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Evolution
DARWIN’S THEORY OF
EVOLUTION
•
THE PUZZLE OF LIFE’S DIVERSITY
• BIOLOGICAL DIVERSITY – variety of
living things.
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How did all these different organisms arise?
How are they related?
What scientific explanation can account for
the diversity of life?
•
A. Scientific facts, observations, and
hypothesis known as evolution theory
• EVOLUTION – change over time, modern
•
•
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organisms have descended from ancient
organisms
THEORY – well supported explanation of
phenomena that have occurred in the natural
world
Evolution: Videos for Students: Evolving Ideas
Evolution: Isn't Evolution Just a Theory?
Video 1
BRAIN TEASER
*HAVE STUDENTS NAME
DIFFERENT ANIMALS
• *ASK: WHAT DIFFERENT WAYS DO
THESE ANIMALS USE TO MOVE
ABOUT?
• *WHAT TRAITS DOES EACH ANIMAL
HAVE THAT HELP IT MOVE ABOUT
AS IT DOES?
• OBSERVING VARIATION SUCH AS
THIS WAS INSTRUMENTAL IN
DARWIN’S DEVELOPING HIS THEORY
OF EVOLUTION
VOYAGE OF THE BEAGLE
• - voyage around the world
– Darwin would collect plant and animal
specimens at each port
– Study and record information
DARWIN’S OBSERVATIONS
Evolution #2: Who was Charles Darwin? - YouTube
– In 1 day in the Brazilian forest Darwin
collected 68 different beetle species
– Patterns of diversity
• Plants and animals seemed remarkably well
suited to whatever environment they
inhabited
– WHY WERE NO RABBITS IN AUSTRALIA
DESPITE THE PRESENCE OF HABITATS
THAT SEEMED PERFECT FOR THEM?
– WHY WERE THERE NO KANGAROOS IN
ENGLAND?
Living organisms and fossils
Evolution Primer #3 How Do We Know Evolution Happens YouTube
• Fossils – preserved remains of ancient
organisms
– WHY HAD SO MANY OF THESE
SPECIES DISAPPEARED?
– HOW WERE THEY RELATED TO LIVING
SPECIES?
The methods are all based on radioactive decay:
• Certain naturally occurring elements are radioactive, and they decay, or
break down, at predictable rates.
• Chemists measure the half-life of such elements, i.e., the time it takes for
half of the radioactive parent element to break down to the stable daughter
element. Sometimes, one isotope, or naturally occurring form, of an element
decays into another, more stable form of the same element.
• By comparing the proportions of parent to daughter element in a rock
sample, and knowing the half-life, the age can be calculated.
•
Older fossils cannot be dated by carbon-14 methods and require
radiometric dating.Scientists can use different chemicals for absolute
dating:
• The best-known absolute dating technique is carbon-14 dating, which
archaeologists prefer to use. However, the half-life of carbon-14 is only
5730 years, so the method cannot be used for materials older than about
70,000 years.
• Radiometric dating involves the use of isotope series, such as
rubidium/strontium, thorium/lead, potassium/argon, argon/argon, or
uranium/lead, all of which have very long half-lives, ranging from 0.7 to
48.6 billion years. Subtle differences in the relative proportions of the two
isotopes can give good dates for rocks of any age.
Galapagos Island
• Different islands, close together, very different climates
– Hot dry barren
WHAT TRAITS DO YOU THINK AN ANIMAL
MIGHT NEED TO SURVIVE ON A HOT DRY
ROCKY ISLAND?
Conserve water, protection from sun, make use
of scarce resources
– Sparse vegetation
– Rainfall, different assortment of plants and animals
– Rich vegetation for tortoise to reach
WHAT TRAITS DO YOU THINK AN ANIMAL
MIGHT NEED TO SURVIVE ON A RICH
VEGETATED ISLAND?
Move in trees, dim, damp conditions
– Tortoises varied from island to island
Pinta
Pinta Island
Marchena
Tower
Intermediate shell
Fernandina
James
Santa Cruz
Isabela
Santa Fe
Hood Island
Floreana
Isabela Island
Dome-shaped shell
Hood
Saddle-backed shell
The journey home
• After returning Darwin began to wonder if
animals living on different islands had once been
members of the same species?
–
Would have to have been an original species
Questions
• 1. How did Charles Darwin change our
view of the living world?
• 2. How did tortoises and birds differ
among the islands of the Galapagos?
• 3. What is evolution? Why is evolution
referred to as a theory?
• 4. What is a fossil?
• 5. Darwin found fossils of many organisms
that were different from any living species.
How would this finding have affected his
estimates of biological diversity?
Answers
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1. Darwin hypothesized that animals could undergo
change through time. This was in contrast to the
prevailing view that organisms do not change
2. Tortoises and birds showed variation that
reflected the island they lived on or the type of food
they ate
3. Evolution, or change over time, is the process by
which modern organisms have descended from
ancient ones. Evolution is referred to as a theory
because it is a well-supported explanation of
phenomena that have occurred in the natural world
4. A fossil is the preserved remains of an ancient
organism
5. It would have increased his estimates of biological
diversity!
IDEAS THAT SHAPED
DARWIN’S THINKING
People believed all forms of life and earth
had been created only a few thousand years
ago
Since creation nothing hand changed,
example a robin today looks and sounds like
a robin from the beginning of time
Fossils found????????? WHAT DID SUCH
FOSSIL EVIDENCE INDICATE ABOUT
LIFE IN THE PAST??
SEVERAL PERIODS OF CREATION
AND CATASTROPHIES
AN ANCIET CHANGING EARTH
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JAMES HUTTON AND CHARLES LYELL
– Together, Hutton and Lyell helped
scientists recognize the earth is millions
of years old, the process that changed
earth in the past are the same
processes that operate in the present.
Hutton’s Theory of Geological
change, 1795
– Layers of rock are moved by forces beneath
earths surface
» Pushed up from seafloor to make
mountains
» Rocks shaped by natural forces, rain, heat
and cold temperature, this weathers rock
extremely slow
» Proposed earth to be much more then a
few thousand years old
Lyell’s “Principles of Geology”
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Scientists must explain past events in terms of processes that
they can actually observe, since process that shaped the earth
millions of years ago continue in the present
Darwin witnessed a volcanic eruption
Darwin wrote about an earthquake
» ? If we saw these things what can we explain about
geology?
» ? If the earth could change overtime, might life change as
well?
» Thought: Lyell realized that it would have taken many,
many years for life to change in the way he suggested, this
would have been possible only if the Earth were extremely
old.
Sea
level
Sea
level
Sedimentary rocks
form in horizontal
layers.
When part of Earth’s
crust is compressed, a
bend in a rock forms,
tilting the rock layers.
As the surface erodes
due to water, wind,
waves, or glaciers, the
older rock surface is
exposed.
New sediment is then
deposited above the
exposed older rock
surface.
Lamarcks Theory of Evolution
– Among the first scientists to recognize that
living things change over time, and that all
species were descended from other species
– Animals adapted to their environments,
– 1809 – Year Darwin was born
– Lamarck proposed that by selective use or
disuse of organs, organisms acquired certain
traits during their lifetime. These traits could
then be passed on to one’s offspring’s.
Overtime this process led to change in a
species.
» Figure 15.7 and explanation!!!
Figure 15–7 Lamarck’s Theory of
The acquired
Evolution 3.characteristics,
2. Because the
a large
front claw has
been used
repeatedly, it
becomes larger
1. Male crab uses
its small front
claw to attract
mates and ward
of predators.
claw, is then passed
on to the crab’s
offspring.
Tendency towards perfection
– All organisms trying to be perfect
•
Example – an ancestor of a bird wanted
to fly, the organism continued to try and
over generations finally could fly
•
Scientists believe that insects were the first animal to
fly. They had a covering down the sides of their
bodies used to protect their spiracles, breathing
apparatus, eventually they were able to lift these up
and used to glide, then used to flap to help them fly for
short periods of time.
What do we as humans think of as perfect?
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Use and Disuse
– Organisms could altar shape or size of
particular organs by using their bodies in new
ways.
» Example – appendix, wisdom teeth
Inheritance of acquired traits
– Example – an animal sometime
during it’s lifetime, alters a
body structure – leading to
longer legs, of fluffier feathers
? If you became a body
builder would your children
have muscles when they are
born???
Evaluating Lamarck’s theory
Incorrect, an animals behavior and activity have no effect
on it’s inheritable characteristics adapted to
environment
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BUILDING SCIENCE SKILLS
Challenge students to design an experiment to test
lamarck’s theory of the inheritance of acquired traits.
Students’ experimental designs should include a
hypothesis, procedure, and possible outcomes. Ask: WHAT
SPECIES WOULD YOU USE, AND WHAT VARIABLE
WOULD YOU TEST?
Cut off the tails of adult mice and then observed
whether the offspring of the mice also had short tails.
Have students explain how the different possible outcomes
of their experiment would or would not support Lamarck’s
theory
Population Growth
– 1798, Thomas Malthus observed that babies
were being born faster than people dying
– Malthus reasoned that if the human population
continued to grow unchecked, sooner or later
there would be insufficient living space and food
for everyone
– ? WHAT WORKS AGAINST GROWTH?
WAR, FAMINE, DISEASE
– Darwin noticed this worked more strongly with
plants and animals than humans.
? WHY DO HUMANS PRODUCE FEWER
OFFSPRING?
Questions
1. What two ideas from geology were important to
Darwin’s thinking?
2. According to Malthus, what factors limited population
growth?
3. According to Lamarck, how did organisms acquire
traits?
4. Why was Lamarck’s theory of evolution ultimately
discredited?
5. Malthus formed his theory by studying factors that
control the population growth of humans. How might
factors operating on organisms in nature differ from
those of Malthus theory?
Answers
• 1. Earth is very old, and the same processes that shaped
the Earth millions of years ago continue in the present
• 2. Malthus thought that war, famine, and disease limited
population growth
• 3. Lamarck thought that organisms acquired traits by
using their bodies in new ways. For example, birds
might transform their front limbs into wings by trying to
use the limbs for flying
• 4. Lamarck’s theory was discredited because we now
know that acquired characteristics are not inherited.
• 5. Factors operating on organisms in nature might
include competition and predation instead of famine and
war
• What did such
fossil evidence
indicate about life
in the past?
• Some organisms
in the past had no
modern
representatives,
and that some
organisms may
have become
extinct
Darwin Presents his case
Darwin returned 1836 with lots of specimens
His mocking birds resulted in 3 separate species
found no where else in the world
Birds he thought were wrens, warbles, and
blackbirds were all finches and found no where
else
Tortoises, marine iguanas – all species looked
similar to ones from South America yet clearly
different
Phenotypes adapt in
response to the
environment,
with new and
useful traits
arising.
Publication of “On the origin of
Species”
He wrote in notebooks his findings, but did not publish
Discussion: Darwin’s reluctance to publish his work is a good
example of how science is influenced by its social context.
Question: what current areas of scientific research are
controversial, much as evolution was controversial in
Darwin’s time?
Answer???
1858, Darwin received an essay from Alfred Russell
Wallace, it summarized thoughts on evolutionary
change that Darwin had been mulling over for 25 years,
Darwin published 18 months later, “On the origin of
Species”
Natural Variation and Artificial
Selection
Natural Variation – defined as differences among
individuals of a species in nature
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Example – zebras, inherits genes that give it a
distinctive patterns of stripes
some cows give more milk, some plants bear larger fruits
these traits can be inherited
farmers would use selective breeding to determine which
natural variation that they found,
example – only fastest horses, cows that gave the
most milk were allowed to produce off spring
Artificial Selection – nature provided the variation
among different organisms and humans selected
those variations that they found useful.
–
How is this used today?
HowStuffWo
rks Videos
"Cool
Underwater
Creatures"
Evolution: Library: Evolution of Camouflage
Artificial
Selection
– This process
can lead to
great
differences. In
some cases, a
single ancestral
species has
given rise to a
variety of
modern plants.
Evolution by Natural
Selection Evolution Primer #4 How Does Evolution
Really Work Natural Selection - YouTube
The struggle for existence
Darwin was convinced that a process like
artificial selection worked in nature
Struggle for existence – members of
each species compete regularly to
obtain food, living space, and other
necessities of life.
Prey that are faster, better camouflaged or
better protected can avoid being caught
Predators that are faster or outsmart the prey can
catch more prey
Survival of the fittest
how well suited an organism is to its environment
fitness – the ability of an individual to survive and
reproduce in its specific environment
adaptation – an inherited characteristic that increases an
organisms chance of survival
figure 15 – 12 statement and over head
survival of the fittest – individuals better suited to their
environment, high levels of fitness, survive and reproduce
most successfully
Natural Selection – survival of the fittest, takes place with
out human control or direction
Overtime, natural selection causes a change in the
inherited characteristics of a population. It directs these
changes in ways that increase a species fitness in its
environment
?What did Darwin mean when he described certain
organisms as “more fit” than others?
A. he meant organisms that are better suited to their
environment
Weird True &
Freaky: Bear vs
Caribou : Video :
Animal Planet
Wildlife in
disguise:
Amazing animal
camouflage –
YouTube
David Gallo
shows animal
camouflage YouTube
Descent with modification
Each living species has descended with
changes from other species over time
All living organisms are related to one
another
Back in time ancestors were shared by
tigers, panthers, and cheetahs
Common descent – common ancestors of
living things
Tree of life – links all living things on
earth
Evidence of evolution
•
Darwin argued that living things have been evolving on
earth for millions of years. Evidence for this process
could be found in the fossil record, the geographical
distribution of living species, homologous structures of
living organisms, and similarities in early development.
• Fossil record
• Different layers of rock had been formed at
different times in earths history
• figure 15.13 overhead
• ? what are the major changes that occurred as
these cephalopods evolved
• they gradually evolved longer, more coiled
shells.
Sexual Selection
• Evolution: Library: Tale of the Peacock
Geographic distribution of living
species
• ? why can two species that look
very different from each other
be more closely related than
two other species that look
similar to each other?
• it depends on the
environments in which the
species evolved
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Similar Species in Similar
Environments
The existence of similar but
unrelated species was
a puzzle to Darwin. Later,
he realized that similar
animals in different
locations were the product
of
different lines of
evolutionary descent. Here,
the
beaver and the capybara
are similar species that
inhabit similar
environments of North
America and
South America. The South
American coypu also
shares many
characteristics with the
North American
muskrat. Interpreting
Graphics Which animal
has
a larger geographical
range, the coypu or the
muskrat?
Homologous body structures
Similarities among body parts of animals with backbones
the limbs differ greatly in form and function, yet they are
all constructed from the same basic bones.
Over head forelimbs of vertebrates
?what similarities in the limbs suggest that they
developed from the same basic structure?
The number and placement of the bones
?what are some major changes in bone structure that
occurred as these vertebrates evolved along different
paths?
?what is the scientific explanation for these similarities?
Each of these limbs has adapted in ways that enable
organisms to survive and reproduce in different ways in
different environments
Figure 15–15 Homologous Body
Structures
Turtle
Alligator
Bird
Typical primitive fish
Mammals
►Homologous
structures – structures that have different
mature forms in different organisms but develop
from the same embryonic tissue
►Vestigial organs – organ that serves no useful function
in an organism, so reduced in size that it is just a
trace of a homologous organ in another species
►?How might vestigial organs provide clues to an animal’s
evolutionary history?
►They might indicate a change in the animal’s
environment or behavior
►? How can biologists use the idea of homologous structures
to determine whether particular species are closely related?
►The similarities and differences of homologous
structures provide evidence for how recently species
last shared a common ancestor
►
►
Video 3: How do we know evolution happens?
Evolution: Library: Whale Evolution
Vestigial Organs These three animals are skinks, a type of lizard.
In some species the skinks, legs have become vestigial. They are
so reduced that they no longer function in walking. In humans, the
appendix is an example of a vestigial organ because it carries out
no function in digestion. Inferring How might vestigial organs
provide clues to an animal’s evolutionary history?
Similarities in Early Development
Overhead comparing vertebrate embryo
development
?why might you expect the embryos of fishes to be
more similar to the embryos of sharks than to the
embryos of humans?
Because fishes and sharks shared a more recent
common ancestor
Why Does Evolution Matter Today?
• Evolution: Why Does Evolution Matter
Now?
• Video 6
Summary of Darwin’s theory
Individual organisms in nature differ from one another. Some of this variation is
inherited
Example
Organisms in nature produce more offspring than can survive, and many of those that
survive do not reproduce
Example
More organisms are produced than can survive. Members of each species must
compete for limited resources
Example
Because each organism is unique, each has different advantages and disadvantages
in the struggle for existence
Example
Individuals best suited to their environment survive and reproduce most successfully.
The characteristics that make them best suited to their environment are passed on to
offspring. Individuals whose characteristics are not as well suited to their
environment die or leave fewer offspring.
Example
Species change over time. Over long periods, natural selection causes changes in
the characteristics of species, such as in size and form. New species form, and other
species disappear.
Example
Species alive today have descended with modifications from species that lived in the
past.
Example
All organisms on Earth are united into a single tree of life.
Example
QUESTIONS????
1. What types of evidence did Darwin use to support his
theory of change over time?
2. How is artificial selection dependent on variation in nature?
3. The theory of evolution by natural selection explains, in
scientific terms, how living things evolve over time. What is
being selected in this process?
4. What is the struggle for existence? How is it related to
Malthus’s work?
5. Compare and contrast Darwin’s theory of evolution with that
of Lamarck. How are they similar? How are they different?
.
Answers
1. He used the fossil record and the geographical
distribution of living species
2. In artificial selection, nature provides the variation
among different organisms. Humans select those
variations that they find useful.
3. a species’ fitness in its environment
4. the struggle for existence is competition between
members of the same species for food, living space, and
other needs. The greater the population pressure on
food and other resources, the greater the competition.
Malthus argued that population pressure keeps human
population numbers in check.
5. a. Both states the organisms change to adapt to their
environments. Lamarck thought organisms acquire
certain traits in their lifetime. Darwin thought that,
overtime, natural selection causes a change in the
inherited characteristics of a population
Evolution Primer #7: Why Is Evolution Controversial
Anyway? - YouTube
The Simpsons - Homer Evolution - YouTube