Different strategies for coping with temperature

Question 1

Ectotherm/endotherm

Answer 1

classification based on source of body heat

Question 2

Ectotherm

Answer 2

depends almost entirely on ambient heat sources

Question 3

Endotherm

Answer 3

generates its own body heat

Question 4

Heterotherms

Answer 4

are intermediate between ectotherms and endotherms: they generate their own
heat either some of the time, or in part of their body only. Some insects and fish.

Question 5

Poikilotherm/homeotherm

Answer 5

terms refer to constancy of body temperature

Question 6

Poikilotherm

Answer 6

body temperature tends to fluctuate with changes in ambient temperature

Question 7

Homeotherm

Answer 7

regulates body temperature close to a set point. Nearly all endotherms are
homeotherms

Question 8

The terms poikilotherm/homeotherm and ectotherm/endotherm are independent

Answer 8

In
principle, any ectotherm can be homeothermic, given a suitable habitat.

Question 9

Body heat-The rate of change of body heat depends on the rates of three factors:

Answer 9

• heat production through metabolic means
• heat gain from environment
• heat loss to environment

Question 10

Body heat =

Answer 10

= heat produced + (heat gained- heat lost)
= heat produced + heat transfer

Question 11

Heat production:

Answer 11

• Basal metabolism: basic metabolic processes necessary for life result in production of
  heat. Metabolic rate is the sum of all energy-requiring biochemical reactions over a
  given time interval. The basal metabolic rate (BMR) is that of an animal that is at rest, is
  not digesting, and is not experiencing stress.

Question 12

Factors influencing heat production are

Answer 12

• Behavioural mechanisms e.g. exercise
• Autonomic mechanisms such as accelerated metabolism of energy reserves
• Acclimatization (longer term mechanism) : increase basal metabolic rate

Question 13

Heat transfer (gain and loss)
Heat can be transferred by four means:

Answer 13

Conduction, Convection, Radiation and Evaporation

Question 14

Conduction

Answer 14

transfer between objects in contact with each other e.g. animal and water or
rocks. Heat flows from warmer to cooler. Conduction is affected by surface area and
temperature gradient.

Question 15

Convection

Answer 15

transfer of heat contained in a gas or liquid by the movement of the gas or
liquid. Convection e.g. of air can accelerate heat transferred by conduction between a solid
and the air, e.g. wind cools an animal by removing air warmed by its body and replacing it
with cold air. Convection in water results in very rapid cooling. A naked human cannot
thermoregulate in water below 15oC

Question 16

Radiation

Answer 16

occurs without direct contact between bodies e.g. sun warms an animal.

Question 17

Evaporation

Answer 17

evaporation of liquid requires heat which is lost from the surface. Sweating
and panting involve evaporative heat loss.

Question 18

The rate of heat transfer between a body and the environment depends on

Answer 18

Surface area, temp diff, heat conducting properties of an animals surface

Question 19

Surface area

Answer 19

surface area/g tissue decreases with increase in body size, therefore small
animals lose and gain heat faster than large ones.

Question 20

Temperature difference

Answer 20

the closer the body temperature to that of the environment the
less heat is lost or gained

Question 21

Heat conducting properties of animal’s surface (“specific heat conductance”).

Answer 21

Poikilotherms typically have high heat conductance; they gain or lose heat rapidly and
so stay close to environmental temperature. Homeotherms have evolved means of
reducing heat transfer (i.e. insulation), such as feathers, fur or blubber. Fur and feathers
trap air; as air conducts heat poorly, this further retards the loss of heat.

Question 22

Regulation of heat exchange

Answer 22

Behaviour, autonomic process, longer term adaptations

Question 23

(1) Behaviour:

Answer 23

: Move to an environment with suitable temperature e.g. sun or shade
Posture: animals curl tightly to reduce heat exchange, spread out to maximise it

Question 24

(2) Autonomic process

Answer 24

modify blood flow to vertebrate skin
fluffing of hair/feathers (more air increases insulation)
sweating/ panting to increase evaporative cooling