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          Historically, there have been two competing taxonomic systems used to classify the suborders of primates. Tarsiers were initially categorized alongside lemurs and lorises, and apart from humans, apes, and monkeys. This original taxonomic system, known as the gradistic division, held that the two suborders of primates were Prosimii and Anthropoidea. Prosimians, which means “before apes”,  were comprised of lemurs, lorises, and tarsiers, due to the perception that they represented grades of evolution. They were seen to possess many of the same traits, such as similar teeth, skull, and limb anatomy to early, now extinct, primates. These “primitive” features being shared amongst the three extant groups were believed to be evidence of close relation, and were thought to set them apart from the “more evolved” characteristics of anthropoids. The more recent categorization, known as the phyletic division, posits that tarsiers should actually be grouped alongside monkeys, apes, and humans, and apart from lemurs and lorises. In this taxonomic system, the two suborders of primates are instead Strepsirhini and Haplorhini. The reasoning behind grouping tarsiers with the formerly named anthropoids as a new group called haplorhines is that humans, apes, monkeys, and tarsiers all have shared derived features that indicate closer relation amongst them than with the lemurs and lorises which comprise strepsirrhines. Strepsirrhines are defined by features such as wet rhinarium, the presences of a tooth comb, a laterally flaring talus, and a grooming claw on the second digit of the foot. Tarsiers are distinct from the strepsirrhines in that they have a dry rhinarium, lack a tooth comb, as well as having certain skeletal and physiological traits that are more similar to the other haplorrhines.  Furthermore, the extant haplorhines share a number of derived cranial features, including postorbital closure, a retinal fovea in their eyes, a reduced number of nasal conchae, a short, vertical nasolacrimal duct and the lack of a moist rhinarium, giving them the dry nose and continuous upper lip from which the name haplorhine derives. They also all have a hemochorial placenta and an inability to synthesize vitamin D. The tarsiers’ similarities to other prosimians are primitive features, like an unfused mandibular symphysis, molar teeth with high cusps, grooming claws on their second toes, multiple nipples, and a bicornuate uterus. In contrast, their similarities to anthropoid primates seem to be derived specializations indicative of a more recent common ancestor, a hypothesis that has been supported by genomic analysis. The taxonomic system with greater evidentiary support is, therefore, the phyletic division of haplorhines and strepsirrhines.

Dravet's syndrome is a rare, severe, genetic epileptic encephalopathy. Most cases of Dravet's syndrome are caused by a mutation in the SCN1A gene. This gene codes for a sodium channel, voltage gated type 1 alpha subunit. Most of these mutated genes are expressed in GABAergic neurons; hence, GABAergic neurotransmission is compromised. GABA is a neurotransmitter with vast inhibitory functions. As such, seizurelike locomotor behavior and epileptiform brain activity are signs of Dravet's syndrome. In humans, the presence of one mutant allele is sufficient enough for the display of the mutant phenotype but in zebrafish, the common model organism for studying neural networks and disorders, the mutant phenotype is only observed in larvae that have two copies of the mutant allele. Though GABAergic neurotransmission has been found to be most directly affected by the mutations underlying Dravet's syndrome, scientists have explored the potential of other neurotransmitters rescuing the phenotype, relieving mutant zebrafish larvae of epileptic seizures. One of the neurotransmitters that has shown some promise is serotonin (5-hydroxytryptamine). It's been revealed that increasing serotonin levels can reduce epileptic locomotor and brain activity. The drug fenafluramine was identified to be capable of targeting serotonin receptor subtypes, acting as an agonist for those subtypes and allowing serotonergic neurotransmission. However, this drug does not restore the sodium channels that are absent in GABAergic neurons. While this drug is effective at targeting the right subtypes, it does have some comorbidities. It happens to target the serotonin-2B receptor subtype, which leads to cardiac valve hypertrophy. Fenafluramine's off-target activity has made it unsuitable for use in treating Dravet's syndrome.

Viruses demonstrate properties of life and properties of non-life, which makes them difficult to categorize as living or nonliving. However, they belong to both categories that ultimately places viruses in a distinct category. Living properties of viruses include having genetic material (DNA, RNA), being able to reproduce with a host cell, and capable to evolve through mutations. On the other hand, viruses associate in the nonliving group because they lack a metabolism or organelles, cannot maintain homeostasis, and do not grow and develop, which all living cells can accomplish. A virsus' most signitficant feature is the incapability to multiply without host cells. These host cells are crucial for viruses because they reproduce by attaching themselves to a specific host cell and injecting its genetic material into it. Soon after, the host cell lyses and the replicated viruses are released to proceed the same cycle, resulting in greater viral genetic material in its environment.

Acute flaccid myelitis (AFM) is a disease that nearly resembles polio in which the disease includes cold like symptoms followed by loss of muscle control and paralysis of arms or legs. Approximately sixty-two cases have been reported around the States in about twenty-two states. Scientists have slowly, but surely narrowed down suspects in which this disease could be caused by. The enterovirus D68 (EV-D68) was narrowed down to be a possible suspect. Although the evidence doesn’t completely make this assumption conclusive EV-D68 is suspected by many scientists. This enterovirus spreads through saliva and mucus and causes similar cold like symptoms and sudden loss of muscle control. Kenneth Tyler of the University of Colorado (CU) School of Medicine in Aurora reported that several strains of EV-D68 could cause paralysis in mice. EV-D68 seemed to attack nerve cells directly causing this loss of control. If the enterovirus is indeed causing the paralysis, scientists are still unsure exactly of why it is only doing so in few cases. Although there is no vaccine against EV-D68, a possible vaccine developed in China had shown positive results in mice. 

The two pieces of literature are drastically different. “Describing and quantifying interspecific interactions: a commentary on recent approaches” is a piece which argues why certain approaches to interspecific interactions are better than others using the evidence of several studies and experiments, while “Neighbor Relations within a Community of Epiphytic Lichens and Bryophytes” is a report of the study conducted by the writers John and Dale. These are two distinct types of scientific writing; one is analyzing the works of others and determining something from that while the other piece tells of its own study. Therefore, aspects of each paper are different.

Due to the neuroendocrine nature of pancreatic cancer, the researchers are interested in developing an early screening technique involving hormonal and molecular biomarkers through routine blood tests. PanNETs (pancreatic neuroendocrine tumors) are classified into functional tumors, which have symptoms related to excessive hormone secretion, and non-functional tumors, which do not secrete hormones and therefore do not exhibit associated symptoms. In functional tumors, measurement of hormones such as pancreatic polypeptide, gastrin, proinsulin, insulin, glucagon, and vasoactive intestinal peptide can determine if cancerous cells are involved in hypersecretion (Ro et al., 2013). Up to 60% of PanNETs are non-functional, which may pose a challenge to the researchers. However, 85% of PanNETs have an elevated blood marker, which may allow for further research and scrutiny of biomarkers to accomplish this goal (Jensen et al., 2009).

Birds are bipedal vertebrates that evolved from theropod dinosaurs or reptiles. They are from a new class of vertebrates known as Aves which includes all birds. They have feathers and wings. The main function of their feathers is to maintain body temperature and their wings are used for flight. To maintain balance, birds placed their body in the center of the earth so it can be over and between their feet. When landing, they come closer to the ground and slowly rises to minimize the impact. 

Most birds are arboreal, in other words, tree-dwelling species. They grip on tree branches to keep their body upright and to prevent them from falling. Birds do not have claws, but instead, they have 3 digits or toes that they used to climb up trees. They also don't have teeth but instead, they have gizzards that help them digest hard nuts shell, seeds, and insects. Birds are the only species of its kind to reproduce externally. Most birds provide parental care until the eggs hatch after that the babies are on their own. They use their acute senses to help them navigate and communicate, also, they can hear sounds and see a wide range of colors more than humans. Their brain is about six to eleven time larger than reptiles and has lateralization that resembles primate brain.

Mammal and reptile are morphologically different in a few ways. Mammal skulls are synapsid: they have a single, large opening called a temporal fenestra behind each eye that allows for more attachment of jaw muscles. This muscle attachment gives mammals a larger range of motion in their jaws, which allows them to have stronger bites. Reptiles such as alligators are diapsid, which means they have two temporal fenestrae on each side of their heads, while other reptiles such as turtles do not have any of these openings and are thus referred to as anapsid. Another difference between mammal and reptile skulls is the mammalian middle ear is made up of three bones, the malleus, the incus, and the stapes, whereas the reptilian middle ear is made up of only the stapes. Reptiles have articulate and quadrate bones in their mandibles and skulls respectively, and in mammals these bones have migrated up towards the middle ear and formed the malleus and incus. Mammal skulls also differ from reptile skulls in that they have two occipital condolytes at the articulation between the skull and the cervical vertebrae. This allows mammals to move their heads up and down through, which is beneficial to them because this gives them the ability to further manipulate their food. Reptiles on the other hand only have a single occipital condolyte, which limits their head movements, most of which involve moving the entire body.

DNA extraction was performed in the laboratory today. Leaves from the plant Brachypodium distachyon were frozen in liquid nitrogen and placed inside a 2-mL round-bottom tube with two metal balls. A machine was used to shake the tubes vigorously, allowing the balls to grind up the frozen leaves inside into a fine powder. Detergent was added to the powder to break down the cell and nuclear membranes, and ethylenediaminetetraacetic acid was added to stop the cells’ enzymes from degrading the DNA. The tube was then incubated and chilled in ice. A potassium solution was then added to the tube, which caused the proteins and carbohydrates to precipitate. The tube was centrifuged, causing the precipitated contents to form a solid pellet. The supernatant containing the DNA was transferred to a new, clean 2-mL tube, and isopropanol was added to the solution, which caused the DNA to precipitate. The tube was centrifuged, causing the precipitated DNA to form a small, clear pellet at the bottom of the tube. The supernatant was extracted, and the DNA pellet was washed with 70% ethanol. Lastly, the DNA pellet was dissolved in a preservation solution.

During lab today, I looked at several different bones of varying species all of which were mammals. The main focus of the lab was to be able to identify the bones as well as trying to understand the skull morphology. Being able to identify between an anapsid, diapsid, and synapsid was one of the goals of the activity. There were three skulls laid out in front of me which consisted of a goat skull, turtle skull, and crocodile skull. An anapsid skull would be lacking an opening in its skull called temporal fenestrae. The turtle skull is an example of an anapsid, the turtle when consuming food is not able to chew it. This is because it lacks the opening which is where jaw muscles are able to attach. An example of a diapsid would be the crocodile.  A diapsid skull contains two openings on both sides of the skull, these openings are where muscles are able to attach allowing crocodiles to move their mouths up and down when chewing. The third example is of a synapsid is a goat skull. The goat skull contains a large opening where multiple muscles are allowed to attach. Mammals are synapsid and therefore able to move their mouth up and down as well as side to side when chewing. The opening called the temporal fenestrae is the key factor in determining what type of skull it is.