Ch10: Homeostasis

Question 1

Define homeostasis

Answer 1

The maintenance of internal conditions when an organisms external environment is changing

Question 2

Describe how increasing temperature affects homeostasis

Answer 2

Thermoreceptors detect temperature change, sending an impulse to brain (control centre)

The brain compares this with a SET POINT and if this temperature exceeds (or is lower than) this point, the brain sends signals to sweat glands (EFFECTOR CELLS) to sweat

Evaporation cools the body until it reaches the set point

maintaining homeostasis

Question 3

How does increasing temperature affect reaction rate

Answer 3

It increases kinetic energy and thus increases molecular interactions.

Increasing reaction rate until optimum temperature is reached

Question 4

What do thermal response curves do?

Answer 4

They measure the rate of a particular reaction as temperature changes

Question 5

What does Q10 mean and what is its equation?

Answer 5

It measures the rate of change of a reaction over a 10˚C change in temperature
Q10 = RT/R(T-10)

Question 6

If Q10 =1, 2, 3, what does this mean for temperature?

Answer 6

1: reaction is NOT temperature sensitive

2: reaction rate doubles with each 10˚C increase

3: reaction rate triples with each 10˚C increase

Question 7

What are the implications of having a wide optimum temperature?

Answer 7

Generalist species are able to grow and adapt to a wider range of envrionment/climates

Question 8

Can plant optimal temperatures be altered? If so, how?

Answer 8

Yes, if they are grown in higher environmental temperature

Question 9

What are the trends seen in sedentary organisms in terms of optimum temperatures? How do they maintain these temperatures?

Answer 9

They have a broad range of temperatures for optimisation

They maintain them through biochemical reactions

Question 10

How do large, mobile organisms maintain optimum temperatures

Answer 10

Physiological and behavioural measures

Must balance heat gain/lose to their environment

Question 11

Define thermoregulation

Answer 11

the control of internal body temperature via physiological or behavioural means

Question 12

How do simple round worms regulate their temperatures?

Answer 12

Their thermoreceptors synapse directly to interneurons

They carry this signal to motor neurons, which cause the worm to move to a more suitable micro-climate

Question 13

What do vertebrates use to detect temperature change?

How to do control the change? (Hint: there are 2 methods)

Answer 13

Peripheral nervous system:

1) Vasoconstriction: prevents heat loss + allows for conservation of heat

2) Vasodilation: allows heat to be lost (cooling)

Question 14

What is the difference between Endotherms and Ectotherms?

Answer 14

Endotherms: organisms that can regulate their internal body temperature using their metabolic processes that generate their own heat

Ectotherms: cannot regulate their own heat + have to gain heat for thermoregulation from an external source

Question 15

Difference between Homeotherm and Heterotherm?

Answer 15

Homeotherm: body temperatures remain relatively stable, and can be maintained

Heterotherm: unstable/unmaintainable body temperature (fluctuates regularly OR under conditions or life stages)

Question 16

Describe ectothermic heterotherms and endothermic homeotherms (think of what body temp. v environmental temp. graph looks like

Answer 16

See Doc, 10a:
Ectothermic heterotherms: fluctuate at SAME rate as external environment temperature

Endothermic homeotherms: relatively stable body temperature, other than at extremes

Question 17

Describe the regulation of homeothermic ectotherms and heterothermic endotherms:

Answer 17

Homeothermic ectotherms: body temperature is stable throughout their lifetime as their environment’s temperature is stable
- they have adapted to these conditions and cannot lie outside of them

Heterothermic endotherms: when these organisms live in environments with extreme fluctuations, some use TORPOR (hibernation) to survive these condtions
- they drop their body temperature to surrounding temperatures
- they use their own heat to heat up after torpor to exist in conditions that are more favourable

Question 18

Define behavioural thermoregulation

Answer 18

adjusting activity to maintain/gain/lose heat to remain within optimum conditions

Question 19

Define thermal performance curves

Answer 19

They show how temperature affects performance of a variable

Demonstrates a thermal tolerance breadth: determined (bounded) by critical thermal minimum/maximum (Tmin/Tmax) (where performance >0)

Question 20

Define thermoneutral zone, and what happens to the body when it goes below/above this range? (In ENDOtherms)

Answer 20

Where the cost of maintaining optimal body temperature is minimised

Below: metabolise increases to produce heat

Above: metabolism increases to produce energy for cooling mechanisms and to DUMP heat

Question 21

Define thermal conductance. What is this determined by?

Answer 21

rate of exchange of heat between an organism and its environment

Determined by:
- size, shape + thickness of insulation (fat, fur, scales)
- increase thermal conductance = steeper relationship between metabolism and temperature

• decrease thermal conductance = shallower relationship between metabolism and temperature

Question 22

In endotherms what does thermal conductance influence? How does the size of the animals effect this?

Answer 22

Breadth of thermoneutral zone;

Small animals: greater thermal conductance = smaller range of thermoneutral zone

Large animals: lower thermal conductance = increases range of thermoneutral zone

Question 23

Define allometry

Answer 23

relationship between body mass + physiological or morphometric characteristics and behaviours

Question 24

When do we compare metabolic rates? (only 2 words)

Answer 24

At rest

Question 25

What are the rest states of endotherms and ectotherms: describe the conditions

Answer 25

Endotherms: Basal Metabolic Rate (BMR)
- In resting state
- Post adsorptive (not digesting or feeding)
- Non-reproductive

Ectotherms: Standard Metabolic Rate (SMR)
- Resting
- Post adsorptive
- Non-reproductive
- Same environmental temperature as endotherm

Question 26

Describe Max Kleiber’s law

Answer 26

Metabolic rate ~= Body Mass^0.75

NOTE: metabolic rate= cellular respiration

Question 27

Other than Max Kleiber’s law, what other factors may affect metabolic rate?

Answer 27

• Metabolic rate + bodymass = function of fractal geometry: way vascular tissue supplies oxygen to all cells in the body

OR: there is a direct interplay with metabolic rate, growth and reproduction
- leads to the optimisation of phenotypes producing the scaling relationships we see