endotherms ectotherms

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1 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

2 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+]

3 - 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).

4 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 20C / 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

5 - 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.

6 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)

7 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 multicellular organisms Arctic Fox and Char s Responding to 5 degree temperature increase 1. Acute: fox pants, char s blood flow/metabolism increases, enzymes work harder 2. Chronic: acclimatization 3. Generational: extirpation or extinction, natural selection and adaptation to new thermal regime Need to Know Basic Biology - nutritional requirements - reproductive cycle - life history - population census Biology Lecture 17 Acclimatization

8 - adjustment by an individual organism to chronic stress - physiological processes or structures change to function more optimally under new conditions - change is reversible, and may even be repeated Range of Tolerance - similar to fundamental niche, but often refers to a single factor eg temperature - LLT= lower lethal temperature, ULT= upper lethal temperature Clicker Question D is correct, E is incorrect because of the word adapt, implies many generations Musk Ox acclimatize to seasonal changes by shedding fur/pelage in the summer, also have a short migration from lowlands in the summer and highlands in the winter to support their diets. Function flows from structure - eg frog jumping, multiple systems needed to make it happen - should be able to give examples of structure function relationships down to specific levels Example 1: Bears - bone is a type of tissue - connective tissue - so teeth are organ and tissue level Example 2: Arctic Fox - legs have unique structure of blood vessels, warm blood in leg, cool blood in foot - vessels are lined in parallel with blood flowing in opposite directions (counter-current blood flow) - warm blood comes down the right side on the artery, heat flows into cooler vein blood leaving (heat flows hot to cold) - this level of organization is also at the tissue level Example 3: Mammoths - working with hemoglobin, how it affects oxygen in the blood in the cold - mammoths have 3 amino acid difference in structure - level of organization is macromolecular - hypothesis: wooly mammoth hemoglobin had properties that allowed it to function (unload oxygen) in cold extremities and appendages - prediction: the wooly mammoths physiology would be closer to the arctic mammals than to hemoglobin of closely related tropical elephants - result: woolly mammoth hemoglobin unloaded oxygen more efficiently in colder conditions than hemoglobin from living elephants (Remember, the extremities are cold but core temperature is still 37 degrees)

9 - implications: This biochemical specialization may have been involved in the exploitation of high-latitude environments by this African-derived elephantid lineage during the Pleistocene period. Will There Be Polar Bears? - 3 subpopulations of polar bears in Canada - total population is around the bears are hunted: total harvest is no sport hunt in some areas Lecture 18 Adaptations in Arctic Plants and Lichens - water and sunlight - nutrients (N, Ph, K) - CO2 Lichens - a lichen is a combination of algae and fungus - they thrive in the arctic because: - they grow on bare rock - have no roots, instead have rhizines for attaching to substrate - can extract moisture and nutrients from the air - are freeze and desiccation tolerant - fungal partner can utilize low amount of nitrogen - algal partner can photosynthesize at low levels - can be dormant for a long time - asexual reproduction Reduced time on sea ice will - decrease feeding period (reduce stored fat) - increase fasting period (increased need for stored fat)

10 - reduce number of successful pregnant females - reduce survival rates of dependent young (population decline) Biology Lecture 19 Physiological response to temperature change - Q10 provides a measure of how sensitive metabolic processes are to temperature change - always at a jump to ten degrees - if Q10 = 2, that means that the rate doubles for every ten degree increase - related to any rate, metabolic, breathing, heart etc Clicker question answer: E Conformers: allow internal environments to follow external changes eg char, caterpillar Regulators: maintain constant internal environments (homeostasis) in the face of varying environmental conditions eg ptarmigan, polar bear - it is possible to be both a conformer and a regulator depending on the factor you re looking at, eg the char is a conformer for temperature but is also a regulator when they move between fresh water and sea water Heterothermy: an animal who is endothermic at certain times or in certain tissues, but not at all times or in all tissues - hibernating rodents - tuna and billfish - generate heat and retain heat in certain parts of their bodies (brain, muscles, eyes) - Countercurrent (parallel) arrangement of blood vessels transfer heat from warm veins (from the muscles) to cool arteries ---> like legs of arctic fox - veins are blue (cool), arteries are red (warm) - hot muscles - advantageous because if the tuna is 10o C warmer and the Q10 is 3, then power output increases by 3 fold - hummingbirds - bumblebees - bats

11 - arctic fox Metabolic rate is affected by ambient temperature in ectotherms and endotherms. - measuring oxygen consumption to help determine metabolic rate - red line is ectotherms, blue is endotherms - when endotherms are cold oxygen consumption goes up to stay warm Bergmann s Rule - surface area to volume ratio is an indication of how much heat your going to lose or gain, the larger you are the lower your ratio is - in the arctic, body size tends to be larger in endotherms - opposing views - a)...we found broad support for Bergmann s rule as a general trend for mammals; however, our analyses do not support heat conservation as the explanation. - b) Bergmann s rule is a valid ecological generalization for birds and mammals. Video - giant sea life linked to oxygen rich water in the arctic - polar fish are lazy, inability to generate enough energy to sustain swimming. Metabolic processes inhibited by temperature Will there be polar bears? - thick fur - blubber up to 11cm thick - large size, low surface area to volume ratio - hairs reflect visible light but transmit near infrared light to their dark/black skin - hairs are hollow and trap heat emitted from the skin Biotic Interactions - algae gets in hollow hair, turns bears green

12 - polar bear is currently the only large land dwelling predators within its range eg grizzly Biology Lecture 20 Clicker Answer: C Transfer of heat energy from warmer to cooler by: A. Radiation: electromagnetic waves (heat waves) travel through spaces B. Conduction: direct contact (hand touching ice) C. Convection: non-direct, air or water currents (wind makes it colder) D. Evaporation: liquid to gas Diagram 4: radiation 6: reflective radiation 2 & 3: infrared radiation 5: conduction 1: convection 7: evaporation Body Temperature Regulation in Endotherms - The hypothalamus integrates information from thermoreceptors. - Compensating physiological and behaviour responses (inquiry 10) Endotherms Stay Cool By: - skin circulation - evaporation (sweating, panting) - behavioural changes (posture, shelter) Endotherms Stay Warm By: - skin circulation, heat loss by convection and radiation - heat production - muscle activity (running - shivering - non-shivering thermogenesis via brown adipose tissue - digestion - behavioural changes (huddling) - insulation (fur, feathers) Polar Bears and Grizzlies - grizzly bears are found across Russia, Northern Canada and Alaska - very close to polar bear population - brown bears are 90% vegetarian, 10% carnivore - only eat fish, small mammals, occasional deer for meat

13 - polar bears are 100% carnivore - polar bears may be outcompeted in a warmer Arctic - polar bears may be bred out of existence if brown bears move North Lecture 21 Endotherms - Torpor: daily hibernation, body temperature/metabolic rate decrease, reheat with shivering or oxidation of brown fat - hummingbirds, marsupials, shrews, skunks, rodents Seasonal Hibernation - decrease in metabolic rate, blood flow/pressure, heart rate, oxygen uptake - body temp may be as low as -3 degrees (supercooling) - usually found in animals less than 5kg Bears - do not go into deep hibernation because the energetic cost to warm up would be too great - they recycle various metabolites in their body; burn fat to produce waste, CO2 and H2O Will There Be Polar Bears? - closest relative of polar bear is brown bear (sister taxa) - one hypothesis says the divergence happened 600,00 years ago - brown bear and polar bear share 10% nuclear DNA Lecture 22 Supercooling and Ice Nucleation - pure water can be cooled below 0 degrees C without freezing - physical disruption or addition of ice nucleating agents cause rapid freezing of supercooled water Freezing Point Depression - colligative antifreezes lower freezing point of bodily fluids by increasing concentration of solutes - non-colligative antifreezes lower freezing point of bodily fluids with specialized chemical properties (antifreeze protein, multiunit compound) Strategies for Overwintering in Ectotherms Freeze Tolerance - production of antifreeze compounds - synthesis of ice nucleating agents (macromolecules in gut) Freeze Intolerance

14 - behaviour avoidance - production of antifreeze compounds - supercooling (temperate NOT arctic species) Freeze Tolerance in Northern Amphibians - some frogs can freeze solid - glucose acts as cryoprotectant (colligative antifreeze) - takes a lot of energy - go through multiple freeze-thaw cycles throughout the winter - to measure how much energy it takes to freeze, scientists took a frog and put it in a cooling chamber and rated O2 consumption (to find metabolic rate) - big bursts of energy consumption going in and coming out of freezing Freeze Intolerant Winter Flounder - sea water freezes at -1.9 degrees, fish bodies freeze at -1.2 degrees - fish don t freeze because they have antifreeze proteins which decrease the plasma freezing point What triggers the production of antifreeze protein/ - studies show water temperature has no effect - photoperiod seems to be the leading cause Clicker Q: A (due to the non-colligative properties of the bodily fluid) Lecture 23 What are the consequences of an Arctic Ecosystem 8 degrees warmer? - Physiology: the biological impact of rising temperatures depends on the physiological sensitivity of organisms to temperature change - Evolution & Ecology: the biological impact of rising temperatures also depends on differences in survival and/or reproduction among individuals on the basis of differences in heritable traits/characteristics as these individuals interact with each other and their environment. - The largest changes in fauna are predicted for the tundra, Central America, & the Andes Mountains likely to experience over 90% turnover so that faunal distributions in the future will bear little resemblance to those of today - Tundra & Tropical forest ecosystems will lose the greatest number of species because these ecosystems have high richness & slight changes in temperature will disrupt finescaled climatic gradients. - Arctic ecosystems will gain the greatest number of species because these ecosystems have low richness & slight increases in temperature will create new niches allowing many species to establish. - Warmer climates allow for more species, Arctic ecosystems will have the highest rates of species turnover as entirely new communities & ecosystems establish (forest, wetlands) with slight increases in temperature.

15 CLICKER Q: A) Due to the non-colligative properties of bodily fluids. Will there be Polar Bears? - Geographic fidelity: stick to one area - Polar bears can probably den successfully in other than permafrost feature, but will this affect reproductive success? - Cannot switch diet in any substantial way that meets the annual energy budget average needs 43 ringed seal equivalents to meet annual energy budgets. - Suggestions that they will survive by becoming more terrestrial are unrealistic - Ice goes, polar bears go - Main difference between polar bear and brown bear is diet, the polar bear is almost totally carnivorous whereas the brown bear is an omnivore - Convention on International Trade on Endangered Species (denied) - Proposal to ban trade in polar bear parts (supported in USA, Russia) Inuit groups from Canada spoke against it (Polar bears are source of food, money warmth). - Canadian government (plus Denmark, Norway) spoke against it (not enough population information to tell if they are jeopardized). POLAR BEAR CONSERVATION - Polar bears vulnerable in Norway, Greenland & threatened in US. Canada =? - Transportation costs + feeding = 1$ million per month!