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Speciation

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Does evolution always result in a ... functioning or behavior that ... Arial Calibri Wingdings Office Theme Speciation 2 Concepts on Speciation Reproductive Isolating ... – PowerPoint PPT presentation

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Title: Speciation


1
Speciation
  • Process by which a daughter species evolves from
    a parent species
  • Genetic Divergence-
    when populations become
    reproductively isolated
  • Species-population of individuals who can
    interbreed under natural conditions producing
    fertile offspring
  • Does evolution always result in a new species?

2
2 Concepts on Speciation
  • Evolutionary species concept ? every species has
    its own evolutionary history, part of which is in
    the fossil record, and diagnostic traits
  • Biological species concept ? reproductive
    isolation rather than trait differences define a
    species

3
Reproductive Isolating Mechanisms
  • Any heritable feature of body form, functioning
    or behavior that prevents interbreeding between
    species
  • Pre-zygotic and Post-zygotic

4
Pre-ZygoticMechanisms
  • Behavioral
  • Temporal
  • Mechanical
  • Habitat isolation
  • Gametic mortality

5
Post-Zygotic Mechanisms
  • Hybrid mortality ?lower in fitness, early death
  • Hybrid sterility
  • Would natural selection favor pre- or
    post-zygotic mechanisms?

6
Types of Speciation Processes
  • Allopatric Speciation-species form due to
    physical barriers that prevents gene flow
    mountain range, river, island
  • BARRIER
  • Species A becomes distinct from species B cannot
    mate with each other

A
B
7
Allopatric Speciation
  • Salamanders in Central California
  • Washington Sockeye salmon in lakes vs rivers

8
Allopatric Speciation Adaptive Radiation
  • A single ancestral species gives rise to a
    variety of species, each adapted to a specific
    environment
  • Hawaiian honeycreepers
  • Occurred after dinosaur extinction ? mammals
    diversified in only 10 million yrs!

9
Types of Speciation Processes
  • Sympatric speciation-species forms within the
    home range of an existing species in absence of
    physical barrier
  • Species
    A-blue
  • Species
    B-purple
  • Species A and B cannot mate

A
B
10
Sympatric Speciation
  • Polypoidy in plants
  • Autopoidy ? diploid plant produces diploid
    gametes
  • Alloploidy? hybrid plant doubles it chromosome

11
Models of Macroevolution
  • Gradual Model-new species formed through gradual
    changes in traits over time most consistent with
    fossil record

12
Models of Macroevolution
  • Punctual Model-new species formed in a short
    amount of time occurs through bottlenecks/founder
    effects, mutations, directional selection
    (natural selection)

13
Developmental Genes and Macroevolution
all animals share the same control switches for
development
  • Development of eyes is controlled by Pax6 gene
  • It did not matter if it was a lens or compound
    eye
  • Loss of gene results in failure of eye to develop
    in mice, humans

14
Developmental Genes and Macroevolution
  • Development of overall shape is controlled by Hox
    genes
  • Control number and appearance of repeated
    structures
  • Differential expression in chickens vs snakes

animal diversity is due to variation in the
expression of ancient genes
15
Evolution of the Modern Day Horse
Macroevolution is not goal-oriented
  • Does not fit a gradual model perfectly
  • Trends observed
  • Increase in size
  • Toe reduction
  • Change in tooth size/shape
  • Modern horse evolved 4 mya adapted for living in
    open plains

speciation, diversification, and extinction are
common occurances
16
Darwins drawing in The Origin of Species
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