Comparative Animal Physiology Exam 3

Quiz's, Study guide, Lecture slides

For animals, across all species, what is the range of body temperatures that can be tolerated? Is this the same for the range of environmental temperatures at which animals can live?

–1.8°C to over 50°C. No, the range of environmental temperatures varies greatly among species, with some adapting to extreme conditions outside this range.

Why is the lower limit for animal life a body temperature of -1.86°C?

-1.86 is the freezing point of salt water, blow that, tissues start to decay as well as other physiological processes.

What is the range of body temperatures in mammals (placental)? Birds?

Poikilothermic

– variable body temperature (reptiles, fish, amphibians, insects, mole rats)

Homeothermic

– constant body temperature (humans and birds)

Ectotherm

body temperature dependent on external heat sources (reptiles, amphibians, fish, marine invertebrates)

Endotherm

body temperature primarily dependent on internally generated metabolic heat (birds and mammals)

What is temperature?

Temperature is a measure of the intensity of heat energy present in a system. A measure of average kinetic energy

What is the difference between temperature and heat content?

• Temperature: The measure of heat intensity

• Heat content: The amount of energy an object can hold

What factors determine the body heat content (and temperature) of an animal?

Heat production and heat transfer to the environment

In terms of heat production, heat gain from the environment and heat lost to the environment, how does an animal maintain a stable body temperature?

Heat production + Heat gain = Heat loss

What are the physical mechanisms of heat transfer?

• Conduction, Convection, Radiation, Evaporation

Which mechanisms can result in heat gain to the animal? Heat loss from the animal

• loss: Evaporation

• Gain: Conduction, Convection, Radiation

Conduction

heat transfer by the direct contact between two bodies

Convection

heat transfer by the movement of a fluid (liquid or gas)

Radiation

the loss or gain of heat by the emission of electromagnetic radiation – usually in the infrared wavelengths

Evaporation

water loss carries with it heat loss (latent heat of vaporization)

Can a terrestrial ectotherm be warmer than the air temperature it is in? If so, how? Would this be possible for an aquatic ectotherm?

Yes, terrestrial ectotherms can bask in the sunlight and absorb thermal radiation from the surrounding environment.

What physical properties of the animal will influence the rate of heat transfer with the environment?

• Surface area

  • surface area per unit mass decreases with increases in body mass

  • small animals have a high heat flux with environment per unit body weight

• Specific heat of conductance

• Temperature difference

  • the closer an animal is to its ambient temperature (smaller temperature gradient) the less transfer of heat will occur

Ectotherms

• rely on environmental sources of heat

• generally, have lower metabolic rates (heat production) compared with endotherms

• have high thermal conductance

• May regulate temperature by behavioral thermoregulation

What are the benefits to ectothermy?

• Less energy is spent on heat production

• require less food

• need less water

• can be small

What are the costs to ectothermy?

• Must find an environment that is suitable to adjust body temperature

• more limited temperature range

• limitations on the duration of bursts of high energy output

• development of oxygen debt more likely

What are the benefits to endothermy?

• can maintain high and constant body temperature

• can function over wider range of temperature

• higher rates of aerobic metabolism permit sustained periods of intense activity

What are the costs to endothermy?

• must have high rates of food and water intake

• more susceptible to dehydration

• small size problematic because of larger surface-to-volume ratio

• smaller percentage of energy intake used for growth and reproduction.

Ectotherms response to temperature change

• Acute

  • short term, immediate

• Chronic

  • prolonged time period

  • Acclimation and Acclimatization

• Evolutionary

  • Adaption of populations over generations

Which of the following physical processes can result in heat gain from the environment? (select all that apply)

• Radiation

• Conduction

• Convection

Typically, rates of physiological processes in animals will increase _____________ times for each 10 degree C increase in temperature

2 to 3

Marine fish and invertebrates living in consistently cold polar environments would be considered:

Homeothermic ectotherms

Biochemical reaction rates will usually _____________ with increasing temperature.

Increase

All else being equal, the rate of heat transfer (per unit body mass) with the environment will tend to be:

higher in smaller animals

An endotherm generally has:

a high rate of heat production and a low rate of heat transfer

For body temperature to be constant:

heat production plus heat gain must equal heat loss

If an ectothermic animal has an O2 consumption rate of 100 mg O2/h at a body temperature of 20°C, and this process has a Q10 of 2.0, what will be the animal's O2 consumption rate at 10°C?

50 mg O2/h

The lower limit of animal body temperatures that can be continuously tolerated is:

–1.8 degrees celsius

A desert tortoise (turtle) will have:

a body temperature that may be higher than air temperature

Responses to temperature change that are immediate or short term (seconds to minutes) would be:

Acute responses

Ectotherms can regulate their body temperature by:

moving to areas within habitat that provide appropriate heat gain or loss

If the chronic response to temperature change in an ectotherm returns the rate of some process back to its original level, that would be:

complete compensation

If colder body temperatures result in reduced enzyme reaction rates, the acclimation response to compensate could be to: 

increase the amount of enzymes

The response to temperature change in an individual ectotherm that occurs over the time scale of days to weeks is:

an acclimation or acclimatization response

We would predict that, due to natural selection, the peak performance of a physiological process would occur close to:

the normal range of body temperatures

Typically, as temperature increases, an individual enzyme's substrate affinity will:

decrease

The response to temperature change in a species that occurs over many generations would be a(n):

adaptation response

In adapting to colder body temperatures, a species' cell membranes may have:

more unsaturated phospholipids

A 'homolog' is a:

different molecular forms of an enzyme or protein

If the acute response of an ectotherm to a temperature change is an increase in metabolic rate, then the acclimation response would most likely be:

a decrease in metabolic rate

Comparing the affinity of a particular enzyme across species that live in a wide range of habitats at the species normal body temperatures, enzyme affinity will tend to:

stay relatively similar with increasing species body temperature

Thermal neutral zone

basal metabolic rate (heat production) balances with heat loss to the environment

vasomotor responses

shunting blood to or away from the skin

Altering thermal conductance: postural changes

to alter exposed surface area

Lower critical temperature

at the lower end of TNZ (thermal neutral zone), below which the basal metabolic rate is insufficient to balance heat loss

Zone of metabolic regulation

below LCT, metabolic rate increases linearly with decreasing temperature

Upper critical temperature

above upper critical temp., surface insulation cannot be further reduced, so active evaporative cooling mechanisms such as sweating, panting, or gular fluttering (evaporative cooling) must be used to prevent overheating.

Two mechanisms convert chemical energy to heat

1. Shivering thermogenesis

2. Non-shivering thermogenesis (NST)

Shivering thermogenesis

muscle contraction liberates heat, No useful work done, but hydrolysis of ATP produces heat

Non-shivering thermogenesis

enzymatic breakdown and oxidation of fat storage to produce heat.

Insulation (fur, feathers, blubber)

reduction in thermal conductance

What happens to an endotherm's resting metabolic rate when the temperature is outside its thermoneutral zone?

Resting metabolic rate goes up.

An endotherm with greater insulation will have a 'lower critical temperature' that is:

lower

In endotherms, metabolic rate may be increased in the 'zone of metabolic regulation' by: (select all that apply)

• Activating brown fat tissue

• Non-shivering thermogenesis

• Shivering thermogenesis

Brown adipose tissue generates heat by:

having mitochondria that do not make ATP

Hibernating mammals allow their body temperature to drop because:

it saves energy

Within the thermal neutral zone, and endotherm may _____________________ to maintain a stable core body temperature. (Select all that apply)

• change effectiveness of the insulation

• adjust rates of blood flow to the skin

• change posture to alter exposed surface area

Above the upper critical temperature, an endotherm will _____________________ to maintain a stable core body temperature

increase evaporative cooling mechanisms

An insulation that is very effective at preventing heat transfer has a:

low thermal conductance

Heterothermic fishes, such as tunas and mako sharks, increase the temperature of their core swimming muscles:

using counter-current blood flow

The major role of brown fat is to:

warm the body by nonshivering mechanisms.

In a mammal or bird, as environmental temperature increases, body temperature will tend to:

stay the same

Brown adipose tissue is more common in: (select all that apply)

• hibernating mammals

• small mammals

The insulation effectiveness of blubber can be changed by:

shunting of blood either to the skin or beneath the blubber layer

What happens to an endotherm's resting metabolic rate when the temperature is outside its thermoneutral zone?

Resting metabolic rate goes up.

When the hairs in fur are held more upright (pilomotor response):

it is a more effective insulation because it traps a thicker layer of air

Evaporative cooling in endotherms in hot environments can be increased by: (select all that apply)

• gular fluttering

• sweating

• panting