of the history of science.
Lamarck stated that when environments
changed, organisms had to change their
behavior to survive. If they began to use an
organ more than they had in the past, it would
increase in its lifetime. For example, if a giraffe
stretched its neck for the highest leaves of a tree
its neck would become longer. Its offspring
would inherit the longer neck, and continued
stretching would make it longer still over several
generations. Meanwhile organs that organisms
stopped using would shrink.
Incorrect theory of Lamarck
Darwin´s theory of evolution


Nowadays, it is thought that the different
ways of life are related to each other,
and that they come from a common
ancestor called LUCA (Last Universal
Common Ancestor).
The main idea of Darwin´s Evolution
Theory has to do with the concepts of
variability and natural selection.
CHARLES DARWIN

Alfred Wallace and Charles Darwin
observed some morphological variations in
some species that they saw during their
journeys around the World. The
conclusion was related to the existence of
a common ancestor which suffered
changes that lead to the appearance of
new species. The responsible for that
process was the natural selection.
ALFRED WALLACE

The naturalists were aware of the
morphological variability among the
individuals of the same species. However,
Darwin and Wallace realized that some
individuals were better adapted to some
environmental conditions because they
had some specific morphological features.
The conclusion to that fact was that the
Earth wasn´t static and that the
environmental conditions have changed
through time. The adaptation is the clue to
the biological evolution.
 The organisms that are better adapted
have more possibilities to survive and to
reproduce. This is called natural selection.


Those organisms transmit some of their
features to their descendants so that the
individuals that own those characteristics
dominate the biological community.
Neodarwinism
Nowadays, it is known that the morphological
changes depend on changes produced in the
DNA by mutations and recombination during
the sexual reproduction.
Knowledge of DNA + Darwinism
= Neodarwinism




The key of Darwin´s natural selection is that there is
variability in a community.
Using our knowledge of DNA to explain the variability
of species is called Neodarwinism.
Variability is due to the mutations and to the
recombination of genes in sexual reproduction.
Neodarwinism explains the variability in a community.
Natural selection will make the better adapted
members of the community survive and spread their
genes.
Punctuated equilibrium


It is difficult to understand the idea of the
evolution as a gradual process. An important
part of the scientific community defend that there
is not enough evidence in the fossil register to
talk about a gradual process.
In fact, the paleontological evidence shows that
the evolution is not a gradual process but a
process produced by sudden changes.
Punctuated equilibrium

The theory of the punctuated equilibrium
stated by the scientist Stephen Jay Gould,
defends that the mechanisms of evolution
are not gradual. What´s more, they are
accelerated during the periods of
important changes.
2.2.-Scientific Evidence of
Evolution
Paleontological
Fossil
record
Evidence
Molecular
Biological
Genomics
Proteomics
Homologies
vestigial
structures
LUCA
Paleontological:
Fossil record
• Taken together, fossils can be used to construct a
fossil record, which is a timeline of fossils reaching
back through history.
• Several factors must be taken into account when
constructing such a record. The strata of rock in
which fossils are found give us clues about their
relative ages and the environments in which an
animal or plant lived.
• Similarly, new technological techniques such as
radioactive carbon dating help determine the
absolute ages of fossils.
Biological:
Homologies
Evolutionary theory predicts that related
organisms will share similarities that are
derived from common ancestors. Similar
characteristics due to relatedness are known
as homologies. Homologies can be revealed
by comparing the anatomies of different
living things.
Homologous organs
Homologous organs have the same structure
but different function.They prove the existence
of a common ancestor.
Analogous organs
These are organs that have the same
function but different structures. The species
that show analogous structures are not
related (adaptations)
Vestigial organs
These are structures found
in an organism with little or
no known function. Such
structures are thought to be
remnants of a structure that
at one time had a function
in an ancestral species.
For example, both whales and snakes have vestigial
pelvic and leg bones, left over from ancestral species
that walked.
Molecular
Molecular evidence for evolution
includes similarities at the gene,
protein, chromosomal, and genome
levels.
Proteomics
Biologists have found that
the more closely related
two species are, the
greater the similarity in
amino acid sequences of
their proteins. Such
comparisons allow
scientists to deduce
evolutionary relationships
between various
organisms.
Genomics
Since DNA molecules are highly conserved
and passed from one generation to the next,
base sequence pattern should indicate
evolutionary relationships.
Via the process of DNA hybridization,
scientists can accurately determine the degree
of relatedness between various groups of
species.
Matches in base sequence between species
indicate a high degree of relatedness.
For example, in the figure on the
right you can see that more
matches are made between a
human and a chimp than
between a human and a chicken.
This indicates that the human
and the chimp shared a more
recent common ancestor than the
human and the chicken and are
closely related
Phylogenetic trees
All life on earth shares a common ancestor. This
common ancestor of life on Earth gave rise to the
fantastic diversity that we see documented in the
fossil record and around us today. Evolution means
that we're all distant cousins.
How to build a phylogenetic
tree
https://kozmopolitaydinlar.wordpress.com/201
2/09/20/evidence-for-evolution/
3. FROM THE HOMINIDS TO
THE HOMO SAPIENS


Features as a very developed brain, the ability
to make instruments, the use of language or
the lengthening of the learning period
(childhood) caracterise the human being.
We can also mention that we have a very
specific way to walk (bipedalsim) and
opposable thumbs in our hands. These two
features could be useful for carrying objects
and for manipulating tools.

Africa seems to be the home of
hominisation. The majority of the ancient
hominid fossils were found in the Rift
Valley, near the Red Sea. However, in
2002 there were found the most ancient
remains related to the hominids. They
have an age of 6 to 7 million years and
they were found in Chad (Central Africa),
far away from the most known fossils.

Some fossils of Autralopithecus were
found in Kenia, Ethiopia and Tanzania.
Lucy was the famous female
Autralopithecus afarensis that was found
in Kenia and whose skeleton is highly
represented by several hundred pieces of
bone.

It seems that the hominids followed
different evolutionary tracks from 3 to 1.5
million years ago, and it is generally
accepted that the Autralopithecus
afarensis was the only common ancestor.


One of these tracks was the Homo group, whose
eldest ancestor dated back to 2.3 million years
ago. It was discovered in 1996 in Ethiopia and it
was associated with some carved tools.
It seems that the first humans were part of the
Homo habilis species (from 2.3 to 1.8 million
years ago) and of the Homo ergaster (from 1.9
to 1.3 million years ago).

Homo ergaster was considered as a
different hominid. Their height and the size
of their brains were higher than the ones
of their predecessors. They were also
good at making tools and they are thought
to be the ones who abandoned Africa,
giving rise to the Homo erectus.

In Europe, the oldest human remains date
from 780,000 years ago. They were found
in Burgos, in Sierra de Atapuerca, and
they were classified as Homo antecessor.
They were part of the evolutionary track
that led to the Homo neardenthalensis.
That track would have also led to the
Homo sapiens, 100,000 years ago.

Homo sapiens and Homo
neardenthalensis coexisted for thousands
of years. The last Homo neardenthalensis
lived in the South of the Iberian peninsula,
28,000 years ago.

Nowadays, there is a controversy about
the geographical origin of the Homo
sapiens. In 1987, there were some genetic
analyses that pointed that all the current
races come from the African ancestor, that
could have lived from 200,000 to 130,000
million years ago.