-Adnan Jahan
(adnanjahan@gmail.com)
Sunday, March 27, 2011
Shubin describes his trip to the Arctic in saying that "each winter, the temperature sinks to minus 40 degrees Fahrenheit. In the summer, when the sun never sets, the temperature rises to nearly 50 degrees." Given what we have learned pertaining to thermoregulation for animals and plants (especially the photoperiodic control), explain why so few species live in the Arctic. What sort of material adaptations do you think the Inuit people have developed in order to survive in such an environment? Finally, what sort of features do animals such as polar bears have that allow them to survive in the Arctic?
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In order to survive in radical cold temperatures like the arctic, animals must be able to thermoregulate through one or more of the following methods: convection, conduction, radiation, and insulation. Convection includes either climbing up trees or rocks to a higher altitude, entering warm water, or building an insulated nest/burrow. In the arctic, the landscape can be very flat, and if there is a higher altitude that the animal can find, the air surrounding is still very cold, therefore it is not very helpful for heat regulation. Also, there is no warmer water to be found anywhere in the arctic and it is very hard to find materials to build an insulated nest or burrow. Conduction includes lying on warm ground or rock, which is impossible to find in the arctic since temperatures are always below freezing. Radiation includes lying in the sun. In the arctic, most of the year is very dark and there is no sunlight that reaches the area, and if the sun comes out for that short period of time, there is only a very minimal amount of heat or radiation that will reach the animal, which is not very helpful in thermoregulation. Insulation includes changing the shape of the body of the animal to alter surface area or inflate the body. There are not many animals that have the ability to alter their physical body shape or size in order to adapt to the extreme cold weather of the arctic. Because all of these methods of heat regulation is very difficult to achieve in the arctic, not many species can live in the Arctic.
ReplyDeleteThe inuit is a culturally indigenous group of people that live in the Canadian Arctic. The inuit make a diet adaptation of consuming many very large amounts of protein and fat; 75% of their daily energy intake is from fat. Living in such extreme cold temperatures, this high intake of fat can help insulate the bodies in the cold. The inuit also make most of their clothes out of animal furs and skins. By wearing these thick and furry coats made of animal fur, extra insulation is provided to keep the inuit people warmer in the cold weather.
Polar bears are able to survive well in the arctic because they not only have a very thick and warm coat of fur that covers their whole body and keeps them insulated, there is also a very thick layer of blubber under the fur that keeps the polar bears extra insulated and warm. Polar bears also burrow deep under many layers of snow that can keep them safe from harsh cold winds that the arctic faces for longer periods of time.
(Sujin Ko, sujinko93@gmail.com)
The problem that most organisms have with living in the Arctic is that they are either endotherms or ectotherms. Ectotherms would have trouble surviving because the seasons are so extreme that the inconsistency of the weather would end up killing the organism. Endotherms on the other hand, would require an extreme amount of energy in order to be able to maintain a constant body temperature.
ReplyDeleteThe Inuit people that live in the Arctic survive mostly by taking advantage of the resources around them. They hunt everything they eat and use animal parts for warmth. In order to keep enough fat on their bones and enough energy to move around, the civilization, "consumed an average of 75% of their daily energy intake from fat" (http://en.wikipedia.org/wiki/Inuit#Diet). All in all, the people rely on the same resources that the animals in this region do but at the same time get the benefits of what the animals produce in which they cannot.
The animals that live in the Arctic have a wide variety of adaptations in order to survivor in these extreme weather conditions. Birds on one hand, migrate to this region only during the warmer season then fly elsewhere during winter. The animals that live there all year long have thick fur in order to survive the cold. A portion of this fur is often shed during the summer in order to not over heat. Also to avoid freezing to death, they often stick in packs to conserve body heat and protection from the environment (another way is by living in the forests like the caribou). Many smaller animals, and some large ones like polar bears, take protection from the weather and predators in underground dens, especially during the winter. Polar bears, on the other hand, actually do most of their hunting in the winter so before summer comes, they eat a lot to get a thick layer of blubber and then hibernate. All of the sea mammals, in fact, have a thick layer of blubber and many travel north when the ice begins to melt.
http://www.saskschools.ca/~gregory/arctic/Awildlife.html
Jackie James
(jackie.james@comcast.net)
As Sujin and Jackie have stated, the methods of thermoregulation that we commonly see in animals can prove to be ineffective in regions such as the Artic, where the temperature is so low that it can be increasingly difficult to maintain a stable internal body temperature in order for fundamental bodily functions to occur, in the face of a changing external environment. This may be one of the reasons for why there are so few species living in the Artic, as Adnan said—because when the temperature decreases by 10 degrees Celsius, the “rates of most enzyme-mediated reactions decrease two- to threefold” (Campbell & Reece 862), a dangerous predicament, seeing as enzyme-controlled reactions make up our whole bodily function—metabolism (anabolism and catabolism). A specific example of an enzyme-mediated process in our body is that of activating pepsinogen (activating it to become pepsin)—the activated pepsin and the HCl (hydrochloric acid) in the gastric juice of the lumen of the stomach aid in breaking peptide bonds, beginning digestion by “cleav[ing] proteins into smaller polypeptides,” which are then further digested into “individual amino acids in the small intestine” (Campbell & Reece 886). Thus, if the temperature of the external environment was to be too low, these functions could be inhibited, causing bodily malfunctions. Another example can be seen when one is in very cold water for an extended period of time, resulting in a decrease in body temperature as the body is slowly unable to regulate heat exchange with the cold environment. This may result in a condition called hypothermia, a state of dangerously low body temperature. The first symptoms of hypothermia include an increase in “heart rate, breathing rate, and blood pressure” (http://www.emedicinehealth.com/hypothermia/page3_em.htm) in an attempt by the body to circulate more blood to the extremities despite the decreasing temperature. However, over time, the body doesn’t have the energy necessary to increase this cardiac output, and “pulse, breathing rate, and blood pressure all decrease” which may lead to “clumsiness, apathy, confusion, and slurred speech” (http://www.emedicinehealth.com/hypothermia/page3_em.htm). This is just one of the dangers of being in an extremely cold environment, and can give us some insight on why it is so difficult for species to survive in these temperatures.
ReplyDeleteAdditionally, as Jackie discussed, heat regulation when there is such a vast difference between the environmental temperature and internal temperature can require a large amount of energy, another possible explanation for why it is hard for species to survive in the Arctic. Continuing off of that idea, endotherms will generally have a higher metabolic rate than ectotherms because of their higher demand for heat generation, meaning that they will have to consume a larger amount of food (Campbell & Reece 862)—it’s a cycle; species in the Arctic are required to eat more food, yet there is no food to eat since so few species live there, adding to the disadvantages of such a harsh environment. However, though it is difficult for endotherms to survive in places such as the Arctic, it is also necessary to keep in mind that it is nearly impossible for ectotherms to survive there. As Sujin discussed, ectotherms “use heat acquired from the environment and behavioral adaptations to regulate body temperature” (
http://www.caudata.org/forum/f1-general-topics/f5-general-discussion-news-members/f1165-glossary-project/f1168-glossary-completed-words/68332-ectotherm-ectothermic-cc-amphib-glossary.html), and seeing as there are so little sources of external heat for animals residing in the Arctic, regulation by ectotherms is thus near impossible.
(continued from last post...)
ReplyDeletePhotoperiod, as Adnan suggested, may also have an effect on how we regulate our temperature. Photoperiod, or our exposure to certain periods of light followed by certain periods of darkness, relates to our “biological clock” (http://photoperiodeffect.com/) and circadian rhythm, or “physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment” (http://www.nigms.nih.gov/Publications/Factsheet_CircadianRhythms.htm). These circadian rhythms control functions of our body such as bodily temperature and sleep-wake cycles. The importance of photoperiods can also be seen in plants, where some require a certain period of time of exposure to light in order to bloom and grow correctly. A study performed on the ‘blind’ mole rat shows results that may contribute to our understanding of how animals survive in such cold temperatures. The conclusions of the study show how when cold-sensitive subjects were “acclimate[ed] [to a] short photoperiod (8L:16D) [they] increased their thermoregulatory capacity in cold conditions”, compared to those individuals which were “acclimated to a photoperiod of 12L:12D at the same [ambient temperature]” (http://www.ncbi.nlm.nih.gov/pubmed/6668463). Consequently, over time animals that live in cold conditions such as in the Arctic may have adapted to the shorter photoperiods (less exposure to sunlight) by using this short photoperiod as a signal to increase their thermoregulatory capacity. Otherwise, animals such as the polar bear may opt to instead utilize their thick, furry coat and layer of blubber to aid in their survival of arctic conditions, as Sujin and Jackie have previously stated.
Sources:
Campbell & Reece
http://www.emedicinehealth.com/hypothermia/page3_em.htm
http://www.caudata.org/forum/f1-general-topics/f5-general-discussion-news-members/f1165-glossary-project/f1168-glossary-completed-words/68332-ectotherm-ectothermic-cc-amphib-glossary.html
http://photoperiodeffect.com/
http://www.nigms.nih.gov/Publications/Factsheet_CircadianRhythms.htm
http://www.ncbi.nlm.nih.gov/pubmed/6668463
Kathy Li, kathy2132@gmail.com