Ectothermy, Endothermy or Mass Homeothermy?

Ectothermy, Endothermy or Mass
Homeothermy?
!  Metabolism
– sum of all chemical reactions
within an organisms to keep it alive
!  Ecothermy – internal body temperature that
varies with external/environmental
conditions
!  Endothermy – internal body temperature
that remains constant despite changes in
external conditions
!  Mass Homeothermy – internal body
temperature that remains relatively constant
because of large size, not metabolism
Evidence
Ectotherms
Endotherms
Posture/Leg
Position
Legs extend
from the
side,
permitting
side to side
movement
Legs extend
beneath
body,
allowing
faster
locomotion
Evidence
Ectotherms
Endotherms
Shape and size of chest
cavity/rib cage
Rib cage long + narrow, Rib cage rounded with
less size for lungs
greater volume for
heart + lungs
Bone Structure
Low density of
Haversian canals to
supply blood to bone
High density of
Haversian canals to
supply blood to bone
Evidence
Ectotherms
Endotherms
Growth rate
Bone growth rings
represent seasonal
growth
Lack of growth rings
represent constant
growth
Evidence
Ectotherms
Endotherms
Growth rate
Slower growth of
embryos and young
from nest sites
Faster growth of
embryos and young
from nest sites
Evidence
Ectotherms
Endotherms
Speed (from trackways)
Shorter stride lengths
indicate slower speed;
movement is sporadic
Longer stride lengths
indicate faster speed;
movement is constant
Evidence
Ectotherms
Endotherms
Feeding
(from
predator/
prey ratios)
Higher
predator/
prey ratio,
because
predators
require less
food
Lower
predator/
prey ratio,
because
predators
require more
food
Water Loss
(from
turbinates –
small bones
in nasal
cavities)
No turbinates
to help
reduce water
loss
Turbinates
(or similar
structures)
present to
reduce water
loss
Evidence
Ectothermy
Geographic Distribution Dinosaurs found at high
latitudes – requires
hibernation, migration
or mass homeothermy
Endothermy
Dinosaurs found at high
latitudes because of
endothermic
metabolism
Physical Law: Large objects retain heat longer than small objects of
the same composition.
Mass Homeothermy: Large organisms (like dinosaurs) maintain
constant body temperature because they are large, not because they
are endothermic
Fishes
Amphibians
First
Reptiles
Ectothermy
Modern
Reptiles
Endothermy?
Endothermy
Dinosaurs
Endothermy?
Mammals
Birds
Ecothermic Dinos
Endothermic Dinos