Evolution #1

Download Report

Transcript Evolution #1

Evolution
Dr. James R. Whitfield, Ph.D
Evolution


"Nothing in Biology Makes Sense Except
in the Light of Evolution”
- Theodosius Dobzhansky
What is Evolution?

Evolution is the process by which
different kinds of living organism are
believed to have developed from earlier
forms during the history of the earth.
What is Evolution?
Evolution is the process by which
different kinds of living organism are
believed to have developed from earlier
forms during the history of the earth.
 Evolution is the story of the origin of life
and the formation of the vast biodiversity
on Earth

Origin of Life

The Universe is old – about 20 billion
years old!
Origin of Life
The Universe is old – about 20 billion
years old!
 When we look out at the stars we are
looking millions of years and trillions of
miles into the past

Origin of Life
The Universe is old – between about 14
and 20 billion years old
 When we look out at the stars we are
looking millions of years and trillions of
miles into the past
 However, no matter how long we look at
those stars we are limited in how far back
we can actually see – the light from the
oldest stars simply has not had enough
time to reach us yet!

The Big Bang

The Big Bang theory is the prevailing
cosmological theory attempting to explain
the origin of the Universe.
The Big Bang
The Big Bang theory is the prevailing
cosmological theory attempting to explain
the origin of the Universe.
 It describes a single huge explosion,
unimaginable in physical terms resulting
from tremendous heat and pressure

The Big Bang
The Big Bang theory is the prevailing
cosmological theory attempting to explain
the origin of the Universe.
 It describes a single huge explosion,
unimaginable in physical terms resulting
from tremendous heat and pressure
 As the universe continued to expand it
cooled down

The Big Bang

This cooling allowed for the formation of
subatomic particles and then simple
elements such as hydrogen and helium
(the two most abundant elements in the
Universe today)
The Big Bang
This cooling allowed for the formation of
subatomic particles and then simple
elements such as hydrogen and helium
(the two most abundant elements in the
Universe today)
 Over the next few billions years cooling
and gravity allowed for the formations of
galaxies. Our galaxy – The Milky Way
formed about 4.5 billion years ago

The Early Earth

There was no atmosphere on the early
Earth
The Early Earth
There was no atmosphere on the early
Earth
 Water vapor (H2Ov), ammonia (NH3),
methane(CH4) , carbon monoxide (CO),
and carbon dioxide (CO2)

The Early Earth
There was no atmosphere on the early
Earth
 Water vapor (H2Ov), ammonia (NH3),
methane(CH4) , carbon monoxide (CO),
and carbon dioxide (CO2)
 UV light broke up the water vapor into
hydrogen and oxygen. The oxygen
combined with ammonia and methane to
form more water, carbon dioxide and
ozone (O3)

The Early Earth

As the planet continued to cool the water
vapor continued to condense and fall as
rain
The Early Earth
As the planet continued to cool the water
vapor continued to condense and fall as
rain
 The rain eventually filled in the
depressions on the Earth forming the
oceans

The Early Earth
As the planet continued to cool the water
vapor continued to condense and fall as
rain
 The rain eventually filled in the
depressions on the Earth forming the
oceans
 Life first appeared about 500 million years
later or about 4 billion years ago

HOW?

The previous slide said life appeared 500
million years ago but it does not say
anything about how
HOW
Now that’s the
big question!
Theories on the Formation of Life

Some scientists believe that life came
from outer space
Theories on the Formation of Life
Some scientists believe that life came
from outer space
 The early Greeks believed that “spores”
transported life from planet to planet

Theories on the Formation of Life
Some scientists believe that life came
from outer space
 The early Greeks believed that “spores”
transported life from planet to planet
 This “Theory of Panspermia” is still
believed by many scientists today

Theories on the Formation of Life

For a long time people believed in the
“Theory of Spontaneous Generation” –
that life appeared form nowhere
Theories on the Formation of Life
For a long time people believed in the
“Theory of Spontaneous Generation” –
that life appeared form nowhere
 However Franscisco Redi and later Louis
Pasteur proved that this theory was
incorrect

Theories on the Formation of Life

Pasteur proposed the “Theory of
Biogenesis” which states that, “Omne
vivum ex vivo” all life come from life
Theories on the Formation of Life
Pasteur proposed the “Theory of
Biogenesis” which states that, “Omne
vivum ex vivo” all life come from life
 If you remember one of the principle of
the modern cell theory states that, “omni
cellulae e cellula” all cells come from cells

Pasteur’s Experiment
Theories on the Formation of Life

Oparin and Haldane proposed that the
frst life could have come from preexisting, non-living organic molecules
(RNA, proteins, etc,..) and that the
formation of life was preceded by
chemical evolution
Theories on the Formation of Life
Oparin and Haldane proposed that the
frst life could have come from preexisting, non-living organic molecules
(RNA, proteins, etc,..) and that the
formation of life was preceded by
chemical evolution
 i.e., the formation of diverse organic
molecules from inorganic components

Theories on the Formation of Life

In 1953 Stanley Miller and Harold Urey at
the University of Chicago (Chicago,
Illinois, USA) designed an experiment to
recreate the conditions present on the
early Earth in a laboratory setting
Theories on the Formation of Life

They created an electric discharge into a
flask containing, methane, water vapor,
ammonia, and hydrogen
Theories on the Formation of Life
They created an electric discharge into a
flask containing, methane, water vapor,
ammonia, and hydrogen
 They observed the formation of amino
acids – which as we know are the building
blocks of proteins, which build organelles,
which build cells, …

Millers Flask
Theories on the Formation of Life

Other researchers performing similar
experiments have been able to produce,
sugars, glycoproteins, and fats
Theories on the Formation of Life
Other researchers performing similar
experiments have been able to produce,
sugars, glycoproteins, and fats
 The theory that chemical evolution
proceeded biological life is now generally
accepted

However
However

None of these experiments have
answered how the first self replicating
metabolic life arose
However
None of these experiments have
answered how the first self replicating
metabolic life arose
 Miller and Urey simply said, “given the
conditions in the early atmosphere the
building blocks of life could develop”

But

We do know that the first non-cellular
“life” could have originated about 3 billion
years ago
But
We do know that the first non-cellular
“life” could have originated about 3 billion
years ago
 That is was probably large RNA
molecules, proteins and polysaccharides

But
We do know that the first non-cellular
“life” could have originated about 3 billion
years ago
 That is was probably large RNA
molecules, proteins and polysaccharides
 The first cellular life did not appear until
about 2 billion years ago

But
We do know that the first non-cellular
“life” could have originated about 3 billion
years ago
 That is was probably large RNA
molecules, proteins and polysaccharides
 The first cellular life did not appear until
about 2 billion years ago
 These were unicellular, prokaryotes that
lived in a watery environment

Biogenesis
This version of biogenesis that the first
form of life slowly arose through
evolutionary forces from non-living
molecules is generally accepted today
 However, this is only the beginning

Biogenesis
This version of biogenesis that the first
form of life slowly arose through
evolutionary forces from non-living
molecules is generally accepted today
 However, this is only the beginning
 We now need to look at how these first
unicellular organisms could have evolved
into the complex biodiversity of today

The Modern Theory of Evolution

Many religious beliefs hold the theory of
“Special Creation”
The Modern Theory of Evolution
Many religious beliefs hold the theory of
“Special Creation”
 This idea of creationism is laid out in the
Christian Bible in the Book of Genesis

The Modern Theory of Evolution
Many religious beliefs hold the theory of
“Special Creation”
 This idea of creationism is laid out in the
Christian Bible in the Book of Genesis
 Proponents of this theory believe that

1- All living this we see today were created as they are now – perfect
and unchanged
2- The diversity we see now was as it was in the past and will be in the
future
3- The Earth is about 6,000 years old (your book says 4,000)
The Modern Theory of Evolution

These ideas were strongly challenged
based on the Work of Charles Darwin
and the observations he made while
travelling on the H.M.S. Beagle
The Modern Theory of Evolution
These ideas were strongly challenged
based on the Work of Charles Darwin
and the observations he made while
travelling on the H.M.S. Beagle
 Darwin concluded that existing life forms
show similarities to varying degrees not
only among themselves but with long
extinct life forms

The Modern Theory of Evolution

He further concluded that there had been
extinctions of life forms in the past and
that new life forms arose at various
periods in the history of the Earth.
The Modern Theory of Evolution
He further concluded that there had been
extinctions of life forms in the past and
that new life forms arose at various
periods in the history of the Earth.
 There had been a gradual evolution of life
forms

Darwin’s Theory

Darwin theory can be summarized as
Darwin’s Theory
Darwin theory can be summarized as
 Natural selection

Darwin’s Theory
Darwin theory can be summarized as
 Natural selection
 Descent with Modification


Darwin was Influenced by Thomas Malthus
Natural Selection

Natural selection states that within any
population there will be built in variation.
This variation will allow some individuals
to survive better than other. These
organisms will outbreed the other
members of the population and produce
more offspring with the desired
characteristics
Natural Selection
Natural selection states that within any
population there will be built in variation.
This variation will allow some individuals
to survive better than other. These
organisms will outbreed the other
members of the population and produce
more offspring with the desired
characteristics
 This is called fitness

Descent with Modification

Descent with modification simply means
that as organisms reproduce mutations
will occur. Any mutation that is beneficial
and increases an organisms fitness will
stay in the population. Given the
immensity of time the slow accumulation
of mutations will lead to the formation of
new species
Descent with Modification
Descent with modification simply means
that as organisms reproduce mutations
will occur. Any mutation that is beneficial
and increases an organisms fitness will
stay in the population. Given the
immensity of time the slow accumulation
of mutations will lead to the formation of
new species
 It does not mean that the original
organism will go extinct

Descent with Modification

Million of years ago men and monkeys
shared a common ancestor. Then a
branch came we went one way but the
monkeys continued on the way they were
Not Accurate
The Other Player

Alfred Wallace was a contemporary of
Darwin. He independently developed his
own Theory of Evolution while working in
the Malay Archipelago. Darwin was
hesitant to publish his work (because of
the social and political ramifications)
however upon learning of Wallace’s work
he felt compelled to publish first
Evolution Before Darwin

Prior to Darwin Evolution was discussed and
tried to be explained by French Naturalist –
Jean Baptiste Lamarck. Lamarck proposed that
evolution was driven by use and disuse. He
believed that traits could be acquired during
ones lifetime and then passed on. For example,
giraffes could acquire longer necks because they
needed to browse high in tress. Once they got
this longer neck they could pass on the trait to
their offspring. This theory is no longer
believed
The Evidence for Evolution

Fossils – the remains (of usually the hard
parts or organisms) preserved in stone
The Evidence for Evolution
Fossils – the remains (of usually the hard
parts or organisms) preserved in stone
 Rocks form sediment. A cross section of
the Earths crust indicates the
arrangement of the sediment over very
long periods of time

The Evidence for Evolution
Fossils – the remains (of usually the hard
parts or organisms) preserved in stone
 Rocks form sediment. A cross section of
the Earths crust indicates the
arrangement of the sediment over very
long periods of time
 Different sediments contain different
fossils

The Evidence for Evolution
Fossils – the remains (of usually the hard
parts or organisms) preserved in stone
 Rocks form sediment. A cross section of
the Earths crust indicates the
arrangement of the sediment over very
long periods of time
 Different sediments contain different
fossils

The Evidence for Evolution

We can see that life forms vary over time,
that they become extinct and that new
forms of life have appeared in Earth’s
history
Relative vs Absolute Dating

Relative dating simply states that this is
older or younger than that but gives no
indications as to its actual age
Relative vs Absolute Dating
Relative dating simply states that this is
older or younger than that but gives no
indications as to its actual age
 Absolute dating using such techniques as
radioactive carbon dating, Potassium –
Argon dating (K-Ar) or Uranium – Lead
dating (U-Pb) uses half-life techniques to
determine the absolute age of objects

The Evidence for Evolution

Comparative anatomy and morphology
show similarities and differences between
today’s organisms and those from the past
The Evidence for Evolution
Comparative anatomy and morphology
show similarities and differences between
today’s organisms and those from the past
 From this we can determine the presence
(or lack of) a common ancestor

The Evidence for Evolution
Comparative anatomy and morphology
show similarities and differences between
today’s organisms and those from the past
 From this we can determine the presence
(or lack of) a common ancestor
 Homologous structures – The forelimb
pattern of whales, bats, humans and cats
all show similar bone structure but have
different functions

The Evidence for Evolution

Therefore a homologous structure is a
structure that looks the same but does
different things – It demonstrates a
common ancestor and divergent
evolution
The Evidence for Evolution

Analogous structures represent the
opposite scenario. These are structures
that look different but do the same thing.
For example a bird and butterfly wing are
anatomically very different but they both
enable flight. This represents convergent
evolution
The Evidence for Evolution

Similar habitats often result in the
selection of similar adaptive features in
different groups of organisms but toward
the same function. Consider whales and
sharks they have not had a similar
common ancestor for tens of millions of
years (or more) but because of where
they live they have evolved to have similar
body types
The Evidence for Evolution

Similarities in protein and gene function
among diverse organisms give clues to
common ancestry
The Evidence for Evolution

One argument for evolution that your
book makes that most sources do not is
that through artificial selection man has
created new species (both plants and
animals) in a few hundred years then why
could it not happen in nature over a few
million years
Industrial Melanism

The peppered moth is an example of industrial
melanism. Prior to the industrial revolution in England.
The white variant of the moth was most common with
lesser amounts of the melanised version. The moths
lived on the near-white lichens that covered the trees.
As the Industrial revolution progressed the trees
became black from coal-fired plants. The population of
black moths increased as being this color gave them a
competitive advantage (they were harder to spot) and
the white moth population declined. Several years after
the passage of the clean air acts as the trees returned
to the normal color there was a shift once again toward
white moths (Remember – no variant was totally wiped
out)
Vestigial Structures
Vestigial Structures
A vestigial structure is a structure that
had a function at one time but no longer
does. Some examples in humans include
the wisdom teeth, pinnae cartilage of the
ear and eyebrows
 While most people consider the appendix
to be a vestigial structure there is some
controversy about this
 Plica semilunaris

Adaptive Radiation

There is an expression that says, “Nature
abhors a vacuum”
Adaptive Radiation
There is an expression that says, “Nature
abhors a vacuum”
 This means that wherever life can exist –
life will exist

Adaptive Radiation
There is an expression that says, “Nature
abhors a vacuum”
 This means that wherever life can exist –
life will exist
 Some examples of this are the plants
present in the Hawaiian Islands, The
finches of the Galapagos Islands and the
marsupials od Australia

Adaptive Radiation

In each of these situations you had
ancestral stock that radiated outward as
various mutations allowed them to take
advantage of diverse habitats – Consider
how the beaks of the finches are adapted
to the types of seeds found in different
areas
Mechanisms of Evolution

Darwin was a gradualist. He believed that
mutations were small and random but
moved in one direction
Mechanisms of Evolution
Darwin was a gradualist. He believed that
mutations were small and random but
moved in one direction
 Hugo deVries was a proponent of
Saltation which states that large
mutations could occur rapidly, leading to
the formation of a new species in a single
generation

Mechanisms of Evolution

Stephen J. Gould proposed a theory called
“Punctuated Equilibrium” which stated
that organisms stayed stable for veru long
periods of time and then for any number
of reasons orgnaisms went through rapid
periods of evolution (100,000s of years to
a few million) and then returned to a
period of stability for many millions of
years
Hardy – Weinberg Equilibrium

Hardy-Weinberg can be used to
determine the frequency of a particular
allele in a population
Hardy – Weinberg Equilibrium
Hardy-Weinberg can be used to
determine the frequency of a particular
allele in a population
 Hardy-Weinberg provides a snapshot of
that population

Hardy – Weinberg Equilibrium

HWE states that the alleles in a
population will remain constant from
generation to generation in the absence
of other evolutionary influences.
Hardy – Weinberg Equilibrium

Hardy-Weinberg requires a variety of
conditions to be met in order for it to be
used (as you will see HWE) is more of an
intellectual exercise than an actual thing.
HWE requires that
Hardy – Weinberg Equilibrium

Populations be large
Hardy – Weinberg Equilibrium
Populations be large
 That there be no immigration or
emigration from the population

Hardy – Weinberg Equilibrium
Populations be large
 That there be no immigration or
emigration from the population
 All mating’s be random (No mate
selection)

Hardy – Weinberg Equilibrium
Populations be large
 That there be no immigration or
emigration from the population
 All mating’s be random (No mate
selection)
 There are no mutations

Hardy – Weinberg Equilibrium
Populations be large
 That there be no immigration or
emigration from the population
 All mating’s be random (No mate
selection)
 There are no mutations
 All organisms are equally fit

Hardy – Weinberg Equilibrium
HWE – is an algebraic formula that states:
 p + q =1 where
 p2 + 2pq + q2 = 1 So if
 p = represents the Homozygous
dominant phenotype, pq represents the
heterozygous phenotype and q represents
the recessive phenotype, then

Hardy – Weinberg Equilibrium
.6 + .4 = 1 and
 (.6)2 + 2(.6)(.4) + .42 = 1
 .36 + .48 + .16 = 1 Therefore
 36% of the population is AA
 48% of the population is Aa
 16% of the population is aa
 A change in the frequency of the alleles in
the population would be interpreted as
evolution
