Transcript CHAPTER 23 LECTURE SLIDES Prepared by Brenda Leady

CHAPTER 23
LECTURE
SLIDES
Prepared by
Brenda Leady
University of Toledo
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Biological evolution
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Heritable change in one or more characteristics
of a population or species from one generation
to the next
Viewed on a small scale relating to changes in a
single gene in a population over time –
microevolution
Viewed on a larger scale relating to formation of
new species or groups of species –
macroevolution
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
Species
 Group
of related organisms that share a
distinctive form
 Among species that reproduce sexually,
members of the same species are capable of
interbreeding to produce viable and fertile
offspring

Population
 Members
of the same species that are likely
to encounter each other and thus have the
opportunity to interbreed
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Theory of evolution

Empirical thought
 Relies
on observation to form an idea or
hypothesis, rather than trying to understand
life from a non-physical or spiritual point of
view

Shift toward empirical thought encouraged
scholars to look for the basic rationale
behind a given process or phenomenon
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
Mid- to late-1600s, John Ray was the first
to carry out a thorough study of the natural
world
 Developed
an early classification system
 Modern species concept
Extended by Carolus Linnaeus
 Neither proposed that evolutionary change
promotes the formation of new species

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Late 1700s, small number of European
scientists suggest life forms are not fixed
 George Buffon says life forms change over
time
 Jean-Baptiste Lamarck realized that some
animals remain the same while others
change

 Believed
living things evolved upward toward
human “perfection”
 Inheritance of acquired characteristics
 Giraffe neck example
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Charles Darwin
British naturalist born in 1809
 Theory shaped by several different fields
of study

 Geology
 Economics
 Voyage
of the Beagle
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
Uniformitarism hypothesis from geology
 Slow
geological processes lead to substantial
change
 Earth was much older than 6,000 years

Thomas Malthus, an economist, says that
only a fraction of any population will
survive and reproduce
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HMS Beagle (1831-1836)
Darwin’s ideas were most influenced by
his own observations
 Struck by distinctive traits of island species
that provided them ways to better exploit
their native environment
 Galapagos Island finches

 Saw
similarities in species yet noted that
differences that provided them with
specialized feeding strategies
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Formulated theory of evolution by mid-1840s
Spent several additional years studying
barnacles
1856, began writing his book
1858, Alfred Wallace sends Darwin an
unpublished manuscript proposing many of the
same ideas
Darwin’s and Wallace’s papers published
together
1859, Darwin’s The Origin of the Species is
published detailing his ideas with observational
support
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Descent with modification

Evolution based on
 Variation
within a given species
Traits heritable – passed from parent to offspring
 Genetic basis not yet known

 Natural
selection
More offspring produced than can survive
 Competition for limited resources
 Individual with better traits flourish and reproduce

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Surviving
birds that
reproduce
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Surviving
birds that
reproduce
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Surviving
birds that
reproduce
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The Grants Have Observed Natural Selection in
Galapagos Finches
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Since 1973, the Grants have studied natural
selection
Focused much of their work on Daphne Major –
moderately isolated, undisturbed habitat and
resident finches
Compared beak sizes of parents and offspring
over many years
Birds with larger beaks survived better during
drought years
In the year after drought, average beak depth
increases