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Lecture 3

Biology 2483A Lecture Notes - Lecture 3: Skipjack Tuna, Acclimatization, Frostbite


Department
Biology
Course Code
BIOL 2483A
Professor
Hugh Henry
Lecture
3

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Abundance Across Environmental Gradients
Climate and Aspen Distribution
Physiological Ecology Study of interactions between organisms and the physical environments that influence their
survival and persistence.
Deviations from the optimum reduce the rate of the process.
Physiological processes have optimal conditions for function.
Stress - environmental change results in decreased rate of physiological processes, lowering the potential for
survival, growth, or reproduction.
Environmental Control of Physiological Processes
Availability of energy and resources - impacts
growth and reproduction.
1.
Extreme conditions can exceed tolerance limits
and impact survival.
2.
The physical environment influences an organism's
ecological success in two ways
Energy supply can influence an organism's ability to
tolerate environmental extremes.
The actual geographic distribution of a species is also
related to other factors, such as disturbance and
competition.
Because plants don't move, they are good
indicators of the physical environment.
A species' climate envelope is the range of
conditions over which it actually occurs.
Example: Aspen distribution can be predicted
based on climate. Low temperatures and drought
affect reproduction and survival.
Lecture 3: Coping with Environmental Variation -
Temperature and Water
Monday, September 21, 2015
10:32 PM
Lecture Slides Page 1

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Short-term, reversible process
Acclimatization to high elevations involves higher breathing rates, greater production of red blood cells, and
higher pulmonary blood pressure.
Adjusting to stress through behavior or physiology.
Acclimatization
Individuals with traits that enable them to cope with stress are favoured. Over time, these genetic traits
become more frequent in the population.
Over time, natural selection can result in adaptation of a population to environmental stress.
Organismal Responses to Stress
Populations with adaptations to unique environments.
Ecotypes can eventually become separate species as populations diverge and become reproductively isolated.
Environmental temperatures vary greatly throughout the biosphere.
Survival and functioning of organisms is strongly tied to their internal temperature.
Lower limits are determined by temperature at which water freezers in cells (-2 to -5 C)
Some archaea and bacteria in hot springs can function at 90 C.
Ecotypes
Temperature Ranges for Life on Earth (internal body temperature)
Start out a high level of performance
Performance goes down once stress hits
Eventually over generations, populations will be
better adapted to the new stress and have high level
of performance again.
Acclimatization causes better performance
Giant ears = good for hot days = frost bite in cold
days - easier to be seen by predators.
Acclimatization and adaptation require investments of
energy and resources, representing possible trade-offs
with other functions that can affect survival and
reproduction.
Endotherms have a together temperature range in
which they can maintain body that.
Plants maintain their body heat over a much larger
range .
Metabolic reactions are catalyzed by enzymes,
which have narrow temperature ranges for optimal
function. High temperature destroys enzymes
function (denatured).
Bacteria in hot springs - enzymes stable to 100
degrees; Antarctic fish and crustaceans- enzymes
function at -2 degrees; soil microbes active at
temperatures as low as -5 degrees.
Some species produce different forms of enzymes
(isozymes) with different temperature optima that
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Regulate body temperature through energy exchange with the external environment.
Surface area to volume ratio of the body is an important factor in exchanging energy with the environment.
A larger surface area allows greater heat exchange, but makes it harder to maintain internal temperature.
Small aquatic ectotherms remain the same temperature as the water
Some large ectotherms can maintain higher body temperature.
Ectotherms
function at -2 degrees; soil microbes active at
temperatures as low as -5 degrees.
Some species produce different forms of enzymes
(isozymes) with different temperature optima that
allow acclimatization to changing conditions.
Temperature also affects the properties of cell
membranes, which are composed of two layers of
lipid molecules.
At low temperatures, these lipids can solidify,
embedded proteins can't function, and the cells
leak metabolites.
Plants that thrive at low temperatures have high
proportions of unsaturated lipids (with double
bonds) in their cell membranes.
Unsaturated lipids don't line up as well so they
don't solidify as quickly
Example: Skipjack Tuna
Skipkjack tuna use muscle activity and heat
exchange between blood vessels to maintain a
body temperature 13 degrees warmer than the
surrounding seawater.
Many terrestrial ectotherms can move around to adjust
temperature.
Many insects and reptiles bask in the sun to warm up after a
cold night, but this increases predation risk, increasing benefits
of camouflage
Ectotherms in temperate and polar regions must avoid or
tolerate freezing. Avoidance behavior includes seasonal
migration to lower latitudes or to microsites that are above
freezing (e.g. burrows in soil).
Some insects have high concentrations of glycerol, a
chemical that lowers the freezing point of body fluids.
Tolerance to freezing involves minimizing damage associated
with ice formation in cells.
Vertebrates generally do not tolerate
freezing temperatures.
Two frog species live in the Arctic
tundra and can survive winter in a
semi-frozen state.
They freeze overwinter in shallow
Cryonics is the preservation of bodies by
freezing, in hope that they can be brought
back to life in the future.
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