Thermoregulation in Ectotherms (chapter 2 of homeostasis)

Question 1

Thermoregulation

Answer 1

The maintenance of a relatively constant core temperature

Question 2

Organisms are constantly heating up and cooling down as a result of their surroundings. These changes depend of a number of physical processes. These include:

Answer 2

1. Exothermic chemical reactions
2. Latent heat of evaporation - objects cool down as water evaporates from a surface
3. Radiation - transmission of electromagnetic waves to and from the air, water, or ground (convection and conduction)

Question 3

Ectotherms

Answer 3

• Animals that use their surroundings to warm their bodies so their core temperature is heavily dependent on the environment
• Include all invertebrate animals, along with fish, amphibians, and reptiles

Question 4

Why do ectotherms living in water not need to thermoregulate?

Answer 4

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

Question 5

Why do ectotherms that live on land need to thermoregulate?

Answer 5

The temperature of the air can vary dramatically both between seasons and even over a 24-hour period from the middle of the day to the end of the night

Question 6

Endotherms

Answer 6

• Animals that rely on their metabolic processes to warm their bodies and maintain their core temperature
• Their metabolic rate is 5x higher than ectotherms, so they need to consume more food to meet their metabolic needs than ectotherms of similar size
• e.g. mammals and birds

Question 7

Ectotherms - behavioural responses to warm up

Answer 7

• Basking in the sun
• Orientate their bodies towards the sun - maximum surface area exposed
• Pressing themselves to warm ground - conduction of heat
• Exothermic metabolic reactions - e.g. marine iguanas contract their muscles and vibrate which increases cellular metabolism to raise their body temperatures

Question 8

Ectotherms - behavioural responses to cool down

Answer 8

• Shelter from the sun - seek shade, hide in cracks in rocks, digging burrows
• Press their bodies against cool surfaces - earth, stone - or move into water or mud if in close proximity
• Orientate their bodies so that minimum SA is exposed to the sun
• Minimise movements - reduced metabolic heat generated

Question 9

Ectotherms - physiological responses to warming

Answer 9

• Change of skin colour to darker colours - able to absorb more radiation than light colours
• Altered heart rate - increases/decreases the metabolic rate, affects the warming/cooling across the body surfaces

Question 10

Example of an ectotherm

Answer 10

Namaqua Chameleon (lives in the Namib Desert)