Thermoregulation In Ectotherms

Question 1

what is thermoregulation?

Answer 1

the maintenance of a relatively constant core body temperature.

Question 2

why is it important to maintain a constant core body temperature?

Answer 2

to maintain optimum enzyme activity.

Question 3

what physical processes determine changes in temperature?

Answer 3

• exothermic chemical reactions
• latent heat of evaporation
• radiation
• convection
• conduction

Question 4

what is radation?

Answer 4

the transmission of electromagenetic waves to and from the air, water, or ground.

Question 5

what is convection?

Answer 5

the heating and cooling by currents of air or water, warm air or water rises and cooler air or water sinks setting up convection currents around an organism.

Question 6

what is conduction?

Answer 6

heating as a result of the collision of molecules. Air is not a good conductor of heat but the ground and water are.

Question 7

what is an ectotherm?

Answer 7

animals that use their surroundings to warm their bodies.

Question 8

which animals are ectotherms?

Answer 8

invertebrate animals, fish, amphibians and reptiles.

Question 9

why do ectotherms living in water not need to thermoregulate themselves?

Answer 9

the high heat capacity of water means that the temperature of their environment does not change much.

Question 10

what are some examples of endotherms?

Answer 10

mammals and birds.

Question 11

what is an endotherm?

Answer 11

animals that rely on their metabolic processes to warm up and they usually maintain a very stable core body temperature regardless of the environment.

Question 12

do ectotherms or endotherms have higher metabolic rates?

Answer 12

endotherms - 5 times higher.

Question 13

why do endotherms need to consume more food than ectotherms of a similar size?

Answer 13

endotherms have higher metabolic rates.

Question 14

how do ectotherms regulate their temperature?

Answer 14

they have evolved behavioural responses that allow them to overcome the limitations imposed by the temperature of their surroundings.

Question 15

why might ectotherms need to increase the radiation they absorb from the sun?

Answer 15

they need to warm up to reach a temperature in which their metabolic reactions happen fast enough for them to be active.

Question 16

what are some behavioural responses for ectotherms to increase the radiation they absorb from the sun?

Answer 16

• basking in the sun (lizards so they can get get warm enough to move fast and hunt for prey.)
• orientate their body so that the maximum surface area is exposed to the sun.
• extend areas of their body to increase the surface area exposed to the sun. (butterflies spread their wings to increase the available surface area to get warm enough to fly.)
• conduction by pressing their bodies against warm surfaces
• exothermic metabolic reactions (butterflies may vibrate their wings to warm their muscles before they take flight.)

Question 17

why might ectotherms have to cool down?

Answer 17

to prevent their core temperature reaching a point where enzymes begin to denature.

Question 18

what are some behavioural responses for ectotherms to cool down?

Answer 18

• seeking shade.
• hiding in cracks in the rocks.
• digging burrows.
• move to mud/water
• press their bodies against cooler surfaces.
• orientate their body so that the minimum surface area is exposed to the sun
• minimise their movements to reduce the metabolic heat generated.

Question 19

why do lizards living in cooler regions often have darker coloured bodies?

Answer 19

dark colours absorb more radiation thanlight colours.

Question 20

are ectotherms or endotherms more vulnerable to fluctations in the environment?

Answer 20

ectotherms. however, they can survive in areas with lower food supply as they have lower metabolic demands.

Question 21

where does the Namaqua chameleon live?

Answer 21

the Namib desert (one of the most inhospitable hot and waterless environments on Earth)

Question 22

what observations have been made about the Namaqua chameleon?

Answer 22

• it is black in the morning.
• it orientates its body sideways to the sun.
• an increased heart rate early in the morning when basking.
• it inflates its body in the early morning.
• it presses its body to the desert sand in the morning.
• during the day the chameleon deflates its body.
• the animal becomes a very pale grey.
• it holds itself well away from the desert surface.
• the heart rate slows down.
• the chameleon opens its mouth andpants in the middle of the day.