metabolism

Metabolism and vertebrates are discussed in this presentation. The metabolic rate of animals is compared based on body mass, with larger animals having lower specific metabolic rates. The article analyzed the metabolism of vertebrates in extreme environments such as the ocean, desert, and high altitudes. Challenges faced by vertebrates include regulating body temperature, maintaining water balance, and adapting to changes in gas pressure and oxygen levels. Different adaptations are observed in animals such as countercurrent heat exchange and nasal salt glands. Marine mammals have blubber layers to conserve heat and adaptations to conserve water. Deep-diving species have specific adaptations to cope with high pressures. Hello, everyone, and today we'll be presenting metabolism and vertebrae. My name is Emily. My partner is Annie. And then to get us started, I do want to just go over a brief. Introduction on what is metabolism so specific metabolism is the metabolic rate of an animal per unit of body mass is used to directly compare cell and tissue metabolic rates and animals from a variety of sizes. Larger animals do tend to have lower specific metabolic rates and small animals. And so this leads to them having less metabolic heat to their bodies. The paper that we chose to analyze was vertebrae metabolism in extreme conditions by James H. Jones. And in the article, they look at different extreme environments in regards to the ocean. Temperate of the desert oxygen levels and then pressure and altitude. The first one I'm going to go over is their challenges. So, homeotherms do regulate their body temperature. That typically stays within a certain range that is. So, in mammals, it ranges between 96 to 100 degrees Fahrenheit. In birds, it's about 102 to 105. And then they regulate this heat through many different forms, such as conduction, radiation and evaporation. Their evaporation is by them sweating or salivating on their fur to keep themselves moist and just kind of cool down from the heat. Because their body temperature is ultimately determined by balancing all sources of heat gain, whether that be metabolic heat production, conduction and radiation. And with any imbalance, their bodies are going to try to alter it and try to create a new equilibrium. And one of the main figures in this article, it shows the fundamental factors of heat, water, pressure and oxygen that create physiological problems for the homeothermic vertebrae in these environments. One challenge that this article really emphasizes on is water and how we gain the water and how we lose it. So, water does make up a good majority of our bodies, whether that be in birds or mammals. It's mainly regulated to maintain osmotic concentration in between 300 to 400 micro osmometers in the body. And our water input must equal exactly to our output. It has to be an equilibrium and that's how we maintain homeostasis. So, again, how we gain our water, whether that be by food, by any of the carbs we consume or how we absorb it through our body surface. And then our water is mainly lost by our body, whether that be through us sweating or excretions through our pores or through animals licking and keeping themselves moist to maintain that cooler body temperature. And as cooler air is warmed when entering our body through respiration, it has a very good ability to hold in water vapor. And therefore, this warmer air has the capacity to hold more water when it's saturated. So, water is very essential to all of these organisms to maintain homeostasis. The article also discusses the challenges with gas, pressure and oxygen levels. So, obviously, vertebrates rely heavily on oxygen and oxidative phosphorylation to meet with our energy demands. So, the difference in this oxygen can really affect our respiratory system. And any partial pressure changes in the water or in the gas or in our oxygen can be detrimental. And so, when we reach higher altitudes or higher pressures, it gets reduced. So, the driving force for oxygen, of course, is to move through our body to make sure all of our cells get oxygen. So, whenever we go to higher altitudes and the barometric pressure gets reduced, the partial pressure of gas in the air changes. So, when you're diving, additional weight from the water is being compressed against the gas and it causes more pressure alone in itself. And, of course, the lower you go, you're also reducing the volume of gas, which is, again, Boyle's Law, as we talked about in lecture. And it proportionally increases the partial pressure of the gas. Moving along to the desert region, which is an arid region with sparse vegetation and higher temperatures, the heat in the desert itself, most mammals or animals there do become nocturnal just to eliminate the heat and how draining it can be. So, they're actually reducing their metabolic demand and lowering their heat tolerance. Water as well, obviously, is very arid and dry. And so, water can be very hard to come by. So, you try to minimize heat loss by panting or sweating. When you urinate, it may be altered because your body is trying to conserve that water. And then, of course, countercurrent heat exchange. An example of this is seen in small rodents, such as the kangaroo rats, which we've had another presentation about. So, again, these rodents are able to dissipate their heat and they tend to burrow in cooler areas. So, that way, they get to store heat during their activities venturing out again. And their body temperature doesn't have to decrease when it's a bit colder at night. Then, of course, if you're looking at larger mammals, they can't obviously go underground and make these micro-habitats to avoid the heat. So, in order to adapt, for example, camels, they must be able to tolerate high exposures during the daytime to these temperatures and this heat radiation. So, larger animals do tend to have smaller surface areas relative to smaller animals. And a smaller surface-to-volume ratio means that the larger animal is going to gain heat from the environment by conduction and radiation at lower rates. The second figure that the article provides is depicting the countercurrent heat exchange. And there's two different methods. So, at the very top, it's showing how, through the body, the warm blood flows through the arteries. So, it flows through the arteries and it kind of cools down as it gets to the rest of your body, which is a way that these mammals or other small critters have found to help regulate their body temperature. And at the bottom, it shows the airflow through the nose. So, there, the nostrils are able to take in any heat and basically spread. The temperature basically decreases as it goes through the nasal cavity and it goes through the tissue, so it helps keep things cool. In high altitudes, you are having to face low levels of oxygen. So, there is going to be a shift. There's going to be a change in the way your body is going to react. An example of this is with the alpacas and the bar-headed geese. So, these animals have been able to change their metabolic rate in order to accommodate for these lower levels of oxygen. So, birds, for example, the geese, have a higher surface area and thinner blood and an adaptation called peribronchial tubes, which help hold in more oxygen, help the oxygen flow better through their body. And birds also hyperventilate, so that also helps them get in more oxygen. While mammals, on the other hand, cannot do that. So, they will go through hypoxia, which is, you know, you're losing oxygen levels. And they can also go through pulmonary hypertension or pulmonary edema, so swelling. So, not great things. And in the third figure that they show, it's more of a graph, and it shows the relationship between the sea level and the total atmospheric pressure, which is the red line. As you can see, it kind of curves, but the red line does depict the Ruffles Griffin. The Ruffles Griffin is the highest altitude, surpassing Mount Everest. And then when you look at the bottom half, it is showing that the sperm whale and the elephant seals are the deepest diving species. So, they do go way below sea level and way below any kind of pressure that people who are diving can stay in. Moving along to diving, we're going to get into more specifics with the heat and how these mammals are actually able to conserve water that is not salt water. So, with heat, of course, water does conduct heat more efficiently. So, it is easier to have warmer water than it is to maintain your own body temperature. So, the water temperature can fluctuate a lot. And to accommodate for this, marine mammals do have blubber layers. So, they are really efficient in holding in their body temperature, like the warmth of it. And as well as having a low surface-to-volume ratio, and again having that counter-current blood flow that was shown in Figure 2. So, another adaptation is with their water consumption. Their water itself that they consume is three times more concentrated than the osmolarity that they have inside their bodies. So, in order to accommodate for this, for example, birds have a nasal salt gland, which is able to excrete salt and conserve water from their diet. To go into more specifics of the nasal salt gland, it is a salt-concentrating organ that can produce fluid with sodium chloride concentrations exceeding 2,000 micromoles per liter. And because sodium chloride is the primary salt found in seawater, this gives marine birds kind of advantage. And they are able to get fresh water despite the high salt concentrations in their food. So, their diet is very important. It is an adaptation where you are trying to save as much water as you can that is not salty. And again, with the water loss, you are releasing highly concentrated urine because you are making all these other accommodations to get rid of the salt. Another change that these marine mammals and birds kind of have to undergo is any pressure. So, as I mentioned before with Figure 3, we saw that the sperm whales and the deep diving seals, they have different accommodations for going below pressures that we can even go towards. So, of course, you are facing nitrogen narcosis, to which nitrogen builds up. Or you can go through the bends or casein disease. And then, as we also discussed in lecture, cardio and neuroembolism. So, there is a lot of downsides going below what we can handle. But these mammals have been able to change their lean body mass into higher percentages and have smaller percentages to accommodate for this. Their blood volume is just twice the amount that other marine mammals may have because they are trying to accommodate for it. And it is just as concentrated. So, the seals are trying to remove the air before they go underwater to accommodate for this because they don't want their lungs to explode. And the whales even have the ability, basically, to have elastic lungs. And it lets any way for gas to stay in and kind of keep the air more controlled. These deep diving mammals are even able to carry large amounts of O2, not just in their lungs, but also throughout their skeletal muscles. So, the oxygen is bound to their myoglobin. And it is very highly concentrated, especially in these deeper diving species. Lastly, I wanted to touch on their locomotion. So, of course, you see their streamlined bodies. It's able to make them move so much faster underwater with much less energy spent in comparison to flying or running. And the body itself leads to lower metabolic rates. It is estimated that the metabolic costs of swimming for seals and porpoises, it suggests that these animals are capable of maintaining much lower metabolic rates while swimming. Then it would be predicted for them to be able to tolerate extremely long periods of submersion during a dive with limited supply of oxygen.