Lect 17 Flashcards
Continental drift: Paleocene
• Sea levels still high
• Continents resembling modern arrangement
- India still separate from Asia
- North and South America
also separate
Continental drift: Pliocene
• Formation of ice caps at poles caused sea level drop
• Continents in familiar positions
- India part of Asia (India continues to collide with Asia)
- North and South America
connected
- Changed circulation patterns
and climate (due to NA and SA connecting)
Continental drift: Pleistocene
• Extensive glaciation, in multiple pulses (back and forth growing and melting)
• Sea levels drop
- Asian island groups connected
Ice age
Climate
Temperatures drop after meteorite hit
Hottest ever during Eocene after Cenozoic extinction
First half is the warm house the second half is the cool house
Sudden drop of temperature may have been when North America separated from Antarctica
Rate of change right now, the rate of change is faster than ever from record of deep time
Great American Biotic Interchange
• Island hopping allowed early migrations
• Full formation of land bridge completed connection
• Also separated Pacific and Atlantic oceans
• Split populations speciated
Endothermy
• Maintenance of body temperature through internal metabolic processes
Pros: maintain consistent body temperatures and body processes, even in cool environments
Cons: energetically expensive!
• Metabolic rates 7-10 times higher
Metabolic heat production
• Lungs,connectivetissue,digestivetract, resting skeletal muscle
• Liver and brain
• Heart and kidneys
•Active skeletal muscle
• Shivering: uncoordinated muscle contractions to produce heat
Temperature tolerances
Thermal neutral zone
- body works great
Metabolic heat production —> thermoneutral zone —> Evaporative cooling
Hypothermia —> normothermia—> hyperthermia
Lower lethal temperature
- Get past this external sources needed in order for the organism to not die
Energy sources have been used up. The body starts to shut down.
Lower critical temperature
- body Works all right
- Metabolism Rams up to maintain normal body functions
Upper critical temperature
- body Works all right
Upper little temperature
- 
Insulation
• Down feathers or underhairs trap air next to the skin
• This air pocket does not exchange as much with the external environment
• Air pocket can be expanded or reduced by fluffing up or flattening the downy layer
Cooling
• Evaporation
• Panting: evaporation from the
respiratory tract
• Humans and a few other species release water onto the skin via sweat glands
• Kangaroos lick their forearms
Torpor and hibernation
Torpor: a purposeful drop in body temperature into the hypothermic range
• When it is too metabolically expensive to maintain body temperatures and body processes
• Duration varies from overnight to months long
• Regions of the brain maintain the new, hibernating body temperature
Heterothermic endotherms
• Adaptations allow them to tolerate higher body temperatures – hyperthermia
• Behavioural: less activity during the middle of the day; spend time in burrows or shady crevices
• Large animals absorb less heat from the environment, relative to their body size
• Circulatory pattern cools blood before it reaches the brain
Body size
• Endothermy is particularly energetically expensive at small sizes
• Gigantothermy: maintenance of high internal temperatures, despite low metabolic rates, due to low surface area : volume ratios
How and why did endothermy evolve?
• Early mammals were nocturnal, so active during cooler hours • But what about birds?
• Biochemical reactions are more efficient at higher temperatures • But there is a limit
• Adaptations of the respiratory and circulatory systems of sauropsids and synapsids facilitated higher metabolic rates, even at rest
• But resting and active metabolic rates rarely correlate that closely
• Higher temperatures allow embryos to develop more rapidly • But the energy could have gone to producing more gametes
Key Concepts
• Continents (generally) separated farther.
• Second half of Cenozoic marked by cooling temperatures and waves
of ice ages.
• Birds and mammals developed endothermy convergently.
• Endotherms generate and maintain body heat through metabolic activity.
