Drafts

The fitness of a trait expressed an individual in a population is determined by a few factors. In broad sense heritablilty, the proportion is measured by genetic variation to genetic variation and environmental variation. The greater the environmental factors, the less likely that the trait is influenced by genetics and less likely that the trait can be passed down. In terms of narrow sense heritability, other genetic factors are measured to determine if internal/external environmental conditions contribute. If a trait has high fitness, relatively high survivial rate and produce a large number of offspring, then traits with high heritability will likely be passed to offspring. This will result in a selection differential between the mean of the general population and the population of breeders, creating a directional slection pattern if the traits are graphed. The reaction to selection may also be quantified by multiply the heritability of a trait with the selection differential. Fitness does not necessesarily correlate with high frequency. Sometimes traits with low frequency express a higher fitness which is known as negative frequency dependent selection. 

With evidence that 43 species in Massachusetts are flowering earlier due to rising temperatures, other regions throughout the United States or globally may see similar results. A meta analysis was conducted to determine the effects of climate change on both flowering plants and animals. This analysis also showed that there was a shift in phenological process that mirrors the expected outcome predicted using prior knowledge of ecological constraints on individual species (Root, Price, Hall, et al. 2003). This information can be used to understand the results of the study done on the 43 species in Massachusetts and the global implications it indicates.

Climate change can create a cascade of effects throughout entire ecosystems. In marine life, communities that rely heavily on biotic and abiotic factors have experienced the effects of rising temperatures in the ocean. Warming of the sea can be detrimental to life in the future, especially for migrants like beluga whales whose habitat is surrounded by seasonally-ice covered waters. This is why researchers have conducted a study spanning over 30 years to collect data and determine if the ever changing sea ice has had an impact on their migrational behavior. From 1974-2014, scientists followed four traditional migratory routes in beluga whales between wintering and summer  areas of the Alaskan and Canadian arctic.

The methods used to monitor the population included genetic data and harvesting data from whale sightings. Tissue samples from a total of 978 whales were collected and DNA was extracted from each sample and screened. Ariel surveys were taken by native hunters and field biologists which determined the annual arrival times during migration. Lastly, ice conditions were examined through passive microwave-derived sea-ice concentration (SIC). Based on the reports, it was revealed that beluga whales migrated to the Chukchi Sea each summer with its peak population in June at Kotzebue Sound, located in the Arctic.

The results from the SIC demonstrated that the varying sea ice conditions, (5.2% in 1997 vs. 83.7% in 2006), did not affect the times that the distinct populations arrived. However, after the year 1983, the occurrence of beluga whales at this location diminished quite dramatically despite two exceptions in 1996 and 2007. Genetic analysis determined that at one point, in 2007, 90% of the whale migrants to Kotzebue sound had been males, thus, suggesting a link between sea ice conditions and migratory behavior which caused them to alter their course. This phenomena also suggests that changes in the ecosystem may affect gender differently. During the years where sea-ice levels were low, orca whales were able to easily maneuver themselves into the Chukchi Sea. This resulted in an increase in predation, which may have been a contributing factor for evasive shifts in beluga migratory patterns.

The data collected from this study indeed proposed a relationship between ice levels and beluga whale migration, though the research may have been flawed. There most definitely are variables that could have skewed the results that was determined. For example, relying on whale sightings alone does not seem to be a strong enough resource for tracking. There should have been another method used to monitor movement: like attaching a gps tracking device to the mammal. In addition to this, it can be difficult to consistently measure sea-ice conditions that vary considerably throughout the year especially if they are due to underlying factors, which may need more research in the future to eliminate these possibilities.

This study was specifically chosen because of its relation to climate change and as an effort to shine some light on future conservation efforts. If the ocean temperature continues to rise and potentially even affect prey availability for beluga whales, it can pose a huge threat for them in the future. Hopefully soon they receive the rightful attention and action will be taken to conserve, and protect this species.

One important difference between allopolyploidy and autopolyploidy is how they come to be. Meaning, an allopolyploid individual is made when two parent individuals come together with a different number of their pairs of chromosomes (one gamete has 3, the other 2) to form a hybrid that cannot produce viable gametes. An autopolyploid individual happens when the chromosomes of the diploid parent individual go through a meiotic error which causes the chromosomes to divide incorrectly, resulting in gametes having a full set of chromosomes as well (2n). Another major difference between allo- and autopolyploidy is the fact that one could have the opportunity to produce viable gametes with another in its species, while the other self-fertilizes. Allopolyploid hybrids can go through a duplication event and ‘accidentally’ double the number of the chromosomes they have, which allows them to produce sexually again, and meiosis can proceed normally.

Allopolyploid individuals cannot reproduce easily with the two species that made it (similar to autopolyploidy) but can mate and produce viable gametes with another of its species, unlike autopolyploidy, where there is just one parent involved. A third important difference between allo- and autopolyploidy is the amount of genetic variation in each. Because there is only one parent involved for autopolyploidization, there is a small amount of genetic variance within the offspring. But, this is not the case for allopolyploidization. Two species can create a large amount of the allopolyploid hybrids, which can then interbreed between each other. This different origins of the hybrid creates more genetic variation, which allows for natural selection to create more fit hybrids as the generations continue. 

Autopolyploidy occurs when there are additional sets of chromosomes in a cell. The chromosomes in the parent individual with 3 sets of homologous chromosomes (2n=6) go through a meiotic error which results in an unreduced gamete with 6 chromosomes (rather than 3) that self fertilize and create a tetraploid zygote. However, the polyploid offspring is unable to reproduce sexually. Normally, the 2n offspring would mate with another 2n offspring. Then the 1n gametes produced combine with the other and produces another 2n offspring in the parent generation. However, what reproductively isolates this example from its diploid parent species is the fact that through the meiotic error, 4n cells in the the adult occurs.

They are then unable to produce fertile offspring with the parent species. When the 3n offspring results, (or any uneven numbered offspring), mitosis would work just fine because the homologous chromosomes don’t have to match up, BUT, meiosis is faltered because the 3n offspring trying to produce gametes through this genetic mechanism will fail because the cell will not be able to divide. The result is impaired meiosis of unpaired chromosomes. This is a postzygotic isolating barrier. 

Plants require light energy and water to produce energy-rich compounds which can later be used to fuel sugar making mechanisms. In order to first capture light energy, a plant will use chlorophylls a and b in a chloroplast. These kinds of chlorophylls absorb red and blue light, therefore reflect green light waves and appear green to us. The electrons are captured in photosystem 2 and transferred to photosystem 1 and eventually to the NADP reductase where they are used to add a Hydrogen to it and make NADPH. Water is broken down in photosystem 2, removing the hydrogen and producing free hydrogen and a diatomic oxygen molecule. The hydrogen goes into the thylakoid lumen of a chloroplast to create a high gradient that is then used to drive ATP synthase to make ADP into ATP. 

In any given ecological community where multiple species use the same resource, there is bound to be competition. Competition between two species will always hinder both populations as long as both are present because the maximum capacity of the environment can only hold so many individuals. Studying these sorts of interactions allows scientists to understand how two species interact and how stable their interaction is. In order to quantify the competition of two species, scientists use the Lotka-Volterra equation. This equation takes into account the populations of both species, the effect of one on the other, and the total carrying capacity to produce a value indicating how the target population will grow. A graph can be plotted using the zero growth isoclines for each species; the number of individuals that could be sustained given only 1 species is present. Interpreting the graph will grant the best understanding of how these populations are interacting. If the species populations seem to converge at 1 point in the graph then there is said to be a stable equilibrium. An unstable equilibrium happens when there are 'risk' zones and if the number of individuals falls within these zones it is likely one population will push the other to extinction.

There are four primary methods used in biology to produce transgenic organisms: transgene engineering, knock-in engineering using embryonic stem (ES) cells, knock-in engineering using CRISPR, and viral gene delivery. Here, I will go over the first two of these methods. Transgene engineering was the first time foreign genetic material was incorporated into an animal’s genome. Palmiter and Brinster added the gene for human growth hormone (HGH) to zygotic cells during the stage at which the genomes of each parent cell are fusing in order to get random incorporation of the gene. In order to get expression of this gene they also packaged a promoter with the transgene which would ensure its expression in transformed mice. The next step in genetic engineering came with knock-in engineering in ES cells developed by Capecchi, Martin, and Smithies. This method involves using a new kind of transgene that lacks a promoter but has gained a neomycin resistance gene and homologous arms. A promoter is unnecessary as the arms of homology will target the transgene to a specific place in the genome after a promoter that is already active. The transgenes are then added to cultured ES cells. The cells that take up the transgene and undergo a double-stranded (DS) break that matches the transgene’s arms of homology get transformed. Then, the antibiotic neomycin is added to the cultured cells to select for the cells that were transformed. These transformed cells are injected into a blastocyst where they can be expressed.

Located on an island in the south Aegean sea, an ancient civilization known as the Minoans ruled for over 600 years. Archaeologists know of this great civilization in part due to Sir Arthur Evans, a very rich man who was determined to discover who these people were. At some point in his life, Evans came across some seal stones which depicted bulls and mythological creatures with origins supposedly on the island of Crete. Not much else was known at the time, and because of that Evans became inspired to pursue his curiosity. Excavations went underway, lead by specialists Evans hired, and quickly they began to uncover the secrets of Crete. Being the eccentric person Evans was, he took it upon himself to reconstruct many of the damaged sites he was exhuming based on his interpretations. On Crete, there were great palaces and villas, many adorned with paintings referred to as frescos depicting life in ancient Minoan society such as the sport of bull-leaping and elite women. Explorations uncovered large ceramic jars at the palace of Knossos estimated to collectively house 62,000 gallons of liquids. Evidence of the types of foods grown here suggests these liquids were olive oil and wine collected as taxes from nearby estates. 

In the human body, DNA is stored as chromatin when not being actively transcribed. Chromatin refers to the wrapping of DNA around histone proteins to control tangling, proper spatial storage of DNA, and regulation of gene expression. In order for these histones to open, exposing the DNA to RNA polymerase, transcription factors, and other necessary transcriptional hardware, acetyl-CoA is required. This acetyl CoA is derived from the metabolism of acetate by the enzyme ACSS2. Mews et al. have discovered that, through the consumption of alcohol, a rapid increase in levels of blood acetate occur resulting in rapid acetylation of histones in the brain¹. The findings of this study show that alcohol consumption directly results in changes in gene expression in the brain, including those in neuron cells.

(1) Mews, P., Egervari, G., Nativio, R., Sidoli, S., Donahue, G., Lombroso, S. I., … Berger, S. L. (2019). Alcohol metabolism contributes to brain histone acetylation. Nature. doi: 10.1038/s41586-019-1700-7