evolution chapter 15. evolution: the change over time of the genetic composition of populations...
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EVOLUTION
CHAPTER 15
• Evolution: the change over time of the genetic composition of populations
• Natural Selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success)
• Evolutionary Adapations: a prevalence of inherited characteristics that enhance organisms’ survival and reproduction
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EVOLUTIONARY HISTORY– Linnaeus - taxonomy - Lyell - uniformitarianism
– Hutton - gradualism - Darwin - evolution
– Lamarck - evolution - Mendel - inheritance
– Malthus - populations - Wallace - evolution
– Cuvier - paleontology - Count Buffon - evolution
RESISTANCE TO THE THEORY OF EVOLUTION
RESISTANCE TO THE THEORY OF EVOLUTION
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DARWIN’S INFLUENCES
Taxonomy matured during mid-eighteenth centuryLinnaeus believed in:
He developed the binomial system of nomenclature
System of classification for living things Count Buffon:
Wrote 44-volume catalog of all known plants and animals
Suggested descent with modification
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Lamarck = First biologist to: Propose evolution Link diversity with environmental adaptation
Concluded more complex organisms are descended from less complex organisms: SIMPLE TO COMPLEX
Proposed inheritance of acquired characteristics – Lamarckianism
DARWIN’S INFLUENCES
Passing on Acquired Traits
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DESIRE TO CHANGE
Use and Disuse
HMS BEAGLE VOYAGE• 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
• While on the voyage of the HMS Beagle in the 1830s, Charles Darwin observed– similarities between living and fossil
organisms
– the diversity of life on the Galápagos Islands, such as blue-footed boobies and giant tortoises
Figure 13.1A
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FINCHES
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MALTHUSOverpopulation and
species control
LYELLEarth is subject to slow but continuous cycles of erosion
Proposed uniformitarianism, rates and processes of change are constant
DARWIN’S INFLUENCES
• Darwin became convinced that the Earth was old and continually changing– He concluded that living things also
change, or evolve over generations
– He also stated that living species descended from earlier life-forms: descent with modification (originally Buffon and Erasmus Darwin)
• All organisms are related through decent from an ancestor that lived in the remote past.
1. Population has Variation2. Variations may be favorable3. More offspring are produced than survive4. Survivors have favorable traits5. Populations change over time
DARWIN’S 5 MAJOR CONCLUSIONS
ON THE ORIGIN OF SPECIES
• ......ALL THIS LEADS TO HIS THEORY OF NATURAL SELECTION and SURVIVAL OF THE FITTEST
• 1859 Publication
• Wallace influence
Early 19th century
IndustrialRevolution
WITNESSING NATURAL SELECTION
Evolution evidence: Fossils
• The fossil record shows that organisms have appeared in a historical sequence
• Many fossils link early extinct species with species living today
– These fossilized hind leg bones link living whales with their land-dwelling ancestors
Figure 13.2G, H
2006 Fossil Discovery of Early Tetrapod
• Tiktaalik– “missing link” from sea to land
animals
• Similar structure
• Similar development
• Different functions
• Evidence of close evolutionary relationship– recent
common ancestor
Evolution evidence: Homologous Structures
spines
tendrilssucculent leaves
colored leaves
Homologous structures
leaves
needles
Evolution evidence: Analogous Structures
Separate evolution of structures
similar functions similar external
form different internal
structure & development
different origin no evolutionary
relationship
Don’t be fooledby their looks!
Evolution evidence: Comparative
Embryology
• Modern animals may have structures that serve little or no function– remnants of structures that were functional
in ancestral species– deleterious mutations accumulate in genes
for non-critical structures without reducing fitness
• snakes & whales — remains of pelvis & leg bones of walking ancestors
• eyes on blind cave fish
• human tail bone
Evolution evidence: Vestigial Structures
Evolution evidence: Molecular Biology
• Similarities in DNA, proteins, genes, and gene products
• Common genetic code
Closely related species have sequences that are more similar than distantly related species
DNA & proteins are a molecular record of evolutionary relationships
Fig. 22-20
• Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution
• Islands have many endemic species that are often closely related to species on the mainland
Evolution evidence: Biogeography
• Insecticide & drug resistance
–insecticide didn’t kill all individuals
–resistant survivors reproduce
–resistance is inherited
–insecticide becomes less & less effective
NATURAL SELECTION IN ACTION
• Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties”
““descendantsdescendants”” of the wolf of the wolf
““descendantsdescendants”” of wild mustard of wild mustard
ARTIFICIAL SELECTION