Endothermy and ectothermy
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Endothermy and Ectothermy. Ch. 6.7, Bush. Outline. Effects of temperature on life Thermoregulation Ecological aspects of thermoregulation. Outline. Effects of temperature on life Thermoregulation Ecological aspects of thermoregulation. Effects of extreme temperatures.

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Outline

  • Effects of temperature on life

  • Thermoregulation

  • Ecological aspects of thermoregulation


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Outline

  • Effects of temperature on life

  • Thermoregulation

  • Ecological aspects of thermoregulation


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Effects of extreme temperatures

  • Cold -- the effects of freezing

    • physical damage to structures caused by the formation of ice; the membrane bound structures are destroyed or damaged.

  • Heat

    • inadequate O2 supply for metabolic demands (especially in areas where O2 is low, such as water)

  • Heat and Cold

    • reduced activity or denaturation of proteins -- the inactivation of certain proteins with the result that metabolic pathways are distorted.



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Body Temperature

  • Law of Tolerance:

    • for most requirements of life, there is an optimal quantity, above and below which the organism performs poorly

  • There is much variation in the range of temperatures that a species can tolerate


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Outline

  • Effects of temperature on life

  • Thermoregulation

  • Ecological aspects of thermoregulation


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Thermoregulation

  • maintenance of internal temperature within a range that allows cells to function efficiently

  • Two main types

    • ectothermy

    • endothermy



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Ectothermy

  • an animal that relies on external environment for temperature control instead of generating its own body heat

  • “cold-blooded”

  • e.g., invertebrates, reptiles, amphibians, and most fish

  • the majority of animals are ectotherms


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Metabolism and temperature

  • ectotherms cannot move very much unless the ambient temperature allows

  • roughly, for each 10 degree increase in temperature, there is a 2.5 increase in metabolic activity


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Ectothermy

Desert iguanas are active only when ambient

temperature is close to optimal for them



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Endothermy

  • a warm-blooded animal that controls its body temperature by producing its own heat through metabolism

  • evolved approximately 140 mya

  • E.g., birds, mammals, marsupial, some active fish like the great white shark and swordfish



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Outline

  • Endothermy versus ectothermy

  • Behavioural adaptations to thermoregulation

  • Physiological adaptations to thermoregulation


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Behavioural adaptations for thermoregulation

  • animals often bathe in water to cool off or bask in the sun to heat up


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Shivering, sweating, and panting

  • honeybees survive harsh winters by clustering together and shivering, which generates metabolic heat

  • Inefficient – 75% of energy is lost in mechanical movement


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Torpor

  • metabolism decreases

  • heart and respiratory system slow down

  • body temperature decreases

  • conserves energy when food supplies are low and environmental temps are extreme

E.g., hummingbirds on cold nights


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Hibernation

  • Long-term torpor

  • adaptation for winter cold and food scarcity

  • E.g., ground squirrels


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Aestivation

  • summer torpor

  • adaptation for high temperatures and scarce water supplies

  • E.g., mud turtles, snails


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Endothermy and the evolution of sleep?

  • evolutionary remnant of torpor of our ancestors

  • 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


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Colour and Posture

  • Change coloration (darker colors absorb more heat)

    • E.g., lizards, butterflies, crabs

  • Posture:

    • Change shape (flatten out to heat up quickly)

    • Orientation changes


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Chemical adaptations

  • Many Canadian butterflies overwinter here and hibernate

  • they produce sugar-like substances as antifreeze

  • E.g., Mourning Cloak butterfly


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Outline

  • Effects of temperature on life

  • Thermoregulation

  • Ecological aspects of thermoregulation


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Advantages & Disadvantages of Endothermy

  • 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

  • Disadvantage:

    • energy expensive

      • an endotherm will have to eat much more than an ectotherm of equivalent size


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    Where can endotherms thrive?

    • Higher latitudes and deserts

    • Terrestrial environments have more variation in daily and seasonal temperature which contributes to more endotherms in terrestrial environments

    • endotherms (mammals and birds) generally outcompete ectotherms if they are after the same food source


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    Size and thermoregulation

    • Small mammals (such as mice and shrews) have a greater dependence on internally-generated heat than big mammals (such as elephants and hippos)

    • 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)



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    Ectothermy vs. endothermy

    • Many more ectotherms are small in size versus endotherms

    • Ectotherms typically have no insulation

    • Posture is different


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    Where do ectotherms thrive?

    • Where food items are:

      • scarce

      • small

    • In environments low in O2


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    Ecosystem functioning and ectothermy

    • Production Efficiency:

      -can be seen as the ratio of assimilation between trophic levels

      = biomass of predator

      biomass of food species

    • Ectotherms are more efficient than endotherms (up to 15% versus 7%)


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    Thermoregulation and food chains

    • Endotherms are often the top predator in food chains

    • Food chains with lots of ectotherms are often longer in length


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    Summary

    • 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

    • Both endotherms and ectotherms have a variety of behavioural and physiological adaptations to deal with environmental extremes


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    Climate

    Ch. 4, Bush


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    Outline

    • Climate and ecology

    • Solar energy and air circulation

    • Oceanic influences

    • Cycles of climate change


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    Outline

    • Climate and ecology

    • Solar energy and air circulation

    • Oceanic influences

    • Cycles of climate change




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    Outline

    • Climate and ecology

    • Solar energy and air circulation

    • Oceanic influences

    • Cycles of climate change


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    Solar energy

    • Solar energy distribution is not balanced across the globe in

      • intensity

      • constancy

    • Together, these differences explain the distribution of tropical and temperate climates


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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


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    Intensity of solar energy

    more energy per

    square meter in

    the tropics than

    at the poles



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    Differences in Day Length

    • caused by the constant tilt of Earth as it orbits around the sun

    • the reason why temperate environments have four seasons while tropical environments do not


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    Heat and air circulation

    • The disparity in energy input across the globe drives all our weather systems

    • This is because heat energy must flow from warm to cold


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    Hadley cells – the effect of heat transfer

    • Hot air rises and, as it rises, it cools

    • Cool air cannot hold as much moisture as heated air, so it rains

    • This cool, dry air must go somewhere so it pushes towards the poles, where it slows and descends

    • As it descends, it is warmed



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    Hadley cells and climate

    • The downdraft of hot dry air causes the formation of the desert regions of Earth:

    E.g.,

    Sahara

    Sonoran

    Australian

    Gobi

    Atacama


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    Equatorial rainforest

    • Average temp:

      • 20-34 ° C

    • Average rainfall:

      • 124-660 cm


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    Deserts – caused by downdrafts of hot, dry air

    • Average temp:

      • 20 to 25° C

    • Average rainfall:

      • under 15 cm a year





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    Movement of the ITCZ

    • responsible for wet and dry seasons of the tropics


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    Seasonality and ITZC

    • In temperate latitudes, seasonality is closely related to day length

    • In tropical latitudes, seasonality is closely associated with rainfall.

    • Tropical rainfall influences:

      • Germination, flowering, and fruiting in plants

      • Breeding, feeding, migration, and life history strategies in animals


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    Movement of the ITCZ

    • hurricanes are spawned at the most northerly edge of the ITCZ


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    Outline

    • Climate and ecology

    • Solar energy and air circulation

    • Oceanic influences

    • Cycles of climate change


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    Ocean and heat transfer

    • water takes more energy to heat than land or air


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    Water moderates climate

    The ocean makes coastal regions have

    milder climates



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    Gulf Stream

    • Gulf Stream comes up from Gulf of Mexico, across Atlantic Ocean, to moderate climate of Western Europe


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    Effects of the Gulf Stream

    • The Gulf Stream makes snow rare in London but common in Toronto:

      Altitude Ave. Temp (Jan)

      London 51 N 6 C

      Toronto 43 N -4 C


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    Earth’s rotation causes the Coriolis effect

    • Both objects A and B make one rotation on the Earth’s axis per day

    • An object located at the equator is rotating faster than an object at the pole


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    Coriolis Effect

    • Earth rotates eastward making all object deflect in this direction

    • http://www.eoascientific.com/campus/earth/multimedia/coriolis/view_interactive





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    Outline

    • Climate and ecology

    • Solar energy and air circulation

    • Oceanic influences

    • Cycles of climate change


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    Cycles of Climate Change

    • There are two main cycles of climate change that are natural:

      • El Nino Oscillation

      • Glaciation


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    Gulf Stream

    • Gulf Stream comes up from Gulf of Mexico, across Atlantic Ocean, to moderate climate of Western Europe


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    Gulf Stream causes 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



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    El Nino Southern Oscillation (ENSO)

    • A decrease in wind speed of the Trade Winds off Tahiti is observed every 3-7 years

    • causes less warm surface water being piled up around Indonesia

    • Instead, warm surface water piles up off Peru in South America





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    El Nino and ecology

    • Evidence indicates that Galapagos marine iguanas actually shrink during El Nino events

    • El Nino reduces food supply (green and red algae)


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    El Nino and Insect outbreaks

    • In a dry lowland forest near Panama's Pacific coast, moth larvae devoured 250 percent more leaf material than usual

    • Bartonellosis, an insect-borne disease highly fatal to humans, are closely related to the climate event El Niño


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    Glacial and Interglacial periods

    • In the last 4 million years there have been at least 22 ice ages (= glacial periods)

    • Warm periods between glacial periods (interglacial) periods have been brief


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    In general…

    • 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)


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    Glaciation and water level changes

    • About 3 million years ago, a major Ice Age began when the sea level dropped enough to expose the Isthmus of Panama

    • 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

    Glaciation and land changes


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    Last glacial period ended 11,000 years ago

    • 90% of last 2 million years has been glacial

    • For the last 10,000 years, plants and animals have been living in an unusually warm environment


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    Summary

    • 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

  • Weather and climate fluctuate over relatively short time frames and relatively long ones


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