Module 8

 Genetic Variation-

    Both genetic variation and natural selection are good things for populations, but selection would not exist without genetic variation. If there were no different traits to choose from, then selection would not be needed. Genetic variation is not eroded over time because even though the simulations done in the R exercises show a tendency for populations to fix on a better trait over time, these are done in closed systems, with the assumption that fitness for specific traits does not change over time. In real life, the ecosystem a population lives in might be very different from one area to the next, even though the same species lives in both. It's safe to assume that one population that lives in one area would not have the ideal traits to live in a different area. Interbreeding between two different populations introduces new genes to the populations, which increases genetic variation. On top of that, ecosystems can change over time. If one trait has a very high fitness rating at a certain time, it might have a negative fitness rating 20 years later. One good example of this is the effect the industrial revolution had on moths. Before the revolution, moths with brown color thrived as they were able to hide on trees and other things easier, but as the revolution went on and coal was burned, soot was put into the air that tinted things a dark grey, and the grey colored moths had a higher fitness. With no genetic variation, those moths might have gone extinct, at least in that area. But, because the species had variation, the population was able to evolve over time and thrive again, with selection picking the best traits at the time to persevere. For this reason, it's especially important in populations that they maintain a diverse genetic pool to reduce the chance of extinction. Random mutations accruing in a population also keep introducing new diverse genes into populations, meaning even if a population did get fixated all traits and looked identical, eventually mutation would introduce a new gene for the species to adapt. All of these reasons combined show why genetic diversity does not erode over time in a population, and the downside to selection being the only force driving populations' gene pools. 

Comments

  1. Shaun BaughmanOctober 22, 2021 at 10:39 AM

    Hi Ian,

    You bring up some great examples such as the R-Exercises we've done for class and the effect the industrial revolution had on moths. Explaining genetic variation using scenarios inside and outside of class helped my understanding of why genetic variation is maintained in populations.

    ReplyDelete
  2. Luke EvansDecember 16, 2021 at 10:01 PM

    Hi Ian. I think you did a good job describing how selection only arises as a function of variation. Great overall post!

    ReplyDelete

Post a Comment

Popular posts from this blog

Module 12

  Disease-  One disease that I have studied quite a bit is diabetes. Type II diabetes is growing at an alarming rate around the world, In 2018 the CDC estimated that 26.9 million people in the United States alone had been diagnosed with diabetes (RHIhub 2019). What is more alarming, however, and what may give clues about what is causing this disease is the prevalence of type II diabetes in rural areas, at 12.6%, compared to urban areas at 9.9% (RHIhub 2019). It is well known that a large risk factor for type II diabetes is being overweight, or obese. Rural areas have a higher amount of overweight and obese people than urban areas, which may be partly due to it being harder to obtain fresh fruits and vegetables in rural areas compared to urban areas (RHIhub 2019). One study done by the US Diabetes Prevention Program showed that the best way to prevent or slow diabetes is through proper diet and exercise. The study found that increasing the amount of physical activity and decrea...
Read more

Module 11

 Speciation      Speciation, or the act of a population branching off and becoming their own species through evolution, is something that's hard to have a definitive timeline on in my opinion. Speciation in my mind can happen fast or over a long period of time. The tricky part is deciding when their genetics have changed enough that they become their own species. For this you might look at phylogenetic trees to see where the branching off occurred, how far down that branch they are, and if any other species or types of the same species still exist. In a situation where a population's environment gets changed rapidly and stays in the new different conditions, it makes sense that the organisms in the population that are able to survive and adapt to the new changes would produce offspring that is very different from the normal organisms of a species in their normal habitat. In this case, I would expect speciation to happen much sooner than if there was a gradual change ...
Read more

Module 1

 Evolution      Evolution is a very hard to describe term that tries to explain how organisms change from generation to generation. Even that doesn't do the term justice, as organisms themselves don't evolve throughout their life. Populations of a species evolve from generation to generation, and eventually new species are born. Survival of the fittest, natural selection, and mutations all contribute to evolution. Evolution states that all species came from one original species, which is what blows my mind the most. Millions of years of evolution has had a single celled organism divulge into the millions of species of life today. Through natural selection and survival of the fittest, organisms in a population die off due to changes in the environment. Whether that be changes in the food that is available, changes in the climate, or other environmental factors. The other animal populations in an area can also contribute to natural selection, such as if an an...
Read more