C. Gatschet - BIOL 520

The ocean is home to the most extraneous creatures that we know of on this planet. From brightly colored, poisonous lionfish in the coral reefs, to ancient, practically immortal jellyfish in the open ocean, to large fanged creepy fish surviving in the harshest depths of the ocean floor, life seems to get stranger the further from the surface you look. One such deep-sea creature is the bloody belly comb jelly, of the class ctenophores (the cone jellies). To combat the lack of light this far down, bioluminescence is present in almost all deep-sea creatures and is used as a mechanism for communication, to lure prey, to attract mates, and defend against predators. The majority of bioluminescent animals glow blue due to the fact that blue wavelength light travels the furthest in water, this is the same phenomenon responsible for our observation of the ocean's blue color. If you have looked at the image below, though, the translucent bloody belly comb jelly lights up a brilliant shade of...

The issue with this question, or rather perspective on the topic, is that it implies selection is the only force acting on a population. While selection can limit the variation in a population, especially a small one, other forces will also act on that same population to counteract the effects of selection and revamp variation. So to redefine variation in evolutionary terms, genetic variation is essentially the diversity of allele frequency at a certain gene locus. On a molecular level, this results from single nucleotide polymorphisms (SNPs) in the DNA to produce different variations of the same gene. The most major player in increasing genetic variation is the force of mutation. No matter how great the strength of selection is, mutations will always be present in a population, adding variance with their effects, and creating a new gene pool for selection to act on again and again. In the the Module 7 R exercise, we saw the effects of the molecular clock, ticking away and producing vi...

I assume it will be a common thread across everyone's blog posts this module, but the biggest obstacle I've been overcoming is working with R and learning how it works. I'm certainly glad to be gaining the basic concepts behind R, the mechanisms of coding are less foreign to me now than at the start of the semester. Secondly, I appreciate the discussion format of the class in that it truly challenges my critical thinking skills, forcing me to consider perspectives I might not have before and question my preconceptions of what evolution really is. On that topic, I first defined evolution as "the result of a combination of several mechanisms which eventually contribute to changes in the genomes of a species, the most well-known of these mechanisms being natural selection." While I wasn't exactly wrong, I definitely didn't capture the mere scope of what evolution entails. Along with selection, other forces such as mutation, genetic drift, migration, and non-r...

Photograph by Christian Heeb / Redux (The New Yorker) As we talked about in class, recessive deleterious alleles can become more frequent in populations with inbreeding, where fixing of alleles generally results in an increase in homozygosity within a population. In larger populations where inbreeding is less common, heterozygous individuals mask the function and consequences of deleterious recessive alleles. With inbreeding as a factor in a population however, the deleterious allele, originally recessive, is exposed due to homogenization and becomes more common in an the population; thus, variation is depleted through selection (Waller and Keller, 2020). A example of this from the 1990s occurred in a population of Florida panthers (aka cougars, pumas, etc.). With a period of habitat destruction, the population of panthers weaned to about only 20-30 individuals. The resulting limited number of breeding pairs available led to excessive inbreeding within the population. Consequently, g...

The idea that mutation rates can evolve shatters the predisposition that mutations are entirely random. However, environmental factors can certainly act on the evolution of mutations and their frequency throughout a population. According to Lynch et al., the evolution of mutation rates depends on three main factors: first, the production rate of a deleterious mutation in a population, second, the reduction in fitness of each mutation, and third, the heritablity or persistence of that mutation through generations (2016). Consider a scenario where a natural disaster randomly wipes out a significant amount of a species' population. Through this event of genetic drift, we can imagine that the variation and mutation frequency in the species would be fairly high; thus, this has become a perfect population for selection to act on. As selection acts against the force of genetic drift, the mutation rate will decrease until an equilibrium is reached over time. This is displayed by the red an...

Fitness's definition certainly has the connotation of being physically in shape, strong, or able to endure long periods of strenuous activity. However, biological fitness is more defined by an organism's or species' reproductive success, which is determined through how well adapted the organism is to its environment. Before fitness though, there must be variation in a population allowing the mechanism of natural selection, and thus fitness, to occur. According to  Sedeer el-Showk, fitness can be measured by comparing the ratio of a specific genotype before and after selection, or simply by measuring change over a long period of time where there is some sort of major environmental change (2014). A prime example of fitness is the order Crocodilia, a practically unchanged species since the Jurassic era. In a study by Stockdale and Benton, the body size of crocodiles was measured and compared against major environmental changes such as the Cretaceous–Palaeogene extinction perio...

Derivation from a Common Ancestor: Homologous Evolution of Biofluorescence in Sharks [Fun fact: I actually made a Canva for this, but my links didn't transfer over :( and I wasn't about to re-copy+paste everything. So if you'd rather view the graphic (without links), you can find it  >here<  .] Taking a dive into the depths of the ocean, the water becomes continuously bluer and darker as red wavelengths from the sun are filtered out. In order to combat the increasing darkness, biofluorescence among marine life is widely expressed across taxa - more than 180 species of fish! (Sparks et al., 2014) . Not to be equated with bioluminescence where light is self-generated by a series of chemical reactions, biofluorescence occurs when green fluorescent proteins (GFPs) along with brominated tryptophan-kynurenine metabolites absorb filtered blue UV light from the sun and re-emit lower energy green light (Park et al., 2019) . A more detailed description of the mechanism of bi...