Asexual reproduction: the first step to extinction When species become asexual t

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Asexual reproduction: the first step to extinction
When species become asexual they could be taking the first step to
extinction, say researchers who have been studying the genetic structure
of Penicillium marneffei, an asexual fungus only found in parts of south­
east Asia. Their research found that although P. marneffei spores were
able to spread over large distances on currents of air, they were not able
to ‘invade’ the new environments in which they landed.
‘We believe the failure of P. marneffei to adapt to new environments is
because the fungus has largely dispensed with sexual reproduction.
Without sex, you will not have the mixing of genes it causes, something
all organisms need in order to be able to adapt to new environments’, said
a member of the research team. Evolutionary theory predicts that while
asexual organisms can initially prosper and out-compete their sexual
cousins, they pay a price for being unable to adapt through the
recombination of genes caused by sexual reproduction.
DNA typing was used to show that different clones of the fungus are
found in different environments, and the researchers believe that the
adaptation of the fungus to these environments is limiting their ability to
adapt to other areas. They believe this is why P. marneffei is only
endemic to a relatively small area of south-east Asia. Even though the
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fungus makes spores which can spread over very large distances, the
researchers found that all the samples from any given location were
genetically very similar. This led them to the conclusion that the fungus
becomes highly adapted to its local environment, making it highly
successful there, but stopping it spreading to other areas.
‘By being asexual, P. marneffei is not only limiting its ability to adapt, it
may be at risk of becoming extinct. If it is unable to adapt to new
environments, it will be unable to adapt to changes in its current
environment. While becoming asexual may provide short term
advantages to a species, in the long term, they are likely to end up in
evolution’s ultimate dustbin – extinction’, concluded a member of the
research team

You should introduce your article by very briefly explaining the purpose of
biological reproduction and touching upon the strategies used to achieve it, then
write your account using the following list as a guide to the points you should
discuss in your answer:
? How does asexual reproduction differ from sexual reproduction in terms of
the biological processes involved and the genetic diversity and variation of
the DNA produced?
What are the advantages and disadvantages of asexual and sexual
reproduction?
In terms of survival and adaptation, which reproduction strategy is more
likely to allow a species to evolve rapidly (or to become extinct)? In your
answer briefly describe the two main mechanisms used to create genetic
variation. Also, explain the factors and pressures that are likely to drive the
process of adaptation.

Explanation / Answer

Asexual reproduction   

Sexual reproduction

Asexual reproduction   

Sexual reproduction

Single parent Two parents Crossing over of gametes absent Crossing over of gametes is present Genetic diversity absent Genetic diversity is present Fertilization absent Fertilization present Variation absent variation present

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