Chapter 14
Answers
1
QUICK-CHECK questions
Identify the following as true or false.
a
Lamarck proposed that changes acquired during the lifetime of an organism
could be passed to the next generation.
True: Lamarck proposed that any changes, such as enlargement of an organ,
acquired during the lifetime of an organism could be transmitted to its offspring.
b
De Maillet’s view of evolution involved sudden changes in the structures of
an organism.
True: His account of the origin of birds has them arising from sudden changes in
fish structures, such as fins, into structures characteristic of birds, such as wings.
c
Chambers proposed a cause for evolution that could be tested by
observation and experimentation.
False: Chambers’ view of evolution was that it was due to some unknown law.
Explanations of this nature fall outside science since they cannot be tested by
observation or experimentation.
2
Identify an important observation made by Darwin during his time in Australia.
While in Australia, Darwin saw that niches that were occupied by one species in the
northern hemisphere were occupied by very different species in the southern
hemisphere. Darwin wrote that he ‘reflected on the strange character of the animals in
this country [Australia] as compared with the rest of the world’. So, this caused him to
wonder about questions such as: Why are there platypus in creeks in Australia rather
than water rats in streams as in England? Why are there kangaroos on grasslands in
Australia rather than wildebeest as in southern Africa?
3
Identify two features of the Darwin–Wallace theory of evolution by natural
selection that distinguished this theory from most other views about evolution.
The Darwin–Wallace theory of evolution can be distinguished from other views about
evolution in that:
 it identified a clearly defined mechanism for evolution, namely natural selection
 the mechanism proposed could be tested by observation and by experimentation.
4
Identify two methods used in the nineteenth century to estimate Earth’s age.
In the nineteenth century, the age of the Earth was estimated by various means
including:
 estimation of the rate of cooling of the Earth from its initial molten state (Lord Kelvin)
 extrapolation of the salt content of oceans derived from river waters (Joly).
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Chapter 14: QUICK-CHECK answers
5
List a particular contribution of the following to the debate about the age of the
Earth:
a
James Hutton
Based on observation of unconformities, James Hutton recognised that repeated
cycles of sedimentation, compression into rock, uplift and erosion had occurred
and that ‘countless ages’ were required. Hutton was one of the first to identify that
the age of the Earth was far greater than the view prevailing at that time; he
published his views in 1785.
b
Charles Lyell.
Charles Lyell recognised that the geological forces that acted in the past, and that
resulted in sedimentation, compression into rock, uplift and erosion, were similar
to those acting at the present time and that landforms were a result of these slow
and gradual processes.
6
Identify the following statements as true or false.
a
Absolute age gives a number in years.
True
b
Radiometric methods of dating yield the relative age of an object.
False: Radiometric dating can yield the absolute age of an object.
c
Carbon dating could be used to tell the age of Australian coal deposits from
the Permian period.
False: The coal deposits of the Permian period, whichh began about 299 million
years ago, do contain carbon, but this coal is far too old for carbon dating. Carbon
dating is useful only for carbon-based materials up to about 60 000 years old.
d
When half of a radioactive parent element has decayed, an equivalent
amount of daughter element(s) will have been produced.
True: The decay of one parent atom generates one daughter atom, so when half
of the parent atoms decay, an equivalent amount of daughter atoms are produced.
e
Over two half lives, the initial amount of a radioactive parent element will be
halved.
False: Over one half life, the initial amount of radioactive parent element will be
halved by radioactive decay, and, after a second half life, half of the remaining
amount of parent element will also have decayed. So, after two half lives, only
one-quarter of the original parent element will be present.
f
All radioactive elements have equal rates of decay.
False: The rate of decay is expressed as a half life and this differs for various
radioactive elements.
(Note: See some examples of half lives in table 14.1.)
7
Explain briefly the principle of superposition.
The principle of superposition simply states that rock layers at the bottom of a
sequence are older than those above them.
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Chapter 14: QUICK-CHECK answers
8
List the following geological periods in order, from oldest to most recent:
Cretaceous, Triassic, Cambrian, Carboniferous.
Cambrian, Carboniferous, Triassic, Cretaceous
(See figure 14.14 for the ages of the various geological periods.)
9
Identify the following as true or false:
a
No transitional fossils have been found in the fossil record.
False: Transitional fossils that provide a link between an ancestral group and its
descendants have been found in the fossil record. The most famous example is
Archaeopteryx.
b
The order of appearance of different kinds of organism in the fossil record is
random.
False: The order of appearance of different kinds of organism in the fossil record
is not random. Single-celled organisms appeared before multicellular organisms,
invertebrates appeared before vertebrates. Among the vertebrates, fish appeared
before amphibians, which appeared before reptiles, which appeared before
mammals.
c
A whale flipper and a bat wing are homologous structures.
True: In terms of their bony structure, a whale flipper and a bat wing are
homologous, both having been derived from the forelimb of their common
vertebrate ancestor.
d
The reduction in melting temperature for human–chimp hybrid DNA would
be less than that for human–gibbon hybrid DNA.
False: The melting temperature would be higher for human–chimp hybrid DNA
than for human–gibbon hybrid DNA because there is greater complementary
pairing between chimp DNA and human DNA than between gibbon DNA and
human DNA. The greater degree of complementary pairing between the two
chains of a human–chimp hybrid DNA molecule leads to more hydrogen bonding;
as a result, the melting temperature is higher than for human–gibbon hybrid DNA.
10
Select the appropriate alternative:
The longer the time since two species shared a common ancestor, the more/less
similar is the amino acid sequence of a protein common to the two species.
The longer the time since two species shared a common ancestor, the less similar is
the amino acid sequence of a protein common to the two species.
11
What was the most likely chromosome number in the common ancestor of the
great apes?
The most likely chromosome number in the common ancestor of the great apes is 48
as this is the chromosome number seen in all the great apes, except human beings.
The human diploid number of 46 is a result of a fusion between two non-homologous
chromosomes, which occurred early in the evolution of the hominins, after the hominin
line had diverged from the chimp line. (See table 14.7.)
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Chapter 14: QUICK-CHECK answers
12
Identify the following as true or false:
a
Cacti and euphorbia provide an example of adaptive radiation.
False: The succulent swollen stems and leafless habit of species of cacti and
species of euphorbia are features that equip both groups of species to survive in
arid environments. However, these features arose independently in each group
and so this is an example of convergent evolution or adaptive convergence.
b
The diversity of elapid snakes in Australia provides an example of parallel
evolution.
False: The many Australian elapid snake species evolved from an ancestral
species that reached Australia from Asia. Over millions of years since then,
populations of descendants of the ancestral species have evolved into a variety of
elapid species, each adapted for a specific habitat. This is an example of
divergent evolution or adaptive radiation.
13
Give one example of adaptive radiation.
One example of adaptive radiation is the evolution of the various species of kangaroo
and wallaby in the family Macropodiidae from an ancestral species.
(Note: Many other examples of adaptive radiation exist and include the finches of the
Galapagos Islands and the honeycreepers of the Hawaiian Islands.)
14
List two structural changes that occurred during the evolution of modern
kangaroos.
Structural changes that have occurred during the evolution of the modern kangaroo
include features that equip them for their hopping locomotion such as:
 lengthening and strengthening of the hind limbs
 enlargement of the fourth toe
 presence of strong elastic tendons in the hind legs
 lengthening of the tail, which acts as a stabiliser.
(Note: Other changes related to adaptations for a changed diet are listed on
page 550.)
15
Identify the following as true or false:
a
The more recently that two species diverged, the greater the similarity
expected in their DNA sequences.
True: The more recently two species diverged, the less time has been available
for mutational changes to occur in their DNA sequences and the more similar their
corresponding DNA sequences.
b
Comparative genomics can show the degree of relationship between
species.
True: By comparing genomes, it is possible to draw conclusions about the degree
of similarity between species.
c
Figure 14.58 indicates that there is a greater degree of similarity between
human DNA and rat DNA than between human DNA and cat DNA.
False: This figure shows that, for this particular DNA sequence, the alignment
between human DNA and cat DNA was more than 60 per cent, whereas the
alignment between human DNA and rat DNA was about 40 per cent.
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Chapter 14: QUICK-CHECK answers
16
Examine figure 14.59:
a
How are exons denoted?
In this figure, exons are shown as blue segments.
b
Which organism shows a greater degree of similarity with human DNA: fish
or frog?
Greater similarity exists in the case of the frog.
(Note: The greatest similarity with human DNA is with the only other mammalian
species shown, the mouse.)
17
List two possible outcomes of comparative genomics.
Using comparative genomics, it is possible to:
 identify genes that are conserved in different species
 make inferences about the evolutionary history of a species
 estimate the degree of evolutionary relationship between two species.
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