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Chapter 15: Darwin

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Chapter 15: Darwin s Theory of Evolution Source: donsmaps.com Source: http://anthro.palomar.edu/evolve/evolve_2.htm – PowerPoint PPT presentation

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Title: Chapter 15: Darwin


1
Chapter 15 Darwins Theory of Evolution
2
Theory of Evolution
  • Evolution
  • Gradual process (over millions of years!) by
    which modern organisms have descended from
    ancient ancestors
  • Evolution is based on scientific facts,
    observations and hypotheses
  • Proposed by Charles Darwin lets examine his
    voyage and data.

3
Charles Darwin
  • English naturalist
  • Set sail on a 5 year cruise on the HMS Beagle in
    1831

4
The Voyage
  • At each stop, Darwin
  • Made biological and geological observations
  • Collect plant and animal specimens
  • Collected Fossils

5
Darwin Observed
  • A great deal of biodiversity!
  • Vast number or plants animals
    species lived at each location
  • Each species seemed well adapt to its environment
  • An intriguing geographic distribution of species
  • Today we know that there are about 1.75 million
    species on the planet.
  • This number only represents 1 of all species
    that ever lived on Earth!

6
The Galapagos Islands An Important Influence on
Darwin
  • Small group of Islands located 1000km west of
    South America
  • The Islands had very different climates
  • Darwin noticed that plants and animals varied
    noticeably from island to island.
  • Ex
  • Land Tortoises
  • 14 different sub-species
  • 4- extinct
  • 1 almost extinct
  • 9- living

7
Darwin found the shell shape corresponds to the
habitat
The Giant Tortoise
Lonesome George
8
Darwins Thoughts
Has everything always been here?
How old is the earth?
Where did all the animals come from?
Do plants ever change?
Where did humans come from?
What happened to all the dinosaurs?
What about fossils?
9
  • Darwins ideas were heavily influenced the ideas
    of the time

10
 Early Explanations of Change
  • James Hutton (1726-1797)
  • Thought that geological changes were the result
    of gradual change over a long period of time
  • Earth is 4.6 billion years old!
  • Significant
  • many at and before his time
  • believed the earth was only
  • a few thousand years old.

11
 Early Explanations of Change
  • Charles Lyell (1797-1875)
  • Developed the theory of
  • uniformitarianism
  • the present is key to the past
  • The current geologic processes have shaped the
    earths topography.
  • Geologic processes take a long time! (millions of
    years!)

12
 Early Explanations of Change
  • Jean Baptiste Lamarck (1744-1829)
  • Proposed a theory of evolution based on
    selective use or disuse of traits
  • All organisms have a tendency toward perfection
  • Organisms are continually changing and acquiring
    features that help them
  • Use and Disuse
  • Organisms can alter the size/shape of a
    particular appendage by using it in a new way
  • Inheritance of Acquired Traits
  • modifications could be passed on to offspring
  • giraffes who developed longer necks from
    stretching could pass these long necks onto their
    offspring

13
 Early Explanations of Change
  • Jean Baptiste Lamarck (1744-1829)
  • Lamarck did not know how traits were acquired and
    passed on.
  • His hypothesis had many flaws.
  • His ideas helped ideas about adaptation paved the
    way for Darwins theory

14
 Early Explanations of Change
  • Thomas Malthus (1766-1834)
  • Was an economist
  • Notice babies were being born faster than people
    were dying.
  • Figured, sooner or later living space and food
    supplies would be in short supply
  • Events such as famine, war and disease would
    limit population growth
  • Darwin would later apply this idea to plants and
    animals

15
Darwin Presents His Case
  • Darwin reflected on his findings for many years
    after returning home.
  • He wrote about his theories in, On the Origin of
    Species.
  • Published in 1859
  • 23 years after the voyage of the Beagle

16
Inherited Variation vs. Artificial Selection
  • Variations
  • Different forms of alleles for a trait
  • Inherited Variations
  • Traits passed on from parent to offspring
  • Artificial Selection
  • Humans select useful variations from naturally
    occurring traits
  • Selective breeding practices

17
Evolution by Natural Selection
  • The Struggle for Existence
  • Darwin thought nature used an artificial
    selection process
  • Members of each species compete for resources
  • Natural Selection
  • Processes in nature that over time results in
    only the survival of the fittest species
  • Results in changes of inheritable characteristics
    of a population.
  • Changes increase a species fitness in its
    environment

18
Survival of the Fittest
  • Fitness
  • Ability of an individual to survive and
    reproduce.
  • Fitness is a result of adaptations
  • Adaptation
  • Physical and behavioral traits that allow an
    organism to survive in its environment

19
Darwin Concluded
  • Over long periods of time, natural selection
    produces organisms that have different
  • Structures
  • Niches
  • Habitats
  • Species descended with modifications from a
    common ancestor.
  • Implies all living things are related to one
    another
  • This principle is known as common descent

20
Darwins Finches
21
Darwins Proof
  • Evidence of Evolution
  • The Fossil Record
  • Geographical Distribution
  • Similarities
  • Embryology
  • Chemical Compounds
  • Body Structures

22
The Fossil Record
  • By comparing older fossils with younger fossils,
    evidence of change is clear.
  • Lets look at Cephalopods

23
Geographic Distribution of Living Species
  • Darwin discovered the existence of similar but
    unrelated species in different locations
  • Darwin later realized the similar animals were
    products of different lines of evolutionary
    descent.

24
Similarities in Early Development
  • Lets examine embryos
  • In the late 1900s many thought, embryos looked
    the same
  • While thats not exactly the case
  • Similar genes are at work in early development
  • As they grow the become more dissimilar
  • Differences caused by genes that have changed due
    to evolution

25
Similarities in Early Development
26
Similarities in Body Structure
  • Embryos develop limbs that look similar
  • Evolutionary changes altered the structure and
    appearance
  • Limbs of different species are adaptations
    enabling organisms to survive in their
    environment
  • Structures that develop from the same body part
    are called Homologous Structures

27
Homologous Structures
28
Vestigial Organs
  • Organs that have no or little purpose.
  • Evolution has lead to adaptations that suit
    particular organisms

29
Similarities in Chemical Compounds
  • All organisms use DNA and/or RNA
  • Many organisms have similar proteins
  • The more closely related two species are, the
    more their chemical properties resemble each
    other.

30
Similarities can be explained with Darwins
theory
  • Living organisms evolved with gradual
    modification of earlier forms of an ancestor with
    common descent.

31
Lets Look at an Example
  • In pre-industrial England, there was a species of
    moth called the
  • Peppered Moth (Biston betularia)
  • Almost all peppered moths were gray with dark
    flecks
  • Rarely were they black

32
The Peppered Moth
  • The peppered moth tend to rest on tree trunks
    during the day
  • The gray moth were well camouflaged on the gray
    tree trunks
  • Black moths stand out and are easy targets for
    birds.

33
The Peppered Moth
  • Now, turn to England during Industrial Times
  • Pollution from the factories turned tree trunks
    black with soot.
  • Now, the black moths were camouflaged on the
    trees.

34
The Peppered Moth
  • The black moths had a better chance of survival
  • They had a higher fitness
  • After many moth generations, almost all the
    months in industrial areas were black

35
The Peppered Moth
  • Black coloration is an adaptation to an
    environment with black tree trunks
  • In an industrial environment, black moths survive
    to reproduce better than gray moths.
  • Therefore, their genes are passed on to future
    generations

36
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