Endotherms

Question 1

What are endotherms?

Answer 1

An organism that is able to regulate its own body temperature

Question 2

What is the issue with a larger sa:v

Answer 2

Lose heat more rapidly
Small bodies

Question 3

Substances with a low conductivity have what?

Answer 3

High insulation

Question 4

Why does fur & feathers have low conductivity?

Answer 4

They trap air between them (provide good insulation)

Question 5

Why is fur invaluable to small mammals in cold climates?

Answer 5

Impractical to have very thick/long fur

Question 6

What is meant by ‘thermal windows’?

Answer 6

Many large, furred animals have shorter fur on underparts, particularly legs & feet

Question 7

How is the colour of mammal’s fur determined?

Answer 7

• The need for camouflage or mimicry
• Display
• Thermoregulation

Question 8

What is the thermal neutral zone?

Answer 8

Range of temperatures over which an endothermic animal can maintain a constant temp without a change in heat production

Question 9

What is the lower critical temperature?

Answer 9

The point at which heat production is increased to prevent a drop in Tb

Question 10

What is the upper critical temperature?

Answer 10

The point at which an endothermic needs to actively invoke cooling measures (e.g. panting)

Question 11

What are the 3 trends in the thermal neutral zones of different animals?

Answer 11

• The lower the critical temp of high latitude + polar species is lower than tropical species
• The width of thermoneutral zone is usually larger in high latitude + polar species
• The conductance’s of cold-adapted species are generally lower (because of good insulation)

Question 12

What are the 2 forms of heat production?

Answer 12

1. Shivering
2. Non-shivering thermogenesis (NST)

Question 13

What is non-shivering thermogenesis?

Answer 13

• Doesn’t involve muscles
• Brown fat (brown adipose tissue BAT), usually located in anterior parts of body + vital organs, is capable of very high rates of metabolism
• We don’t have brown fat (other than when a baby, in between shoulder blades)

Question 14

What is hibernation?

Answer 14

A state of minimal activity + metabolic depression

Question 15

Why do animals hibernate?

Answer 15

• Keeping warm in cold is energy-expensive
• Food is limiting
• Finding food is energy-expensive

Question 16

What is the difference between torpor and hibernation?

Answer 16

• Torpor is generally shorter (often daily basis) + hibernating is a long period (months)
• Requires more energy to arouse from torpor than it does hibernation

Question 17

What is nocturnal hypothermia?

Answer 17

Allowing body temp to drop but up to 10°C overnight

Question 18

Why do larger mammals not use torpor or hibernation?

Answer 18

• Lower SA:V ratio, conserve body heat much better
• Lose heat relatively slowly
• Warming back up is too energetically expensive

Question 19

What is regional heterothermy?

Answer 19

• Extremities have little/no insulation + lose heat rapidly to cold air/substrate
• blood flowing into these extremities is cooled rapidly
• if cool blood re-entered body, animal would rapidly lose heat from its core
• Some species defend core temp b allowing temp of extremities to fall
• E.g. Arctic foxes

Question 20

Why do some animals arouse periodically (torpor)?

Answer 20

Recent evidence:
- High rates of water loss (replenish water supply)

Question 21

What is an issue with allowing limb temp to drop close to freezing?

Answer 21

Animal fats become hard + brittle at low temps

Question 22

What is used to keep leather supple at low temps?

Answer 22

Neatsfoot oil from hooves of cold-adapted animals