Download Biol 211 (2) Chapter 27 KEY

Professor: Hufford/Biederman
S.I. Leader: Stephanie Schneider
Biology 211 (2) Week 12!
Chapter 27!
KEY CONCEPTS:!
1. Compare and contrast allopatric and sympatric speciation. Which is more common?
a. Allopatric: Speciation that begins with geographic isolation
b. Sympatric: Speciation that occurs in the same geographic area due to the result
of their genetic isolation
2. What are the 3 most common approaches for identifying species?
a. 1) The biological species concept
b. 2) The morphospecies concept
c. 3) They phylogenetic species concept
3. State the biological species concept in your own words. What are the advantages and
disadvantages of this species concept? Name and describe the tow mechanisms that
stop gene flow between populations.
a. According to the biological species concept, different species are
reproductively isolated from each other. They either do not interbreed, or they
fail to produce viable fertile offspring
b. Advantage: Reproductive isolation=evolutionary independence
c. Disadvantages: Reproductive isolation cannot be evaluated in fossils or species
that reproduce asexually, and cannot be applied only to populations that
overlap geographically
d. Prezygotic isolation: Individuals of different species are prevented from mating
e. Postzygotic isolation: Individuals from different populations do mate, but the
hybrid offspring do not survive or reproduce
Prezygotic Isolation
Process
Example
Temporal
Populations are isolated because
they breed at different times.
Bishop pines and Monterey pines release
their pollen at different times of the year
Habitat
Populations are isolated because
they breed in different habitats
Parasites that begin to exploit new host
species are isolated from their original
population
Professor: Hufford/Biederman
S.I. Leader: Stephanie Schneider
Prezygotic Isolation
Process
Example
Behavioral
Populations do not interbreed
because their courtships displays
differ
To attract male fireflies, female fireflies
give a species-specific sequence of
flashes
Gametic Barrier
Matings fail because eggs and
sperm are incompatible
In sea urchins, a protein called bindin
allows sperm to penetrate eggs.
Differences in the amino acid sequence
of bindin cause matings to fail between
closely related populations
Mechanical
Matings fail because male and
female reproductive structures
are incompatible
In alpine skypilots (a flowering plant), the
length of the floral tube varies. Bees can
pollinate in populations with short tubes,
but only hummingbirds can pollinate in
populations with long tubes.
Postzygotic Isolation Process
Example
Hybrid viability
Hybrid offspring do not develop
normally and die as embryos
When ring-necked doves mate with rock
doves, less than 6% of eggs hatch.
Hybrid sterillity
Hybrid offspring mature but are
sterile as adults
Eastern meadowlarks and western
meadowlarks are almost identical
morphologically, but their hybrid offspring
are usually infertile.
4. What is the main criterion for identifying populations as different species according to
the morphospecies concept? What are advantages and disadvantages of this concept?
a. According to the morphospecies concept, individual species differ in size,
shape, or other morphological features
b. Advantage: Widely applicable
c. Disadvantage: This concept is subjective
5. Why are cryptic species a problem for the morphospecies concept?
a. It cannot identify cryptic species—a species that cannot be distinguished from
similar species by easily identifiable morphological traits
6. How are species classified according to the phylogenetic species concept? What is a
monophyletic group? What are the advantages and disadvantages of this species
concept?
a. The phylogenetic species concept identifies species based on evolutionary
history
b. A monophyletic group consists of an ancestral population plus all of its
descendants; these groups are identified by synapomorphies
Professor: Hufford/Biederman
S.I. Leader: Stephanie Schneider
c. Advantages: It can be applied to any population, and it is logical
d. Disadvantages: Phylogenies are currently available for only a tiny subset of
populations of the tree of life; critic point out that it would probably lead to
recognition of many more species than either of the other species concepts
7. In actual practice, researchers use which of the species concepts to identify
evolutionary independent populations in nature?
a. All three species concepts
8. Compare and contrast speciation by dispersal and speciation by vicariance. Are these
forms of sympatry, allopatry or both? The formation of the isthmus of Panama caused
speciation by which process (dispersal or vicariance)?
a. Dispersal: A population moves to a new habitat, colonizes it, and forms a new
population
b. Vicariance: A physical barrier splits a widespread population into subgroups
that are physically isolated
c. These are forms of Allopatry
d. Vicariance of the snapping shrimp