Is Sexual Reproduction Important?

Is Sexual Reproduction Important?

In Dr. Tatiana’s Sex Advice To All Creation, Olivia Judson personifies animals, insects, and other organisms to explain and compare sexual and asexual reproduction. Asexual reproduction is common among prokaryotes and some eukaryotes, while sexual reproduction is common among eukaryotes, especially mammals. We read about how Philodina Roseola is an asexual organism. However, she is not just an asexual organism, but she is apart of a population that has asexually reproduced for 85 million years. To add to her already impressive accomplishments, she is one of 360 different species, all rooting from one organism and reproducing asexually. She explains to the audience how she functions and how her family has lived 85 million years without men. Her ancestors before her have ridden their population of men, and Philodina Roseola  had urged the rest of the world to do the same. However, as she continued to talk about asexual reproduction, a ram stepped in a questioned her asexual reproduction. He brought up many different species who had claimed to be asexual for a long period of time, but lied. One of these species, the chaetenotoid gastrotichs. This species lived in puddles and mosses, just like the Philodina Roseola, and claimed to be asexual reproducers. Unfortunately for them, scientists discovered the organisms making sperm, a sexual component, and they were found out to be sexual reproducing organisms. To this, Philodina Roseola brought up substantial evidence proving her abstinence.  

Asexual reproduction, or cloning, is much more efficient, and easier. The mother only has to have one offspring to maintain population, and there is less time and energy involved. Asexual reproduction is very efficient, but it is also dangerous. Sometimes, mutations can develop in a large population constantly cloning themselves. Considering the fact that mutations are usually bad, and affect the organism in a negative way. This is where sexual reproduction has the upper hand. In this type of reproduction, the offspring has a random half of genes from the father, and the other random half from his mother. This ensures a different offspring from the parents, and no transfer of harmful mutations. There are many different theories why asexual reproduction leads to an eventual extinction. The first of the three front-runners is Muller’s Ratchet. This theory states that asexuals are evolutionarily short-lived due to a development of harmful mutations that will “irrevocably and inevitably carry ratchet upward. Imagine a population that has just become asexual...Over time, copying errors will lead to mutations among their descendants, and gradually the population will consist of individuals who carry several mutations...this process continues until all the individuals are so sick that they die and the population goes extinct”. Muller’s theory, fortunately or unfortunately, contains many assumptions. One large assumption is that the population is small to being with. This is where Kondrashov’s hatchet comes in to solve the holes in Muller’s theory. This Russian’s theory is not affected by the size of the population. This theory has a theoretical threshold number of the amount of mutations that any individual can carry. In a population that has sex, the shuffling of genes creates some lucky creatures with a only few harmful mutations. This means that there are some unlucky ones with many mutations. With asexual reproduction, many more organisms will cross the threshold with one to many mutations According to Olivia Judson, who is summarizing this theory, “‘Harmful mutations could be the reason most asexuals go extinct’”.

The last two theories has been based on mutations. The last of the theories, the Red Queen, is based on something entirely different. Parasites. To easier explain this theory to the audience, Olivia Judson tells the story of the Atta colombica. This ant is apart of a 23 million year old species, and they farm fungus in order to eat and survive. These ants are under constant fear of an outbreak of Escovopsis. The ant then explained this as a “virulent disease of the fungus, and if it breaks out, it will destroy the whole garden...Our fungus is also asexual. Not quite as ancient as you, Miss Philodina…We propagate the fungus clonally and when a new queen leaves her natal nest to start her one colony, she takes some cultivars of fungus with her...This means our fungus gardens are like modern human crops: they are monocultures, whole fields that are genetically identical…”. He then told the bacteria at the center of all this that a disease starting somewhere would have a “field day” and destroy the fungus everywhere. This is why sex would be advantageous so fungus with different genes could have an edge over the unevolved disease. The Red Queen theory states that since asexuals keep the same genes from one generation to another generation, parasites can easily evolve to infiltrate their defenses, annihilating clones. However, ses, by mixing up genes, prevents parasites from becoming too well adapted to their hosts. “Sex is an advantage because it breaks up gene combinations…”.

This passage was quite confusing in some areas, mostly due to the vocabulary and the writing format of personifying animals. I would like to learn more about things such as the armadillo, and other living organisms that use both sexual and asexual reproduction.