2. 14.1 The Definition of a Species
Macroevolution
Requires the origin of species
Observed best within the fossil record
Speciation
Splitting of one species into two or more or the
transformation of one species into a new species
over time
14-2
3. Evolutionary Species Concept
Members of a species share the same distinct
evolutionary pathway and that species can be
recognized by diagnostic trait differences
Diagnostic traits distinguish one species from another
Assumes that the members of a species are
reproductively isolated
Biological Species Concept relies primarily on
reproductive isolation rather than trait
differences to define a species
14-3
12. 14.3 Allopatric speciation utilizes
a geographic barrier
Allopatric speciation
Requires that the subpopulations be separated by a
geographic barrier
Ex: Ensantina salamanders in California
Distinct forms no longer interbreed
Ex: Sockeye Salmon in Washington State
Some introduced to Lake Washington
Colonized different habitats and different traits favored
14-12
15. 14.4 Adaptive radiation produces many related
species
Adaptive radiation
Single ancestral species gives rise to a variety of
species, each adapted to a specific environment
An ecological niche is where a species lives and how
it interacts with other species
Ex: Common goldfinch-like ancestor arrived in
Hawaii from Asia or North America about 5 mya
Today honeycreepers have a range of beak sizes and
shapes for feeding on various food sources, including seeds,
fruits, flowers, and insects
14-15
17. Sympatric speciation
Speciation without the presence of a geographic
barrier
More common in flowering plants than in animals due
to self-pollination
Polyploidy – chromosome number beyond the
diploid (2n) number
14-17
19. HOW BIOLOGY IMOPACTS OUR LIVES
14A The Many Uses of Corn,
an Allotetraploid
Modern corn’s (Zea mays) ancient ancestor was
teosinte from southern Mexico
Between 4000 and 3000 B.C., the hand of
artificial selection began to shape the evolution
of corn
Corn is an allotetraploid – it is 4n
Hybridization between 2 related species followed by
doubling of the chromosomes
Corn is America’s number-one field crop, yielding
9.5 billion bushels yearly
14-19
21. 14.6 Speciation occurs at different tempos
Many evolutionists accept a gradualistic model
evolution which proposes that speciation occurs
after populations become isolated
Some paleontologists think that species appear
suddenly, and then they remain essentially
unchanged phenotypically until they undergo
extinction
Based on these findings, other evolutionists
developed a punctuated equilibrium model to
explain the pace of evolution
14-21
24. HOW SCIENCE PROGRESSES
14B The Burgess Shale Hosts a
Diversity of Life
Burgess Shale contains fossils of marine life
some 540 mya
Many of the fossils are remains of soft-bodied
invertebrates
Fossils tell us that the ancient seas were
teeming with weird-looking, mostly invertebrate
animals
All of today’s groups of animals can trace their
ancestry to one of these strange-looking forms
14-24
26. Figure 14B cont’d
An artist’s depiction of the variety of fossils is accompanied by photos of the
actual fossilized remains
14-26
27. Figure 14B cont’d
An artist’s depiction of the variety of fossils is accompanied by photos of the
actual fossilized remains.
14-27
28. 14.7 Development plays a role
in speciation
Investigators have discovered genes whose
differential expression can bring about changes
in body shapes
These regulatory genes found in all organisms
Genes must date back to a common ancestor
that lived more than 600 MYA
14-28
30. Figure 14.7B Differential expression of a Hox genes causes (a) a chick to have
fewer vertebrae than (b) a snake in a particular region (colored pink) of the spine
14-30
31. 14.8 Speciation is not goal-
oriented
Modern horses evolved about 4 mya
Have features adaptive for living on an open plain:
large size long legs, hoofed feet, and strong teeth
Family tree of Equus tells us once more that
speciation, diversification, and extinction are
common occurrences in the fossil record
14-31
33. Connecting the Concepts:
Chapter 14
Macroevolution is the study of the origin and
history of species on Earth
Speciation usually occurs by allopatric
speciation but can occur after sympatric
speciation
Gradualistic vs punctuated equilibrium model for
speed of speciation
Ancient regulatory genes can bring about
changes in body shape and organs
Evolution is not goal-oriented
14-33