SOMEONE HELP: Complete sentences, stating the differences and relationships between the two terms, and give specific examples where appropriate. 1. gene flow / genetic drift 2. sexual selection / artificial selection 3. ring species / biological species concept 4. hybrid inviability / temporal isolation 5. autopolyploidy / allopatric speciation 6. molecular clock / cladogram 7. gradualism / uniformitarianism 8. extreme thermophiles / viroids 9. HIV / Creutzfeld-Jakob disease 10. biofilm / microbial fuel cell Solution Q.No 1 Genetic drift is a mechanism of evolution of biological species that takes place because of the change in the frequency of alleles in a population. These changes in the allele frequency in a population occur randomly. One very common example to describe the genetic drift would be that most of the human families have different number of boys and girls, as the X or Y alleles have been passed differently into the new generation from the parents. Although the X and Y alleles do not really contribute for the evolution, the frequency changes in other alleles would have a considerable effect for evolution. Gene flow is a process of evolution that takes place when genes or alleles move from one population to another. It is also known as the Gene Migration, and that could cause changes in the allele frequency as well as some variations in the gene pool of both populations. There are some good examples to support this phenomenon from humans regarding a developed immunity for malaria among new Western Africans after their parents mated with Europeans who initially had the immunity. It is interesting to notice that gene flow could take place between two species, as well. Q.No 2 Sexual selection enhances mating success or the number of copulations, while natural selection tends to produce well-adapted individuals to their environment. Sexual selection does not adapt the individuals to their environment. Unlike sexual selection, natural selection acts on traits which increase the fitness of members in a population. Certain adaptations have been derived from the sexual selection which could never have been arisen from natural selection alone (Ex: the neck of the giraffe, various plumages of most male birds etc.). Generally sexual selection depends on the success of one sex while natural selection depends on the success of both sexes in relation to the general condition of life. In most of the animals, certain traits related to their sexual selection process do not express their characteristics until the organism is able to mate, but naturally selected traits may occur at birth of the organism during the process of natural selection. Q.No 3 A ring species is a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two \"end\" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between e.

1. SOMEONE HELP: Complete sentences, stating the differences and relationships between the
two terms, and give specific examples where appropriate.
1. gene flow / genetic drift
2. sexual selection / artificial selection
3. ring species / biological species concept
4. hybrid inviability / temporal isolation
5. autopolyploidy / allopatric speciation
6. molecular clock / cladogram
7. gradualism / uniformitarianism
8. extreme thermophiles / viroids
9. HIV / Creutzfeld-Jakob disease
10. biofilm / microbial fuel cell
Solution
Q.No 1
Genetic drift is a mechanism of evolution of biological species that takes place because of the
change in the frequency of alleles in a population. These changes in the allele frequency in a
population occur randomly. One very common example to describe the genetic drift would be
that most of the human families have different number of boys and girls, as the X or Y alleles
have been passed differently into the new generation from the parents. Although the X and Y
alleles do not really contribute for the evolution, the frequency changes in other alleles would
have a considerable effect for evolution.
Gene flow is a process of evolution that takes place when genes or alleles move from one
population to another. It is also known as the Gene Migration, and that could cause changes in
the allele frequency as well as some variations in the gene pool of both populations. There are
some good examples to support this phenomenon from humans regarding a developed immunity
for malaria among new Western Africans after their parents mated with Europeans who initially
had the immunity. It is interesting to notice that gene flow could take place between two species,
as well.
Q.No 2
Sexual selection enhances mating success or the number of copulations, while natural selection
tends to produce well-adapted individuals to their environment. Sexual selection does not adapt
the individuals to their environment. Unlike sexual selection, natural selection acts on traits
which increase the fitness of members in a population. Certain adaptations have been derived

2. from the sexual selection which could never have been arisen from natural selection alone (Ex:
the neck of the giraffe, various plumages of most male birds etc.). Generally sexual selection
depends on the success of one sex while natural selection depends on the success of both sexes in
relation to the general condition of life. In most of the animals, certain traits related to their
sexual selection process do not express their characteristics until the organism is able to mate,
but naturally selected traits may occur at birth of the organism during the process of natural
selection.
Q.No 3
A ring species is a connected series of neighbouring populations, each of which can interbreed
with closely sited related populations, but for which there exist at least two "end" populations in
the series, which are too distantly related to interbreed, though there is a potential gene flow
between each "linked" population. A classic example of ring species was the Larus gulls'
circumpolar species "ring". The biological species concept defines a species as members of
populations that actually or potentially interbreed in nature, not according to similarity of
appearance. Although appearance is helpful in identifying species, it does not define species.
Q.No 4
Hybrid inviability is a post-zygotic barrier, which reduces a hybrid's capacity to mature into a
healthy, fit adult. The relatively low health of these hybrids relative to pure-breed individuals
prevents gene flow between species. An example of hybrid inviability: when certain species of
irises are crossed, the offspring die before a seed can be formed. Temporal isolation means
'isolated in time,' so this is a mechanism that prevents species from mating because they breed
at different times. These differences can be time of day, season, or even different years. One
example of seasonal temporal isolation is the American toad and the Fowler's toad. These are
closely related species, but the American toad mates in the early part of summer, while the
Fowler's toad mates later in the season.
Q.No 5
Allopatric speciation, the most common form of speciation, occurs when populations of a species
become geographically isolated. When populations become separated, gene flow between them
ceases. Over time, the populations may become genetically different in response to the natural
selection imposed by their different environments. If the populations are relatively small, they
may experience a founder effect: the populations may have contained different allelic
frequencies when they were separated. Selection and genetic drift will act differently on these
two different genetic backgrounds, creating genetic differences between the two new species.
Autopolyploidy describes the multiple occurrence of a set of chromosomes in a cell, a tissue or a
whole organism. Autopolyploidy happens regularly in plants in the course of their tissue
differentiation, though, to distinguish it from autopolyploidy, it is then called somatic polyploidy

3. or endopolyploidy.
Q.No 6
The molecular clock is a technique that uses the mutation rate of biomolecules to reduce the time
in prehistory when two or more life forms diverged. The biomolecular data used for such
calculations are usually nucleotide sequences for DNA or amino acid sequences for proteins. A
cladogram can look at trees that may have been derived from a common ancestor to arrange
organisms on different branches. But those branches used aren't representative of the relative
amount of change or evolutionary time that has occurred between organisms. Plus, a cladogram
doesn't necessarily show exact relationships between ancestors and descendants.
Q.No 7
Gradualism is the view that large-scale changes occurs by the accumulated effects of small
changes over long periods of time, rather than by rare cataclysmic events of massive effect.
Uniformitarianism is the view that the same forces that shaped the world in the past continue to
operate today. Historically, uniformitarianism has often included aspects of gradualism (i.e.
definitions by Lyell), e.g. by assuming uniformity of rates. Uniformitarianism was also originally
proposed as the opposite of Catastrophism. However, in modern use, the focus lies on uniformity
of processes, and rapid catastrophic changes are allowed under uniformitarianism.
Q.No 8
Extreme thermophiles have an optimum above 75oC and thus can grow at the highest
temperatures tolerated by any organism. An extreme example is the genus Pyrodictium, found on
geothermally heated areas of the seabed. It has a temperature minimum of 82o, optimum of 105o
and growth maximum of 110oC. Viroids are the smallest infectious pathogens known. They are
solely composed of a short strand of circular, single-stranded, RNA without protein coat. The
apple scar skin, cleus blemei and coconut cadang-cadang viroids are examples of these subviral
agents.
Q.No 9
AIDS (Acquired immune deficiency syndrome or acquired immunodeficiency syndrome) is a
syndrome caused by a virus called HIV (Human Immunodeficiency Virus). The illness alters the
immune system, making people much more vulnerable to infections and diseases. This
susceptibility worsens as the syndrome progresses. HIV is found in the body fluids of an infected
person (semen and vaginal fluids, blood and breast milk). The virus is passed from one person to
another through blood-to-blood and sexual contact. In addition, infected pregnant women can
pass HIV to their babies during pregnancy, delivering the baby during childbirth, and through
breast feeding. Creutzfeldt–Jakob disease (CJD) is an incurable and universally fatal
neurodegenerative disease.[2] CJD is at times called a human form of mad cow disease (bovine
spongiform encephalopathy or BSE). CJD is caused by an infectious agent called a prion. Prions

4. are misfolded proteins that replicate by converting their properly folded counterparts, in their
host, to the same misfolded structure they possess. CJD causes the brain tissue to degenerate
rapidly, and as the disease destroys the brain, the brain develops holes and the texture changes to
resemble that of a kitchen sponge.
Q.No 10
Biofilms are microbial consortia physically aggregated from a competitive advantage in forming
a community function. A biofilm can be formed from a single species, but it is more commonly
comprised of many, often distantly related, microorganisms that utilize specific metabolic
pathways. These consortia have become the object of study in the development of efficient
microbial fuel cells. Microbial fuel cells (MFC) are a relatively new technology that harnesses
the electrons released transferred during microbial respiration to generate an electrochemical
potential difference between an anode and a cathode. Biofilms on the electron source (i.e. anode)
have been demonstrated to increase the current due to the direct electron transfer between the
microbes and the surface of the anode. Only specific groups of microbes can be used to power a
microbial fuel cell, due to their adaptation to donate electrons externally during respiration, and,
so, researching the physiology of these organisms can improve the efficiency of the cell.
A microbial fuel cell (MFC) is a device that converts chemical energy to electrical energy by the
action of microorganisms. These electrochemical cells are constructed using either a bioanode
and/or a biocathode. Most MFCs contain a membrane to separate the compartments of the anode
(where oxidation takes place) and the cathode (where reduction takes place). The electrons
produced during oxidation are transferred directly to an electrode or, to a redox mediator species.
The electron flux is moved to the cathode. The charge balance of the system is compensated by
ionic movement inside the cell, usually across an ionic membrane. Most MFCs use an organic
electron donor that is oxidised to produce CO2, protons and electrons. Other electron donors
have been reported, such as sulphur compounds or hydrogen. The cathode reaction uses a variety
of electron acceptors that includes the reduction of oxygen as the most studied process. However,
other electron acceptors have been studied, including metal recovery by reduction, water to
hydrogen, nitrate reduction and sulfate reduction.