CHAPTER 22
REVIEW QUESTIONS
22.1
Biological evolution: ordered and sequential change in organisms over time.
22.2
a.
b.
c.
d.
Organs / appendages used often developed whilst those which were not used atrophied.
Muscle building exercises leads to increased development of muscles.
Lamarck believed that characteristics acquired during the lifetime of an individual were
transmitted to that individual's offspring.
Weismann cut of the tails of mice for hundreds of generations. Each new generation was
born with tails.
22.3
The theory of natural selection attempts to explain:
 why reproductive potential is not achieved
 existing variations within any population
 changes in a population over time with respect to certain features
 interactions between organisms and environment and thus selection of individuals
with the best reproductive potential at any time.
2.4
Three main ideas are:
 Individuals within a population have a great reproductive potential.
 The numbers of individuals in a population remain approximately constant.
 Variations exist within populations.
Thus many individuals fail to reproduce and this results from a selection of those with the best
reproductive potential at that time passing information on to offspring – those individuals not
suited to their environment will fail to reproduce – causing a shift in the features of the
population.
22.5
The male's antlers are used in territorial disputes – defending his group of females from other
enroaching males. Each spring (breeding season) males will fight to claim the rights of the
cows. The moose with the largest antlers will have an advantage, all other factors (e.g. age,
general health etc.) being equal.
a. Lamarck: due to much fighting the antlers will become larger. The male offspring will also
inherit large antlers.
b. Darwin: within any population some males will have larger antlers than others. Those
males with larger antlers will win more fights and thus breed whilst the males with shorter
antlers will not breed. Those who breed will pass their genes for large antlers on to their
male offspring.
22.6
Artificial selection: humans deliberately select organisms to breed with on the basis of specific
characteristics. This has been used in breeding specific strains of animals (e.g. tick-resistant
cattle; breeds of dogs etc.) and plants (rust-resistant wheat, larger tomato crops etc.) for the
benefit of people.
22.7
Genes which can be altered by mutation.
22.8
a.
b.
There are different alleles for the expression of a gene.
Mitosis – same characteristics passed on.
Meiosis – different gametes from an individual can have different alleles for a
characteristic.
Fertilisation – different combinations of alleles can occur as a result of fertilisation –
produces variability in offspring.
c.
Mutation causes changes in genes which can be inherited if the mutations occur in the
gametes.
Crossing over brings about variations in linked genes.
d. DNA codes for protein synthesis – mis-transcription or translation can bring about
changes in the individual but copying errors during DNA replication can result in
mutations which may cause variation in the individual and eventually the population.
All support the theory that there is natural variation in any population which may be acted
upon by environmental selection pressures.
22.9
See Table 22.1
22.10
a.
b.
22.11
Sedimentary rocks: where sediments settle they become compacted by new sediments
washing over them. There is a gradual hardening of the sediments to form rocks. Thus
the oldest sedimentary rocks are usually those on the bottom of any strata. Bits and
pieces of plants and animals washed down in the sediments quickly become covered and
were protected from decay by the rapid burial, anaerobic conditions or acid or mineral
rich waters. Thus fossils found in the lower strata are also the oldest. However, uplifting
of the earth’s surface and subsequent erosion in earth’s natural rock cycle, could place
the old sediments and their fossils out of order.
Radioactive decay dating methods assume that at the time of fossil formation there was
the same amount of radio-isotopes present in the earth's atmosphere as there is currently.
Thus by knowing the half-life of any particular isotope, the age can be determined by
measuring the proportion of isotope still present in the fossil. Similarly the surrounding
rocks can also be measured for the presence of other isotopes to cross-check the data.
The accuracy of dating depends on the age of the fossil, e.g. carbon dating is only valid
for fossils up to 20,000 years old.
1/4 of the original carbon-14 left.
1/2 life carbon-14 is 5,760 years.
Thus after 5,760 years
1/2 carbon-14 left
After 2 x 5.760 years
1/4 carbon-14 left
Thus fossil is 11,520 years old.
22.12
a.
b.
c.
Homologous organs: similar structure and development although they may have different
functions – suggests common ancestral origin.
All vertebrate embryos go through a stage of visceral clefts, notochord and a tail
regardless of the adult form., showing inheritance from a common ancestor.
Serum protein analysis: the more similar the serum proteins of two organisms are the
more closely related they are since protein similarities indicate gene similarities.
22.13
Homologous structures:
b, c, d
22.14
Adaptive radiation: competition for resources within a species or group of species and the
availability of different niches in the environment result in the selection of certain members in
the population with existing variations to occupy a different niche to fill it. Thus over time
different organisms will evolve to fill all available niches. Thus primitive marsupials which
first existed in Australia through divergent evolution came to occupy a variety of niches, e.g.
browsing kangaroos and wombats, arboreal leaf eating koalas, fruit, blossom and leaf eating
possums, gliders etc. through to insectivorous and carnivorous marsupials such as the numbat
and tasmanian devil.
22.15
Deep ocean floor is relatively young (150 million years old) compared with continents.
Age of rocks decreases towards the oceanic ridges.
Measurement of movement of plates.
Distribution of fossil plants and animals on the continents.
Shapes of continental boundaries.
22.16
Serum analysis works on antigen-antibody reactions. The more alike the serums of two
different species the less will be the precipitation between them. Since each serum protein is
the product of a gene, this indicates the similarities between the genes coding for the proteins.
22.17
DNA hybridisation compares the sequence of nucleotides in single chains of sections of DNA
strands from two species. The greater the number of hydrogen bonds forming between
complementary nucleotides on the hybrid DNA, the more alike the DNA of the species and
thus their evolutionary relatedness.
22.18
More than one triplet code can specify a particular amino acid. Thus although similar proteins
may be formed in two species, the actual nucleotide sequences in the two types of DNA might
be different and the two species may not be as closely related as originally thought to be.
22.19
The karyotype is determined by the number and types of chromosomes in a species. The types
of chromosomes are identified by the position of the centromere and banding patterns of each
chromosome.
22.20
Regulator genes code for proteins that switch on or off structural genes and thus control the
production of cellular proteins. Since most cellular proteins are enzymes involved in metabolic
pathways they greatly influence the phenotypic expression of traits.