Transcript Evolution

of
Evolution
Charles Darwin and
The Origin of Species
What do you think of when you hear the word
“EVOLUTION”
Science?
Animals?
Evolution is a very complex and controversial issue. This lesson is just a
Humans?
basic introduction to the theory of evolution and natural selection
as
presented by Charles Darwin
Change?
Charles
Darwin?
Religion?
Survival?
Fossils?
Extinction?
Charles Darwin (1809-1882)
► He
was an English Naturalist
► He traveled around the world on his
ship, the Beagle
► Studied species and fossils in the
Galapagos Islands and around the
world
► Why did some species survive while
others became extinct?
► Natural selection
► Published The Origin of Species in
1859
Darwin’s Theory
►
Darwin's theory of evolution has four main parts:
All organisms
come
common
ancestors
by
a living
process
of branching.
Change
Organisms
is gradual
have
changed
andfrom
slow,
over
taking
time,place
and over
the ones
a long
time.
today
This
are
was
Over time,
split
different
species,
which
are
related
supported
different
from
bypopulations
the
those
fossil
that
record,
livedinto
and
in the
was
past.
consistent
Furthermore,
with
the
many
fact
that no
because had
they
are
descended
from
a common
Thus,
if one goes
naturalist
organisms
that
observed
once
lived
theare
sudden
now extinct.
appearance
Theancestor.
of
world
a new
is not
species.
far enough
in time, any pair of organisms has a common ancestor.
constant,
butback
changing.
This explained the similarities of organisms that were classified together - they were similar because of shared traits inherited from their common
ancestor.
It also explained
why similar
species
to selection.
occur in the
The
mechanism
of evolutionary
change
wastended
natural
same geographic region.
Natural Selection
► “I
have called this principle, by which each slight
variation, if useful, is preserved, by the term of
natural selection.”
– Charles Darwin from “The Origin of Species”
► Darwin's
theory of natural selection holds that
variation within species occurs randomly and that
the survival or extinction of each organism is
determined by that organism's ability to adapt to
its environment.
On The Galapagos Islands
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Darwin found mockingbirds that were similar to ones that were native
to Chile, but differed slightly from island to island
He studied different species of finches and the slight variations in their
beaks
He noticed that the shapes of tortoise shells also varied slightly from
island to island
He found fossils of animals that had recently become extinct
He kept a journal and collected fossils and specimens for further study
Darwin’s Finches
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These are some of the finches
that Darwin studied on his
voyage
Though they are all finches,
their beaks distinguish them
from one another
Some finches developed short,
strong beaks that made it
possible for them to crack nuts
Some developed long, fine
beaks to reach insect larvae in
tiny holes
This is an example of how these
finches adapted to their
environment to survive (natural
selection)
Darwin’s Finches
Darwin believed that all of the different finches came from a common ancestor
and that their differences were a result of natural selection
Example of Natural Selection
Peppered Moth
 Moths can camouflage with trees to avoid
being eaten by birds.
► There were light moths and dark moths living
near English industrial cities in the 19th century
 The dark moths stood out on the light
colored trees and were more likely to be seen
and eaten by birds
► Thus, there were many more light
colored moths than dark colored moths.
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As English factories produced more and more
soot, the trees turned a darker color. This was
able to camouflage the dark moths, but not the
light moths
 THEN, the light moths stood out on the dark
trees and were more likely to be seen and
eaten by birds!
► Thus, there were more dark colored
moths than light colored moths.
Because the dark moth was able to
camouflage it was able to avoid
being eaten.
If the light colored moth is not
able to adapt to its environment
then it will eventually become
extinct.
Camouflage
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Many animals have evolved to resemble the environment around them.
This makes it very difficult for predators to find them and eat them, thus increasing their
chance of survival.
Can you spot them?
Brimstone Butterfly
Camo Moth
Stick Bug
Large Fly
Lion
Preying Mantis
Seal
Patterns of Evolution
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Darwin believed that natural selection can
ultimately lead to the formation of new
species.
Sometimes many species evolve from a
single ancestral species.
Similarities in skeletal and muscular
structure of Hawaiian honeycreepers led
scientists to conclude that the 23 species
of honeycreepers evolved from one
ancestral species.
Such an evolutionary pattern, in which
many related species evolved from a
single ancestral species, is called adaptive
radiation.
Adaptive Radiation
► Adaptive
radiation most
commonly occurs when
a species of organisms
successfully invades an
isolated region where
few competing species
exist. If new habitats
are available, new
species will evolve.
Divergent Evolution
Red Fox
Divergent evolution is the process of two or
more related species becoming more and
more dissimilar.
► Example: The red fox and the kit fox
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 The red fox lives in mixed farmlands and
forests, where its red color helps it blend in with
surrounding trees.
 The kit fox lives on the plains and in the
deserts, where its sandy color helps conceal it
from prey and predators. The ears of the kit fox
are larger than those of the red fox. The kit
fox's large ears are an adaptation to its desert
environment
Kit Fox
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Similarities in structure indicate that the red
fox and the kit fox had a common ancestor. As
they adapted to different environments, the
appearance of the two species diverged, or
became more and more different.
Convergent Evolution
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Convergent evolution is the opposite of divergent
evolution
In convergent evolution, unrelated species become more
and more similar in appearance as they adapt to the
same kind of environment.
Frogs and Chameleons are examples of convergent
evolution because although they are different
amphibians, they have both developed harpoon-like
tongues to catch insects
Co-evolution
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Co-evolution is the joint change of two or more
species in close interaction. Predators and their prey
sometimes co-evolve; parasites and their hosts often
co-evolve; plant-eating animals and the plants upon
which they feed also co-evolve.
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One example of co-evolution is pollination of orchids
by African moths.
 These species co-evolve because the moths depend on
the flowers for nectar, and the flowers depend on the
moths to spread their pollen so that they can reproduce.
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The relationship between the moth and the orchids is
mutually beneficial because they help each other
survive.
Why is This Important?
► Divergent,
convergent and co-evolution are
different ways organisms adapt to the
environment. These are examples of how
the diversity of life on earth is due to the
ever-changing interaction between a species
and its environment.
Extinction
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Extinction is the disappearance of an entire species
If a species does not have the genetic traits to survive in its
environment, then the species will eventually become extinct forever
Some examples of extinct animals are:
Galapagos Tortoise
Bali Tiger
Dinosaurs
Thylacine
Steller’s Sea Cow
Quagga
Laughing Owl
Dodo Bird
Reasons for Extinction
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Rarity- when there are very few animals of a species left (Galapagos tortoise)
Inbreeding- when animals mate too much within their own group the offspring become
less able to survive and adapt in a healthy way
Hybridization-When two animals from different sub-species mate, they might pass on
genes that are less healthy (Quagga-half horse half zebra)
Gradual loss of habitat- When an animal's habitat is slowly destroyed and they have
nowhere to live. (Bali Tiger)
Long-term environmental trends- Scientists think that dinosaurs became extinct because
of a slow cooling of the earth
Catastrophe- Volcanic eruption, dramatic change in climate, tsunami, etc.
Extinction or reduction of mutualistic population- If two species are dependent on each
other, then the endangering of one also endangers the other
Competition- When a new species is introduced to a habitat, then the stronger of the
two species will be more likely to survive.
Predators-When the population of a species of predator in a habitat suddenly increases,
the population of their prey decreases
Disease- If a particular sickness spreads quickly throughout a particular species, then
many may die before they can reproduce
Hunting and collecting- Hunters have been largely responsible for the endangerment of
many animal species.
Applications
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Knowledge about evolution and natural selection has benefited our
society in many ways, and has helped make numerous technological
advances, especially in the field of biology and medicine
 Using Darwin’s theory of natural selection, scientists have been able to
identify the desirable traits which would improve the probability of survival
in certain species
 It has helped scientists and doctors in treating viruses and diseases.
For example: Did you know that when a doctor gives you antibiotics, you need
to continue taking them until all of the pills are gone, even if you start to feel
better? When a doctor gives you antibiotics, they start to fight of the bacteria
in your body, little by little. It starts with the weak bacteria, and eventually kills
the strongest bacteria.
► BUT, if you stop taking your medicine, then it is only the STRONG bacteria that
are left in your body. That means that they will continue to reproduce and
become stronger and stronger, and it will be much harder for the medicine to
kill them. This is an example of natural selection because the strong bacteria
survives and grows.
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Conclusion
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Darwin’s observations have
made a great impact in the
scientific community. Because
of his observations, we are
better able to understand why
some species survive and
some die.
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We are also better able to
take precautions to protect
species that are endangered.
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Lastly, we can understand the
diversity in the world around
us and learn to appreciate it.
References
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http://www.lucidcafe.com/library/96feb/darwin.html
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http://outreach.mcb.harvard.edu/teachers/Summer06/BethMick/TheoryEvolution.ppt#264,9,EVID
ENCE OF EVOLUTION
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wikipedia.com
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http://www.globalchange.umich.edu/globalchange1/current/lectures/selection/selection.html
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http://people.rit.edu/rhrsbi/GalapagosPages/DarwinFinch.html
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http://bioweb.cs.earlham.edu/9-12/evolution/HTML/converge.html
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http://biol1114.okstate.edu/study_guides/scenarios/5-galapagos/images/adaptive_radiation.gif
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http://en.wikipedia.org/wiki/List_of_examples_of_convergent_evolution#Reptiles
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http://www.pbs.org/wgbh/evolution/extinction/index.html
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http://images.google.com/imgres?imgurl=http://sciencegnus.com/Quagga.jpg&imgrefurl=http://s
ciencegnus.com/Extinct%2520Animals.html&usg=__jvKRAbOBBqLDKizo6r_GeeZqXo8=&h=301&w
=400&sz=10&hl=en&start=1&um=1&tbnid=XgWOxV3IPxCzGM:&tbnh=93&tbnw=124&prev=/ima
ges%3Fq%3Dextinct%2Banimals%26hl%3Den%26rls%3Dcom.microsoft:en-us%26um%3D1
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http://library.thinkquest.org/J002558F/extinction.htm