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Biology of Cells and Organisms (sem 1) > Thermoregulation > Flashcards

Thermoregulation Flashcards

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1
Q

Describe the ways in which biochemical reactions are temperature sensitive.

A

Body temp too low: metabolism slows, bodily functions disrupted

Body temp too high: enzyme function destroyed, proteins denature

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2
Q

What is body temperature a critical determinant of?

A

An animal’s rate of metabolism as well as many other physiological processes, such as growth and reproduction.

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3
Q

What is body temperature subject to?

A

It is subject to homeostatic regulation due to its influence on physiological processes including metabolism.

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4
Q

What is the optimal body temp range for most animals?

A

0 to 37 degrees Celsius

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5
Q

What is the least to most extreme body temp range for animals and which species do they apply to?

A

-2 degrees Celsius (polar ice fish) to 80 degrees Celsius (animals at thermal vents)

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6
Q

Why is the key difference between the optimal body temp ranges for active and dormant animals?

A

Dormant animals can survive even more extreme body temperatures.

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7
Q

What is ambient temperature?

A

Temperature of immediate environment (i.e external)

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8
Q

What is thermoconformation?

A

Animals adapting to the same temperature as their surroundings (e.g reptiles). Therefore the ambient temperature range of the environment of these animals is appropriate enough for their survival.

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9
Q

What is thermoregulation?

A

Animals using behavioural and/or physiological mechanisms to maintain body temp independent of ambient temperature.

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10
Q

***Why is thermoregulation essential?

A

It is essential in order to maintain body temperature within a range that is optimal for physiological functions and biochemical reactions.

This does however come at a metabolic cost.

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11
Q

What is body temperature determined by?

A
  • metabolism: this generates heat as biochemical reactions in the body are doing work (increase in body temp increases metabolic rate)
  • heat exchange: conduction, convection, evaporation, radiation
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12
Q

What is conduction?

How does conduction work?

A

Transfer of heat between two solid objects in direct contact with each other.

Thermal energy is exchanged between adjacent molecules, with heat energy moving down its thermal gradient from the warmer temperature to the cooler temperature.

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13
Q

What is the rate of heat transfer proportional to?

A

It is proportional to the initial temperature difference between the objects, the area of contact and the objects’ thermal conductivity.

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14
Q

What is convection?

A

Transfer of heat from an object via the movement of a fluid, such as air or water.

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15
Q

What is forced convection?

A

Movement of fluid is generated by an external force (e.g wind or water currents)

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16
Q

What is free convection?

Describe an example.

A

Movement of fluid is driven by convection currents that are generated by heat lost by the object.

As an animal loses heat to surrounding air, the air becomes warmer. This causes the air to become less dense and rises, and this is then replaced by cooler, denser air at the animal’s surface.

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17
Q

What is heat exchange by convection proportional to?

A

It is proportional to the temperature difference between the object and the fluid, as well as the rate of movement of the fluid.

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18
Q

What is radiation?

A

The transfer of heat from a warmer to cooler object via electromagnetic waves.

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19
Q

What is heat exchange via radiation proportional to?

A

Background: all objects with a surface temperature greater than zero emit electromagnetic radiation.

The energy of this radiation is proportional to this surface temperature.

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20
Q

What is evaporation?

A

Evaporation is when water changes from a liquid to a gas. The energy required for this change of state is absorbed from the surface of the animal, therefore cooling them.

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21
Q

What is the rate of evaporation proportional and inversely proportional to?

A

Rate of evaporation is proportional to the ambient temperature and inversely proportional to the ambient relative humidity. This is because hot, dry air has a greater potential to hold water vapour than cool, moist air.

i.e the greater the humidity in the environment, the less evaporation that will occur.

22
Q

Define poikilothermic.

A

Body temp varies and fluctuates according to environmental (ambient) temp. Therefore associated with thermoconformation.

23
Q

Define homeothermic.

A

Constant body temperature, maintained independently of environmental (ambient) temp. Therefore associated with thermoregulation.

24
Q

What is an ectotherm?

Why are certain animals ectotherms?

A

Body temperature solely determined by environment (ambient) temperature; therefore depend on external sources of heat to determine body temp. They do this because their metabolic heat production is negligible and they do not have insulating fur, fat or feathers to retain it.

25
Q

Do ectotherms live in environments with little or maximal temperature fluctuation?

What type of environment is most common for ectotherms? Explain why.

A

Little. The most common environment is large water bodies such as water and lakes because they are generally thermally stable.

26
Q

Explain why it is difficult for aquatic ectotherms to regulate their body temp above or below the surrounding water temperature. (I.e difficult to thermoregulate)

A
  • water has a high specific heat and thermal conductivity (compared to air), and so aquatic species, which have their surface area in direct physical contact with this highly conductive medium, would rapidly lose any metabolic heat.
  • the physical requirements to maximise gas exchange in an aquatic environment (gills with large surface areas, small diffusion distances and large blood supply) also result in maximum heat exchange with the environment via the respiratory surface.
  • water absorbs infra red radiation so heat gain through radiation in animal is insignificant
  • evaporation cannot occur in water
27
Q

Do all ectotherms thermoconform?

A

No. All aquatic ectotherms thermoconform, but only some terrestrial ectotherms thermoconform (e.g nocturnal geckos) while other terrestrial ectotherms are able to thermoregulate (e.g reptiles).

28
Q

How do ectotherms thermoregulate?

A

Through behavioural thermoregulation strategies such as:

  • moving from sun to shade
  • modifying body contour to maximise or minimise surface area exposed to radiation
  • evaporative cooling via panting
  • Change skin colour (e.g darker colours absorb more heat)
29
Q

What is the metabolic rate of ectothermic animals dependent on?

A

Ambient temperature

30
Q

Describe the relationship between metabolic rate and ambient temperature for ectotherms.

A

As ambient temperature increases, body temperature of ectotherms increases also. This leads to an exponential increase in metabolic rate.

This increase continues until the ambient temperature exceeds the animal’s optimal body temperature, after which the metabolic rate plateaus and decreases as the enzymes that drive the metabolic processes become denatured and cease to function.

31
Q

Is the daily energy expenditure of ectotherms higher or lower than that of endotherms?
Explain why.

A

The daily energy expenditure of ectotherms is only one twentieth of that of endotherms. This is because ectotherms exploit external heat sources in the environment to maintain an optimal body temperature, therefore meaning that much of its energy can be instead devoted to processes such as growth and reproduction.

32
Q

What is a disadvantage of being an ectotherm?

A
  • they are limited to daily and seasonal cycles in solar radiation
  • must devote time and energy to thermoregulatory activities.
  • spend long periods inactive
33
Q

What is an endotherm?

A

An animal that maintains body temperature independent of ambient temperature by regulating metabolic heat production to balance heat lost to the environment.

34
Q

How do endotherms reduce loss of metabolic heat to environment?

A

They possess insulating fur, feathers and fat that retain heat.

35
Q

What causes a high rate of heat loss from an endotherm?

What must be increased to counter this?

A

The greater the temperature difference between ambient and body temp, the greater the rate of heat loss.
The animal’s metabolic rate must be raised in order to produce more heat to replace the lost heat to the environment.

36
Q

What is the thermoneutral zone?

A

Range of ambient temperatures at which the endotherm maintains a basal metabolic rate, aka where metabolic rate is minimal and constant, and the animal does not have to use energy to regulate body temperature (doesn’t have to heat or cool itself).

37
Q

What occurs above and below the ambient temperature range of the thermoneutral zone?

A

Above - metabolic rate increases again as endotherm has to use energy to facilitate heat loss through panting and sweating
Below - metabolic rate also increases as more metabolic heat has to be produced to replace the heat lost to the environment.

38
Q

What are the benefits of being an endotherm?

A
  • ability to regulate body temperature using metabolic heat and therefore independently of ambient temp allows animal to occupy environments with extreme or fluctuating temperatures (normally inhabitable to ectotherms)
  • greater efficiency of physiological processes
39
Q

What are the disadvantages of being an endotherm?

A
  • energetically expensive
40
Q

How are the disadvantages of endothermy combated?

A
  • employ a range of behavioural mechanisms to minimise thermoregulatory energy expenditure
  • such as basking in sunlight or resting in shade, climbing or flying to higher elevations
41
Q

State a number of methods that mammals and birds (endotherms) use to regulate body temp in hot conditions.

A
  • increase peripheral circulation (vasodilator aka cool blood)
  • increase evaporative cooling (sweating, panting)
  • go into shade and therefore decrease solar radiation
  • live in a burrow during the day and be nocturnal
  • store fat reserves in one place (e.g camel’s hump) to avoid its insulating effect. Accompanied by camel’s long thin legs which insulate with environment
  • adaptive hyperthermia (body gets very hot)
42
Q

State a number of methods that mammals and birds (endotherms) use to regulate body temp in cold conditions.

A
  • decrease peripheral circulation (vasoconstriction) (fingers going pale)
  • increase muscle contraction to generate the metabolic heat needed to maintain body temp at low ambient temperatures (exercise, shivering thermogenesis)
  • piloerection (goosebumps) which uses small muscles attached to feather or hair shafts to distort skin surface as hair shaft is made more erect
  • increase insulation (fur, feathers, fat, shelter)
  • increase metabolic rate by burning more food
  • have a larger body size to decrease SA:V ratio, making it easier to maintain body temperature
  • be dark in colour to absorb heat from sun (this comes at a cost as more visible to predators)
43
Q

Why do emperor penguins envelop eggs with their legs?

A

So egg doesn’t lose heat via conduction with contact on ice surface.

44
Q

How is huddling effective in maintaining body temp?

A
  • reduces surface area to volume ratio, therefore easier to maintain core body temp
  • reduce individual energy usage by half
  • ambient temperature in huddle increased by 5C Celsius
  • animals sleep to reduce metabolic rate
45
Q

What is adaptive hypothermia?

A
  • means of reducing energy expenditure when not eating as endothermy is very energetically expensive especially for small animals as they have a large SA:V ratio
  • exists in forms of torpor and hibernation
46
Q

What is torpor?

A
  • body temp dramatically drops for several hours
  • reduced metabolic rate and therefore reduced energetic demands
  • occurs with small endotherms, species where adults are less than 10kg
  • response to low food availability
  • during torpor, body temp is very close to ambient temperature, therefore animal doesn’t have to use energy to maintain body temp
47
Q

Explain why torpor is beneficial for hummingbirds in particular.

A

Hummingbirds are very small in body size, must eat 2-3x body weight to meet energetic needs. They also lack down feathers, therefore difficult for them to maintain body temp via insulation.

Torpor enables hummingbirds to reduce body temp and metabolism overnight and reduce energy demands by 50%.

Hummingbirds also vibrate wing muscles (shivering) to generate heat

48
Q

What is true hibernation and what animals experience it?

A
  • hedgehogs, mountain pygmy possum, ground squirrels, marmots
  • VERY low metabolic rate and body temp (reduced from 150bpm to 5bpm)
  • will store body fat prior to hibernation
  • gradual entry into hibernation after “test drops”
49
Q

What type of hibernation do bears and badgers experience?

A

They do not undergo “true” hibernation like hedgehogs etc.
Body temp is only reduced from 37 degrees Celsius to 31 degrees Celsius - doesn’t drop down to ambient temp.
They have a much lower SA:V ratio so maintaining body temp is much easier.
Can be roused, essentially a prolonged sleep.
— benefit is saving energy over an unproductive season (e.g winter)

50
Q

What is therapeutic hibernation?

A

Lowered body temp results in lowered metabolic rate and therefore reduces tissue damage.
Because brain is cooler, it has a lower energy requirement.
Protects sensitive organs and especially to prevent brain injury
Used in medical emergencies in cases of reduced blood flow or low oxygen availability

Biology of Cells and Organisms (sem 1) (17 decks)

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