Temperature relations of animals Flashcards
What is an endotherm?
An animal that generates its own body heat e.g., birds & mammals
What is an ectotherm?
An animal that depends almost entirely on ambient heat sources e.g., invertebrates, fish, amphibians, reptiles
What is a heterotherm?
An animal whose heat depends on their regional environments
What is a poikilotherm?
Animal whose body temperature fluctuates with changes in ambient temperature
What is a homeotherm?
Animal who regulates body temperature close to a set point
Nearly all endotherms are homeotherms
What endotherm does not regulate about a set point?
Naked mole rate which is poikilothermic lives in a stable environment
The rate of change of body heat depends on the rates of which
three factors
- Heat production through metabolic means
- Heat gain from environment
- Heat loss to environment
What is basal metabolism?
The basic metabolic processes used to produce heat
What is the metabolic rate?
The sum of all energy-requiring biochemical reactions over a given time interval
What is the basal metabolic rate (BMR)?
The basal metabolic rate
(BMR) is that of an animal that
is at rest, is not digesting, and
is not experiencing stress
What factors influence heat production?
- Behavioural mechanisms e.g., exercise
- Autonomic mechanisms e.g., accelerated metabolism of energy reserves
- Acclimatization (longer term): increase BMR
What are the 4 methods of heat transfer?
- Conduction
- Convection
- Radiation
- Evaporation
What is conduction and what is it affected by?
- Heat transfer between objects in direct contact with each other
- It is affected by surface area and temperature gradient
What is convection?
Transfer of heat contained in a gas or liquid by the movement of the gas or liquid.
- Accelerates heat transfer
- In water it causes rapid cooling
What are the methods of heat transfer?
- Radiation- no direct contact between bodies
- Evaporation- evaporation of liquid needs heat, lost to surface
What does the rate of heat transfer between a body and the
environment depends on?
-Surface area: surface area/g tissue decreases with
increase in body size, therefore small animals lose and
gain heat faster than large ones
- Temperature difference: the closer the body temperature
to that of the environment the less heat is lost or gained
- Heat conducting properties of animal’s surface (“specific
heat conductance”)
What are the heat conducting properties of poikilotherms?
- High heat conductance
- Gain or lose heat rapidly,
- Stay close to environmental temp
What are the heat conducting properties of homeotherms?
- Insulation reduces heat transfer
- Feathers, fur or blubber
- Fur & feathers trap air; (poor heat conductor)
How do autonomic processes regulate heat exchange?
- Modify blood flow to vertebrate skin
- Fluffing of hair/feathers (more air increases insulation)
- Sweating/ panting to increase evaporative cooling
What long term adaptions regulate heat exchange?
Changes in thickness of fur/blubber
How does behaviour regulate heat exchange?
- Animals move to area with suitable temperature e.g., sun or shade
- Posture: curl tightly to reduce heat
exchange, spread out to maximise it
Factors influencing heat production
Regulation of heat exchange
See slide 20 of temperature relations lectures
What do temperature relations of ectotherm depend on?
- Heat from environment
Behavioural thermoregulation of reptiles
Reptiles typically regulate their body temperature behaviourally, by moving to sun or shade to absorb more or less heat
What are the advantages of ectothermy?
- Can invest larger proportion of
energy in growth and reproduction - Need less food.. less time foraging, more time hiding from predators
- Need less water (do not require
water for evaporative cooling
What are the disadvantages of ectothermy?
- Dependent on environment
- Sustained high levels of activity
not possible
Give an example of heterothermy in insects
- In locusts, moths and butterflies
- Warm flight muscles to 40oC before take-off by shivering movements of
flight muscles - Thorax is insulated
How do bees regulate temperature?
- Hive is at constant temp of 35 degrees: fan wings to evaporate water for cooling
-Swarms: shivering for warmth, swarm as dense shape reduces airflow and conserves heat
An example of regional heterotherms in fish
Tuna. maintain core temperature above ambient
What constant core body temperature do endotherms maintain?
37-41 degrees
What is the ambient temperature in humans?
20 degrees
What is the core temperature in humans?
37 degrees
What are some characteristics of homeothermic endotherms?
- High basal metabolic rate (BMR)(generates heat)
- Heat-conserving mechanisms
- Heat-dissipating mechanisms
- Maintain stable core body temperature over a wide range of environmental temperatures
What is the thermal neutral zone?
The body temp maintained by changing conductance of body surface
- no extra energy needed
- bound by upper & lower critical limits UCT & LCT
Where is the zone of metabolic regulation
Cold ambient temp- below LCT
- By thermogenesis
Where is the zone of
active heat dissipation
At warm ambient temp- above UCT
- By increasing evaporationg cooling
How is temperature regulated at moderate temperatures?
- Adjust heat transfer (gain/loss from environment) e.g.
- Fluff hair/feathers (pilomotor response)
- Postures to conserve/dissipate heat
- Adjust blood flow to periphery (vasomotor response)
What is the vasomoter response?
It is the change in blood flow to skin help regulate heat conductance of body surface
- Response to cold: vasoconstriction
Response to warmth: vasodilation
How is temperature regulated below critical levels (below LCT)?
Increase heat production above
basal levels (thermogenesis) by
converting stored energy
reserves into heat
What occurs during shivering?
– Contraction of groups of antagonistic muscles
– No useful physical work
– Chemical energy from hydrolysis of
ATP released as heat
What happens during non-shivering thermogenesis?
– Metabolism of fat (incl. brown fat)
to produce heat
What is brown fat?
-It is a special store between
neck and shoulders of some mammals
-It has adapted for rapid massive
heat production
What are the characteristics of brown fat?
- many mitochondria
- fat-metabolizing enzyme systems
- many blood vessels – rapidly transfer heat to rest of body
- activated by sympathetic nervous system
- important in animals emerging from hibernation
- increases during cold-acclimation
