1) Regulators: Maintain constant internal environments in the face of varying environmental
• Mammals and birds are regulators of temperature and ions. Fish and reptiles are regulators of
2) Conformers: Allow internal environments to follow external changes (body temperature in
• Reptiles and fish are conformers in temperature regulation. Invertebrates are conformers in
temperature and ion regulation.
-In periods of hibernation or torpor, regulation or conformation may change.
Generate their own internal heat through metabolism to regulate body temperature. Examples are birds
Homeostasis in endotherms: Must regulate blood pH, ions, glucose and temperature in a narrow range.
Large gradient between internal and external temperatures when the temperature drops
Hibernating animals: Reduces metabolic rate and body temperature for a prolonged period of time.
• Smaller animals hibernate more because their metabolic rate is much higher than larger animals
• Smaller mammals also lose heat faster then larger mammals because they have a higher surface
area to volume ratio.
• White fat keeps lower metabolic rate throughout hibernation
• Brown fat allows animals to arouse themselves out of hibernation.
-Has higher mitochondrial density and contains the protein thermogenin which raises body heat
much faster than white fat
-Bringing metabolic rate back up using brown fat is called non shivering thermogenesis
-Regulated by adrenaline
• No DEEP hibernators because the low heart rate during deep hibernation would not be sufficient
to maintain blood flow to all parts of the large body
• In bear hearts, a lowered heart rate changes myosin structure of the heart muscle which stiffens
the heart wall to maintain heart function. This is an example of a chronic acclimatization.
Torpor: Similar to hibernation, but only for short periods of time
Environmental sources of heat determine body temperature. Examples are fishes, reptiles and
• Can modify protein expression with changing seasons.
• Change LDH activity in seasonal changes, increasing concentrations of LDH to maintain cell
processes despite the cold.
Homeostasis in ectotherms: Regulate blood concentrations
1) Freeze intolerant ectotherms: Avoid freezing
• Behavioural avoidance
• Production of antifreeze compounds: Slows ice crystal formation
• High concentrations of glucose and glycerol can limit imbalance and avoid ice freezing in the ICF • Supercooling: Pure water can be cooled to below zero degrees without freezing
Antifreeze compounds stabilize super-cooled state by binding to ice crystals to stop formation.
Only works at very low winter temperatures.
• Dessication resistant eggs laid to hatch when weather warms while adult dies
2) Freeze tolerant ectotherms: Promote controlled freezing.
3) Adrenaline also turns on the synthesis of antifreeze compounds
Allows tells liver to convert glycogen to glucose
• Ice nucleating agents: Controls where ice crystals form on the body so they do not form on
critical tissues or membranes
Ice crystals in ECF form reducing water outside cells and increases osmotic pressure,
shrinking cell due to dehydration and resulting in ice crystals possibly puncturing important
membranes or tissues if formed inside cells or cytosol.
Increased glucose acts as an antifreeze Formation of ice in large hollow cavities is better
because there is more room for the water to freeze as it expands.
• Freezing point depression:
1) Colligative antifreezes: Lower freezing point of body fluids by INCREASING solute
2) Non-colligative antifreezes: Lowers freezing point of body fluids using specialized chemical
properties. Not dependent on solute concentrations.
Maintenance of constant membrane fluidity regardless of tissue temperature.
1) Too hot: Increase in saturated fats to increase fluidity of membranes
Longer chained fatty acids
Higher freezing point
2) Too cold: Increase in unsaturated fats to decrease membrane fluidity
Shorter chained fatty acids
Lower freezing point
1) Acute: Immediate
Example: Daily fluctuation in temperature
Biological response: Physiological responses such as sweating
2) Chronic: Change in physiology to adjust set points because of prolonged changes in the
Example: Seasonal fluctuation in temperature
Biological response: Migration, acclimatization or death
3) Evolutionary: Multi-generational
Acute (Immediate) Chronic(Physiology change in Evolutionary
response to prolonged periods of (Over
environmental conditions) generations)
Molecular ?? Release of glucagon increases Adaptations in
breakdown of fatty acids haemoglobin
related to cold and
diving Cellular/Tissue Counter current Decrease metabolism More fat and
exchange regulation feathers than other
Organism Rock back on heels, Preening to maintain feather insulation Large bodies with
tuck in flippers small appendages
Population Huddle together Breeding season in large colonies ??
Assessment of changes:
1) Acclimation: Climate change in a laboratory setting
2) Acclimatization: Natural environment changes environment resulting in a response in the wild.
Reversible adjustments of organisms to chronic stresses
Adaptive trait of huddling allows penguins to decrease surface area to volume ratio to minimize
3) Adaptation: Evolution across generations through natural selection
Q10: Divide rate at temperature T by the rate at ten degrees above or below temperature T
Provides index of how much oxygen uptake or other rate processes change with temperature
Can measure oxygen intake, enzyme activity rate, swimming rate, breathing rate
Range of Tolerance: The range an organism can tolerate while maintaining functional capacity. Many
Arctic organisms can tolerate lower temperatures in winter and higher temperatures in summer.
Interstitial Fluid: Fluid around cells which allow cells not in contact with the environment to exchange
• Hypertonic solutions: Cause cells to shrink
• Hypotonic solutions: Cause cells to swell
Regional Hetherothermy: When arteries give up warmed blood to veins, sending cooled blood to
vascularized limbs to avoid sending cold blood to key organs.
Polar bear DNA mitochondrial assessments: Low genetic variation indicating a population bottleneck
at some point since the polar bear species is very old.
1) Absolute Metabolic Requirements: Increase with increasing body size
2) Relative metabolic requirements: Decrease with increasing body size because of lowered
efficiency in exchange with environment. Smaller animals require more food, oxygen per gram.
Surface Area to volume ratio:
Amount of surface area exposed to environment relative to the total volume of the object.
• Increasing body size means a decreasing surface area to volume ratio
• Compensates for this by harbouring organs with folded membranes to increase surface area
• Decreasing body size means an increasing surface area to volume ratio
Disparity: Refers to how physically different species are from each other
Diversity: Measure of the number of different species
Variation: Refers to different traits that are capable of being passed on to an individual's offspring that
arose from genetics or the environment. This results in different features and/or different genes within the
same species, and thus variation. The best example I can think of is humans; with the exception of
identical twins, we all look different and ~1% of our genes are different.
Variant Proportion Changes
Mutation: New genetic variation Genetic drift: Changes due to chance.
Founder Effect: Species become genetically isolated, reducing variation.
Population Bottleneck: Sudden even reduces variation within a po