CHapter 6: part 2 Flashcards
What is the purpose of bursa of Fabricus?
- manufactures B-lymphocytes in birds
- lymphocytes are antibodies
Describe importance of myoglobin
- offers oxygen in muscles for aerobic respiration
- allows certain animals to stay under water longer(aquatic birds)
metabolic rate
Rate at which energy (ATP) is produced and used (because very little ATP is stored) from ingested or stored substrates
Usually measured (in the laboratory) as oxygen consumption
basal metabolic rate
the amount of energy per unit of time needed to keep the body functioning at rest
Mass-specific metabolic rate
the resting energy expenditure per unit body mass per day
Describe the differences between basal and mass-specific metabolic rate
As body mass increases, the basal metabolic rate also increases
As a bird gains body mass, its mass‐specific metabolic rate decreases
Describe daily energy budget in birds
- varies from existence metabolism, reproduction, and migration
- can have less energy during months before migration, has spike in metabolism and energy use in migration
- Metabolism and daily energy expenditures typically increase with body size
Describe daily energy expenditures with body size
- flight metabolism varies from two to 25 times as high as basal metabolic rate
- Total daily energy expenditures do not increase as fast with increasing body size as does basal metabolism
Small birds are more active than large birds
Describe aerobic scope of birds
Most birds have a greater aerobic scope, (ratio of active to resting metabolism) than do most mammals
- running birds are the exception, in most cases, not all, to fall under mammals
What is the thermoneutral zone?
- a range of temperatures where a bird can maintain its normal expected body temperature without using energy above basal metabolic rate
What are the upper and lower critical temperatures?
- lower is where shivering begins, pectoralis muscles produce heat this way
- upper is where evaporative cooling is used, big on heat loss
When bird is below/above thermoneutral zone…
- below: increase heat production and/or decrease heat loss
- above: decrease heat production and/or increase heat loss
How do birds insulate themselves
- plumage generally thicker in winter
- contour feathers can be thicker in colder habitats
- thick layer of down
- subcutaneous fat forms insulator layer only in few birds (penguins)
Peripheral Vasoconstriction
- can create regional hypothermia: Regions of the body are maintained at temperatures lower than the body core
- restricts blood flow through certain areas of body, lets them become cold
How do countercurrent heat exchangers conserve core temperature?
- Birds that swim in cold water or stand on ice minimize heat loss by allowing temperatures inside their feet to drop, nearly to ambient levels
- Cools blood flowing to the feet (artery),
Heats blood as it returns to the body (vein) - Steep temperature gradient reduces heat loss and saves a tremendous amount of energy
Acclimatization
Changes in a bird’s physiology after it has been in a new environment for several days or weeks that allow it to function better in the new conditions
Facultative Hypothermia
- body temp drops below normal
Daily cycles of hypothermia (mild or pronounced) may be tied to internal clocks
Also triggered on a day-to-day basis by food deprivation and low energy stores
Saves critical energy supplies
Torpor
- A resting state in which the body temperature drops, metabolic processes slow, and reactions to external stimuli are slow or lacking
(allows body temp. to reach closer to ambient(outside body temp.)
More pronounced than facultative hypothermia - example: purple throated warbler, common poorwill
postural changes to deal with cold temps.
Ptiloerection: erecting feathers to trap heat
Microclimate selection
- bushes, trees, under snow to stay warm in cold temps.
Huddling
- provides thermoregulation, cycle of huddling in middle vs. outwards
- ex: penguins
Food caching
- food storage for when the body needs it in the cold, have to remember location and access
Adaptations to heat in body size/location
- smaller struggle to stay warm, bigger struggle to stay cool
- Body size (which is directly proportional to wing length) increases to the north, but individual birds in the warm, humid Mississippi Valley and coastal areas are small compared with those at other localities at similar latitudes
Peripheral vasodilation
- Allows heated blood from core to get to the surface and be dissipated
- change from restricted to normal blood flow
- heat to leave body
Controlled hyperthermia
- controlled elevation of body temp
- store heat
- birds have rete mirable opthalium, blood vessels in eyes that pull up heat and dissapate it
- birds throat flutter to get rid of heat
Evaporative heat loss
- Metabolism increases above the UCT because of panting and other efforts that facilitate heat loss
- major source of water loss to environment
Describe importance of the toucan bill
- it is not insulated, therefore making it easier to produce heat loss and cooling of the bird in its environment (huge thermal window for blood flow)
Cutaneous water loss
- Evaporate water directly through the skin (without sweat glands)
Describe the heat adaptations of birds in pstural adjustment, microclimate, and urohydrolysis
- these are basically the opposite of adjustments in cold temps!!!
Urohidrosis
Defecating onto the scaly portions of the legs as a cooling mechanism, using evaporative cooling of the fluids.
