Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 23
Test Yourself Questions
1. The process involving changes in one or more characteristics of a population that are heritable and
occur across many generations is called
a. natural selection.
b. sexual selection.
c. population genetics.
d. biological evolution.
e. inheritance of acquired characteristics.
Answer: d. Biological evolution is heritable change in one or more characteristics of a population or
species across many generations.
2. Lamarck's vision of evolution differed from Darwin's in that Lamarck believed
a. living things evolved in an upward direction.
b. behavioral changes modified heritable traits.
c. genetic differences among individuals in the population allowed for evolution.
d. a and b only
e. all of the above.
Answer: d. Lamarck’s vision of evolution was that living things evolved in an upward direction, toward
“perfection,” and that behavioral changes modified heritable traits. Darwin, in contrast, suggested that
evolution was the result of selection on heritable traits that influenced the survival and reproductive
success of individuals in a population.
3. Which of the following scientists influenced Darwin's views on the nature of population growth?
a. Cuvier
b. Malthus
c. Lyell
d. Hutton
e. Wallace
Answer: b. Malthus’s Essay on the Principle of Population was an important influence of Darwin's views
of population growth and changes over time.
4. An evolutionary change in which an organism's characteristics change in ways that make it better
suited to its environment is
a. natural selection.
b. an adaptation.
c. an acquired characteristic.
d. evolution.
e. both a and c.
Answer: b. An adaptation is an evolutionary change in which an organism's characteristics change in
ways that make it better suited to its environment.
5. Vestigial structures are anatomical structures
a. that have more than one function.
b. that have no function.
c. that look similar in different species but have different functions.
d. that have the same function in different species but have very different appearances.
e. of the body wall.
Answer: b. Vestigial structures are anatomical structures that have no function.
6. Which of the following is an example of developmental homologies seen in human embryonic
development?
a. gill ridges
b. umbilical cord
c. tail
d. both a and c
e. all of the above
Answer: d. The gill ridges and bony tail seen in human embryonic development are developmental
homologies with evolutionary ancestral organisms.
7. Two or more homologous genes found within a particular species are called
a. homozygous
b. orthologs
c. paralogs
d. heterologs
e. duplicates
Answer: c. Paralogs are two or more homologous genes found within a particular species.
8. The phenomenon of exon shuffling
a. creates new gene products by changing the pattern of intron removal in a particular gene.
b. creates new genes by inserting exons and flanking introns into a different gene sequences,
thereby introducing a new domain into the gene product.
c. rearranges the sequence of exons in a single gene.
d. rearranges the introns in a particular gene creating new gene products.
e. both a and d
Answer: b. The phenomenon of exon shuffling creates new genes by inserting exons and flanking
introns into a different gene sequences, thereby introducing a new domain into the gene product.
9. Horizontal gene transfer is
a. the transmission of genetic information from parent to offspring.
b. the exchange of genetic material among individuals of the same species.
c. the exchange of genetic material between mates.
d. the exchange of genetic material among individuals of different species.
e. none of the above.
Answer: d. Horizontal gene transfer is the exchange of genetic material among individuals of different
species.
10. Genetic variation can increase as a result of
a. random mutations in genes.
b. exon shuffling.
c. gene duplication.
d. horizontal gene transfer.
e. all of the above.
Answer: e. Random mutations, exon shuffling, gene duplication, and horizontal gene transfer are
examples of processes that increase genetic variation in a population.
Conceptual Questions
1.
Briefly describe the various observations that support the theory of biological evolution.
Answer:
a.
Fossil record – When fossils are compared according to their age from oldest to youngest,
successive evolutionary change becomes apparent.
b.
Biogeography – Unique species found on islands and other remote areas have arisen because the
species in these areas have evolved in isolation from the rest of the world.
c.
Convergent evolution – Two different species from different lineages sometimes become
anatomically similar because they occupy similar environments. This indicates that natural selection
promotes adaptation to a given environment.
d.
Selective breeding – The traits in domesticated species have been profoundly modified by artificial
selection practices.
e.
Anatomical homologies – Evolutionarily related species may possess homologous structures that
have been modified in ways that allow them to be used differently by each species.
f.
Developmental homologies – Embryonic development often reveals similar anatomical features
that suggest past evolutionary relationships.
g.
Molecular homologies – Certain molecular characteristics are found in all cells, suggesting that all
living species are derived from a common ancestor.
2.
Define convergent evolution and give an example.
Answer: The process of convergent evolution produces two different species from different lineages that
show similar characteristics because they occupy similar environments. An example is the long snout
and tongue of both the giant anteater found in South America and the echidna, found in Australia. This
enables these animals to feed on ants but the two structures evolved independently.
3.
Explain how homologous forelimbs support the idea of biological evolution.
Answer: The same set of bones is found in the human arm, turtle arm, bat wing, and whale flipper,
although it has been modified to perform different functions. This supports the idea that all of these
animals evolved from a common ancestor.
Experimental Questions
1. What features of Daphne Major made it a suitable field site for studying the effects of natural
selection?
Answer: The island has a moderate level of isolation but is located near enough to the mainland to have
some migrants. The island is an undisturbed habitat so the researchers would not have to consider the
effects of human activity on the study. Finally, the island had an existing population of ground finches
that would serve as the study organism over many generations.
2. Why is beak depth in finches a good trait for a study of natural selection? What environmental
conditions were important to allow the Grants to collect information concerning natural selection?
Answer: First, the researchers were able to show that beak depth is a genetic trait that has variation in
the population. Second, the depth of the beak is an indicator of the types of seeds the birds can eat.
The birds with larger beaks can eat larger and drier seeds; therefore, changes in the types of seeds
available could act as a selective force on the bird population.
During the study period, there were annual changes in rainfall. This had an impact on the seed sizes
produced by the plants on the island. In the drier year, fewer small seeds were produced so the birds
would have to eat larger, drier seeds.
3. What were the results of the Grants' study following the drought in 1978? What impact did these
results have on the theory of evolution?
Answer: The researchers found that following the drought in 1978, the average beak depth in the finch
population increased. This indicated that birds with larger beaks were better able to adapt to the
environmental changes due to the drought and produce more offspring. This is direct evidence of the
phenomenon of natural selection.
Collaborative Questions
1. Discuss evolution and how it occurs.
Answer: Evolution is a heritable change in one or more characteristics in a species over time. Evolution
can occur on a small scale in the case of a single gene or on a larger scale in the case of the formation
of a new species. Regardless of the scale, the main mechanism that drives evolution is natural
selection. Natural selection is when natural forces select some individuals to live and reproduce and
others to die and not reproduce. For natural selection to work there needs to be variation within a
population of organisms. Organisms with the most suitable characteristics will be selected for and those
who do not have favorable characteristics will be selected against and will not reproduce. Over many
generations, natural selection leads to adaptation.
2. Discuss horizontal gene transfer.
Answer: Evolution largely occurs by vertical evolution, which is the accumulation of genetic changes that
are transferred from one generation to the next. Along with vertical evolution, a process called horizontal
gene transfer involves the exchange of genetic information among different species. Due to horizontal
gene transfer, organisms not only gain genetic changes from their ancestors but from other species as
well. Examples of horizontal gene transfer are fairly widespread. An example is antibiotic resistance,
which has spread among many different bacterial species.