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Last Updated: Apr 9, 2008 - 12:27:46 AM |
Special Topics
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Evolution
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Reproduction
Artificial human sperm could make men redundant: experts
Hamburg -, April 7 - Artificial human sperm could come to the aid of infertile men, according to a team of German scientists who have used lab-grown sperm to inseminate female mice.
Apr 7, 2008 - 11:35:21 AM
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Evolution
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Reproduction
Is Sex Necessary for Evolution?
If you own a birdbath, chances are you are hosting one of evolutionary biology's most puzzling enigmas: bdelloid rotifers. These microscopic invertebrates - widely distributed in mosses, creeks, ponds, and other freshwater repositories -abandoned sex perhaps 100 million years ago, yet have apparently diverged into nearly 400 species. Bdelloids (the "b" is silent) reproduce through parthenogenesis, which generates offspring with essentially the same genome as their mother from unfertilized eggs. Biologists have yet to find males, hermaphrodites, or any trace of meiosis- the process that creates sex cells - challenging the long-held assumption that evolutionary success requires genetic exchange.
Mar 26, 2007 - 7:59:12 AM
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Special Topics
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Evolution
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Reproduction
Infection Status Drives Interspecies Mating Choices in Fruit Fly Females
Hybridization is a constant possibility for two closely related species. Geographic isolation prevents interbreeding in some cases, but when the range of the two overlap, other mechanisms must come into play if they are to remain genetically distinct. Behavioral isolation is one such mechanism. If members of each group preferentially mate with their own kind, the two species can remain distinct even while residing together. Over time, such isolating behaviors may become more pronounced, and the genes governing them more widespread, a phenomenon termed reinforcement.
Oct 11, 2006 - 5:25:00 AM
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Special Topics
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Evolution
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Reproduction
Why Does Sex Exist?
Why does sex exist? A long-popular view holds that sexual reproduction creates new gene combinations that help the next generation resist rapidly co-evolving parasites. Each species constantly changes to achieve the same resultevolutionary advantageprompting evolutionary biologists to dub this hypothesis the Red Queen (who tells Alice in Through the Looking Glass it takes all the running you can do, to keep in the same place).
Aug 7, 2006 - 1:51:00 PM
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Special Topics
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Evolution
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Reproduction
Declining Human Fertility is Evolutionary Adaptation
Before society criticises teenage girls for having sex behind the bike sheds and becoming pregnant, or women in their 60s for seeking IVF treatment, it is important to consider fertility not just in terms of the 21st century but in the context of the past 150,000 years.
Jun 21, 2006 - 2:52:00 PM
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Special Topics
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Evolution
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Reproduction
Genetic quality of sperm worsens as men get older
New research indicates that the genetic quality of sperm worsens as men get older, increasing a man's risk of being infertile, fathering unsuccessful pregnancies and passing along dwarfism and possibly other genetic diseases to his children. A study led by scientists at Lawrence Livermore National Laboratory (LLNL) and the University of California, Berkeley, found a steady increase in sperm DNA fragmentation with increasing age of the study participants, along with increases in a gene mutation that causes achondroplasia, or dwarfism. The first changes were observed in men in their early reproductive years. Earlier research by the same team indicated that male reproductive ability gradually worsens with age, as sperm counts decline and the sperm lose motility and their ability to swim in a straight line. In the current study, the researchers analyzed DNA damage, chromosomal abnormalities and gene mutations in semen samples from the same subjects 97 healthy, non-smoking LLNL employees and retirees between 22 and 80 years old and found that sperm motility showed a high correlation with DNA fragmentation, which is associated with increased risk of infertility and a reduced probability of fathering a successful pregnancy.
Jun 8, 2006 - 4:46:00 PM
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Special Topics
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Evolution
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Reproduction
Songbirds boost size of eggs when hearing sexy song
When the females started egg-laying they varied the size of their eggs in the nest according to the attractiveness of the male's song. That is, the more attractive the song, the larger the eggs.
Jun 8, 2006 - 6:04:00 AM
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Special Topics
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Evolution
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Reproduction
Fish have menopause, study determines
A UC Riverside-led research team has found that as some populations of an organism evolve a longer lifespan, they do so by increasing only that segment of the lifespan that contributes to "fitness" the relative ability of an individual to contribute offspring to the next generation. Focusing on guppies, small fresh-water fish biologists have studied for long, the researchers found that guppies living in environments with a large number of predators have adapted to reproduce earlier in life than guppies from low-predation localities. Moreover, when reproduction ceases, guppies from high-predation localities are far older, on average, than guppies from low-predation localities, indicating that high-predation guppies enjoy a long "reproductive period" the time between first and last reproduction.
Dec 29, 2005 - 4:19:00 PM
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Special Topics
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Evolution
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Reproduction
Dancing ability determines mate quality
Dance has long been recognized as a signal of courtship in many animal species, including humans. Better dancers presumably attract more mates, or a more desirable mate. What's seemingly obvious in everyday life, however, has not always been rigorously verified by science. Now, a study by scientists at Rutgers, The State University of New Jersey, for the first time links dancing ability to established measures of mate quality in humans. Reporting in Thursday's edition of the British science journal Nature, Rutgers anthropologists collaborating with University of Washington computer scientists describe how they created computer-animated figures that duplicated the movements of 183 Jamaican teenagers dancing to popular music. The researchers then asked peers of the dancers to evaluate the dancing ability of these animated figures. The figures were gender-neutral, faceless and the same size all to keep evaluators from boosting or dropping dancers' scores based on considerations other than dance moves.
Dec 22, 2005 - 5:11:00 AM
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Special Topics
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Evolution
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Reproduction
How sense of smell affects mating and aggression
New research by scientists at UCSF sheds light on how the odor detecting system in mice sends signals that affect their social behavior.
Dec 22, 2005 - 3:42:00 AM
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