Thermoregulation in Ectotherms

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Thermoregulation in Ectotherms

• Benny Cheong
• 3I305

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Ectotherms

• Ectotherms are animals which regulate their body
  temperature via external means.
• These animals are reliant on the environment for
  the gain or loss of heat.
• As such, they need behavioral and structural
  adaptations for regulation of heat.

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Adaptations to Warm Up

• As ectotherms need to gain heat from the
  environment, they display certain behaviour which
  allows them to warm up.
• Basking in the Sun is the most commonly seen
  method, especially with the terrestrial reptiles,
  amphibians and arthropods, as the Sun is the main
  source of the Earths heat.

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Marine Iguana

• The marine iguana inhabits only the Galapagos
  Islands, and it is the only lizard to have
  evolved to forage at sea.
• They occupy the barren rocks by the shore which
  are devoid of food, as such, they mainly feed on
  seaweed, found in the sea around them.
• Marine Iguanas in Life in Cold Blood by
  Attenborough http//www.youtube.com/watch?v6vANM
  V23XMw

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Marine Iguana

• The Challenge The sea around the Galapagos
  Islands remains cold all year round. Marine
  iguanas must thus gain enough body heat for them
  to survive the chilling temperatures of the sea
  (15-16oC).

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Marine Iguana

• The Solution The marine iguana exploits the
  rocks they live on to increase their body
  temperature rapidly.
• They gather at the uppermost rocks (which are the
  warmest) near the shore and bask in the sun for
  approximately half-an-hour before entering the
  seas to forage for seaweed.

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Marine Iguana

• The Physics behind the solution
• The iguanas conduct heat through conduction and
  radiation.
• Conduction The iguanas conduct heat from the hot
  rocks. As heat is conducted more quickly through
  solids via lattice vibration, they are able to
  conduct heat rapidly.
• Radiation Heat energy from the Sun is
  transferred by EM waves to the iguana. Marine
  iguanas are also black, increasing heat absorbed
  via radiation as black surfaces are good
  absorbers of radiant energy.

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Radiation
Conduction
Image Credits http//www.photostuff.org/galapagos
.html
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Namaqua Chameleon

• The Namaqua Chameleon lives in the extreme
  conditions of the desert.
• Living solitarily, they spend much time searching
  for mates.
• The Challenge To heat up as quickly as possible
  in the morning, the only time of the day it is
  cool enough for them to be active.
• Namaqua Chameleon in Life by BBC
  http//www.youtube.com/watch?vwPjgfEzmhAs

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Namaqua Chameleon

• The Solution The Namaqua Chameleon uses its
  colour changing abilities.
• The side of the body facing the sun becomes
  darker-coloured.
• The side of the body facing away from the sun
  becomes lighter-coloured.

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Namaqua Chameleon
Image Credits http//www.johanmarais.co.za/Lizard
sChameleons/chamaeleonamaquensisnamaquachameleon.h
tml
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Namaqua Chameleon

• The Physics behind the solution
• Darker-coloured surfaces are good absorbers of
  radiant energy from the sun.
• As such, making the side facing the sun
  darker-coloured increases the heat energy
  absorbed from the sun, allowing it to warm up
  quickly
• Lighter-coloured surfaces are poor emitters of
  radiant energy.
• As such, making the other side white decreases
  the heat energy lost from the chameleon by
  reducing the heat emitted.

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Adaptations to Reduce Heat

• Since ectotherms have no control over how much
  heat they gain, they would overheat and perish if
  they gain too much thermal energy.
• Hence, they need adaptations to enable them to
  cool down/reduce heat gain.

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Crocodile

• Crocodiles often lies near the river bank with
  its mouth wide open in the heat of the afternoon,
  remaining almost motionless.

Image Credits http//the-i.org/photos/animals/9
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Crocodile

• The Physics behind their behaviour
• The greater the exposed surface area, the more
  heat lost through radiation.
• As such, by opening its mouth and increasing its
  exposed surface area, the crocodile increases the
  rate of heat loss.
• Increase the rate of water vapour escaping from
  its body.
• As water absorbs thermal energy from the
  crocodile when it changes into water vapour, the
  body temperature of the crocodile is reduced.

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Sidewinder Snake

• Just like the Namaqua Chameleon, the Sidewinder
  also lives in the extremely hot desert.
• They are also active during parts of the day when
  temperatures are relatively low.
• The Challenge To prevent themselves from
  overheating in the desert.
• http//www.youtube.com/watch?vJyXNBAHu32o

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Sidewinder Snake

• The Solution The sidewinder moves in a manner
  which obtained it its name- sidewinding, moving
  via side-to-side motions across the sand.

Image Credits http//en.wikipedia.org/wiki/FileC
rotalus_scutulatus_03.jpg
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Sidewinder Snake

• The Physics behind The Solution
• Recall the formula for the rate of conduction
• A in the formula represents the cross-sectional
  surface area between two objects.

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Sidewinder Snake
Parts of body coming into contact with sand
circled in yellow- Only two parts of snake come
into contact with sand at any point in time.
Image Credits http//en.wikipedia.org/wiki/FileC
rotalus_scutulatus_03.jpg
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Sidewinder Snake

• The Physics behind The Solution
• Through sidewinding, at any one point in time,
  only two small sections of the snakes body comes
  into contact with the desert sand, reducing the
  cross-sectional surface area A.
• As such, Q/t is reduced greatly, preventing the
  sidewinder from conducting too much heat.

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Credits

• BBC Life in Cold Blood (2008) by David
  Attenborough
• BBC Life (2009)
• Animal Planet
• http//heatransfer.wikispaces.com/
• Information on this PowerPoint obtained by data
  from the videos coupled with application of
  Physics concepts learnt about Heat Transfer on
  Wikispaces.