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Chapter 5

BIOLOGY 2F03 Chapter Notes - Chapter 5: European Badger, Eastern Fence Lizard, Richard Levins

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D R.Kajura

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Ecology Chapter 5 – Temperature Relations
Peter Kevan
-Studied sun-tracking behaviour by the arctic flower Dryas Integrifolia
-Found: the flowers acted like a solar reflector by tracking the sun (and thus facing
the sun for days), and kept their temperatures at about 25 degrees C regardless of
the air temperature around them
oThis attracted insects that needed to warm their bodies to the flowers
which the flowers depended on for pollination.
Temperature is a major factor influencing the growth of individuals & the distributions of
-Small differences in temperatures influence performances of enzymes and
-Large differences can cause death or reduced fitness  can lead to extinction
although some may thrive in the new temperatures
5.1 – Microclimates
Macroclimate interacts with the local landscape to produce microclimatic variation in
Macroclimate: determined by the global patterns of air and water circulation among
other forces.
-Ex: what weather networks communicate to us.
Microclimate: climatic variation on a scale of a few km, m, or cm measured over short
periods of time
-Ex: we acknowledge this when deciding if we should stand in the sun (because
it’s cold) or in the shade (because its hot)
-Influenced by landscape features
oEx: altitude, aspect, vegetation, colour of the ground, presence of boulders
and burrows, and physical nature of water.
Altitude and Aspect
Temperatures are lower at higher elevation because:
-Atmospheric pressure decreases with elevation  air rising expands and to keep
the air in motion, it takes kinetic energy from the surrounding air which causes it
to cool.
-Less atmosphere to trap and radiate heat back to the ground
Hills, mountains and valleys create microclimates that don’t happen on flat lands.
-Hills/mountains: shade part of the land
oNorthern hemisphere: shaded areas on the north-facing sides (northern
aspects) which face away from the equator
oSouthern hemisphere: southern aspects face away from the equator
-Supports different types of vegetation
oTemperature & moisture affect plant growth
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Vegetation and Ground Colour
Plants create & respond to microclimates
-Ex: in the desert, there are many different microclimates created by bare land vs
land where there are low shrubs
Colour and cover influence local albedo (reflectivity of the landscape)
-White objects  high albedo
-Dark objects  low albedo
-Green objects (most vegetation)  somewhere in between low and high albedo
-Albedo is a changing factor (ex when snow is present and then melts)
oCan have significant impacts on regional climate
Ex: deforestation (human-induced change)
Presence of Boulders and Burrows
Stones create distinctive microclimates
-Ex: Ligia Oceanica can choose air temperatures ranging from 20-30 degrees
Celsius within a few cm  heated to 34-38 degrees Celsius
Animal burrows usually have temperatures that are more moderate than outside ambient
-Ex: Meles meles (Eurasian badger) constructs burrows (setts) which have an
average temperature fluctuation of less than 1 degree Celsius although the surface
temperature fluctuated by 9 degrees Celsius.
oOrganisms can also change their microclimates  shown because unused
setts were 2.5 degrees Celsius colder than occupied setts
Aquatic Temperatures
Individual locations are thermally stable but differences in topography, distance to land,
and chemical properties contribute to substantial spatial variation in microclimates in an
aquatic system.
Thermally stable because:
-Specific heat capacity is higher in water than air
-When water evaporates, a lot of heat is absorbed by it  latent heat of
-When water freezes, it gives up water to its surroundings  latent heat of fusion
Large aquatic environments have the greatest thermal stability.
Limits to thermal stability:
-Water temperature generally decrease with depth  because of reduced
penetration of solar radiation
Other factors that affect temperature of aquatic environment:
-Riparian Vegetation: grows along rivers and streams which provides shade thus
reducing temperature fluctuations by insulating the stream environment
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Major consequences of temperature change in aquatic environments:
1. Direct effects of altered temperatures on organisms living in the water
2. Effect that the changes have on the amount of dissolved oxygen in the water
-Low oxygen levels are a hazard for organisms in the water
-Cold water holds more dissolved oxygen than warm
5.2 – Evolutionary Trade-Offs
Adapting to one set of environmental conditions generally reduces fitness in other
environments.  stated by Richard Levins
All organisms are adapted to a limited range of environmental conditions partially
because of energy limitations.
The Principle of Allocation
Energy is allocated into different life’s functions (ex reproduction, defense against
disease, growth) which takes energy away from other things
 Richard Levins used math to describe this trade-off  Principle of Allocation
Testing the Principle of Allocation
Researchers: Albert Bennett and Richard Lenski
Organism used: microbial populations (goes through hundreds of generations in a week)
Escherichia coli (E.Coli)
Question: Would an adaptation to low temperature (20°C) be accompanied by a loss of
fitness at a high temperature (40°C)?
-Testing the principle of allocation
Methods: had an ancestral line (no adaptation made) vs a low-temperature selected line
-Compared the two lines fitness in different temperatures
-Fitness measurement: rate of population doubling when the two lines were grown
Major Results (2):
1. Lines grown at 20°C had HIGHER fitness at the 20°C temperature compared to
their ancestors
2. Lines grown at 20°C had a LOWER fitness at the 40°C temperature compared to
their ancestors
Conclusion: supports the principle of allocation
5.3 – Temperature and Performance of Organisms
Most organisms perform best in a fairly narrow range of temperatures
Ecologists study how the environment affects the “performance” of organisms
Victor Shelford  law of toleration
-The abundance and distribution of an animal can be determined by the deviation
between the local conditions and the optimum set of conditions for a species.
-At extreme levels of local conditions, many species are unable to survive whereas
at moderate levels, most organisms thrive.
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