Writing in Biology - Section 1

The high androgen levels in women (mild to moderate AD) in low stress environments showed the altered metabolism of the androgens. The significant correlations between DHEA and cortisol, androstenedione and cortisol indicated that hormone production in the adrenal cortex of the kidneys were like that of younger people. In another study mentioned in this paper, associated high levels of cortisol and DHEA with cognitive dysfunction. There were higher chances of performing better with lower levels of DHEA. Later in the study, they had said that further investigation was required to assess the androgen and gonadal hormone metabolism as they had only reported increased basal androgen levels. In another study, they investigated the thyroid hormone levels in the cerebrospinal fluid (CSF – present to keep the brain afloat and washout any toxins) and found a correlation to the AD severity in patients with normally functioning thyroids. Thyroid hormone (TH) helps in metabolism in the brain and hence can be found in the CSF. There are several forms of TH – they are usually numbered as T_2, T₃, T₄etc. They used something called lumbar puncture to extract spinal fluid from people (sounds pretty painful!). They used highly specific techniques called mass spectrometry and high performance liquid chromatography to assess the CSF containing thyroid hormones. They had about 35 patients (9 males and 26 females, approximately 66 years). The CSF TH concentrations were representative of the blood TH concentration. The AD patients were diagnosed through CT scans, neuropsychological tests, MRI and Mini-Mental State Examination (MMSE). The control group had 10 subjects with normal cognitive abilities and normal MMSE. They had undergone lumbar puncture due complains of severe headaches. Exclusion criteria included thyroid problems, abnormalities of CSF routine analysis or any proof that the barrier between their blood vessels and brain was damaged by in depth analysis of the CSF. 

In a study, ghrellin was elevated in mice (either through caloric restriction or subcutaneous injections) showed less depressive like symptoms in forced swim test. On the chronic social defeat stress scale, ghr-KO mice showed more social avoidance than wild-type after periods of struggle with a dominant animal. Systemic treatment with a neuroprotective compount enhanced neurogenesis in the hippocampus leading to antidepressant effects - it was speculated that ghrelin’s antidepressant properties are mediated by neurogenic properties. The same effects were seen after administration in mice that had undergone olfactory bulbectomy, same with group with reduced AVP gene expression. Ghrelin also increases noradrenergic and serotonergic  transmission. Two studies suggested contrasting results - increased long term ghrelin caused depressogenic properties through decreased serotonergic transmission in the dorsal raphe nuclei and pro depression effects; and then injecting anti-sense strand into the lateral ventricle induced anti-depressant effects(but authors did not measure ghrelin level to give a clearer indication that the observed effects are related to ghrelin system).

In intersexual sleection, there are many, nonmutually exclusive indirect benefits to the female and her offspring. Females wnat to receive "good genes" for their offspring, and they ensure this by evaluating a potential male in a number of ways. Females will look for high amounts of symmetry because it has evolved to represent developmental stability. They will look at display vigor and quality, like in spider displays and canary trills. Females will counter in longetivity, meaning that they will generally go for an older male sice he has alreay proven that he can live long. In Bowerbirds, the amount of decorations on a male indicates his age, and therefore his wisdom. Freedom from disease is anotehr factor, and this could be indicated by plumage. Potential handicaps could also be something the female considers, in the thought process that if his male can survive with a handicap, he must be really otherwise fit. Lastly, lots of females try to mate with the correct amount of inbreedng and outbreeding in mind, based on the hypothesis that local mates are better. Swans do this by looking at facial markings, and mating with those that are similar but not identical. 

Intersexual selection in animal behavior involves mate choice, which is usually done by the females since they invest more energy into each offspring. Some direct benefits of a choosy female include nuptial gifts, parental care, territory quality, and resource benefits. Nuptial gifts are things a male might bring a female to encourage her to mate with him. These are a lot of the time rey items, such as in the empid fly, spermatophores, such as in insects or salamanders, or body parts, like how female crickets are allowed to gnaw off the wing of a male they are mating with. Being choosy can benefit the female by providing her with better parental care. This is true in stickeback fish, where males with red bellies are preferrable since they indicate the mall will be better at fanning the eggs with oxygen after they are fertilized. Territory quality is another way the female wins by being choosy. Lots of female birds will assess a territory established by the male before choosing, ensuring her a safe place to mate and rear her young. Lastly, there are other resource benefits a hosen male may provide. In chimpanzees, males provide the females with food, and in dung beetles, males provide a dung ball for feed and a place to mate. These hypotheses are not mutually exclusive, meaning that in any given species, more than one can be true at any time.

Bateman’s principle states that variance in reproductive success is greater in males than females. Females always invest more energy to produce their offspring. Sperm are cheaper than eggs. Males reproductive success is limited by the number of mates. Female reproductive success is limited by how many eggs she can produce. This results in sexual selection in which males compete with each other. And females become choosy in which males to choose. As a result of Bateman’s principle, the predictions follow; males should try to mate with as many females as possible and should compete with other males for female attention. Females should try to choose the best mates. In addition, we expect higher variance in reproductive success in males compared to females. 

• The reflection assignment helped me build self-awareness of all the projects I conducted during the semester. This assignment helped me take my time and ask my self some important questions regarding my writing process. By doing this, I gained a better understanding of my strengths and weaknesses. 

• I would like to end by writing a quick note to say that I enjoyed your class.  I always learned something that challenged my scientific writing perspectives and enjoyed doing so! Thank you, again, for such a wonderful learning experience, and good luck in your new class.

• I was excited about conducting my project in the class. Thanks to my team, I had a great time conducting and completing my research project. The research project had us divided into teams to figure out a scientific question. Our work was performed outside of class. Furthermore, the project was one of the most important activities for me because it allowed me to creatively apply scientific and technical practices to use. The semester project has allowed me to learn about the process that goes into creating a science project. Such skills will definitely help me in the future to solve my own research problems. 

• My team wrote about hox genes. I found it difficult to choose a scientific project regarding hox genes. At first, I was confused about how the project was going to go forward, but my team managed to work on the project early and turn it in on time. Similar to the methods project, the proposed project will help me write a proposal for my honor’s thesis. Although the two will not share the same topics, I have learned about the process regarding writing a scientific proposal. Things to keep in mind are to avoid wordiness and use an active voice when writing scientific work.