Life's top priority is to continue. While the longevity of a single organism is finite, the organism contributes to everlasting life by passing its DNA on to its progeny. This, essentially, is how one lives forever. Organisms reproduce either sexually or asexually, but is one better than the other?
Asexual Reproduction is Less Costly, but Promotes Little Genetic Diversity
An asexual organism produces a new organism that is either an exact copy or quite similar. This is done without the genetic contribution of another organism. The benefits of asexual reproduction are that it uses less energy than sexual reproduction and does not require as much time from the parent.
Sexual reproduction results in genetic diversity because only half of a parent's genes are passed on to its progeny. It combines the genetic material of two organisms to produce an individual. With sexual reproduction, an organism must find a suitable mate. This may be especially difficult if a particular organism is itself an undesirable mate.
Some monogamous bird species demonstrate the difficulty of reproducing when mate selection is involved. Some females have been shown to cheat on their mates with males possessing more desirable traits. The result is that a male with less desirable genetic traits unknowingly raises another's progeny without producing young of its own.
DNA Mutations Accumulate More Often with Asexual Reproduction
Even though asexual reproduction is beneficial in terms of time and energy, the majority of organisms sexually reproduce. University of Iowa professor and researcher Maurine Neiman and her colleagues set out to discover why the more costly sexual production predominated over asexual reproduction.
According to a January 20, 2010 University of Iowa news release, "Study shows value of sexual reproduction versus asexual reproduction," Dr. Neiman's "study looked at sexual, as well as asexual, varieties of a New Zealand freshwater snail, Potamopyrgus antipodarum, by sequencing mitochondrial genomes and found that the sexually reproducing snails had accumulated harmful DNA mutations at about half the rate of the asexual snails."
Natural Selection Allows for Progeny with Fewer Accumulated Genetic Mutations
The theory of natural selection coupled with sexual reproduction may explain why there are fewer harmful mutations with sexual reproduction. If the harmful mutations prevent an organism from reaching adulthood, the organism will not live to pass the genetic mutation on to its offspring. Even if the organism reaches maturity and reproduces, it may not pass on the mutated gene because only half of its genetic material is used to create the new organism. Examples of harmful mutations in humans are cystic fibrosis and Huntington's disease.
According to the Kimball's Biology Pages section on " Mutation and Evolution," by former Harvard graduate and teacher of biology, Dr. John W. Kimball, most observed mutations are harmful. Asexual reproduction allows these mutations to continue in the presence of new mutations. Sexual reproduction offers a solution to this problem.
Since genetic material from two organisms is combined in sexual reproduction, mutations have the opportunity to exist in different genetic combinations. In this situation, the mutation can eventually "lead to a new function," according to Dr. Kimball, or it could disappear. If the mutation leads to a negative development, such as disfigurement or shortened life span, the organism with the mutation most likely will not reproduce, and the mutation will be lost by process of natural selection.
The findings of Dr. Neiman's research team regarding the presence of harmful mutations in sexually versus asexually reproducing organisms support the theories that the more costly sexual reproduction is more beneficial with regard to genetic material. Dr. Neiman will continue her research to further understand the benefits of sexual reproduction and genetic diversity.
Diane Ursu - Diane Ursu joined Suite101 as a contributing writer in August 2009 and became a Feature Writer in January 2010. She is a freelance writer ...
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