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Darwin

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Darwin & Evolution by Natural Selection Warbler finch Ground finches Tree finches Cactus eater Insect eaters Seed eaters Bud eater 2006-2007 * * * * * * * * * Charles ... – PowerPoint PPT presentation

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Title: Darwin


1
Darwin Evolution by Natural Selection
2
Charles Darwin
  • born into a fairly wealthy family.
  • Had a father who was a medical doctor and
    grandfather was Josiah Wedgewood (the
  • started medical school, but lost interest.
  • attended theologian school, but was more
    interested in biology and geology.

3
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

4
Darwins influences
  • Charles Lyell- wrote Principles of Geology
    (1830). Believed in uniformitarianism which
    states that the earth was shaped entirely by
    slow-moving forces still in operation today,
    acting over a very long period of time.

5
  • Thomas Malthus- (1797 )wrote Essay on the
    Principle of Population which argued that because
    of the natural human urge to reproduce, human
    population increases geometrically (1, 2, 4, 16,
    32, 64, 128, 256, etc.). But food supply
    increases arithmetically (1, 2, 3, 4, 5, 6, 7, 8,
    etc.). Therefore, since food is necessary to
    human life, population growth in any area or on
    the planet, if unchecked, would lead to
    starvation.
  • Darwin thought, this would apply to plants and
    animals too.

6
  • http//www.biography.com/articles/Charles-Darwin-9
    266433
  • Check out the videos.

7
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
8
Voyage of the HMS Beagle
  • Stopped in Galapagos Islands
  • 500 miles off coast of Ecuador

9
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
10
Darwin foundmany unique species
Many of Darwins observations made him wonder
Why?
Darwin asked Why were these creatures found only
on the Galapagos Islands?
11
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?
12
Darwin found Different shells on tortoises on
different islands
Darwin asked Is there a relationship between the
environment what an animal looks like?
13
Darwin found birds
  • Darwin found
  • Many different birds on the Galapagos Islands.

Finch?
Sparrow?
He thought he found very different kinds
Warbler?
Woodpecker?
14
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
Finch?
Sparrow?
Darwin asked If the Galapagos finches came from
the mainland, why are they so different now?
Warbler finch
Tree finch
Warbler?
Woodpecker?
15
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
16
Relationship between species (beaks) food
17
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

18
From 1 species to 14 species
natural selection for best survival reproduction
variation
19
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

20
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

?
21
Darwin found more fossils
Darwin found Evidence that creatures have
changed over time
Darwin asked Why should extinct sloths modern
sloths be found on the same continent?
22
Darwin Publishes His Results
  • On the Origin of Species By Natural Selection
  • Alfred Wallace also came to the same conclusions
    as Darwin and they published their results
    together.

23
Not a lot was known in the 1840s
  • the basic mechanism for speciation was unknown
  • there were (and still are) gaps in the fossil
    record
  • little known about genes and inherited traits
  • age of the earth was still disputed
  • people believed each species was a distinct and
    unchanging entity.

24
Natural selection was based on the following
observations.
  • 1) Species have great fertility. They make more
    offspring than can grow to adulthood.
  • 2) Populations remain roughly the same size, with
    modest fluctuations.
  • 3) Food resources are limited, but are relatively
    constant most of the time.
  • From these three observations it may be inferred
    that in such an environment there will be a
    struggle for survival among individuals.
  • 4) In sexually reproducing species, generally no
    two individuals are identical. Variation is
    rampant.
  • 5) Much of this variation is heritable.

25
  • To summarize Darwin's Theory of Evolution
  • 1. Variation There is Variation in Every
    Population.2. Competition Organisms Compete for
    limited resources.3. Offspring Organisms
    produce more Offspring than can survive.4.
    Genetics Organisms pass Genetic traits on to
    their offspring.5. Natural Selection Those
    organisms with the Most Beneficial Traits are
    more likely to Survive and Reproduce.

26
  • The End
  • Adapted from Regents Biology
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