Intraspecific variation

1
Intraspecific variation

• Variation accounted for by individual, age, and
  sex differences seen within every biological
  species

2
Interspecific variation

• Variation representing differences between
  reproductively isolated groups

3
Fossil Genera and the evolution of homo

• A genus is a group of species composed of members
  more closely related to each other than to
  species from any other genus.
• Ex dogs belong to the Canidae genus that
  includes wolves, jackals, coyotes and foxes
• We (and all the other extinct Homos ie
  Hohabilis, Homo erectus) belong to the Genus Homo
• 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.

4
Ancestral and Derived (Modified) Characters

• Derived (Modified) Characters that are modified
  from the ancestral condition and thus are
  diagnostic of particular evolutionary lineages.

• Ancestral
• Characters inherited by a group of organisms from
  a remote ancestor

5
Homologies

• More forelimb similarities. These ancestral
  characteristics are called Homologies

6
Generalized and Specialized Characteristics

• Refer to the adaptive potential of a particular
  trait
• Generalized if a trait is adapted for many
  functions a mammalian limb with five fairly
  flexible digits, adapted for many possible
  functions
• Specialized if a trait is limited to a narrow set
  of functions hand or foot suited for specialized
  function of stable weight support in an upright
  posture

7
Principles of Classification

• The field that establishes the rules of
  classification is 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.

8
Principles of Classification

• Homologies
• Similarities based on a common ancestor.
• Analogies
• Superficial similarities that are a product of
  separate evolutionary responses to roughly
  similar functional demands.
• Homoplasy
• The process that leads to Analogies.

9
Constructing Classifications and Interpreting
Evolutionary Relationships

• 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 (those
  considered to be derived characters).

10
Cladogram

• A chart showing evolutionary relationships as
  determined by cladistic analysis.
• Its based solely on interpretation of shared
  derived characters.
• It contains no time component and does not imply
  ancestor-descendant relationships.

Birds?
11
Shared Derived

• Relating to specific character traits shared in
  common between two life-forms and considered the
  most useful for making evolutionary
  interpretations.
• The presence of feathers in the proposed
  relationship between some (theropod) dinosaurs
  and birds is an example

Archaeopteryx Late Jurssaic Period 150mya
12
Clade -- car example

• From a common ancestor of all passenger vehicles,
  the first major divergence is between cars and
  trucks (I).
• A later divergence occurs between luxury cars and
  sports cars (II).
• Derived features of each grouping appear after
  its divergence from other groups.

13
Clade car example

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

14
Evolutionary systematics

• Traditional approach to interpreting evolutionary
  relationships with the goal of producing
  classifications.

15
Phylogenetic Tree

• A chart showing evolutionary relationships as
  determined by evolutionary systematics.
• It contains a time component and implies ancestor
  descendant relationships.

16
Evolutionary systematics cladistics

• Revised view, common ancestry of birds and
  dinosaurs.

17
Tempos and Modes of Evolutionary Change

• Macroevolution is the change from one species to
  another
• Macroevolution is only partly understandable
  through microevolutionary models.
• There are TWO main theories regarding
  Macroevolution

18
Missing link? -- The Theory of Gradualism

• Gradualism refers to change accumulating
  gradually in evolving lineages, or a series of
  forms with finely graded transitional differences
  between ancestor and descendant, with missing
  links present

19
Punctuated Equilibrium

• Punctuated equilibrium refers to no missing
  links, with real gaps representing uneven,
  nongradual process of long stasis and quick
  spurts
• These quick spurts still take A LOT of time,
  some 10,000-50,000 years.

20
Evolutionclassified

• Organizes diversity into categories and, at the
  same time, indicates evolutionary relationships.
• The kingdom Animalia includes 20 major phyla
  (singular, phylum)
• Chordata is one phyla and includes all animals
  with a nerve cord, gill slits and supporting cord
  along the back.

21
Mammalian Evolution

• The Cenozoic era, the Age of Mammals.
• 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

22
Mammalian Evolution

• Characteristics
• The enlargement of the cerebrum, especially the
  neocortex, which controls higher brain functions,
  resulting in more nerve cells\

23
Mammalian Evolution
Monotremes

• Characteristics
• A longer, more intense period of growth in utero

Placental Mammals
Marsupials
24
Mammalian Evolution

• Characteristics
• Distinctive dentition, termed a heterodont
  dentition, with 3 incisors, 1 canine, 4
  premolars, and 3 molars in each quarter of mouth

25
Mammalian Evolution

• Characteristics
• Maintenance of constant internal body
  temperature, warm-bloodedness, and ENDOTHERMIC

Ectothermic
26
Mammalian evolution

• Lateral view of the brain in fishes, reptiles,
  and primates.
• Note the increased size of the cerebral cortex of
  the primate brain.