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Darwin

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Title: Darwin


1
(No Transcript)
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Charles Darwin
born in Shrewsbury, England, in 1809
studied medicine at Edinburgh University
(1825-1827) where the sight of blood and surgery
without anesthetics repulsed him
studied to become a clergyman at Cambridge
University (1827-1831)
3
After Cambridge, Charles was recommended for a
surveying trip on the HMS Beagle.
He sailed aboard the Beagle for 5 years, working
as a naturalist.
4
The Beagle sailed around the world.
This voyage lasted from 1831 to 1836.
5
At the time Darwin made his trip, the majority of
people believed the Earth and all of its forms of
life had been created only a few thousand years
in the past.
6
People also believed that the Earth had not
changed during those few thousand years.
People also believed in fixity of species in
other words, species never changed.
After careful observation and study of new
scientific discoveries, Darwin began to think
otherwise.
The first dinosaur to be described scientifically
was Megalosaurus by William Buckland in 1824.
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Darwin was influenced by geologist James Huttons
writings that described geologic forces he
thought had changed and were still changing the
earth.
The Father of Geology
Hutton proposed that the Earth had to be much
more than a few thousand years old.
8
Darwin was also influenced by geologist Charles
Lyell who wrote Principia Geologica.
Lyells book proposed that tremendous geologic
processes had shaped the Earth such as seen in
volcanoes active in the present.
9
On the voyage, Darwin noticed that everywhere he
went, the animals and plants differed vastly.
Patterns in the species suggested that the
species had changed over time and had given rise
to new and different species.
10
Many of Darwins conclusions were based on
observations of wildlife in the Galapagos Islands.
The Galapagos Islands lie 500 miles west of
Ecuador in the Pacific Ocean, directly on the
equator.
Galapagos means turtle.
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Galapagos finches
Darwin noticed on these islands, there were
several types of finches.
What it must have been like to be Darwin
12
Galapagos finches
In particular, Darwin observed something odd
about the finches they all looked like a bird he
had seen on the South American continent.
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Darwin wondered if the birds and other animals
had been created to match their environment, why
didnt these birds look like the birds of the
African continent, since the environments of both
the Galapagos and Africa were similar.
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Darwin guessed that some of the birds from South
America migrated to the Galapagos.
Once on the islands, the birds must have changed
over the years.
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large ground finch
woodpecker finch
cactus finch
This would explain the numerous species of birds
present.
16
Darwin concluded Each species has descended,
with changes, from other species over time.
Darwin called this
Descent With Modifications
or
evolution
(change in species over time)
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Darwin based his theory on his own observations
and the writings of Thomas Malthus.
Malthus was a British social scientist who made
these observations about humans
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Darwin extended these principles to biology,
which helped him form his theory of
Natural Selection
or Survival of the Fittest.
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Five basic components of
Natural Selection
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1. All species have genetic variation.
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Variations
  • Differences in traits
  • Come about by mutations in genes
  • Random
  • Occur in sex cells
  • Passed on to future generations

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2. Organisms produce more offspring than can
survive. Many that survive do not produce
offspring.
The female green sea turtle lays a clutch of
about 110 eggs. She may lay several clutches.
It is likely that less than 1 of the hatchlings
will ever reach sexual maturity.
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3. Since more organisms are produced than can
survive, there is competition (struggle for
existence).
Competition exists WITHIN and AMONG species.
Within and Among Species for
And Within a Species for
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The constant struggle for survival is affected by
short-term natural disasters. (drought, fires,
floods, snowstorms, hurricanes, and tornadoes)
The constant struggle for survival is also
affected by long-term changes in the environment.
(ice ages, biome shifts, etc)
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4. Survival of the fittest Some organisms are
more suited to their environment as a result of
variations in the species.
Individuals that are fit to their environment
survive and leave more offspring than those who
arent.
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5. Decent with modification Living species today
are descended with modifications from common
ancestral species that lived in the past.
Characteristics of fit individuals increase in a
population over time.
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Natural Selection Survival of the Fittest
An adaptation is any inherited characteristic (a
genetic variation) that can increase an
organisms chance of survival.
An organism does not change because of need or
desire to survive. The organism either already
has the variation that enables it to survive or
it dies.
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1. Adaptations feautres suited to a particular
environemnt that allow organisms to survive
  • Inuit people, who live in the extreme cold of the
    Arctic, have short, stout bodies that conserve
    heat.

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  • Masai people, who live in the arid lands of
    eastern Africa, have tall, lean bodies that
    disperse heat well.

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Plant Adaptations
  • Venus Fly Trap
  • Captures Animals
  • Acquires Minerals
  • For Photo-
  • synthesis

Help!!!
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Leaf Adaptations
  • Succulents
  • Thick
  • Store Water
  • Prevent Drying out

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Leaf Adapatations
  • Pine Needles
  • Shed snow
  • Less water loss
  • Reduced surface area
  • Tolerate wind

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Flower Adaptations
  • Fly pollination
  • Hair along petals
  • Putrid smell
  • Bee pollination
  • Smooth petal
  • Sweet smell

34
Extinction
As the environment changes, organisms must have
variations that allow them to survive (adapt) to
those changes or die
If an entire population of a species cannot
adapt, that species becomes extinct.
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Mass Extinction
There have been at least 5 MASS extinctions
during Earths history where a huge of the
living species were destroyed
At least one of these has been attributed to
meteor impact and its consequences.
36
Many scientists say that the earth is currently
experiencing a mass extinction crisis.
It is estimated that 1/5 or more of the worlds
species will become extinct if the rainforests
are destroyed.
37
If we are in a period of mass extinction . . .
What animals will your grandchildren be able to
see in the wild?
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Mechanisms of Natural Selection
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Lamarks Theory
  • Use and Disuse
  • Use of structure results in evolution
  • Does not take into account DNA or sex cell
    mutations

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Gene pool Changes
  • Group of reproducing organisms
  • Specific frequency of allele types
  • 25 AA
  • 50 Aa
  • 25 aa

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Changes in the Gene Pool
  • Changes in the environment
  • New mix of allele frequencies
  • 10 aa
  • 60 Aa
  • 30 AA
  • Dominant had advantage

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Bird Beak Adaptations
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Genetic DriftChanges in the gene pool due to
  1. Random mating
  2. Over a long time period
  3. No immigration of males
  4. No emigration of females
  5. Sufficient resources that match the adaptations

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Same Species Must
  • Show similar characteristics
  • Successfully
  • interbreed
  • Producing fertile offspring

Donkey Horse Mule (infertile)
45
Speciation
  • Evolution forming a new species over time
  • By Isolation of Natural Barriers

46
Geographic Isolation
  • Separation of organisms by geographic features
  • Mountains
  • Lakes, oceans, rivers
  • Desserts
  • (May result in new species over time)

47
Reproductive IsolationWhen two different species
can not mate and have successful offspring
  • Reasons why they cant mate
  • Geographic barriers
  • Anatomy or physiology
  • Social behaviors

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Gradualism
  • Small changes over a long time

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Punctuated Equilibrium
  • Large changes with periods of no change
  • Happens rapidly

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  • Punctuated Equilibrium
  • Gradualism

S P E C I E S
Time
51
Divergence
Human arm
  • diverge branch off
  • Homologous structures
  • Same origin
  • Different Environments
  • Same underlying structure
  • Different functions

Bat wing
Cat limb
Whale flipper
Original Species Mammal
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Convergence
Bird wing
  • convergecome together
  • Analogous features
  • From different origins
  • Similar environments
  • Similar functions
  • Different structures

Organisms that fly
Butterfly wing
Bat wing
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Comparative Anatomy Structures
  • Homologous
  • Same ancestor
  • homosame
  • Same underlying structures
  • Different Functions
  • Different Environments
  • Analogous
  • Different ancestors
  • analogylike
  • Different underlying structures
  • Same Function
  • Similar Environments

54
Works Cited
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