Descent with Modification

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Descent with Modification A Darwinian View of
Life

• Chapter 22
• A.P. Biology
• Liberty Senior High School
• Rick L. Knowles

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• Concept 1.4 Evolution accounts for lifes unity
  and diversity
• The history of life
• Is a saga of a changing Earth billions of years
  old

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Theodosius Dobzhansky

• Nothing in biology makes sense except in the
  light of evolution.
• The American Biology Teacher (1973)

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• Overview Darwin Introduces a Revolutionary
  Theory
• A new era of biology began on November 24, 1859
• The day Charles Darwin published On the Origin of
  Species by Means of Natural Selection

Charles Darwin, 1831, age 22, starting his voyage
on the HMS Beagle
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• Concept 22.1 The Darwinian revolution challenged
  traditional views of a young Earth inhabited by
  unchanging species
• In order to understand why Darwins ideas were
  revolutionary
• We need to examine his views in the context of
  other Western ideas about Earth and its life

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• The historical context of Darwins life and ideas

Fig. 22.2
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The Scale of Nature and Classification of Species

• The Greek philosopher Aristotle
• Viewed species as fixed and unchanging
• The Old Testament of the Bible
• Holds that species were individually designed by
  God and therefore perfect
• Intelligent Design

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• Carolus Linnaeus
• Interpreted organismal adaptations as evidence
  that the Creator had designed each species for a
  specific purpose
• Was a founder of taxonomy, classifying lifes
  diversity for the greater glory of God
• Viewed species similarities not as evolutionary
  relationship, but as patterns of creation.

Carolus Linnaeus, 1707 -1778
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Fossils, Cuvier, and Catastrophism

• The study of fossils
• Helped to lay the groundwork for Darwins ideas
• Fossils are remains or traces of organisms from
  the past
• Usually found in sedimentary rock, which appears
  in layers or strata

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• Paleontology, the study of fossils
• Was largely developed by French scientist Georges
  Cuvier
• Observed that upper strata were younger and lower
  strata were older
• Noticed that new species would appear in an older
  strata and then disappear in a newer strata.
• Cuvier opposed the idea of gradual evolutionary
  change
• And instead advocated catastrophism, speculating
  that each boundary between strata represents a
  catastrophe (flood or drought).

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Theories of Gradualism

• Gradualism
• Is the idea that profound change can take place
  through the cumulative effect of slow but
  continuous processes.
• 1795, James Hutton proposed that Earths geologic
  features could be explained by gradual mechanisms
  currently operating (ex. valleys are created by
  rivers)

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• Geologists Hutton and Charles Lyell
• Perceived that changes in Earths surface can
  result from slow continuous actions still
  operating today
• Lyell proposed uniformitarianism same geologic
  processes are operating today as in the past and
  at the same rate.
• Exerted a strong influence on Darwins thinking

Charles Lyell, 1797-1875
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One of the First Ideas of Evolution

• Lamarck compared species today with the fossil
  record.
• 1809, hypothesized that species evolve through
  use and disuse and the inheritance of acquired
  traits.
• Organisms have an innate drive to become more
  complex.
• But the mechanisms he proposed are unsupported by
  evidence

Jean-Baptiste de Lamarck, 1744 - 1829
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• Lamarcks View of Evolution
• Plants and animals changed over time through the
  use and disuse of certain characteristics.
• These acquired characteristics were inherited by
  the next generation.
• No support for this notion.

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Darwin and the HMS Beagle

• During his travels
• Darwin observed and collected many specimens of
  South American plants and animals
• Darwin observed various adaptations of plants and
  animals
• That inhabited many diverse environments

Charles Darwin, 1831, age 22, starting his voyage
on the HMS Beagle
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Fig. 22.5 The Voyage of the HMS Beagle
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Name Two (2) Observations that Darwin Made
Leading to His Theory.Name One (1) Observation
Weve Since Made About the Natural World.
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Darwins Observations about Evolution

• 1. Fossil Record noticed that the fossils of
  South America resembled living species of that
  continent.
• Example Glyptodon related to modern armadillo?

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Glyptodon
Modern Armadillo, Omaha Zoo, 2009
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Darwins Observations of Evolution

• 2. Biogeography plants and animals in temperate
  regions of South America resemble tropical
  species in South America than the temperate
  species in Europe.
• The distribution of life across similar climates
  is not always the same (climate alone is not
  causing diversity).
• Closely related species are found in same
  geographic region.

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• Different geographic regions, different mammalian
  brands
• Have evolved independently from different
  ancestors

Marsupial Mammal
Placental Mammal
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Charles Darwin, 1835, Galapagos
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Whats so special about a bunch of
islands?National Geographic SeriesGalapagos,
Tape 254
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Darwins Finches
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The Galapagos Archipelago
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Bartoloma Island
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Isabela Island
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• Darwin proposed that natural selection
• Could enable an ancestral species to split into
  two or more descendant species, resulting in a
  tree of life

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Seen one tortoise, youve seen them all?
Dome-shaped Carapace
Saddle-shaped Carapace
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Galapagos Tortoise Distribution
Galapagos tortoise distribution, Galapagos
Islands. Redrawn from Iverson (1992).
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Galapagos Tortoise-Env. Club 2008, Omaha Zoo
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Darwins Focus on Adaptation

• Years later, Darwin reassessed all that he had
  observed during the voyage of the Beagle
• He began to perceive adaptation to the
  environment and the origin of new species as
  closely related processes

Fig. 22.6
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Alfred Russel Wallace, 1823-1913

• Explored Indonesia and southeast Asia, from
  1854-1861,
• Observed Tigers, Orangs, and Rhinos, Oh My!

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Indian Rhino
Sumatran Rhino
Javan Rhino
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Other Observations about Evolution

• 3. Artificial Selection - humans have modified
  other species over many generations by selecting
  and breeding individuals that possess desired
  traits

Fig. 22.10
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• The Origin of Species articulated two main
  points
• Descent with modification
• Natural selection

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Natural Selection

• Darwin proposed natural selection
• As the mechanism for evolutionary adaptation of
  populations to their environments

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• Natural selection is the evolutionary process
  that occurs
• When a populations heritable variations are
  exposed to environmental factors that favor the
  reproductive success of some individuals over
  others.

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The Origin of Species

• Darwin developed two main ideas
• Evolution explains lifes unity and diversity
• Natural selection is a cause of adaptive
  evolution
• The phrase descent with modification
• Summarized Darwins perception of the unity of
  life
• States that all organisms are related through
  descent from an ancestor that lived in the remote
  past

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Elephant Phylogeny
Fig. 22.7
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Summary of Natural Selection

• Natural selection is differential success in
  reproduction
• That results from the interaction between
  individuals that vary in heritable traits and
  their environment
• If an environment changes over time
• Natural selection may result in adaptation to
  these new conditions

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• Over time natural selection can produce an
  increase
• In the adaptation of organisms to their
  environment

Fig. 22.11
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• Concept 22.3 Darwins theory explains a wide
  range of observations
• Darwins theory of evolution
• Continues to be tested by how effectively it can
  account for additional observations and
  experimental outcomes
• Natural Selection in Action Evolution continues
  today!
• Guppies
• HIV
• Humans

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Differential Predation in Guppy Populations

• Researchers have observed natural selection
• Leading to adaptive evolution in guppy populations

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The Evolution of Drug-Resistant HIV

• In humans, the use of drugs
• Selects for pathogens that through chance
  mutations are resistant to the drugs effects
• Natural selection is a cause of adaptive evolution

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Anatomy of HIV
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Inside HIV
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• Researchers have developed numerous drugs to
  combat HIV
• But using these medications selects for viruses
  resistant to the drugs

Figure 22.13
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New Evidence that Darwin Did Not Have

• How old did most 19th Century people believe the
  Earth was?
• About 6,000 years old (Cuviers young Earth)
• 1. Age of the Earth- 4.5 billion year old.
  Better dating techniques than in Darwins time
  more complete fossil record.

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2. Transitional Species

• Have intermediate characteristics of two groups
  of animals may represent a link in evolution
  (missing link?).
• Changes in structures may be small difficult to
  identify in fossils.
• Species replaced quickly not common in fossil
  record.

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Archaeopteryx (150 million years ago)
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Archaeopteryx
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Archaeopteryx at the KU Natural History Museum
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Evolution Happens in Small Steps

• Show me the frogs!
• Discover- Weird Nature Marvelous Motion, tape
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Other Transitional Examples?
Rodhocetus balochistanensis
Modern Whales
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A Walking Whale?
Ambulocetus natans
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Transitional Skulls
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Rodhocetus Foot
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Transitional Diatoms in Yellowstone
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3. Vestigial Structures

• Existing structures that have no apparent
  function, but resemble structures of presumed
  ancestors.
• Examples human appendix muscle set in humans
  for moving ears

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The Pelvis of a Whale
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Evidence of Transitional Species Today!

• Vestigial Structure- blue whales with femurs?
• Life of Mammals-Return to the Water video, tape
  110

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Vestigial Organs in Humans?

• Structures of little or no use but may represent
  historical remnants of structures that had
  important functions in ancestors.

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Vermiform Appendix
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Goosebumps?
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Vomeronasal or Jacobsons Organ
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JunkDNA L-gulonolactone oxidase gene
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Extra Ear Muscles auriculares muscles
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Plantaris Muscle 9 dont have it
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Wisdom Teeth mandible becoming smaller
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Third Eyelid Plica semilunaris
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Darwins (Auricular) Tubercle only 10.4 have
it.
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Coccyx
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Four-Finned Dolphin Oct, 2006
Divers hold a bottlenose dolphin which has an
extra set of human palm-sized fins near its tail
in Taiji, Wakayama prefecture in western Japan.
-USA Today, Nov. 6, 2006
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Four-Finned Dolphin Oct, 2006
Divers hold a bottlenose dolphin which has an
extra set of human palm-sized fins near its tail
in Taiji, Wakayama prefecture in western Japan.
-USA Today, Nov. 6, 2006
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Show me more vestigial structures!

• Do snakes have feet?
• The story of boas and pythons.

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4. Anatomical Homologies

• Homologous structures between organisms
• Are anatomical resemblances that represent
  variations on a structural theme that was present
  in a common ancestor

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Homology

• Homologous Structures structures in different
  species that are similar because of commons
  ancestry.

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Sophie and a Mosasaur
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Analogy

• Analogous Structures similarity in structures
  due to adaptations from similar evolutionary
  pressures (convergent evolution) and not a common
  ancestor.

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• The products of natural selection
• Are often exquisite adaptations of organisms to
  the special circumstances of their way of life
  and their environment

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• 5. Comparative Embryology
• Reveals additional anatomical homologies not
  visible in adult organisms

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Show me an example of homologous structures!

• Compare a human hand and bat wing.
• Life of Mammals- Life in the Trees video, tape
  110

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6. Molecular Homologies

• Biologists observe homologies among organisms at
  the molecular level
• Genes and proteins that are shared among
  organisms inherited from a common ancestor.

Fig. 22.16
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Darwins Theory of Evolution

• Natural selection is the driving force of changes
  within species populations.

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Can we see evolution?

• Weiner, J. 1994. The Beak of the Finch. Knopf,
  New York.
• The video What Darwin Never Saw

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I want to see evolution in action!

• Scientific American Frontiers-Voyage to the
  Galapagos, 2000, VT 551.4 SCI