1.1. Explain the pH in simple terms.
Felicetti (2019), states that pH is an abbreviation for potentiometric hydrogen ion concentration. This is a scale which represents whether a solution is acidic, neutral or alkaline. The more acidic a solution, the greater the hydrogen ion concentration would be. A pH of 7.0 indicates neutrality, a pH less than 7 indicates acidity and a pH of more than 7 indicates alkalinity. An acceptable pH level within the body is between 7.1 and 7.5 (Allen, 2017).
A common use of acid in the body is gastric acid within the stomach. This consists mostly of hydrochloric acid combined with potassium chloride and sodium chloride. Its pH level is 1 to 2. When digested food enters the stomach, the acid begin to break down the protein structure and then its bonds. Antacid tablets can be used to neutralize excess stomach acid if it exceeds its natural pH levels (NHS 2016).
Once the human body contains too much acid problems can occur such as acidosis. This arises when the lungs and kidneys have difficulty keeping the balance of the bodies’ pH at a level. These organs can usually compensate with slight imbalances although, problems can proceed leading to excess acid collecting in the body. There are two types of acidosis, respiratory acidosis and metabolic acidosis which are characterised by different causes. Respiratory acidosis takes place when too much CO2 accumulates within the body. Ordinarily the lungs would remove CO2 while breathing. however, due to chronic airway conditions, injury to chest, sedative misuse or even a deformation with the chest structure the Body can find it difficult to remove adequate CO2 (Boskey, 2017).
1.2. Explain how the tubule cells of the kidney nephron collecting duct work to maintain the pH of the blood.
The distal convoluted tubule has a function of maintaining the pH of the blood. The cells of the tubule contains an enzyme called carbonic anhydrase. This merges water and carbon dioxide to create carbonic acid (H2CO3). The acid then splits inside the cell into hydrogen ions and hydrogen carbonate ions. Cells then pump the hydrogen ions into the lumen within the second tubule. Hydrogen phosphate ions (HPO42) in the lumen combines with hydrogen ions to form dihydrogen phosphate (H2PO4). When the hydrogen ion mixes, a sodium ion is released within the lumen and sodium dihydrogen phosphate (NaH2PO4) is created. This molecule is then eliminated in the urine, removing the hydrogen. The hydrogen carbonate ions (HCO3–) then moves from the tubule cells into the blood. This is where they encounter the sodium ions which were found in the lumen within the tubule (wiseGEEK, 2017). Bicarbonate will also form to counterbalance the metabolic acids.
A.C 6.3. Briefly describe the three main buffer systems found in the blood.
Three main buffer systems found within the blood are protein buffer systems, phosphate buffer system and the bicarbonate buffer system. The protein buffer system is a fundamental component of the pH controlling mechanism for blood Hydrogen (H ) ion homeostasis. Both intracellular and extracellular proteins have negative charges which serve as buffers for changes within hydrogen ion concentration.
The phosphate buffer system consists of two ions, hydrogen phosphate ions and dihydrogen phosphate ions. The pH level of the blood falls below 7.4 if the H ions in the blood increase. Hydrogen phosphate ions accept all added H ions to restore the stability between the hydroxide and hydrogen ions within the blood. When the pH level of the blood increases above 7.4 the dihydrogen phosphate ions deliver further hydrogen ions to restore the pH level of the blood to its foremost 7.
The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of carbonic acid (H2CO3), bicarbonate ion (HCO?3), and carbon dioxide (CO2) in order to maintain pH in the blood and duodenum to support proper metabolic function. Produced by carbonic anhydrase, carbon dioxide (CO2) reacts with water (H2O) to form carbonic acid (H2CO3), which quickly dissociates to form a bicarbonate ion (HCO?3) and a hydrogen ion (H ).
The pH is balanced by the occurrence of a weak acid (for example, H2CO3) and its base (for example, HCO?3) so that any excess acid or base introduced to the system is neutralized (Physiol, 2010).
A.C 6.1. The respiratory centre in the medulla oblongata in the brain controls the blood pH by regulating breathing. Explain how the centre is stimulated by changes in blood CO2, and how it responds to those changes to help regulate blood pH.
According to normalbreathimg.com (2018) the respiratory centre located in the medulla oblongata regulates the concentration of H y controlling the rate and depth of respiration. Chemoreceptors within the body work by sending the pH of their environment through the concentration of hydrogen ions due to carbon dioxide eing converted to carbonic acid in the bloodstream. This making chemoreceptor able to use the bloods pH as a way of measure carbon dioxide levels of the blood. Main chemoreceptors used in the respiratory feedback are the central chemoreceptors which are located on the ventrolateral surface of the medulla and detects changes of the pH in the spinal fluid, another being peripheral chemoreceptors which includes the aortic body and carotid body. The aortic body detects changes within the bloods oxygen and carbon dioxide but not pH, whereas, the carotid body detects changes in all three. There are three main components in the respiratory feedback response. One being sensor, in this case the sensor would be the chemoreceptors detecting the changes in the bloods pH, the medulla and the pons from the integrated centre and the respiratory muscles as the effector.
Giving thought to a case in which a person is hyperventilating from anxiety. Their increased ventilation rate will remove too much carbon dioxide, leading to less carbonic acid within the blood. This meaning the concentration of hydrogen ions decreases allowing the pH of the blood to increase. In response to this the peripheral chemoreceptors detect these changes leading to the transport of signals to the respirator centre of the medulla. After receiving these messages more signals will be sent through the nerves to the respiratory muscles to decrease the ventilation rate so the carbon dioxide levels and pH can return to its normal levels. Three types of important respiratory nerves are the phrenic nerves which stimulate the activity of the diaphragm, the vagus nerve which encourages the diaphragm movement but also helps the larynx and pharynx and lastly the posterior thoracic nerves which enables the movement of the intercostal muscle located around the pleura. These types of nerves lead to signals of the escalating respiratory pathway from the spinal cord to stimulate the muscles that perform the needed movements for respiration (Lumen, 2017).
The Nervous System
A.C 5.1. Briefly describe the main functions of the nervous system.
The nervous system is formed by two parts, the central nervous system and the peripheral nervous system. The central nervous system includes the brain and spinal cord whereas the peripheral nervous system contains the nerves which branches off from the spinal cord to all other parts of the body. The nervous system transmits signals between the brain and to the rest of the human body, this includes the internal organs. The functions of the nervous system is to process input form sensory receptors, transfer and interpret impulses and to control the bodily functions. The nerves within the nervous system are made up of specialised cells known as neurons.
The autonomic nervous system regulates many of the body’s processes which takes place without conscious effort. This nervous system controls a variety of internal processes including digestion, circulation, heart rate, body temperature, sexual response and metabolism.
A.C 5.2. Use diagrams and tables to explain the differences in structure between sensory, relay and motor neurons. The functions of each of the three types of neurons.
Overall functions of the neurone, position and function of the cell body, dendrite or dendron structure and function, axon structure and function.
Found in receptors such as eyes, ears, tongue and skin. They carry nerve impulses to the spinal cord and brain. When these nerve impulses reach the brain, they will be translated into sensations such as visions, hearing and taste. They have long dendrites and short axons (PsychologyHub 2018). The axons divide into two branches, the peripheral which extends from the soma into the receptor cells present on the peripheral sensory organs through the spinal nerve, and the central branch, this extends from the soma into the posterior horn of the spinal cord forming a synaptic junction (Ray, 2017).
Found in the visual system, the spinal cord and the brain. They receive messages from the sensory neurons and pass messages to either other interconnecting neurons or to motor neurons. They have short dendrites and short or long axons (PsychologyHub 2018).
Carry electrical impulses away from the brain and spinal cords central nervous system to the organs and muscles in the body. They have short dendrites and long axons (PsychologyHub 2018).
A.C 5.3. Describe the structure of the knee jerk reflex arc with the aid of a diagram.
The knee jerk reflex is also known as the patellar reflex. It is a sudden kicking movement of the lower leg showing a response of a sharp knock of the patella tendon. Pressure on the stimulus, in this case the ligament joining the patella to the tibia pulls the patella downwards. This downwards motion of the patella pulls on the tendon attached to the thigh muscle and stretches it. The stretch rector at the end of the sensory neuron is stimulated, and an impulse then travels up the sensory neuron to the spinal cord. Intermediate neurones will then be stimulated by chemical neurotransmitters from the sensory neuron. Intermediate neuron may stimulate neutrons running up the spinal cord to the brain, this will also stimulate the motor neuron leading to one of the thigh muscles rectus femoris. The motor neuron is stimulated by a chemical neurotransmitter from the intermediate neurone which sends impulses to the motor end plates attached to the rectus femoris. This encouraging the release of the neurotransmitter and stimulates the contraction of the rectus femoris. Contraction of this muscle will then pull on the patella which in turn pulls on the tibia. Meaning this motion will pull the lower leg in an upwards movement (Augustyn, 2019).
A.C 5.4. Write short notes with appropriate diagrams on the roles of the sodium/potassium pump and the sodium and potassium channels in creating resting and action potentials across the membrane.
According to Zeidan, (2017) the resting potential is the axon membrane paralysed. For example, electrically excitable neurons. It is negative on the inside about -70mV due to the being more positive sodium ions (Na ) and potassium ions (K ) on the outside of the membrane than the inside. This forming an electrochemical gradient between the outside and the inside of the membrane. Active transport by the sodium/potassium pump forces Na out of the axon and pulls K into the axon. This does not create a resting potential because K can also leak out. The membrane is considered to be excitable and ready to create an electrical impulse along the axon.
Depolarisation is caused a stimulus reaching the neuron. This causes the Na channels to open in a patch of the axon membrane. Some Na moves into the axon which reduces the electrochemical to about -50mV. Then more Na that flows into the axon which changes polarity to 40Mv (Wong, 2009). The action potential is the depolarisation which creates a flow of electric currents in the membrane. This stimulates next to the membrane which opens up the next group of Na channels. Leading to the action potential moving down the axon (Yelle, 2009).
Allen, S. (2017). Acidosis. Available at: https://www.healthline.com/health/acidosis. (Accessed: 1 March 2019).
Augustyn, A. (2019). Knee-jerk reflex. Available at: https://www.britannica.com/science/knee-jerk-reflex (Accessed: 6 March 2019).
Boskey, E. (2017). Acidosis. Available at: https://www.healthline.com/health/acidosis#causes. (Accessed: 2 March 2019).
Felicetti, M. (2019). How to Balance Your Ph. Available at: https://www.mindbodygreen.com/0-6243/How-to-Balance-Your-pH-to-Heal-Your-Body.html. (Accessed: 1 March 2019).
Lumen. (2017). Respiration control. Available at: https://courses.lumenlearning.com/boundless-ap/chapter/respiration-control/ (Accessed: 1 March 2019).
NHS, (2016). Available at: https://www.nhs.uk/conditions/antacids/. (Accessed: 15 March 2019).
Physiol, J. (2010). Hydrogen ion dynamics in human red blood cells. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036193/ (Accessed: 2 March 2019).
PsychologyHub. (2018). The structure and function of sensory, relay and motor neurons. Available at: https://psychologyhub.co.uk/the-structure-and-function-of-sensory-relay-and-motor-neurons/ (Accessed: 19 March 2019).
Ray, A. (2017). Location, Structure, and Functions of Sensory Neurons with Diagrams. Available at: https://bodytomy.com/sensory-neurons-location-structure-function (Accessed: 19 March 2019).
WiseGEEK. (2017). Roles of the tubule cells in the kidney. Available at: https://www.wisegeek.com/what-is-the-distal-convoluted-tubule.htm. (Accessed: 2 March 2019).
Wong, E. (2009). Physiology of cardiac conduction and contractility. Available at: http://www.pathophys.org/physiology-of-cardiac-conduction-and-contractility/ (Accessed:19 March 2019).
Yelle, D. (2009). Physiology of cardiac conduction and contractility. Available at: http://www.pathophys.org/physiology-of-cardiac-conduction-and-contractility/ (Accessed: 15 March 2019).
Zeidan, A. (2017). Resting potential. Available at: https://www.britannica.com/science/resting-potential (Accessed: 2 March 2019).
Adaptations of Alces alces, The North American Moose
Having spent my childhood in the woods of northern Maine, I have long been familiar with moose. I have always found them to be intriguing, and my admiration for them has only grown as I have gotten older. They are massive, stoic creatures — gentle giants when they aren’t directly threatened or protecting their young. It is important to realize that the moose’s many curiosities aren’t novelties or mistakes, but adaptations that enable them to thrive in their environment. Three of these adaptations will be explained and their importance discussed in this paper.
The Moose, Alces alces, is a large even-toed ungulate of the cervidae (deer) family and artiodactyla order. They stand up to 6 feet tall at the shoulder, with dark brownish/blackish fur, long legs, a bell of skin and fur hanging from their neck, and large antlers (Geist, 2019). North American Moose populations spread throughout the boreal regions of Canada and the United States, from Alaska across Canada to Maine. The climate of these areas are characteristic of most boreal regions, with long cold winters and short cool summers (Hiltz et al., 2004). According to a study performed in British Columbia in 2004, moose habitats include areas close to water, shrublands, treeless wet meadows made up of mosses and herbs, coniferous and deciduous forests, and even areas characterized by human disturbance such as “cut areas, burned areas, and industrially disturbed areas in various stages of regeneration” (Hiltz et al., 2004). The study showed that while some habitats were preferred over others, there were noticeable differences in habitat preference among individual moose (Hiltz et al., 2004). This may be an indication that in general moose are adapted to their boreal environment to such a degree that individual moose can afford the luxury of unique sub habitat choice.
The space use of moose has largely to do with food availability and predation. Moose are typically active throughout the day, especially dawn and dusk. Despite heightened behavior at dawn and dusk, Moose feeding periods are dispersed throughout the day, separated by 2-3 hour resting periods (Geist, 1963). Most moose tend to feed on trees and small plants, both or either of which can be found in each sub habitat listed above. According to an article published in 1981 titled “Plant Selection by a Generalist Herbivore: The Moose”, moose eat several parts of trees and small plants, including aquatic plants, forbs, deciduous leaves and twigs, and coniferous twigs. Interestingly, a study from Isle Royale National Park, Michigan showed that while leaves and twigs were chosen relative to their energy content, moose preferences for aquatic plants were largely correlated to their sodium concentrations (Bolevsky, 1981). The natural predators of moose include wolves, black bears, and brown bears. According to a study published in the Canadian Journal of Zoology in 1994, “In naturally regulated ecosystems, predation on moose by bears and wolves is often limiting and may be regulating” (Ballard and Ballenberghe, 1994). This is not surprising, considering the effects that predation can have on behavior and evolution throughout the animal kingdom.
In North America, four subspecies of moose are recognized: Alces alces americana (the eastern moose), Alces alces andersoni (the northwestern moose), Alces alces shirasi (the Shiras moose), and Alces alces gigas (the Alaskan moose). These subspecies are mostly differentiated by fur, antler shape, and size (Encyclopedia Britannica, 2019). These differences are probably adaptations to the environment of each subspecies’ respective region, a phenomenon that will be discussed in greater depth later in this paper. Moose belong to the family cervidae: the deer family, a group of 43 species of cud-chewing ungulates (even-toed hooves) with antler wearing mature males (Encyclopedia Britannica, 2019). The phylogeny of cervidae below shows that, other than A. alces pfitzmayeri and A. alces cameloides (two eastern subspecies of moose), Alces alces’ closest relatives are the roe deer and the water deer, two species found predominantly in Europe and Asia.
Figure 1: Phylogeny of Cervidae (Fickel et. al., 2004)
Tests of Adaptation:
As mentioned above, there are noticeable connections between space use and predation among moose. According to a study performed in Isle Royale, Michigan, there is evidence to suggest that mother moose with calves, when given the option, spend more time around human camps than away from human camps (Peterson and Stephens, 1984). I hypothesize that the proclivity for mother moose to spend more time around human camps than other areas is a behavioral adaptation to utilize human activity to avoid predation. To test this, I would isolate two groups of moose from the same region. This experiment would be most feasible if a fenced nature preserve was used, so that boundaries are known and temporary fences may be erected to facilitate the experiment. The control group would be exposed to the level of predation that is common in its region, and the experimental group would be isolated from predation. Human camps would then be set up among both groups. Over the course of several weeks, I would monitor the behavior of mother moose and their prefered proximity to the human camps. If the mother moose in the experimental group spent more time around human camps than away from them, the theory that the proposed behavior is due to predation would be disproven.
As mentioned above, the four subspecies of North American moose are largely differentiated by size, fur, and antler shape, and these differences are likely adaptations to the specific environmental conditions of each subspecies’ respective region. I hypothesize that the differences in size, fur, and the characteristics of physical appendages between subspecies of Alces alces are morphological adaptations to thrive in the climate of each respective region. To test this, I would use the comparative approach, as well as an understanding of Bergmann’s rule and Allen’s rule. Bergmann’s rule states that within a broadly distributed species or taxonomic group, populations/species of larger size will be found in colder climates and those of smaller size will be found in colder climates (Freckleton et al., 2003). Allen’s rule states that animals adapted to colder climates will have shorter appendages and limbs than those adapted to warmer climates (Nudds and Oswald, 2007). I would sample populations of each subspecies and examine their size and fur. Then I would measure appendages and limbs such as ears and legs. Once I had acquired this data, I would acquire as much data as I could concerning the climate of each region. I would expect thicker fur, larger size, and shorter ears and limbs to be characteristic of those from colder regions, thinner fur, smaller size, and larger ears and limbs for warmer regions, etc. For my hypothesis to be correct, the data would have to clearly show the expected trend, and the subspecies would have to clearly show differences in these characteristics according to the expected trend.
As mentioned above, a characteristic of cervidae is cud chewing, a mechanism of feeding made possible by multiple stomachs and aided digestion by gut bacteria (Geist, 2019). This symbiotic relationship with bacteria is one that moose depend on to properly digest their food, especially cellulose, which they cannot digest on their own (Ishaq and Wright, 2012). I hypothesize that the ability for moose to harbor bacteria in their stomachs is a biochemical adaptation to best digest cellulose and other components of their diet. To test this, I would compare the digestive system of a moose to an organism without a similar specialized multi-chambered stomach. For example, horses are odd toed ungulates of the order perissodactyla, with a single chamber stomach. I would isolate gut bacteria and digestive enzymes from both the gut of a moose and that of a horse, and compare how efficiently each metabolizes cellulose, taking into account each organisms digestive process. If the more efficient system was that of a moose, then my hypothesis is correct. Research on ruminant (multi chambered) and monogastric (single stomach) digestion shows that to be the case (Watkins et al., 2010).
Moose have many interesting traits that make them fascinating creatures to observe, whether that observation is with one’s own eyes in the wild or from those of another through videos and journal articles published online. North American moose are an example of how the mechanisms of evolution allow organisms to creatively thrive in their environment, even if that environment is cold and wet. I plan to venture back into northern Maine’s woods once more this coming December, perhaps I will once again have a chance to witness these adaptations in action.
Ballenberghe, V. V.,