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The Importance of Sex
Sex is
important to life on Earth. It is not just Humans and the higher
animals that need sex. Whether species were created or evolved, or
both, there are not many that have no form of sexual reproduction. Of
course, many species also can reproduce without sex, but the fact that
they can reproduce sexually is of great evolutionary significance. If a
species loses its ability to sexually reproduce, its ability to adapt
is much less.
Humans usually reproduce sexually. The great
majority of Humans are the result of purely sexual reproduction.
Although on fairly rare occasions Humans do reproduce asexually by
binary fission, splitting into two separate individuals this only
accounts for a small percentage of the Human population of the world.
It
is also worth noting that quite often, even when asexual reproduction
occurs; it follows on from sexual reproduction.
From
the evolutionary point of view, sexual reproduction is very necessary.
Even relatively simple creatures like bacteria can exchange genetic
material and can adapt very quickly.
Imagine life on a planet
that had no means of sexual reproduction. I would suggest that they
would not have the ability to evolve in the same way as life on Earth
can.
Of course my suggestion that sexual reproduction is
necessary implies that species that have lost this ability and rely on
asexual reproduction only are at risk of being evolutionary dead
ends. For example, a plant called the sour sob, Oxalis pes-capri, was
formed by a Chromosome mutation resulting in it being pentaploid, that
is it has two and a half times as many chromosomes as the plant it came
from. At
first this was believed to be an evolutionary dead end that was unable
to adapt further. Now a population of this highly successful plant has
been discovered that sets seed, so it is now reproducing sexually.
Another
plant, Duckweed (Genus Lemna) normally reproduces only asexually by
budding into two genetically identical individuals. However, on rare
occasions this plant will flower and can change by recombination of genes.
In the evolutionary sense this is of great importance to the plant.
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Population Growth & Evolution 
