Writing in Biology - Section 1

There are three types of point mutations. There are missence mutations, nonsense mutations, and silent mutations. Missence mutations happen when there is a change of a single base pair. This tiny change causes te substitution of a different amino acid in the protein. This small letter change may have no effect, if the individual is lucky, but it may render the protein malfunctional. An example of this would be sickle cell anemia. Second type of point mutation is nonsense mutation. This leads to an early stop codon. Unfortunately, when there is an early stop codon, the protein as a whole cannot be fully developed. This would be very bad if this protein is necessary to the individual. Lastly, silent mutation. This one is very interesting as it actually is not bad for the individual. This kind of mutation changes a base pair, but the amino acid stays the same, as some amino acids have different base pair letterings, but pair for the same protein.

Among different species, there is some varioation in chromomsome numbers that are tolerated by the species.  For example, plants are quiet tolerant and can survive with varying chromosome number.  In nature, three mechanisms which chromosome numbers can chamge is through meiotic nondisjunciton, mitotic abnormalities, and interspecies crossing.  Meoitic nondisjuction is when the chromosomes do not seperate properly during gamete production.  This can happen in both meiosis 1 and meiosis 2.  In meosis 1, gametes are monosomic and trisomic.  In meosis 2, half the gametes formed will be normal while the other half are abnormal.  In a very rare case, there is complete nondisjuction when all the chromosomes go to a single cell.  For example, a dipoloid species would form a tetraploid species.  The condition is called autopolyploidy.  In interspecies crosses, the recult is allopoidy.  The first generation with the cross will likely survive but when the chromosomes line up  in meosis there might be some issues.  It is possible but not likely.  

There are key behavioral traits that humans had in their environment of evolutionary adaptiveness that creates the eating patterns we experience now.  One key difference is the risk and energy early humans put into getting the food.   With the advent of cars and grocery stores, humans expend less energy to get more food than would be available in their environment of evolutionary adaptiveness.  As a result, the calorie intake exponentially exceeds the calorie expenditure used to get food.  The human body also evolved to hold large energy reserves for times when food is scarce.  In our novel environment, this means our body is designed to hold onto the food we eat.  If we exceed the amount of food we should intake, we are designed to retain the energy as fat which increases our vulnerability to obesity.  In our environment of evolutionary adaptiveness, our central nervous system has evolved to crave “palatable, energy-dense food”.  Because our novel environment put these types of food in easy access, there is nothing stopping us from over-indulging.  All these eating patterns humans evolved to have were designed to capitalize on high energy food and maximization of energy storage.  With the availability of food in the novel environment, it is important to recognize these behavioral patterns and make choices to fight these behaviors.

    Throughout the evolution of humans, we have consistently changed to a novel environment which no longer matches our environment of evolutionary adaptiveness.  As a result, humans have become vulnerable to different conditions we were not vulnerable to before.  For humans, a majority of physiological changes including increased brain size occurred during the Paleolithic Era which lasted for 2 million years (Easton 67).  Because a majority of the evolutionary traits which defines us as a species occurred during this time, our diet played a key role in giving us the energy and nutrients that enabled these changes.  The human diet is something that has changed considerably from the environment of evolutionary adaptiveness and we are now facing a slew of health consequences as a result.  One of major heath consequences is obesity, which often leads to the other conditions are at risk of developing.  There are two aspects of the the human diet which varies from the environment of evolutionary adaptiveness: the eating patterns of humans and the composition of the diet.  With both these factors different in the novel environment of humans, humans are now vulnerable to a variety of detrimental health conditions.

Development of a human embryo and its brain comes about in three stages: blastulation, gastrulation, and neurulation. First, the egg and sperm fuse into a zygote which has an internal plasma membrane and an external zona pellucida. The zygote cleaves internally, maintaining the same volume inside the zona pellucida but multiplying the number of cells inside it, at which point it is called a morula. The cells inside the zona pellucida go through compaction and differentiation starts to occur. A sphere of trophoblasts develops just under the zona pellucida and around the mass of embryoblasts inside the embryo. The embryoblasts then accumulate at the top half of the embryo, leaving a space called a blastocoel under them. This whole process is known as blastulation and the resulting structure is a blastocyst. Gastrulation follows blastulation first by the loss of the zona pellucida. Then, the mass of embryoblasts forms an inner cavity called the amniotic cavity. The cells under the amniotic cavity become epiblasts and the cells under the epiblasts become hypoblasts. These two cell layers are collectively known as the bilaminar disc. The primitive streak forms along the middle of the bilaminar disc, on the epiblast layer. This primitive streak is composed of epiblast cells migrating down and forming a middle layer of cells between the two original layers of the bilaminar disc. This forms a trilaminar disc with three layers known as germ layers. The topmost layer is the ectoderm, the middle layer is the mesoderm, and the bottom layer is the endoderm. The ectoderm will form the nervous system and the skin. The mesoderm will make the muscles and bones. The endoderm will make the viscera. The formation of these layers is known as gastrulation.

For species who do not reproduce asexually, mechanimss of sex determination are essential to the survival of species.  In humans, the sex of an individual is determined by the presence of a Y chromosome.  It is important to note that sex and gender are two different concepts.  Sex is determined by biology while gender is a social construct.  In other species, sex is determined through other mechanisms.  The sex of fruit flies is determined by the ratio of sex chromosomes and autosomal chromosomes.  Some species have their sex determined through temporal influences.  

Our bodies require the formation of proteins at all times - whether it is for cellular function or intercellular function or it is needed for an organ in general. All systems in our body need protein to function. The process involves two parts to it: transcription and translation. Transcription is the process by which the DNA transfers its information to an mRNA, while translation is the process by which mRNA helps to create the protein. During transcription, DNA unwinds and mRNA nucleotides (cytosine, guanine, adenine and uracil) align along the sense strand according to the base-pairing rule. Once the strand forms, it is transported out to the ribosome subunit where translation takes place. There are tRNA nucleotides floating around in the cytoplasm. They bind to amino acids and transport them to the same ribosomal subunit where the mRNA is waiting to br translated. The tRNA align the corresponding amino acids and form a polypeptide chain. Then the tRNA leaves and the polypeptide chain is either transported within the cell or out of the cell via exocytosis. Most of the time the chain is transported to the Golgi body for modification. Once done, they are packaged into vesicles and transported out via exocytosis. 

Pressure, temperature and volume interact with one another as shown by the equation: PV = nRT. Pressure and volume are inversely related while pressure and temperature are directly proportional. This can be seen through an example using a fire syringe. A fire syringe is a simple glass cylinder with a piston that pushes down inside. When a small piece of gun powder cotton is placed inside and the piston is pushed down quickly, the cotton ignites and a spark can be seen. The science behind it lies in the aforementioned equation. When the piston is moving down, the volume is decreasing. With this drop, the pressure starts building up. The pressure causes the temperature to start increasing. This makes the gun cotton powder to ignite, causing a spark. 

The flu shot is often something that is not a priority. The flu shot changes every  year to keep up with the varying proteins on the virus. The vaccine is important for the recipient's protection against the flu, as well as everyone surrounding them. Certain individuals are vulnerable to disease, they are the elderly, infants, those recieving chemo-therapy, and individuals with an autoimmune disease. Individuals who are immunocompromised cannot get vaccines, vaccines should be administed several weeks before the individual becomes immunocompromised (if that is possible, such as several weeks before chemo-therapy). These immunocompromised individuals can be protected through herd immunity; when the majority of a population is vaccinated, the virus has a hard time infecting individuals.  Therefore everyone should keep up with their flu vaccines to prevent contraction of the virus for themselves, as well as immunocompromised individuals who cannot recieve the vaccine and rely on others for protection.

As global temperatures rise, phenological changes have occurred causing flowering times of plant species to occur earlier than previously recorded in the past (Bartomeus, Ascher, Wagner, Danforth, Colla, Kornbluth, Winfree, 2011). The New England Cranberry, Vaccinium macrocarpon, is not an exception to this phenomena. Cranberries act similar to wild plants in the case of the phenology differing in warmer temperatures. Since cranberries have been an important part of New England culture, cultivators have kept records of cranberry growth and production. Cranberry cultivators have been spraying fungicide on the crop when 10% of the flowers have bloomed. This quantifies timing of cranberry flowering over the years. The earlier flowering times of cranberries affects not only cultivators, but other species that interact closely with the plant. Cranberry shoots and leaves are an important food resource for the bog copper butterfly, Lycaena epixanthe. As global temperatures rise, the concern for earlier flowering times affecting both human cultivation and other species interactions continues to grow.