Presentation.pptxIntroduction to Darwinian Evolution
Evolution What is evolution?
Accumulation of inherited changes within a population over time
Unifying concept of biology
links all fields of life sciences into a unified body of knowledge
Jean Baptiste de Lamarck 1744-1829 Widely regarded as one of the most influential naturalists and an important forerunner of evolution.
He proposed that organisms:
change over time by natural phenomena,
not divine intervention
had vital force that changed them toward
greater complexity over time
could pass traits acquired during lifetime to offspring (this theory has since been refuted
by modern genetics)
Charles Darwin
Developed the Theory of evolution
based on observations during his
five-year voyage on the HMS Beagle
Found similarities between organisms
on arid Galápagos Islands
on humid South American mainland
Voyage of HMS Beagle
Charles Darwin
Influenced by artificial selection
variety of domesticated plants and animals
Applied Thomas Malthus’s ideas on human populations to natural populations
Malthus 1766-1834 was an English economist
and demographer
Also influenced by geologists such as Charles Lyell 1797-1875
Lyell popularized the concept that the Earth was extremely old, shaped by geological processes
Genetic Variation
Artificial selection:
“a process in the breeding of animals
and in the cultivation of plants by which
the breeder chooses to perpetuate only
those forms having certain desirable
inheritable characteristics.”
Natural Selection:
“a process resulting in the survival and
reproductive success of individuals or
groups best adjusted to their environment,
leading to the perpetuation of genetic qualities
best suited to that particular environment.”
Ideas about evolution originated long before Darwin’s time
What are the
four premises of evolution
by natural selection
as proposed by Charles Darwin?
4 Premises of Evolution by Natural Selection
1) Genetic variation
exists among individuals in population
2) Reproductive ability of each species
causes populations to geometrically increase over time
3) Organisms compete with one another
for resources: food, living space, water, light
4) Offspring with most favorable characteristics
most likely to survive and reproduce, and to
pass genetic characteristics to next generation
Natural Selection Darwin’s voyage on the Beagle provided the basis for his theory of evolution by natural selection
Results in adaptations
evolutionary modifications
improve chances of survival and reproductive success in a particular environment
Over time
accumulated changes in geographically separated populations produce new species
Galapagos Finches
Fig. 18-4a, p. 395
Figure 18.4: Three species of Galápagos finches.
Darwin inferred that these birds are derived from a common ancestral population of seed-eating birds from South America. Variation in their beaks is the result of adaptation to different kinds of food.
Fig. 18-4b, p. 395
Figure 18.4: Three species of Galápagos finches.
Darwin inferred that these birds are derived from a common ancestral population of seed-eating birds from South America. Variation in their beaks is the result of adaptation to different kinds of food.
Fig. 18-4c, p. 395
Figure 18.4: Three species of Galápagos finches.
Darwin inferred that these birds are derived from a common ancestral population of seed-eating birds from South America. Variation in their beaks is the result of adaptation to different kinds of food.
KEY CONCEPTS
Natural selection occurs because individuals with traits that make them better adapted to local conditions are more likely to survive and produce offspring than are individuals that are not as well adapted
Mutation provides genetic variability that natural selection acts on during evolution
Fossil Record What evidence for evolution can be obtained from the fossil record?
Fossils
remains or traces of ancient organisms
provide direct evidence of evolution
Fossil Record
Sedimentary rock
layers occur in sequence of deposition
recent layers on top of older ones
Index fossils
characterize specific layer
Radioisotopes
in rock accurately measure rock’s age
Sedimentary Rock
Fossils
Whale Evolution
Fig. 18-8a, p. 399
Mesonychid
Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Fig. 18-8b, p. 399
Ambulocetus natans
Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Fig. 18-8c, p. 399
Rodhocetus
Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Fig. 18-8d, p. 399
Basilosaurus
Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Fig. 18-8e, p. 399
Balaenoptera
Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Homologous Features What evidence for evolution is derived from comparative anatomy?
Basic structural similarities
structures may be used in different ways
Derived from same structure
in common ancestor
Indicate organism’s evolutionary affinities
Fig. 18-10, p. 401
HUMAN
CAT
WHALE
BAT
Humerus
Ulna
Radius
Humerus
Carpal
5
Radius
Metacarpal
Ulna
4
1
Carpal
Radius
Ulna
1
5
Carpal
Metacarpal
1
3
Phalanges
4
2
1
2
Phalanges
3
5
4
3
2
2
3
4
5
Figure 18.10: Homology in animals.
The human arm, cat forelimb, whale flipper, and bat wing have a basic underlying similarity of structure because they are derived from a common ancestor. The five digits are numbered in each drawing.
