Topic 10

What is homeostasis?

The ability to maintain stable internal conditions in response to external environmental conditions

What is needed to coordinate physiological changes to maintain internal conditions?

Receptors that relay sensory information in the form of nerve pulses to control centres that signals effectors

What is the effect of temperature on reaction rate?

Increases because reactant kinetic energy increases

When does reaction rate slow down when temperature continues increasing?

Once the rate of reaction reaches the optimal level

What are temperature response curves used for?

To compare reaction rates to temperature changes, and between organisms

What is Q10 a measure of?

Temperature sensitivity in regards to the how a reaction rate changes over a 10 degree range

What does a Q10 value of 1 mean?

The reaction is not temperature sensitive

What is the Q10 value of most physiological processes?

Between 2 and 3

What is photosynthesis dependent on?

Temperature, specifically the plant's optimum temperature

What does a wider optimal temperature range provide?

Selective advantages in unstable or extreme weather

Are temperature response curves fixed?

No if acclimatisation occurs

How does acclimatisation or adaptation affect the metabolism of species?

It either shifts their optimal reaction rate or increases the range of optimal temperatures

How do non-mobile organisms regulate their internal temperature?

Acclimation and adaptation

How do mobile organisms regulate their internal temperature?

Thermoregulation

What do thermoregulatory adaptations determine?

Species' thermal tolerances and their geographic ranges

How do species exchange heat with their surroundings?

They can gain It from external sources and lose it through metabolism

What is the purpose of thermoregulation?

To balance heat loss and gain for homeostasis

What is thermoregulation?

The control of internal body temperature

How does thermoregulation occur?

Thermoreceptors are activated, send sensory information to control centres to provide feedback from heating and cooling

How do simple animals thermoregulate?

Thermoreceptors directly interact with interneurons that interact with motor neurons to move between appropriate climates (behavioural thermoregulation

How do vertebrates thermoregulate?

Skin thermoreceptors detect temperature change, relays this to the PNS, which relays this to the CNS (hypothalamus) to produce appropriate physiological responses.

What are endotherms?

Organisms that produce most of their heat from internal metabolic processes

What are ectotherms?

Organisms that rely on external heat sources for thermoregulation

What are homeotherms?

The maintenance of a stable body temperature

What are heterotherms?

Organisms that have a body temperature that fluctuates with temperature

Are endotherms usually homeo- or heterothermic?

Homeothermic

Are ectotherms usually homeo- or heterothermic?

Heterothermic

When do homeothermic ectotherms exist?

when external temperature is stable throughout their lifetime

When do heterothermic endotherms exist?

When external temperatures fluctuate extremely

What is behavioural thermoregulation?

Migrating between microclimates to balance heat loss and gain

Who relies on behavioural thermoregulation?

Ectotherms

What else influences internal body temperature besides the external temperature?

Metabolic rate

Why are temperature response curves used for when the relationship between ectothermic metabolic rate and environmental behaviour is easy to measure?

To predict how ectothermic animals respond to environmental changes and identify their thermal tolerance

What is thermal tolerance bound by?

The critical thermal minimum and maximum

What can metabolic rate determine?

The optimal performance ranges for growth and reproduction

What is the thermoneutral range?

A specific temperature range where little physiological effort is needed to maintain their internal temperature

What occurs to endotherms if the environmental temperature falls outside of this range?

metabolic heat production increases.

What is thermal conductance?

The rate at which animals exchange heat with the environment

What determines heat conductance?

Shape, size and insulation layers of a species

What effect does increased thermal conductance have on metabolic rates?

Increased metabolic rates

What effect does decreased thermal conductance have on metabolic rates?

Decreased metabolic rates

What effect does increased thermal conductance have on the thermal neutral zone?

It shrinks the range because heat exchange occurs faster and metabolic rates must occur faster to compensate

How is licking a form of behavioural thermoregulation?

It evaporatively cools the blood underneath to send to the rest of the body

How do insulated animals thermoregulate?

They offload heat at poorly insulated areas which also have a high surface area: volume ratio

What can oxygen levels act as an index of?

Metabolism

Why do the metabolic rates and therefore body temperature fluctuate massively when some mammas are sleeping?

Some mammals have evolved this mechanism to conserve energy.

What general conditions must the metabolic rates of species be compared under?

Comparable conditions and thermoregulatory states, such as both species being active or resting and not ectotherms with endotherms due to their differing metabolic rates

What rate are endotherms classified under?

Under the basal metabolic rate which is within the thermoneutral zone and where heat loss and gain are effectively equal

What conditions apply to the basal metabolic rate?

What rate are ectotherms classified under?

The standard metabolic rate

What conditions apply to the basal metabolic rate?

What is allometry?

The study of the relationship between body size and anatomy to physiological processes and behaviour.

What is the formula for calculating metabolic rate from body mass?

Body mass with an exponent of 0.74

Why do larger animals have a larger metabolic rate than smaller ones?

Their increased size means they have more cells and more metabolic processes occurring

What are other theories as to why increased body mass increases metabolic rate?

It is a function of fractal geometry or selection

What is fractal geometry?

The way vascular tissue networks supply oxygen to cells