Species
The Origin of
Species and
Speciation
Characteristics used to distinguish species
Appearance, biochemistry, genetic makemake-up,
behavior
Speciation
Figure 24.1 Two patterns of speciation
The Biological Species Concept
Different species can
look a lot alike
There can be a lot of
variation within the
species
Figure 24.4 Reproductive Barriers
Prezygotic barriers impede mating or hinder fertilization if mating does occur
Habitat
isolation
Behavioral
isolation
Temporal
isolation
Individuals
of different
species
Gametic
isolation
Mechanical
isolation
BEHAVIORAL ISOLATION
Viable
fertile
offspring
REDUCED HYBRID
VIABILITY
GAMETIC ISOLATION
TEMPORAL ISOLATION
(b)
Hybrid
breakdown
Fertilization
Mating
attempt
HABITAT ISOLATION
Reduce
hybrid
fertility
Reduce
hybrid
viability
MECHANICAL ISOLATION
(g)
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
(k)
(j)
(d)
(m)
(e)
(l)
(f)
(a)
(c)
(h)
(i)
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Figure 24.3 Courtship ritual as a behavioral barrier between species
species
Morphological species
Other species concepts
Coral Snake
Yellowjacket
Scarlet King Snake
Paleontological
Ecological
Phylogenetic
Clearwing moth
Figure 24.7 Allopatric speciation of squirrels in the Grand Canyon
Figure 24.5 Two main modes of speciation
(a)
(b)
Allopatric speciation
Sympatric speciation.
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Figure 24.8 Has speciation occurred during geographic isolation?
isolation?
Autopolyploidy
Figure 24.14b The new primrose species of botanist Hugo de Vries
Allopolyploidy
Habitat and Mate choice in two species of Lake Victoria cichlids
cichlids
Adaptive
Radiation
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In Lake Victoria alone there are 300 species of cichlids that
differ in color, size, shape, behavior and parental care.
Figure 24.13 Two models for the tempo of speciation
Today more
than 100 of
these are extinct
due to various
pressures such
as the
introduction of
the Nile Perch a
highly
predatory
animal and high
levels of water
pollution
Time
(a) Gradualism model. Species
descended from a common
ancestor gradually diverge
more and more in their
morphology as they acquire
unique adaptations.
(b) Punctuated equilibrium
model. A new species
changes most as it buds
from a parent species and
then changes little for the
rest of its existence.
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