Darwin and the Theory of Evolution-Changes over Time

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Darwin and the Theory of Evolution-Changes over
Time
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Evolution
Whats the Standard?

• S7L5. Students will examine the evolution of
  living organisms through inherited
  characteristics that promote survival of
  organisms and the survival of successive
  generations of their offspring.
• a. Explain that physical characteristics of
  organisms have changed over successive
  generations (e.g. Darwins finches and peppered
  moths of Manchester).

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Darwin Evolution by Natural Selection
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Charles Darwin

• Proposed a way how evolution works
• How did creatures change over time?
• by natural selection
• Collected a lot of evidence to support his ideas
• 1809-1882
• British naturalist

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Voyage of the HMS Beagle

• Invited to travel around the world
• 1831-1836 (22 years old!)
• makes many observations of nature
• main mission of the Beagle was to chart South
  American coastline

Robert Fitzroy
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Voyage of the HMS Beagle

• Stopped in Galapagos Islands
• 500 miles off coast of Ecuador

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Galapagos
Recently formed volcanic islands. Most of animals
on the Galápagos live nowhere else in world, but
they look like species living on South American
mainland.
800 km west of Ecuador
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Darwin foundmany unique species
Many of Darwins observations made him wonder
Why?
Darwin asked Why were these creatures found only
on the Galapagos Islands?
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Darwin foundclues in the fossils
Darwin found Evidence that creatures have
changed over time
Darwin asked Why should extinct armadillos
modern armadillos be found on same continent?
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Darwin found more fossils
Darwin found Evidence that creatures have
changed over time
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Darwin found Different shells on tortoises on
different islands
Darwin asked Is there a relationship between the
environment what an animal looks like?
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Darwin found birds

• Darwin found
• Many different birds on the Galapagos Islands.

He thought he found very different kinds
Finch?
Sparrow?
Warbler?
Woodpecker?
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But Darwin found a lot of finches

• Darwin was amazed to find out
• All 14 species of birds were finches

But there is only one species of finch on the
mainland!
Large ground finch
Small ground finch
Darwin asked If the Galapagos finches came from
the mainland, why are they so different now?
Finch?
Sparrow?
Warbler finch
Tree finch
Warbler?
Woodpecker?
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The finches cinched it!

• different beaks are inherited variations
• serve as adaptationsthat help birds compete for
  food
• these birds survive reproduce
• pass on the genes for those more fit beaks
• over time nature selected for different species
  with different beaks

• Darwin found
• The differences between species of finches were
  associated with the different food they ate.

Darwin said Ahaaaa! A flock of South American
finches were stranded on the Galapagos
Large ground finch
Small ground finch
Big seed eater
Small seed eater
Warbler finch
Tree finch
Insect eater
Leaf bud eater
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Relationship between species (beaks) food
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Darwins finches

• Darwins conclusions
• variations in beaks
• differences in beaks in the original flock
• adaptations to foods available on islands
• natural selection for most fit
• over many generations, the finches were selected
  for specific beaks behaviors
• offspring inherit successful traits
• accumulation of winning traitsboth beaks
  behaviors
• separate into different species

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From 1 species to 14 species
natural selection for best survival reproduction
variation
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Earlier ideas on Evolution

• LaMarck
• evolution by acquired traits
• creatures developed traits during their lifetime
• give those traits to their offspring
• example
• in reaching higher leaves giraffes stretch their
  necks give the acquired longer neck to
  offspring
• not accepted as valid

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Darwins view of Evolution

• Darwin
• giraffes that already have long necks survive
  better
• leave more offspring who inherit their long necks
• variation
• selection survival
• reproduction inheritance of more fit traits

?
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What did Darwins Travels reveal

• The diversity of living species was far greater
  than anyone had previously known!!
• These observations led him to develop the theory
  of evolution!!

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Natural Selection Examples

• Are these two butterflies the same species?

These are the Monarch and Viceroy
butterflies. The Monarch on the left is poisonous
and the Viceroy is not.
Question Why would it be beneficial for the
Viceroy to look like the Monarch?
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Natural Selection Examples

• Checkpoint A species of hare (rabbit) that is
  found in a cold tundra environment. How are
  oversized feet an advantage to the Arctic Hare?

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Natural Selection Examples

• How many moths do you see?

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Darwins Theory REVIEW.

• 1. Organisms differ variation is inherited
• 2. Organisms produce more offspring than survive
• 3. Organisms compete for resources
• 4. Organisms with advantages survive to pass
  those advantages to their children
• 5. Species alive today are descended with
  modifications from common ancestors

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Evolution is a Theory Just like Gravity!

• Evolution is a well supported explanation of
  phenomena that have occurred in the natural world
• A theory in science is a well tested hypothesis,
  not just a guess

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Differences among Organisms

• Adaptation-a different characteristic that helps
  an individual survive
• Species-a group of organisms that can mate and
  produce fertile offspring
• Within any population there are variations among
  members
• Some variations are helpful and some are not

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Evolution

• Those variations that are helpful accumulate in
  the population
• Eventually a new species forms with the new
  variations
• This is Evolution
• Defined as the process in which populations
  change over time to form new species.

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Do species change over time?

• Evidence suggests that species have changed over
  time.
• Many organisms have appeared and died out.
• As populations change over time new species arose
  and other species became extinct.

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Extinction

• Several periods of mass extinction have occured

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Evidence for evolution

• the fossil record show change from earlier
  species to present day species
• There are chemical and anatomical similarities
  between related life forms
• the recorded genetic changes in living organisms
  over many generations-DNA evidence
• the geographic distribution of related species

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Evidence-Fossil record

• Show estimated age and physical similarities of
  organisms
• Show changes from earlier life forms

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Fossil record
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Fossil Record
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Evidence-Common Ancestry
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Common ancestors in canines
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Cladogram showing common ancestry among some
lizards
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Evidence from Whales
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Horse Evolution
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Evidence of Evolution
Turtle

• Homologous Body Structures
• Structures that have different mature forms but
  develop from the same embryonic tissues
• e.g. Wing of bat, human arm, leg of turtle

Alligator
Bird
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Homologous structures
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Homologous structures in Embryos
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Embryological development
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DNA evidence

• Many organisms share common DNA
• The more DNA that is shared, the more closely
  related the two organisms are

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Pangea and the fossil record
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Pangea and the fossil record
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Evolution took a long time
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Evidence for Evolution

• The Fossil Record These imprints allow
  scientists to see an entire evolutionary history,
  including in between fossils.
• Homologous Body Structures Why else use the
  same skeletal plan for very different appendages?
  And Similarities in Embroylogy During the very
  early stages of life (in the womb), many
  organisms go through similar stages of
  development.
• DNA evidence-shows close relationship between
  different species

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