Evolution History
Evolution Part I:
Who was
Darwin?
The story begins here
Europe
United
Kingdom
Shropshire
county
Incountry
the town
Shrewsbury
InInthe
of of
England
livedname
this famous
naturalist
whose
was Charles
Darwin
Age 65
Charles Darwin
1809 - 1882
This was his home and his garden
Darwin would spend much time walking in his garden
thinking about his discoveries and ideas.
This was his glasshouse and his study
Darwin spent a lot of time in his glasshouse and study
examining various plants and animals and developing
his theory of natural selection.
Evolution History
Evolution Part II:
Darwin finds his
niche.
As a young man,
Darwin started
medical studies at
Edinburgh’s famous
medical school,
but switched over to
a course in scientific
inquiry, becoming a
naturalist instead.
Darwin’s Occupation
A naturalist is a person
who studies past and
present plant and
animal life.
Naturalists spend a lot
of time collecting and
classifying plants and
animals.
Like most naturalists, Darwin used
Linnaeus’ Hierarchy of Taxononmic
Levels to classify organisms.
Carolus Linnaeus
1707 - 1778
Domain
Eukarya
Kingdom
Animal
Phylum
Chordata
Class
Order
Mammalia
Family
Canidae
Genus
Canis
Species
Canis lupus
Carnivora
Darwin on Classifying
Darwin spent eight years in his study looking through a
microscope at barnacles he collected from around the world
What’s a barnacle you ask?
Barnacle Structure
The classic barnacle is an
animal with the body plan
of a volcano — a cone with
a crater at the top.
Barnacles live in water and
colonize rocks, docks, and
ships’ hulls, which cause
the ships to slow down.
Barnacle Life
Every day when the tide rolls in,
each barnacle pokes out of its
crater a long foot like a feather
duster and gathers food.
When the tide goes out, each
barnacle pulls in the feather
duster and clamps its crater
closed with an operculum—a
shelly lid.
“Barnacle Bill”
Darwin found so much variation
in barnacle structure and
function that he had great
difficulty classifying them.
Before Darwin’s time, most
people believed that
all life suddenly appeared
in its present form,
(Special Creation);
life was immutable
(unchanging);
the Earth was less than
10,000 years old.
Some individuals however thought the
earth was much older
Georges Buffon James Hutton
1707 - 1788
1726 - 1797
The earth appears to be
formed by slow action on
natural causes.
Some proposed that evolution occurred, but lacked
convincing evidence for the driving mechanism.
Inheritance of Acquired Characters
Came up with
The behavior of the individual
determines the character that its
offspring inherit.
Jean Babtiste Lamarck
1744 - 1829
But example,
that would
involveon
For
passing
modifying
thebyDNA
of
longer
necks
stretching
specific
order
for
food genes
seems in
reasonable.
for it to be inherited.
We know Lamarck’s Inheritance of Acquired
Characters doesn’t work because
Seeds
from
trained
When
the tails
dogs are
and
children
of of
body
bonzai
always
cut off,trees
the
builders
are“docked”
not
born look is
produce
offspring
never inherited
bythat
their
looking
like
Arnold
grow
to normal size.
puppies.
Schwartznegger
Evolution History
Evolution Part III:
Darwin sets sail
on the HMS
Beagle.
Darwin goes sailing
In 1831 Charles Darwin, a 22
year-old college graduate set
sail as Captain’s companion on
the HMS Beagle for a voyage
around the world.
The main mission of the voyage
was to chart poorly known
stretches of the South American
coastline for the British Navy.
Darwin goes sailing
Darwin’s main interest
was to study the geology,
plants, and animals
encountered on the
voyage.
It was a tour that would
greatly affect Darwin’s
thinking and eventually
the thinking of others.
Darwin sees the world
The map below shows the route the ship followed.
Darwin’s Observations
Darwin spent most of his time
on shore while the ship’s crew
was busy surveying.
There, he observed and collected
thousands of specimens of South
American plants and animals
from diverse environments.
Darwin’s Observations
He studied organisms and their
adaptations from places as
different as
-the Brazilian jungle
-the grasslands of the
pampas
-and the frigid lands
near Antarctica.
Darwin’s Observations
Throughout the voyage and
the rest of his life, Darwin
maintained extensive journals
of his observations, studies,
and thoughts.
These journals provide a
window into Darwin’s thinking.
Darwin’s mindset
Before the voyage Darwin felt that
the concept of fixed or
unchanging species best
described nature.
During the voyage, he began
questioning this concept.
Sometime after he returned to
England, Darwin became
convinced that species change as
they adapt to their changing
environments.
Fixed species
Of a South American flavor
Darwin noticed on his voyage
that the South American plants
and animals were quite different
from the species of Europe.
Common Sloth 6 kg
Even the fossils Darwin
found were uniquely
South American.
Some of the fossils were
gigantic versions of the
modern animals.
Extinct Giant Sloth 3000 kg
The Galapagos Archipelago
His observations supported
the idea that species living
in South America today
were descended from
ancestral species on that
continent.
For example, The camelids of
South America were believed
to have descended from the
long extinct camelid
Poebrotherium wilsoni.
The Galapagos Archipelago
Darwin was also intrigued
by life on islands such as
the Galapagos.
The Galapagos are a chain of
relatively young volcanic islands
about 900 km off the western
coast of South America.
Life on the Galapagos
Darwin observed that the islands
had many unique organisms.
For example, Galapagos iguanas
are unique because they swim in
the ocean to feed on algae.
Life on the Galapagos
He observed that even the
individual islands in the
chain had some different
species of plants and
animals from one another.
For example, Galapagos is
famous for these unique,
long-necked giant land
tortoises whose shell patterns
differ from island to island.
Life on the Galapagos
Darwin inferred from these
observations that mainland
species had changed after
they colonized the islands
and adapted to their
various new environments.
Case in point: All South
American cormorant
species can fly, but the
Galapagos cormorant is
flightless.
Galapagos
S. America
Evolution History
Evolution Part IV:
Darwin begins to
change his world
view.
Catching up on some reading
During the Beagle’s long sails
between ports, Darwin managed to
do a lot of reading.
The writings of the geologist
Charles Lyell had a particular
influence on Darwin.
Lyle proposed that gradual and
observable geologic processes
such as erosion could explain the
physical features of today’s Earth.
Charles Lyell
1797 - 1875
Erosion and Earthquakes
For instance, the gradual erosion
of a riverbed over thousands or
millions of years can result in a
deep, river-carved canyon.
A mighty mountain range can be
thrust up centimeter by centimeter
by earthquakes occurring over
millions of years.
All that was required for an
understanding of these changes
was an Earth far older than
previously thought.
Rising land
Darwin personally experienced an
earthquake while doing field
studies in the Andes Mountains of
Chile.
In a harbor, he observed a block of
land that had been underwater
move upward above the water level
as a result of the quake.
Seashells on high
He also collected fossils of ocean
organisms high in the Andes.
Applying Lyell’s ideas, Darwin
reasoned that earthquakes
gradually lifted the rock bearing
those marine fossils from the sea
floor.
Drawing conclusions
The geologic evidence presented
by Lyell and others pointed to two
conclusions.
1. The slow processes of
mountain building and erosion
suggested an Earth that must be
very old.
2. The slow and gradual
processes occurring over vast
spans of time could cause
enormous change on Earth.
Darwin would
eventually apply
this idea of gradual
change to the
evolution of Earth’s
life forms.
Darwin’s Collection
When Darwin and the
Beagle returned to England
after five years, he analyzed
his collection and became
convinced that Earth was
ancient and species can
change through time.
The evolution of the horse is
an example of how species
can change over time.
Eohippus
Front foot = 4 toes
Hind foot = 3 toes
Darwin learned there
were larger and
smaller versions of
animals living today
that lived in the past.
Selective Breeding
Darwin then visited
many farms and
learned how farmers
used selective breeding
to bring about new
varieties or species of
plants, like those that
come from a common
wild mustard.
Selective Breeding
Darwin also learned how
farmers used selective
breeding to produce new
varieties of dog, sheep,
pig, horse and cattle.
Darwin wondered if
nature, like a farmer,
could cause a selective
breeding-like effect too.
Selective Breeding
Of course, there are some things that selective
breeding and evolutionary changes cannot make.
Pigeon Fancier
Darwin tried his hand as a pigeon
fancier. He was amazed to
occasionally find that when he crossed
purebred pigeons (like white fantails)
he would occasionally get distinct rock
pigeon markings in the F2 generation.
x
Darwin believed that despite the
great differences between
breeds, all pigeons were
descended from the rock pigeon,
or common pigeon.
Common pigeon
Pigeon Fancier
Darwin also noted that
domestic “fancy” pigeons,
when released as breeding
pairs into the wild, do not fair
well and produce no
successful future generations.
Darwin inferred that the rock
pigeon is successful in the wild
because it adapts well to
environmental demands.
Evolution History
Evolution Part V:
Darwin develops
his theory of
natural selection.
Population Studies
In 1838, as Darwin continued to
think about the question of how
species change, he read an essay
on human populations written a
few decades earlier by Thomas
Malthus.
Thomas Malthus
1766 - 1834
Feast and Famine
Malthus contended that much of
human suffering, such as disease,
famine and homelessness, was
due to the human population’s
potential to grow.
That is, populations can grow
much faster than the rate at
which supplies of food and other
resources can be produced.
Struggle for existence
Darwin recognized that Malthus’
ideas applied to all species.
Numbers are kept in check by
disease and the fight for space.
Some die from a lack of water.
Some die from lack of food.
Struggle for existence
Some die when they end up as
someone else’s food.
The production of more
individuals than the environment
can support leads to a struggle
for existence.
Struggle for existence
To prove his point, Darwin
counted the seeds from a single
orchid plant.
There were 24,080 seeds. That
was 24,078 more offspring than
were needed to replace the two
parents.
If each of these seeds grew into a
plant and if all of these plants had
24,080 seeds, the whole world
would be knee-deep in orchids.
Struggle for existence
But this is not the case.
Some seeds are eaten
by bugs.
Some land on poor soil.
Seedlings become sick or are
crowded out by other plants.
These are the losers in the
struggle for existence.
Natural Selection
This concept helped Darwin
to propose a mechanism of
evolutionary change.
He called it:
NATURAL SELECTION
Putting it all together
In 1844, Darwin wrote a 200
page essay that outlined his
idea, but he didn’t release it
to the public.
He told only a few of his
closest colleagues about his
theory, who encouraged him
to publish his work before
someone else came to the
same conclusions.
Darwin’s “Bulldog”
Thomas Huxley
1825 - 1895
Another source
In 1858, another British
naturalist, Alfred Wallace,
presented similar evidence
and inferences.
Within a month, Darwin and
Wallace submitted joint
papers to the public.
Alfred Wallace
1823 - 1913
Evolution History
A year later, Darwin
published his book,
The Origin of Species.
“It is not the strongest of the
species that survive, nor the
most intelligent, but the one
most responsive to change.”
Charles Darwin
Darwin’s main points
1. Decent with modification
Species of organisms living on
Earth today descended from
ancestral species. These
descendents spread into
various habitats over millions
of years. In these habitats,
they accumulated different
modifications, or adaptations,
to diverse ways of life.
Darwin’s main points
2. Natural Selection
The process by which
individuals with inherited
characteristics well-suited
to the environment leave
more offspring on average
than do other individuals.
Evolution Timeline