Transcript Evolution

Evolution
Charles Darwin
• Developed a scientific theory of
biological evolution that explained
how modern organisms evolved over
long periods of time through
common ancestors.
• Evolution- change over time.
• The most famous of his observations
were in the Galapagos islands.
How Darwin made his
observations
• Whilst traveling on the ship the
Beagle, Darwin came upon
three major conclusions when
observing the organisms on his
voyage. They were:
• 1. Species vary globally
• 2. Species vary locally
• 3. Species vary over time
Species vary Globally
• Darwin didn’t just say, “Trust
me on this one.” He sailed all
over the world including to
Australia, South America and
Africa.
• Darwin noticed that different,
yet ecologically similar,
habitats around the globe.
Species Vary Locally
• Darwin noticed
that although
different, yet
related, animals
species often
occupy different
habitats within a
local area.
Species Vary Over Time
• Darwin noticed that fossils of
extinct animals were similar to
living species.
James Hutton
and
Charles Lyell
• Many Europeans in Darwin's day
believed the Earth was only a
few thousand years old.
• Over the course of time, the
science of geology began
supporting other theories.
Hutton and Lyell’s
contribution to modern day
evolutionary theory
• Hutton and Lyell (geologists)
concluded that Earth is
extremely old (approximately
4.55 billion years old) and that
geological processes that
changed earth in the past are
the same as processes that
operate in the present.
Hutton and geologic
change
• Hutton explained through his
research of studying rocks, soil,
mountains, and other geologic
features that rocks can be built up
and squeezed into layers.
• In turn, mountains can be worn down
by rain reducing the sediment on the
mountain’s surface.
• Hutton’s conclusion was
that the earth must be
much more than thousands
of years old.
• He introduced the concept
of deep time- the idea that
earth history stretches so
far back that it is hard for
humans to conceive- to
help explain his postulate.
Lyell’s principle of
geology
• Lyell’s big argument was that laws
of nature that shaped the earth in
it’s past are constant over time, so
scientists must be able to explain
what has happened in the past to
understand what happens in the
present.
• People called this thinking
uniformitarianism.
For example
• Water erodes surfaces it runs
across.
• It takes a long time for a little
erosion to wear away at a rock.
• If the earth were only a couple
thousand years old, then how
could water carve out a valley
or canyon?
Jean Baptiste Lamarck
• Darwin was given the credit, but
was not the first person with
the idea that organisms change
over time.
• Enter Jean Baptiste Lamarck
Theory of Evolution by
acquired characteristics
• Lamarck is famous for
the theory of evolution
by acquired
characteristics.
• The most famous
'example' of the theory
is the giraffe's neck,
which supposedly
stretched
as the creatures
reached for higher
leaves in trees.
Problem Lamarck?
• Lamarck had a few major holes in his
theory. They are:
• Organisms don’t have the inborn desire to
become perfect.
• Evolution does not mean a species becomes
better in some way.
• Evolution does not proceed in a predetermined
direction.
• Traits acquired in an organism’s lifetime cannot
be passed on to future generations.
• However, Lamarck was one of the first to
try and explain evolution naturally through
scientific process.
Population growth
• Thomas Malthus, an economist,
predicted that if left unchecked,
a population (in his observation
it was human) would not have
enough food or space to live in.
Theory behind
population growth
• Darwin noticed that the theory
behind population growth really
applied more to other animals
than humans.
• One oyster can lay over 1
million eggs in a year. If they all
hatched, oysters would destroy
the world!
Artificial Selection
• A.k.a selective breeding, this
has allowed for desirable
characteristics and even
animals to survive over long
periods of time.
Evolution through
natural selection
• Combining Lamarck’s, Lyell’s,
Hutton’s, and Malthus’s ideas,
Darwin attempted to explain a
natural process that in itself
operated like artificial selection.
• He named the book On the
Origin of Species.
The struggle for
existence
• Darwin realized that if more
individuals are produced than
those that could survive, then
organisms must compete for
food, living space, and other
limited resources.
Variation and adaptation
• Darwin understood that there is
a variation amongst traits in
every individual.
• Darwin hypothesized that some
of these variations allowed for
certain individuals to survive
better in their environments.
For example
• If a predator was faster than
other individuals in its
population, it would be able to
catch more prey.
• If the prey species were to be
faster than a predator, then that
prey would more likely avoid
being caught.
• A heritable characteristic that
allows for a creature to survive
and reproduce in it’s
environment is called
adaptation.
Examples of Adaptation
Survival of the fittest
• Different adaptations help an
organism’s fitness (an
organism’s ability to reproduce
and survive) in it’s environment.
• Survival means more than just
living, it means passing on the
heritable trait to the next
generation.
Natural Selection
• Natural selection occurs in any
situation in which more
individuals are born than can
survive, there is a heritable
variation, and there is a variable
fitness among individuals.
Common Descent
• The principle of common
descent states that all species,
living and extinct, are
descended from common
ancestors.
Evidence of Evolution
• Biogeography- The patterns in
the distribution of life.
• Patterns and distribution of
living and fossil species tell us
how modern organisms evolved
from their ancestors.
Biogeography and the
Galapagos:
similar, yet different
• To Darwin, Galapagos species
of finch had evolved from
mainland species. Due to
natural selection on each island
produced the variation between
species of finch.
Different, yet similar
• Similar selective pressures can
produce the same types of
result between continents,
resulting in physiologically
dissimilar species that are
exhibit some of the same
properties.
The Age of the Earth,
and fossils
• Evolution is not something that
occurs over night, it takes a long
time to occur. Half a century after
Darwin’s death, physicists
discovered radioactivity.
• Radioactivity can help determine the
age of rocks and minerals.
• Radioactive dating has determined
that the earth is 4.5 billion years old.
Recent fossil finds
• Fossils that have been recently
discovered have created links
between modern day animals
and their extinct ancestors.
• Other finds in the fossil records
have shown links between four
legged creatures and bipedal
organisms.
Embryology
• Embryology is the branch of
biology that studies the
formation and early
development of living
organisms.
• Embryology can be used to
show homologous structures
amongst varying organisms.
Homologous and
analogous structures
• Homologous structuresStructures that have been
shared be related species and
have been inherited from a
common ancestor.
Analogous structures
• Structures that are very
physiologically different, yet
share the same function.
Vestigial Structures
• Structures that are inherited
from our ancestors, but no
longer serve a purpose.
Embryology Providing
evidence of common
descent
• Similar patterns of
embryological development
have provided further evidence
that organisms have descended
from a common ancestor.
On the Genetic Level
• At the molecular level, the
universal genetic code and
homologous molecules provide
evidence of common descent.
Using Molecular Biology
• Molecular biologist have discovered
almost identical versions of a
homologous protein in almost all
organisms from yeast to people,
called cytochrome c.
• Cytochrome c is found in almost
every organism that undergoes
cellular respiration.
Testing Natural
Selection
• One way gather evidence is to see
evolution in action.
• When Darwin figured out that the
birds he observed on the galapagos
were finches, he figured they must
have come from a common ancestor.
• (Enter Peter and Rosemary Grant)
G-UNIT!!
• The Grants have spent more
than 35 years collecting data
and researching the Galapagos
finches.
Darwin’s Hypothesis:
tested
• For Darwin to hypothesize that the
finches had a common ancestor, and
have it be supported, two
assumptions must be tested:
• 1. For beak size to change shape and
evolve, there must be the heritable raw
genetic material needed for natural
selection.
• 2. Differences in beak sizes must
provide differences in fitness.
• The Grants did their testing on
the medium ground finch. The
island was big enough to
sustain the population, and
small enough for the Grants to
capture and analyze the finches
from time to time.
• The Grants recorded data like,
wing size, beak shape and size,
feather color.
• The Grants noticed individuals
of certain beak shape and size
could survive longer depending
on food availability or prolonged
weather conditions.
• When food is scarce, birds with
larger beaks tend to survive
longer. As a result, the larger
beaked finches are more likely
to survive and reproduce.
So what does this research
show us about natural
selection?
• The Grants have documented
that natural selection takes
place in wild finch populations
frequently, and sometimes
rapidly.