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BIOL 1070
Wright& Newmaster

UNIT 8 - CO2 in the air influences the overall mean temperature of the planet - Rising CO2 levels in the atmosphere contribute to warming of the Earth - Canadians have 50% of polar bear land & 65% of its coastline in the Arctic. WHY DOES ARCTIC WARM FASTER THAN LOWER LATITUDES? - Arctic ice melt means more dark land & ocean surface revealed that absorb more sun energy, increasing warming. - More of the extra trapped energy goes directly into warming rather than into evaporation. - The atmospheric layer is shallower in the Arctic that must warm in order to warm the surface. - As sea ice melts, solar heat absorbed by the ocean is more easily transferred to the atmosphere. - Alterations in atmospheric & oceanic circulation can increase warming. - Sub-Arctic regions of Canada contain variety of aquatic & terrestrial ecosystems. - High Arctic, much terrestrial area is dominated by tundra. - Even at very high latitudes, there are freshwater & marine habitats - In general, marine mammals (narwhal, bowhead whale, polar bear) have a thick layer of blubber under their skin.  Animals who generate their own internal heat through metabolism = endotherms  Animals that rely on environmental heat sources (fish, amphibians) = ectotherms - Some terrestrial mammals/birds stay active in winter (musk ox, caribou, arctic fox, rock ptarmigan), find scarce food & maintain a body temperature of 37C when the external temp may be -60C. - Some animals hibernate & drop their temp to just above freezing (arctic ground squirrel). - Some ectothermic animals can’t avoid freezing & survive numerous freeze-thaw cycles (woolly caterpillar). - Plants in the Arctic face short growing season & challenges related to extreme cold.  Vascular plants tend to be small & freeze-tolerant  Lichens are well-suited to these conditions because they lack roots, do not require soil and are tolerant of desiccation & very low temps. IMPACTS AT DIFFERENT LEVELS OF ORGANIZATION Populations: Within a group of individuals of the same species living together climate change may affect survival, growth and reproduction.  EX. An Arctic plant may thrive as temp increases, but they may now dominate an area where a competing species is negatively impacted by increased temp. Communities: When one considers populations of different species living in the same area, climate change may cause changes in species distribution or frequency. Ecosystems: Climate change may have many complex effects that influence nutrient cycling between the abiotic and biotic factors. Molecules: Higher temp increases motion Macromolecules: Most are sensitive to temp change (ex. enzymes) Cell: Temp change can cause cells to undergo a stress response. Long-term temp increase may cause death mostly due to poorly functioning enzymes.  Stress response usually involves increase in amount of heat-shock proteins (HSPs), which attach to other proteins & stabilize them. When temp decreases again, HSPs release. Organ systems: Arctic Char are ectotherms – an increase in water temp would increase the amount of blood pumped to the heart per minute. This, & other factors, would change characteristics of the cardiovascular system.  Endotherms thermoregulate by sensing changes in internal temp & altering physiological processes/behaviour to bring internal temps back to normal.  EX. If a Caribou is too warm it will pant to dissipate some extra body heat.  [Relationship between external & internal temperature in different animals]  Ectotherms don’t maintain a constant body temp but other factors (ions, oxygen) are under homeostatic control. UNIT 9 - Arctic plants and animals must be able to carry out critical metabolic processes, exchange materials with their environment, and maintain physiological parameters within a limited range. - Substances that Arctic animals exchange with the external environment:  Gases, nutrients, waste - Rate of exchange in cells depends on membrane surface area. - Amount of substance that must be exchanged depends on the volume of the animal. - Every cell in an animal must be in contact with an aqueous environment where substances can be exchanged, called interstitial fluid.  Complex animals must also have a circulatory fluid that carries gases, wastes & nutrients to the interstitial fluid.  Respiratory & digestive systems have direct contact with the external environment. HOMEOSTASIS & FEEDBACK MECHANISMS - Endotherms regulate body temp, blood pH, ion concentration & glucose via homeostasis. - Ectotherms regulate other internal variables such an blood [Na+] - TEMP: thermoreceptors send info to the hypothalamus in the brain if the skin and body temp is below or above the set point. This info is integrated in the brain to bring about a response to regulate temp back to set point. - Fixed temp may vary daily, monthly and/or seasonally. - Positive feedback pushes the system farther from the initial state. THE PHYSIOLOGY OF CLIMATE CHANGE Acute: short-term Chronic: long-term Generational: across generations Acclimatization: adjustment by individual organisms to chronic stresses Adaptation: evolution of populations across generations under natural selection. - Naturally, Arctic organisms acclimatize to environmental conditions at that particular time of year.  EX. Arctic Char is more tolerant of warmer water temps in summer than in winter. This is because as seasons change, temperature, photoperiod, food availability and a host of other external factors may also change, in turn modifying the physiology of the fish over that period of time. CELL MEMBRANE ACCLIMATIZATION - Ectotherms change the composition of their cell membranes with changing temperatures to maintain membrane fluidity.  Different lipids have different influences on fluidity.  This is called homeoviscous adaptation  Ectotherms exposed to seasonal changes in temperature in the Arctic undergo cell membrane acclimatization between seasons. CIRCADIAN RHYTHMS - Many organisms link physioloical processes & behaviours to a 24hr cycle  This is called circadian rhythm if pattern is observed of 24 hours. - These rhythms are controlled by an endogenous or internal mechanism that acts like a clock which is set by external light conditions, but not dependent on light (e.g. if you live in a cave with complete darkness you will still sleep ~8 hours per 24 hours!) - Longer time cycles also occur, such as circannual (a year). UNIT 10 BODY SIZE & SURFACE AREA - The larger the animal, the greater its absolute requirements for gases & nutrients.  E.g. absolute requirements increase with body size (linear increase). - However, gram for gram, a mouse uses up more oxygen per unit of body mass than an elephant.  E.g. relative metabolic requirements go down with body size (exponential decrease) - Smaller objects have higher surface area to volume ratios.  This means exchange with the environment is not very efficient for large animals. To compensate, many organs involved in exchange have folded or convoluted membranes with very high surface aeas. The key points are: 1) Bigger body size means lower surface area to volume ratio, which means less efficient exchange with the environment. 2) When more surface area is needed, organs may have specialized structures that increase total area such as extensive folding. METABOLIC RATE & TEMPERATURE - Metabolic rate indicates how much energy or O2 is consumed per unit time. - In ectotherms (woolly caterpillar) a decrease in temp decreases body temp & in turn, decreases overall metabolic rate. Therefore, less O2 will be consumer per unit time at lower temps. - Metabolic rate is calculated using Q10 Q10 = Rate (T) / Rate (T-10) OR Q10 = O2 consumption @ 20C / consumption @ 10C WHY HIBERNATE? - For an endotherm, when temp falls, there is a larger temp gradient between internal & external temp & greater heat loss. - To thermoregulate at normal set point, active mammals in the Arctic require lots of energy – food or fat stores.  Alternatively, they can hibernate to reduce metabolic rate & body temp & this circumvents the need for a lot of energy. - Hibernation usually lasts for several weeks or months - Shorter dormancy period is called torpor (humming birds) - Metabolic rate per kg of tissue is higher in a small animal, therefore small animals need to supply more energy for each cell. - Smaller mammals also lose heat faster than larger animals because they have a higher surface area to volume ratio.  So if you are small, you need more energy & you lose heat faster  For this reason, smaller animals hibernate more than large mammals. BROWN FAT & NON-SHIVERING THERMOGENESIS - Some hibernators store food in their dens & arouse to eat periodically - Arousal consumes a lot of energy. - Brown fat is used to jump start metabolism - Brown fat has a high density of mitochondria, which synthesize ATP for cells.  Brown fat mitochondria contain a protein called thermogenin which enables these specialized cells to generate about 10x more heat that white fat cells.  This process is called non-shivering thermogenesis ACTIVE OVERWINTERING SMALL MAMMALS - Voles & lemmings do not hibernate; they construct long tunnels under snow & build nests on the group. - In winter, voles rely on twigs & shrubs for food, & lemmings eat old grasses beneath the snow. - Research found that lemming populations living under snow increased over winter months, and voles decreased.  Due to lemming winter behaviour, not food or predators.  However rising temps in the Arctic could reduce the offspring window of lemmings because the snow cover will not remain as long in the spring. UNIT 11 - There is evidence to suggest that the arctic was once a lush forest with a variety of terrestrial and aquatic habitats. - The main evidence to support this is that fossils have been found of species that are known to only live and survive in these warmer conditions (fossil brachiopods). - Osmosis: passive movement of water across membranes from low osmotic pressure to high osmotic pressure - Isotonic: cell remains the same - Hypertonic: water leaves cell at a higher [] then coming in, therefore the cell shrinks - Hypotonic: water enters cell at higher [] then going out, therefore the cell swells up and may burst  When tissues are exposed to temps below freezing, ice crystals form in the extracellular fluid, & they reduce the amount of free water outside the cell; increasing osmotic pressure. - Formation of ice crystals inside cells can cause significant physical damage to cell membranes and other cellular structures. Uncontrolled freezing in which ice crystals form in the body is therefore a significant problem for ectotherms living in subzero conditions. Freeze Tolerant Insects/Animals: - These insects/animals start producing ice nucleating agents which allow freezing outside of the cells - If it was to freeze inside the cell, crystals may form and then it can rupture the cell, causing death - The insects/animals produce glycerol and sugars to decrease their own boiling point of the cytosol to protect their cells - The freeze tolerant individuals may also make synthesize anti-freeze proteins which will slow down or inhibit ice crystal formation in specific tissues or cells  EX. woolly caterpillar: thaws, feeds & grows a bit during few weeks of summer.  MORE EX. fish, North American woodfrog. Freeze Avoidance Insects/Animals: - These animals/insects void their digestive tracts to get rid of any ice formatting agents - The insects/animals also produce glycerol and sugars to decrease their own boiling point of the cytosol to protect their cells, this allows the cells and fluid to remain unfrozen even in temperatures below 0. This is called supercooling - Super-cooling can be dangerous because some insects/animals can super-cool too quickly which could cause total freezing of the organism -- causing death.  Thus in the Arctic, supercooling is not the best strategy. - Another strategy is resting eggs; remain dormant during winter & are very tolerant to cold. Biology Lecture 16 - physiology: the study of organism structure and function including homeostasis and encompassing cells, tissues, organs and body systems Arctic Climate Change: Why the Concern? 1. Biological impacts (biodiversity change, disease, migration) 2. Political and economic impacts (Arctic sovereignty, natural resources, environmental policy) 3. Aesthetics (landscapes, tourism) 4. Cultural changes (traditional hunting practices) 5. Other What we Know - abiotic variables - examples of arctic plants and animals - how temperature changes impact organisms at different levels of organization What we Need to Know 1. How climate change impacts organisms on different time scales (Lecture 16, 17) 2. How climate change impacts plants and lichens. (Lecture 18) 3. Physiological responses to temperature change in animals? (Lecture 19, 20, 21) 4. Predicting long term trends in ArcPc populations. (Lectures 22, 23) Time Scales Dealing with Temperature 1. Acute: short term, minutes to hours 2. Chronic: long term, days to weeks 3. Generational: multiple generations, up to thousands of years There are 5 kingdoms, 2 of which have multi
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