Evolutionary Advantages of Sexual Reproduction

 Sexual Reproduction and its Advantages

When it comes to reproduction, we can see two types persisting. There is asexual reproduction which requires only one individual (usually) and through parthenogenesis or the development of an unfertilized egg, results in an essential clone of the parent. The other we are discussing is sexual reproduction. This process requires at least two parents, resulting in the recombination of genes that are then passed to their offspring. 
Asexual reproduction has a lot of advantages, namely, you don't need a partner! As soon as the individual is ready to reproduce they can do so without the ovum needing to be fertilized. Many methods of parthenogenesis can allow for the production of both males and females. A downside to asexual reproduction is that sometimes an individual must incorporate new genes into their offspring thus requiring sexual reproduction, this is cyclic parthenogenesis. Another downside is that it becomes difficult to lose or gain mutations which can lead to the loss of members of the population.  
Sexual reproduction has its advantages but it is ultimately a costly process as some mates can lose their lives in the process and the caregiver in the situation ultimately has to be out of the mating game for an extended period. So why has it persisted if it is more costly than asexual reproduction?
The answer is that the benefits often outweigh the drawbacks. During sexual reproduction, gametes undergo recombination of the parental genes, which can result in new and helpful traits. This recombination, paired with a set of chromosomes from each parent, allows for heterozygosity. All of these benefits can be lost if inbreeding among relatives occurs, it can also lead to an increased risk of diseases. 
Heterozygosity refers to having two different versions of a gene or allele from each biological parent. This can help individuals fight diseases, have certain beneficial traits, and remove unwanted mutations. Heterozygous individuals often experience polymorphism which causes multiple versions of a gene or allele increasing genetic diversity. 
To better understand how sexual reproduction can be more beneficial than asexual, we will dive into The Red Queen hypothesis. This hypothesis states that sexual reproduction persists because it enables host species to evolve new genetic defenses against parasites through polymorphism and heterozygosity. This can be explained through the lens of parasitism. 




A heterozygous sexually reproducing population of fish (1) and a monozygotic asexually reproducing population of fish (2) reside in the same water system. Due to several days of intense storms, we see a new parasite has been washed into the environment. This parasite latches onto both populations and leads to starvation and illness among them as the parasites thrive. Throughout a few generations, we see the sexual reproducers have fewer casualties from the parasites than the asexual fish. We can see the population 1 offspring seems to have developed a resistance to the parasites, which continues as the population continues to reproduce. On the other hand, population 2 does not appear to have developed the same amount of resistance. This could be due to genetic mutations opening the way for resistance or it could be a deleterious mutation of a gene that allows the parasite to thrive. 






Since learning about asexual reproduction I have wondered why sexual reproduction continues, if it is less costly to clone yourself, why would you need a partner? After these last modules, it has become clear to me. The addition or deletion of mutations has a much greater benefit for individuals in ever-changing environments than using less energy in reproduction. Mutations can persist or change over generations allowing populations to adapt and evolve to better suit their niche. In the future, I would like to explore the different versions of parthenogenesis and learn whether the different variations are more or less successful in comparison. 


Comments

  1. Jasmine Plata's Evolution BlogNovember 24, 2024 at 10:03 PM

    Really great brook! your art is always so good!

    ReplyDelete
  2. KennedeeNovember 24, 2024 at 10:48 PM

    there are so many complexities that tie into the diversity that we see today and can be hard to grasp , however your blogs are great and allow me to use imagery to connect the concepts.

    ReplyDelete

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