Transcript Ch. 14 The Origin of Species

Origin of Species
Ch. 14
Ms. Haut
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The origin of species is the source of
biological diversity
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Speciation, the origin of new species
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Is at the focal point of evolution
Figure 14.1
CONCEPTS OF SPECIES
What
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Carolus Linnaeus, a Swedish physician and botanist
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is a species?
Used physical characteristics to distinguish species
Developed the binomial system of naming organisms
Linnaeus’ system established the basis for taxonomy
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The branch of biology concerned with naming and classifying
the diverse forms of life
Species
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Similarities between
some species and
variation within a species
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Can make defining
species difficult
Figure 14.2A
Figure 14.2B
What is a species?
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The Biological Species Concept
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The biological species concept defines a species as
A population or group of populations whose members
can interbreed and produce fertile offspring
 Reproductively isolated by various factors preventing
mixing with other species
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Reproductive barriers keep species
separate
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Reproductive barriers
 Serve to isolate a
species’ gene pool
and prevent
interbreeding
 Are categorized as
prezygotic or
postzygotic
Table 14.3
Prezygotic Barriers
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Prevent mating or fertilization between species
Habitat isolation —species live in same general area
but not the same places
 Behavioral isolation —special signals recognized
 Temporal isolation —breeding occurs at different times
 Mechanical isolation —anatomically incompatible
 Gametic isolation —gamete recognition
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Temporal isolation
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Two species breed at different times
Figure 14.3A
Behavioral isolation
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There is little or no sexual attraction between
species, due to specific behaviors
Figure 14.3B
Mechanical isolation
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Female and male sex organs or gametes are not
compatible
Figure 14.3C
Postzygotic Barriers
Operate
after hybrid zygotes are formed
Prevent the hybrid zygote from developing
into a viable, fertile adult
 Reduced hybrid viability —embryo aborted
 Reduced hybrid fertility —offspring sterile
 Hybrid breakdown —offspring of hybrids
sterile
Hybrid sterility
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Offspring between two species are sterile and
therefore cannot mate
Figure 14.3D
MECHANISMS OF SPECIATION
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Geographic isolation can lead to speciation
 In allopatric speciation
 A population is geographically divided, and new
species often evolve
A. harrisi
A. leucurus
Figure 14.4
Allopatric Speciation
 Geographic
isolation in Death Valley
 Has led to the evolution of new species of
pupfish
Figure 14.5B
A pupfish
http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm
http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm
http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm
MECHANISMS OF SPECIATION
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New species can also arise within the same
geographic area as the parent species
 In sympatric speciation
 New species may arise without geographic
isolation
Sympatric Speciation
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Many plant species have evolved by polyploidy
 Multiplication of the chromosome number
due to errors in cell division
 Results in extra sets of chromosomes
Zygote
Parent species
Meiotic
error
Offspring
may be
viable and
self-fertile
Selffertilization
4n = 12
Tetraploid
2n = 6
Diploid
O. lamarckiana
Unreduced
diploid gametes
Figure 14.6A
O. gigas
Adaptive radiation may occur in
new or newly vacated habitats
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In adaptive radiation, the evolution of new species
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Occurs when mass extinctions or colonization provide
organisms with new environments
Island chains
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Provide examples of adaptive radiation
Cactus-seed-eater
(cactus finch)
A
1
B
2
B
B
C
B
3
C 4
C
C
5
D
Tool-using insect-eater
(woodpecker finch)
Seed-eater
(medium ground finch)
Figure 14.8A
Figure 14.8B
CD
D
Plant speciation
1. Seeds blown over from mainland
and form small colony
2. Gene pool isolated—evolves into
new species B
3. Storms/other agents blow seeds to
nearby island and evolve into
species C
4. Some of species C recolonize the
first island and cohabit with species
B and some populate a new island
5. Speciation continues between new
areas and previously colonized
areas
The tempo of speciation can
appear steady or jumpy
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According to the
gradualism model
 New species
evolve by the
gradual
accumulation of
changes brought
about by natural
selection
Figure 14.12a
The tempo of speciation can
appear steady or jumpy
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The punctuated
equilibrium model draws
on the fossil record
 Species diverge in
spurts of relatively
rapid change, instead
of slowly and
gradually
Figure 14.12b
Nannippus
Pliohippus
Hipparion
Neohipparion
PLIOCENE
unequal
speciation or
unequal survival
of species on a
branching
evolutionary tree
Hippidion and other genera
Sinohippus
Megahippus
Callippus
Archaeohippus
MIOCENE
 The
Equus
Merychippus
Anchitherium
Hypohippus
Parahippus
Miohippus
OLIGOCENE
Evolutionary trends
reflect species selection
Mesohippus
Paleotherium
Epihippus
Propalaeotherium
Pachynolophus
Orohippus
EOCENE
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PLEISTOCEN
E RECENT
Evolutionary trends do not mean
that evolution is goal directed
Hyracotherium
Figure 14.13
Grazers
Browsers
Earth History and
Macroevolution
Macroevolution
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Is closely tied to the
history of the Earth.
The fossil record
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Is an archive of
macroevolution.
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Fossilization
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Most fossils are actually casts of animals or plants.
Animal dies and sinks to the sea floor.
Tissue begins to decay and is buried under layers of sediment such
as mud or sand.
These layers become rock.
The hard parts of the animal are
replaced with minerals such as
iron pyrites or silica.
These minerals form the fossil.
Usually fossils show the hard parts of
the animal or plant - such as shell or
bones.
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Trace fossils—evidence of living plants or
animals, such as worm burrows or dinosaur
footprints.
Most fossils are found in sedimentary rocks rocks which were created when shells or small
loose bits of rock are laid down in layers
(limestone, sandstone, clay and chalk)
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Determining Age of Fossils
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Relative age—
determined by position
in sedimentary rock
http://evolution.berkeley.edu/evosite/lines/images/strat_column.gif
Determining Age of Fossils
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Absolute age—determined by radiometric dating
(radioactive isotopes)
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Based on half-life of an isotope—period it takes for
half the radioactive material to decay
Carbon-14
C-14 Remaining
(atoms)
0
100
1
50
120
100
80
60
40
20
0
1
2
25
3
12.5
4
6.25
5
3.13
2
3
4
5
6
Number of Half-Life
Figure 14.17a
Number of Half-Life
Number of Atoms of C-14
Half-Life of Carbon 14
Plate Tectonics and
Macroevolution
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Figure 14.18
The continents are not locked
in place.
 They drift about Earth’s
surface on plates of crust
floating on a flexible layer
called the mantle.
California’s infamous San
Andreas fault
 Is at a border where two
plates slide past each other.
Plate Tectonics
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About 250 million years ago
 Plate movements formed the
supercontinent Pangaea.
 Many extinctions occurred, allowing
survivors to diversify.
About 180 million years ago
 Pangaea began to break up, causing
geographic isolation.
Figure 14.19
http://www.astrobio.net/articles/images/lib/A08.gif
Mass Extinctions and Explosive
Diversifications of Life
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The fossil record reveals an episodic history,
 With long, relatively stable periods punctuated by
briefer intervals when the turnover in species
composition was much more extensive.
Extinction is inevitable in a changing world and occurs
all the time.
 However, extinction rates have not been steady.
Extinctions typically eliminate various species of
organisms
 And are followed by explosive diversifications of
organisms.
Geologic Time Periods and Mass
Extinctions
Extinction of
Dinosaurs
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The Process of Science:
Did a Meteor Kill the Dinosaurs?
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Scientists discovered an
ancient impact crater buried
underneath the Yucatán
Peninsula in Mexico
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http://www.sunstarsolutions.com/sunstar/geology/BigB
end/Images/Chicxulub.jpg
Figure 14.20
Scientists believe that about
65 million years ago, at the
end of the Cretaceous period
A meteor impact contributed
to the extinction of the
dinosaurs.
Acknowledgements
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
BIOLOGY: CONCEPTS AND CONNECTIONS 5th Edition,
by Campbell, Reece, Mitchell, and Taylor, ©2006. These images
have been produced from the originals by permission of the
publisher. These illustrations may not be reproduced in any
format for any purpose without express written permission from
the publisher.
Unless otherwise noted, illustrations are credited to Pearson
Education which have been borrowed from BIOLOGY:
CONCEPTS AND CONNECTIONS 3rd Edition, by
Campbell, Reece, Mitchell, and Taylor, ©2000. These images
have been produced from the originals by permission of the
publisher. These illustrations may not be reproduced in any
format for any purpose without express written permission from
the publisher.