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Endothermy and Ectothermy
Outline
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Effects of temperature on life
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Thermoregulation
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Ecological aspects of thermoregulation
Ch. 6.7, Bush
Outline
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Effects of temperature on life
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Thermoregulation
Effects of extreme temperatures
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Cold -- the effects of freezing
– physical damage to structures caused by the formation of
ice; the membrane bound structures are destroyed or
damaged.
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Heat
– inadequate O2 supply for metabolic demands (especially in
areas where O2 is low, such as water)
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Ecological aspects of thermoregulation
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Heat and Cold
– reduced activity or denaturation of proteins -- the inactivation
of certain proteins with the result that metabolic pathways
are distorted.
Optimal temperature for enzyme
functioning
Body Temperature
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Law of Tolerance:
– for most requirements of life, there is an
optimal quantity, above and below which
the organism performs poorly
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There is much variation in the range of
temperatures that a species can
tolerate
Outline
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Effects of temperature on life
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Thermoregulation
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Ecological aspects of thermoregulation
Endothermy versus ectothermy
Metabolism and temperature
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ectotherms cannot move very much
unless the ambient temperature allows
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roughly, for each 10 degree increase in
temperature, there is a 2.5 increase in
metabolic activity
Thermoregulation
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maintenance of internal temperature
within a range that allows cells to
function efficiently
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Two main types
– ectothermy
– endothermy
Ectothermy
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an animal that relies on external environment
for temperature control instead of generating
its own body heat
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“cold-blooded”
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e.g., invertebrates, reptiles, amphibians,
and most fish
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the majority of animals are ectotherms
Ectothermy
Desert iguanas are active only when ambient
temperature is close to optimal for them
Ectothermic animals
Endothermy
Endothermic animals
a warm-blooded animal that controls its body
temperature by producing its own heat
through metabolism
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evolved approximately 140 mya
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E.g., birds, mammals, marsupial, some active
fish like the great white shark and swordfish
Outline
Behavioural adaptations for
thermoregulation
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animals often bathe
in water to cool off
or bask in the sun to
heat up
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Endothermy versus ectothermy
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Behavioural adaptations to
thermoregulation
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Physiological adaptations to
thermoregulation
Shivering, sweating, and panting
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honeybees survive
harsh winters by
clustering together and
shivering, which
generates metabolic
heat
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Inefficient – 75% of
energy is lost in
mechanical movement
Torpor
Hibernation
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metabolism decreases
heart and respiratory
system slow down
body temperature
decreases
conserves energy when
food supplies are low
and environmental
temps are extreme
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Long-term torpor
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adaptation for winter
cold and food scarcity
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E.g., ground squirrels
E.g., hummingbirds on cold nights
Endothermy and the evolution of
sleep?
Aestivation
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summer torpor
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adaptation for high
temperatures and
scarce water supplies
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Colour and Posture
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Change coloration
(darker colors absorb
more heat)
– E.g., lizards, butterflies,
crabs
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E.g., mud turtles,
snails
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evolutionary remnant of torpor of our
ancestors
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the body needs sleep in order to offset
the high energy costs of endothermy:
– When animals fall asleep their metabolic
rates decrease by approximately ten
percent
Chemical adaptations
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Many Canadian butterflies
overwinter here and
hibernate
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they produce sugar-like
substances as antifreeze
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E.g., Mourning Cloak
butterfly
Posture:
– Change shape (flatten
out to heat up quickly)
– Orientation changes
Outline
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Effects of temperature on life
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Thermoregulation
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Ecological aspects of thermoregulation
Advantages & Disadvantages of
Endothermy
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Advantages:
– external temperature does not affect their
performance
– allows them to live in colder habitats
– muscles can provide more sustained power
– e.g., a horse can move for much longer periods than
a crocodile can
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Disadvantage:
– energy expensive
– an endotherm will have to eat much more than an
ectotherm of equivalent size
Where can endotherms thrive?
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Higher latitudes and deserts
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Terrestrial environments have more variation
in daily and seasonal temperature which
contributes to more endotherms in terrestrial
environments
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endotherms (mammals and birds) generally
outcompete ectotherms if they are after the
same food source
Surface area to volume ratios
Size and thermoregulation
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Small mammals (such as mice and shrews)
have a greater dependence on internallygenerated heat than big mammals (such as
elephants and hippos)
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leads to:
– presence of insulation (fur - large mammals
generally have less hair)
– voracious appetites of small mammals (a shrew
eats more per unit body weight than an elephant
does)
Ectothermy vs. endothermy
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Many more
ectotherms are
small in size versus
endotherms
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Ectotherms typically
have no insulation
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Posture is different
Where do ectotherms thrive?
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Where food items
are:
Ecosystem functioning and ectothermy
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Production Efficiency:
-can be seen as the ratio of assimilation between
trophic levels
– scarce
– small
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In environments
low in O2
Thermoregulation and food chains
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Endotherms are
often the top
predator in food
chains
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Food chains with
lots of ectotherms
are often longer in
length
= biomass of predator
biomass of food species
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Ectotherms are more efficient than endotherms
(up to 15% versus 7%)
Summary
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Endothermic animals regulate their body heat
to stay within the optimal range for
performance while the temperature of
ectothermic animals fluctuates with that of the
surrounding environment
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Both endotherms and ectotherms have a
variety of behavioural and physiological
adaptations to deal with environmental
extremes
Climate
Ch. 4, Bush
Outline
Outline
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Climate and ecology
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Climate and ecology
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Solar energy and air circulation
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Solar energy and air circulation
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Oceanic influences
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Oceanic influences
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Cycles of climate change
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Cycles of climate change
Climate affects ecology
Temperature and precipitation
Outline
Solar energy
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Climate and ecology
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Solar energy and air circulation
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Oceanic influences
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Cycles of climate change
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Solar energy distribution is not
balanced across the globe in
– intensity
– constancy
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Together, these differences explain the
distribution of tropical and temperate
climates
Intensity of Solar energy
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Intensity of solar energy
Solar energy is more intense at lower
latitudes (that is, closer to the equator)
because:
• the “footprint” of the beam of energy is
smaller at tropical latitudes
• beams have shorter passage through
the atmosphere
Differences in daylength
Heat and air circulation
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The disparity in energy input across the
globe drives all our weather systems
This is because heat energy must flow
from warm to cold
more energy per
square meter in
the tropics than
at the poles
Differences in Day Length
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caused by the constant tilt of Earth as it
orbits around the sun
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the reason why temperate
environments have four seasons while
tropical environments do not
Hadley cells – the effect of heat
transfer
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Hot air rises and, as it rises, it cools
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Cool air cannot hold as much moisture as
heated air, so it rains
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This cool, dry air must go somewhere so it
pushes towards the poles, where it slows and
descends
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As it descends, it is warmed
Hadley cells
Hadley cells and climate
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The downdraft of hot dry air causes the
formation of the desert regions of Earth:
E.g.,
Sahara
Sonoran
Australian
Gobi
Atacama
Deserts – caused by downdrafts
of hot, dry air
Equatorial rainforest
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Average temp:
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– 20-34 ° C
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– 20 to 25° C
Average rainfall:
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– 124-660 cm
Movement of the thermal equator
Average temp:
Average rainfall:
– under 15 cm a year
Hadley cells
Intertropical convergence zone
(ITCZ)
Movement of the ITCZ
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Seasonality and ITZC
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responsible for wet and dry seasons
of the tropics
Movement of the ITCZ
In temperate latitudes, seasonality is closely
related to day length
In tropical latitudes, seasonality is closely
associated with rainfall.
Tropical rainfall influences:
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hurricanes are
spawned at the
most northerly
edge of the
ITCZ
– Germination, flowering, and fruiting in plants
– Breeding, feeding, migration, and life history
strategies in animals
Outline
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Climate and ecology
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Solar energy and air circulation
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Oceanic influences
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Cycles of climate change
Ocean and heat transfer
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water takes more energy to heat than
land or air
Water moderates climate
Intertropical convergence zone
(ITCZ)
The ocean makes coastal regions have
milder climates
Gulf Stream
Effects of the Gulf Stream
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Gulf Stream comes
up from Gulf of
Mexico, across
Atlantic Ocean, to
moderate climate of
Western Europe
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The Gulf Stream makes snow rare in
London but common in Toronto:
Altitude
Ave. Temp (Jan)
London 51 οN
Toronto 43 οN
Earth’s rotation causes the Coriolis effect
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Both objects A and
B make one rotation
on the Earth’s axis
per day
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An object located at
the equator is
rotating faster than
an object at the
pole
6 οC
-4 οC
Coriolis Effect
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Earth rotates
eastward making all
object deflect in this
direction
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http://www.eoascien
tific.com/campus/ea
rth/multimedia/coriol
is/view_interactive
Coriolis Effect and air circulation
Trade winds and the Gulf Stream
Major water currents
Outline
Cycles of Climate Change
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There are two main cycles of climate
change that are natural:
– El Nino Oscillation
– Glaciation
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Climate and ecology
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Solar energy and air circulation
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Oceanic influences
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Cycles of climate change
Gulf Stream
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Gulf Stream comes
up from Gulf of
Mexico, across
Atlantic Ocean, to
moderate climate of
Western Europe
Gulf Stream causes ocean currents
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Ocean currents
Warm water evaporates
Ocean becomes more salty
Loses heat as it moves towards pole
Water becomes more dense as it becomes
more salty and/or loses heat
This dense, cold, salty water sinking off the
coast of Greenland sets in motion an
immense flow of water through the oceans
El Nino Southern Oscillation (ENSO)
El Nino Southern Oscillation (ENSO)
A decrease in wind speed of the Trade
Winds off Tahiti is observed every 3-7
years
v causes less warm surface water being
piled up around Indonesia
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Peru in South America
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El Nino Effects
El Nino and Hurricane Pauline
El Nino and ecology
El Nino and Insect outbreaks
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In a dry lowland forest
near Panama's Pacific
coast, moth larvae
devoured 250 percent
more leaf material than
usual
Bartonellosis, an insectborne disease highly
fatal to humans, are
closely related to the
climate event El Niño
In general…
In the last 4 million years there have
been at least 22 ice ages (= glacial
periods)
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Warm periods between glacial periods
(interglacial) periods have been brief
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Glaciation and water level changes
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El Nino reduces
food supply (green
and red algae)
Glacial and Interglacial periods
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Evidence indicates
that Galapagos
marine iguanas
actually shrink
during El Nino
events
Interglacial periods
– mild in temperature and with more precipitation-periods of diversification and range expansion in
organisms adapted to warmer conditions
Glacial periods
– fragmentation of plant and animal ranges (except
for arctic or cold-desert adapted organisms)
Glaciation and land changes
About 3 million years ago, a major Ice Age
began when the sea level dropped enough to
expose the Isthmus of Panama
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The Panama land bridge made possible one
of the great events in biology-the interchange
of species of two continents.
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Moving into South
America were:
– fox; deer; tapir;
spectacled bear; spotted
cat; llama.
Moving into North
America were:
– parrot; toucan,
armadillo; giant sloth;
howler monkey; anteater;
and capybara
Last glacial period ended 11,000
years ago
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90% of last 2 million
years has been
glacial
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For the last 10,000
years, plants and
animals have been
living in an
unusually warm
environment
Summary
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Most weather patterns are ultimately caused
by the fact that equatorial regions receive
more solar energy than polar regions
– Location of tropical, temperate and desert
ecosystems
– Wind and water currents
– Seasonality of the tropics
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Weather and climate fluctuate over relatively
short time frames and relatively long ones