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Questions and Answers
What type of organism relies on external sources of body heat?
Why do fairy penguins move into the water to cool down?
What physical feature of the Australian fur seal helps reduce heat loss?
Why does the wombat slow its metabolism on hot days?
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Which behavior do red kangaroos exhibit during hot midday?
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What does the mountain pygmy possum do to reduce the surface area exposed to the cold?
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What mechanism do platypuses use to regulate the temperature of their extremities before the blood reaches the heart?
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Why do stomata need to be open in plants?
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What purpose do the white hairs on leaves serve?
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How do eucalyptus leaves adapt to reduce water loss?
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Why do some plants shed leaves?
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Study Notes
Thermoregulation
- Endotherms: organisms that generate heat through metabolic processes to maintain body temperature, despite environmental temperature variations (e.g., warm-blooded organisms)
- Ectotherms: organisms that rely on external sources of body heat (e.g., cold-blooded organisms)
Behavioral Thermoregulation
- Red kangaroos: sit in a shaded position to expose a large surface area of their body to shade during hot midday
- Fairy penguins: move into water to cool down or huddle together to reduce surface area exposed to cold
- Mountain pygmy possums: curl up to reduce exposed surface area to conserve heat in cold temperatures
- Bilbies: retreat to burrows to escape cold temperatures
Structural Thermoregulation
- Fairy penguins: lift feathers to trap a layer of air for insulation against cold; flatten feathers to trap a smaller layer of air in heat
- Australian fur seal: has a layer of thick fat (blubber) to reduce heat loss
- Bilbies: have large, thin ears with a high surface area to volume ratio for rapid heat loss
Physiological Thermoregulation
- Wombats: slow metabolism to 1/3 of normal rate on hot days to reduce heat produced by cell metabolism
- Mountain pygmy possums: hibernate during cold winters to reduce energy required to keep body warm
- Platypuses: use counter-current exchange in extremities to heat cool blood in veins before it reaches the heart
Maintaining Water Balance in Plants
- Water loss in plants occurs through transpiration (evaporation from stomata)
- Stomata need to be open for gaseous exchange and evaporative cooling, but this increases water loss
- Plants with limited water access balance water loss with gaseous exchange and evaporative cooling to avoid dehydration
Adaptations for Water Conservation in Plants
- Leaves with:
- Waxy, thick cuticles that prevent water loss through evaporation
- White hairs to reflect sunlight and reduce evaporation
- Vertical orientation (e.g., eucalyptus) to reduce exposed surface area
- Reduced surface area (e.g., cacti with spine-like leaves)
- Thick waxy cuticle to prevent evaporation and reflect heat
- Some plants shed leaves to reduce water loss
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Description
Test your knowledge on the differences between endotherms and ectotherms, and how they regulate body temperature. Explore the behaviors exhibited by different organisms to cope with temperature changes in their environments.
