Macroevolution: Processes of Vertebrate and Mammalian Evolution

1
Chapter 5

• Macroevolution Processes of Vertebrate and
  Mammalian Evolution

2
Chapter Outline

• The Human Place in the Organic World
• Principles of Classification
• Definition of Species
• Vertebrate Evolutionary History A Brief Summary
• Mammalian Evolution

3
Chapter Outline

• The Emergence of Major Mammalian Groups
• Processes of Macroevolution
• Issue Just When We Thought Things Couldnt Get
  Any Worse Bushmeat and Ebola

4
Classification

• Classification is used to order organisms into
  categories to show evolutionary relationships.
• Example - human classification
• Kingdom Animalia
• Subkingdom Metazoan
• Phyla Chordata
• Subphyla Vertebrata
• Class Mammalia

5
Classification Definitions

• Metazoa
• Multicellular animals.
• Chordata
• The phylum of the animal kingdom that includes
  vertebrates.
• Vertebrates
• Animals with segmented bony spinal columns
  includes fishes, amphibians, reptiles, birds, and
  mammals.

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Principles of Classification

• The field that specializes in establishing the
  rules of classification is called taxonomy.
• Organisms are classified first on the basis of
  physical similarities.
• Basic physical similarities must reflect
  evolutionary descent in order for them to be
  useful.

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Principles of Classification

• Homologies
• Similarities based on descent from a common
  ancestor.
• Analogies
• Similarities based on common function, with no
  assumed common evolutionary descent.
• Homoplasy
• The separate evolutionary development of similar
  characteristics in different groups of organisms.

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Homologies
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Two Approaches to Classification

• Evolutionary systematics
• A traditional approach in which presumed
  ancestors and descendants are traced in time by
  analysis of homologous characters.
• Cladistics
• Attempts to make rigorous evolutionary
  interpretations based solely on analysis of
  certain types of homologous characters.

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Question

• The scientific discipline that delineates the
  rules of classification is
• paleontology.
• stratigraphy.
• homology.
• taxonomy.

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Answer d

• The scientific discipline that delineates the
  rules of classification is taxonomy.

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Ancestral and Modified Characters

• Ancestral characters
• Refers to characters inherited by a group of
  organisms from a remote ancestor and thus not
  diagnostic of groups (lineages) that diverged
  after the character first appeared.
• Derived characters
• Refers to characters that are modified from the
  ancestral condition and thus are diagnostic of
  particular evolutionary lineages.

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Evolutionary Trees Development of Passenger
Vehicles

• The first divergence is between cars and trucks
  (I).
• A later divergence occurs between luxury cars and
  sports cars (II).

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Evolutionary Trees Development of Passenger
Vehicles

• SUVs diverge from trucks, but like sports cars,
  they have a decorative racing stripe.
• This is a homoplasy and does not make SUVs
  sports cars.
• Classifications based on a characteristic that
  can appear independently in different groups can
  lead to an incorrect conclusion.

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Evolutionary Relationships of Birds and Dinosaurs

• (a) Traditional view, showing no close
  relationship. (b) Revised view, showing common
  ancestry of birds and dinosaurs.

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Cladogram

• Shows relationships of birds, dinosaurs, and
  other terrestrial vertebrates. Theres no time
  scale, and both living and fossil forms are
  shown along the same dimension. Ancestor-
  descendant relationships arent indicated.

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Approaches to Classification
Evolutionary Systematics Cladistics
Goal Construction of a phylogenetic tree Construction of a cladogram
Similarities Compare specific traits Construct classifications to show evolutionary relationships Focus on homologies Compare specific traits Construct classifications to show evolutionary relationships Focus on homologies
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Approaches to Classification
Evolutionary Systematics Cladistics
Differences Might use any homologous character Attempts to make ancestor-descendant links Attempts to place fossils in a chronological framework Use only defined derived characters No conclusions regarding ancestor-descendant relationships All members of an evolutionary group are interpreted in one dimension
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Definition of Species

• Biological species concept
• Depiction of species as groups of individuals
  capable of interbreeding, but reproductively
  isolated from other such groups.

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Definition of Species

• Recognition species concept
• A depiction of species in which the key aspect
  is the ability of individuals to identify members
  of their own species for purposes of mating.
• This type of selective mating is a component of a
  species concept emphasizing mating and is
  therefore compatible with the biological species
  concept.

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Definition of Species

• Ecological species concept
• The concept that a species is a group of
  organisms exploiting a single niche.
• This view emphasizes the role of natural
  selection in separating species from one another.

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Definition of Species

• Phylogenetic species concept
• Splitting many populations into separate species
  based on an identifiable parental pattern of
  ancestry.

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Allopatric

• Living in different areas.
• This pattern is important in the divergence of
  closely related species from each other and from
  their shared ancestral species because it leads
  to reproductive isolation.

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Speciation

• Process by which a new species evolves from a
  prior species.
• Speciation is the most basic process in
  macroevolution.

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Speciation Model
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Recognition of Fossil Species

• The minimum biological category we would like to
  define in fossil primate samples is the species.
• Variations
• Intraspecific - Variation is accounted for by
  individual, age, and sex differences seen within
  every biological species
• Interspecific - Variation represents differences
  between reproductively isolated groups.

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Recognition of Fossil Species

• Defining where species boundaries begin and end
  is often difficult.
• Splitters are researchers who claim speciation
  occurred frequently during hominid evolution.
• Lumpers assume speciation was less common and
  see much variation as being intraspecific.

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Recognition of Fossil Genera

• A genus is a group of species composed of members
  more closely related to each other than to
  species from any other genus.
• Species that are members of the same genus share
  the same broad adaptive zone.
• Members of the same genus should all share
  derived characters not seen in members of other
  genera.

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Geological Time Scale
ERA PERIOD Began m.y.a. EPOCH Began m.y.a.
CENOZOIC Tertiary 1.8 Holocene Pleistocene 0.01 1.8
CENOZOIC Quaternary 65 Pliocene Miocene Oligocene Eocene Paleocene 5 23 34 55 65
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Geological Time Scale
ERA PERIOD (Began m.y.a.)
MESOZOIC Cretaceous 136
MESOZOIC Jurassic 190
MESOZOIC Triassic 225
PALEOZOIC Permian Carboniferous Devonian Silurian Ordovician Cambrian 280 345 395 430 500 570
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Geological Time Scale
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Geological Eras

• Paleozoic
• The first vertebrates appeared 500 m.m.y.a.
• Mesozoic
• Reptiles were dominant land vertebrates.
• Placental mammals appeared 70 m.Y.A.
• Cenozoic
• Divided into two periods Tertiary and Quaternary
  and 7 epochs Paleocene, Eocene, Oligocene,
  Miocene, Pliocene, Pleistocene and Holocene.

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Continental Drift

• The movement of continents on sliding plates of
  the earths surface.
• As a result, the positions of large landmasses
  have shifted drastically during the earths
  history.

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Continental drift

• The positions of the continents during the
  Mesozoic (c. 125 m.y.a.).
• Pangea is breaking up into a northern landmass
  (Laurasia) and a southern landmass (Gondwanaland).

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Continental Drift

• (a) Positions of the continents during the
  Mesozoic. Pangea is breaking up into a northern
  landmass (Laurasia) and a southern landmass
  (Gondwanaland). (b) Positions of the continents
  at the beginning of the Cenozoic.

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Ecological Niches

• The positions of species within their physical
  and biological environments, together making up
  the ecosystem.
• A species ecological niche is defined by such
  components as diet, terrain, vegetation, type of
  predators, relationships with other species, and
  activity patterns, and each niche is unique to a
  given species.

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Epochs

• Categories of the geological time scale.
• In the Cenozoic, epochs include
• Paleocene
• Eocene
• Oligocene
• Miocene
• Pliocene
• Pleistocene
• Holocene

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Mammalian Evolution

• The Cenozoic era is known as the Age of Mammals.
• After dinosaurs became extinct, mammals underwent
  adaptive radiation, resulting in rapid expansion
  and diversification.
• The neocortex, which controls higher brain
  functions, comprised the majority of brain
  volume, resulting in greater ability to learn.

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Reptilian and Mammalian teeth

• Mammals are heterodont, they have different kinds
  of teeth incisors, canines, premolars, and
  molars.

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Major Events in Early Vertebrate Evolution
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Question

• The divergence of reptiles into many different
  forms describes
• analogies.
• sexual selection.
• adaptive radiation.
• homologies.

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Answer c

• The divergence of reptiles into many different
  forms describes adaptive radiation.

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Time Unit Conversion Using the Cosmic Calendar
1 yr 15,000,000,000 yrs 1mth 1,250,000,000 yrs1 day 41,000,000 yrs 1 hr 1,740,000 yrs1 min 29,000 yrs1 sec 475 yrs
Big Bang January 1
Formation of the earth September 14
Origin of life on earth September 25
Significant oxygen, atmosphere begins to develop December 1
44
Time Unit Conversion Using the Cosmic Calendar
1 yr 15,000,000,000 yrs 1mth 1,250,000,000 yrs1 day 41,000,000 yrs 1 hr 1,740,000 yrs1 min 29,000 yrs1 sec 475 yrs
Precambrian ends Paleozoic begins invertebrates flourish December 17
Paleozoic ends and Mesozoic begins December 25
Cretaceous period first flowers dinosaurs become extinct December 28
Mesozoic ends Cenozoic begins adaptive radiation of placental mammals December 29
45
Time Unit Conversion Using the Cosmic Calendar
1 yr 15,000,000,000 yrs 1mth 1,250,000,000 yrs1 day 41,000,000 yrs 1 hr 1,740,000 yrs1 min 29,000 yrs1 sec 475 yrs
December 31
Appearance of early hominoids 1230 P.M.
First hominids 930 P.M.
Extensive cave painting in Europe 1159 P.M.
Invention of agriculture 115920 P.M.
46
Time Unit Conversion Using the Cosmic Calendar
1 yr 15,000,000,000 yrs 1mth 1,250,000,000 yrs1 day 41,000,000 yrs 1 hr 1,740,000 yrs1 min 29,000 yrs1 sec 475 yrs
December 31
Renaissance in Europe Ming Dynasty in China emergence of scientific method 115959 P.M.
Widespread development of science and technology emergence of a global culture first steps in space exploration NOW the first second of the New Year
47
Heterodont

• Having different kinds of teeth characteristic
  of mammals, whose teeth consist of incisors,
  canines, premolars, and molars.

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Endothermic

• Able to maintain internal body temperature by
  producing energy through metabolic processes
  within cells characteristic of mammals, birds,
  and perhaps some dinosaurs.

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Question

• An advantage of heterodont dentition is that it
• allows the animal to defend itself more
  efficiently.
• allows for processing a wide variety of foods.
• opens up new ways of interacting with potential
  mates.
• allows the animal to grab prey that it could not
  catch otherwise.

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Answer b

• An advantage of heterodont dentition is that it
  allows for processing a wide variety of foods.

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Major Mammalian Groups

• Monotremes
• Primitive, egg laying mammals
• Marsupials
• Infants complete development in an eternal pouch
• Placental
• Longer gestation allows the central nervous
  system to develop more completely

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Adaptive Radiation

• A process that takes place when a life form
  rapidly takes advantage of the many newly
  available ecological niches.
• A species, or group of species, will diverge into
  as many variations as two factors allow
• Its adaptive potential.
• The adaptive opportunities of the available
  niches.

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Gradualism versus Punctuated Equilibrium

• The traditional view of evolution has emphasized
  that change accumulates gradually in evolving
  lineages, an idea called phyletic gradualism.
• Punctuated equilibrium is the concept that
  evolutionary change proceeds through long periods
  of stasis punctuated by rapid periods of change.