Download Name: Period: ______ Date: Reproductive Barrier Worksheet 1

Name: _______________________ Period: _______
Date: ________________________
Reproductive Barrier Worksheet
1) Throughout the wet years, small seeds were more common and there was such a large
supply of the small seeds that the finches rarely ate large seeds. During the dry years, none
of the seeds were in great abundance, but the birds usually ate more large seeds. The
change in diet of the finches affected the depth of the birds’ beaks in the future generations.
Their beaks range from large and tough to small and smooth. What type of selection am I?
A) Directional
B) Disruptive
C) Stabilizing
2) Some Central American Acacia species have hollow thorns
and pores at the bases of their leaves that secrete nectar (see
image at right). These hollow thorns are the exclusive nestsite of some species of ant that drink the nectar. But the ants
are not just taking advantage of the plant—they also defend
their acacia plant against herbivores. The plants would not
have evolved hollow thorns or nectar pores unless their
evolution had been affected by the ants, and the ants would
not have evolved herbivore defense behaviors unless their
evolution had been affected by the plants. What type of
evolution am I?
A)
B)
C)
D)
Convergent evolution
Divergent evolution (Adaptive radiation)
Co-Evolution
Parallel Evolution
3) The illustration shows four different animals from around the globe. They may look
similar, but it's not because they're close relatives. Instead, they've evolved similar
adaptations because they occupy similar niches -- dining on ants, hunting in the high grass,
or swimming in the dark -- although their evolutionary origins are quite different. What
type of evolution am I?
A) Convergent evolution
B) Divergent evolution (Adaptive radiation)
C) Co-Evolution
D) Parallel Evolution
4) A plant that is too short may not be able to compete with other plants for sunlight.
However, extremely tall plants may be more susceptible to wind damage. Combined, these
two selection pressures select to maintain plants of medium height. The number of plants of
medium height will increase while the numbers of short and tall plants will decrease. What
type of selection am I?
A) Directional
B) Disruptive
C) Stabilizing
5) Two closely related skink species, Eumeces skiltonianus and Eumeces gilberti are very
different in their habitat preferences. E. skiltonianus tends to live in forested and woodland
habitats whereas E. gilberti is an inhabitant of drier and more open habitats like grasslands.
The two also differ in coloration. It turns out, however, that some E. gilberti populations are
closer to E. skiltonianus than they are to another E. gilberti populations. What type of
evolution am I?
A)
B)
C)
D)
Convergent evolution
Divergent evolution (Adaptive radiation)
Co-Evolution
Parallel Evolution
6) Specialization may subdivide a single niche into many new niches. For example, cichlid
fishes have diversified in East African lakes into more than 600 species. This diversification
may have been possible because different fish lineages evolved to take advantage of
different foods (including insects, algae, mollusks, small fish, large fish, other fishes’ scales,
and even other fishes’ eyes!). What type of evolution am I?
A)
B)
C)
D)
Convergent evolution
Divergent evolution (Adaptive radiation)
Co-Evolution
Parallel Evolution
Use the Key Box to match the following examples with the appropriate term.
A. Habitat Isolation B. Temporal Isolation C. Behavioral Isolation D. Mechanical
Isolation E. Gametic Isolation F. Reduced Hybrid Viability G. Reduced Hybrid
Fertility H. Polyploidy I. Bottleneck Effect (Genetic Drift) J. Founder Effect
(Genetic Drift) L. Gene Flow M. Sexual Selection N. Allopatic speciation O.
Sympatric speciation
_______1. Imagine an isolated population in which fifty people have sickle cell anemia, thirty
people are carriers of the disease (meaning that they have one disease-causing allele and
one regular one) and twenty people who do not have sickle cell anemia nor are they carriers
of it. One day, a tremendous tidal wave hits the population and half of the people die. Now,
just ten people have sickle cell anemia, twenty-two people are carriers of it, and eighteen do
not have nor carry it. You can see how genetic drift has caused the predominant allele,
which causes sickle cell anemia, to become less present in the population.
_______2. Different frog species live and breed in the same pond, but they reproduce at
different times of the year. Explain if it is a PRE-ZYGOTIC BARRIER OR a POST-ZYGOTIC
BARRIER and WHY?
_______3. Occurs in some animals, such as goldfish, salmon, and salamanders, but is especially
common among ferns and flowering plants, including both wild and
cultivated species. Wheat, for example, after millennia of hybridization and modification by
humans, has strains that are diploid (two sets of chromosomes), tetraploid (four sets of
chromosomes) with the common name of durum or macaroni wheat, and hexaploid (six
sets of chromosomes) with the common name of bread wheat. Many agriculturally
important plants of the genus Brassica are also tetraploids. This is a mechanism
of sympatric speciation because they are usually unable to interbreed with their ancestors.
_______4. Different species of frog and salamanders are able to mate with each other, but
most hybrids are not even born, while those that do are weak and usually do not survive
long. Explain if it is a PRE-ZYGOTIC BARRIER OR a POST-ZYGOTIC BARRIER and WHY?
________5. In general, the people in Africa today, descendants of the original large gene pool
have the highest genetic diversity in their population, followed by people on the Indian
subcontinent (one of the first places humans settled when they left Africa) and so on. Places
like Iceland, which was settled late and is also an isolated area, have some of the least
genetic diversity on the planet and a high incident of recessive traits like blonde hair and
blue eyes.
_______7. The genus Bradybaena has different spiraled shells. This keeps the two species of
snails from successfully mating because the snails’ genitals cannot be properly aligned.
Explain if it is a PRE-ZYGOTIC BARRIER OR a POST-ZYGOTIC BARRIER and WHY?
_________ 8. One of these native plants, Ulmus pumila, demonstrated a lower prevalence of
genetic differentiation than the plants Vitex negundo, Ziziphus jujuba, Heteropappus
hispidus, and Prunus armeniaca whose habitat is located on the opposite side of the Great
Wall of China where Ulmus pumila grows. This is because Ulmus pumila has windpollination as its primary means of propagation and the latter-plants carry out pollination
through insects. Samples of the same species, which grow on either side, have been shown
to have developed genetic differences.
______9. Sea urchins of different species release both their eggs and sperm into the same
water. But because there are different proteins on the surface of the egg and sperm, the two
different species cannot produce a fertilized egg. Explain if it is a PRE-ZYGOTIC BARRIER
OR a POST-ZYGOTIC BARRIER and WHY?
_______10. There are two different species of cricket that would be indistinguishable unless
you heard their mating song: they are of a noticeably different pitch. A creature will only be
able to conduct successful mating with an animal with similar mating songs. Explain if it is
a PRE-ZYGOTIC BARRIER OR a POST-ZYGOTIC BARRIER and WHY?
_______11. Mules and hinnies have 63 chromosomes, a mixture of the horse's 64 and the
donkey's 62. The different structure and number usually prevents the chromosomes from
pairing up properly and creating successful embryos, rendering most mules infertile.
Explain if it is a PRE-ZYGOTIC BARRIER OR a POST-ZYGOTIC BARRIER and WHY?
________12. It is known that males will often neck with other males in order to exhibit
dominance. Theoretically, the characteristic should be more exaggerated in one of the sexes;
it must be used to indicate dominance; have no direct survival benefits; help the organism
gain survival costs; positive allometry should be observed. For instance, evolution history
shows increased neck length not correlated to increases in other parts of the body, which is
what would be expected in foraging selection.
_______13. This isolation impedes the meeting of potential pairs occurs in two fish species of
the family Gasterosteidae (sticklebacks). One species lives all year round in fresh water,
mainly in small streams. The other species lives in the sea during winter, but in spring and
summer individuals migrate to river estuaries to reproduce. The members of the two
populations are reproductively isolated due to their adaptations to distinct salt
concentrations. Explain if it is a PRE-ZYGOTIC BARRIER OR a POST-ZYGOTIC BARRIER
and WHY?
_______ 14. Lives in same habitat but cannot breed because there is a reproductive barrier.
Genetic isolation without a geographical barrier.
_______ 15. A genetic isolation with a geographical barrier; a new group is isolated from its
parent population.