40) Which of the following descriptions best represents the gradual model of speciation?
A) Speciation occurs regularly as a result of the accumulation of many small changes.
B) An isolated population differentiates quickly from its parent stock as it adapts to its local
environment.
C) Speciation occurs under unusual circumstances and therefore transitional fossils are hard to
find.
D) Species undergo little change over long periods interrupted only by short periods of rapid
change.
41) One of the finest available sequences of fossils shows how horses have changed slowly and
by subtle steps from small shrub-browsing ancestors to the large, grass-grazing modern horse. A
large number of fossil species have been named, and it is often difficult to decide on the identity
of a fossil horse because transitional forms are common. This record of evolution best fits the
idea of
A) the gradual model of speciation.
B) punctuated equilibrium.
C) adaptive radiation.
D) hybrid breakdown.
42) The fossil record shows that for many plant and animal groups, the time between speciation
events
A) is usually about 50,000 years.
B) varies greatly, but averages 6.5 million years.
C) is usually greater than 40 million years.
D) is equivalent to the length of one hundred generations of a species.
43) Speciation has occurred when
A) two populations of organisms have been separated for a very long time.
B) a change in allele frequency has occurred.
C) organisms of one population do not recognize the mating call of another population and so
mating does not occur.
D) offspring of mating from members of two different populations are able to mate with
members of either population.
44) Allopatric speciation is not likely to occur when
A) there is no disruption in gene flow between two populations.
B) a geographic barrier forms between two populations.
C) several populations become isolated from one another as drying conditions cause a large body
of water to become separate smaller bodies of water.
D) separated populations adapt to different environmental conditions.
45) Two populations that have been separated by a river are most likely to become separate
species if
A) fur color is different in the two populations.
B) genes controlling ear development become different so that members of one population have
much longer ears than the other.
C) genes controlling molecules on the surface of the sperm that bind with egg receptors are
different in the two populations.
D) feeding habits are different in the two populations.
46) Speciation often occurs when a habitat becomes more heterogeneous. In Lake Victoria
different species of cichlids are found in different areas of the lake. The best explanation for this
speciation is that
A) natural selection favored different heritable variations in different parts of the lake.
B) male cichlids that lived in deep water needed to be seen by females, so they became colorful.
C) food was scarce in the lake, so some fish had to learn how to scrape algae, some had to learn
to eat insects, and some had to learn to bite leaves.
D) humans selected for many different traits in cichlids in order to market them to the aquarium
trade.
47) A new plant species may arise in a single generation by
A) errors in meiosis leading to polyploidy.
B) a sudden geological disruption causing separation of two populations.
C) mutations in genes for flower color.
D) changes in the pollinator species.
48) For speciation to occur there must be
A) sexual reproduction.
B) genetic variation.
C) isolation.
D) natural selection.
49) In a population of plants with a diploid number of 12, a new individual appeared with a
chromosome number of 24. If this organism could self-fertilize, forming offspring with the same
number of chromosomes (24), scientists would consider this an example of
A) sympatric speciation.
B) behavioral isolation.
C) formation of a hybrid zone.
D) reduced hybrid fertility.
14.2 Art Questions
1) Which species of wheat shown is polyploid?
A) T. monococcum
B) the AB sterile hybrid
C) T. turgidum
D) T. tauschii
2) Which butterfly has changed gradually but significantly from its ancestor through
microevolutionary events that were not part of a speciation event?
A) butterfly A
B) butterfly B
C) butterfly C
D) butterfly D
3) In bowerbirds, the divergence illustrated in the figure is based on
A) how often females visit the bower built by males.
B) the color of the plumage of the females.
C) the females’ preference for types of bower.
D) the color of bowers.
14.3 Scenario Questions
After reading the paragraphs below, answer the questions that follow.
In 2004, scientists announced the discovery of the fossil remains of some extremely short early
humans on the Indonesian island of Flores. The new species has been named Homo floresiensis.
One hypothesis is that H. floresiensis evolved from Homo erectus, another early human species.
How did a population of H. erectus become isolated on this remote island? Early humans
constructed boats and rafts, so perhaps they were blown far off course by strong winds during a
storm.
H. erectus averaged almost 6 feet in height, but the remains show that adults of H. floresiensis
were only about 3 feet tall. It is hypothesized that limited resources on this hot and humid island
(only 31 square miles) exerted selection pressure, and succeeding generations began to shrink in
size. Small bodies require less food, use less energy, and are easier to cool than larger bodies.
Evolution of small size in similar circumstances has been observed in many other species, but
never before in humans. This find demonstrates that evolutionary forces operate on humans in
the same way as on all other organisms.
1) The evolution of H. floresiensis is an example of
A) sympatric speciation.
B) allopatric speciation.
C) adaptive radiation.
D) hybridization.
2) If H. floresiensis were reunited with H. erectus at a much later date, but the two populations
could no longer interbreed, it would be correct to conclude that
A) H. floresiensis is no longer fertile as a species.
B) the two groups had been isolated for more than 50,000 years.
C) H. floresiensis has become less fit than H. erectus.
D) a reproductive barrier had evolved.
After reading the paragraph below, answer the questions that follow.
In the North Pacific Ocean, two groups of the same species of killer whales (Orcinus orca)
appear to be forming two different species based on what they eat. One group eats fish and the
other eats mammals such as seals. Scientists can tell what they eat based on their teeth, because
whales that feed on fish have significantly different wear patterns.
3) Which of the following would not be a useful procedure to perform in determining whether or
not this speciation has occurred?
A) Compare teeth of whales alive today to teeth of whales in ancient samples.
B) Compare DNA samples from fish-eaters and mammal-eaters.
C) Compare stomach contents of whales from each of the two populations.
D) Compare body shape of whales from each population.
4) Which of the following describes the type of speciation event that is occurring in these
whales?
A) sympatric speciation
B) allopatric speciation
C) geographic speciation
D) polyploid speciation
5) Another difference between the two groups is in how they hunt. Whales that hunt fish tend to
travel in large pods (groups of whales) and vocalize often. Whales that hunt seals, however, tend
to travel in very small groups and vocalize very little, likely because of the excellent hearing
ability of seals. If these differences brought about speciation, the separation would be considered
A) habitat isolation.
B) temporal isolation.
C) behavioral isolation.
D) mechanical isolation.
6) One of the finest available sequences of fossils shows how horses have changed slowly and by
subtle steps from small shrub-browsing ancestors to the large, grass-grazing modern horse. A
large number of fossil species have been named, and it is often difficult to decide on the identity
of a fossil horse because transitional forms are common. The species concept most applicable to
these organisms would be
A) the biological species concept.
B) the ecological species concept.
C) the morphological species concept.
D) the phylogenetic species concept.